Merge remote-tracking branch 'aosp/upstream-master' into master am: 65c0aaa266

am: 8141d27f91

Change-Id: I56c10228cdd193fc7fdf208382ff791c11509773

28 files changed, 10187 insertions, 0 deletions

diff --git a/.clang-format b/.clang-format
new file mode 100644
index 0000000..78696f5
--- /dev/null
+++ b/.clang-format
@@ -0,0 +1,21 @@
+ColumnLimit: 100
+
+UseTab: Never
+IndentWidth: 4
+AccessModifierOffset: -4
+NamespaceIndentation: Inner
+
+BreakBeforeBraces: Allman
+AlwaysBreakTemplateDeclarations: true
+BreakConstructorInitializersBeforeComma: true
+ConstructorInitializerAllOnOneLineOrOnePerLine: true
+AllowShortBlocksOnASingleLine: true
+AllowShortFunctionsOnASingleLine: All
+AllowShortIfStatementsOnASingleLine: true
+AllowShortLoopsOnASingleLine: true
+
+PointerAlignment: Left
+AlignConsecutiveAssignments: false
+AlignTrailingComments: true
+
+SpaceAfterCStyleCast: true
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..d452689
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,13 @@
+CMakeFiles
+tests/CMakeFiles
+tests/Debug
+*.opensdf
+*.sdf
+tests/*tests.dir
+*.vcxproj
+*.vcxproj.filters
+*.sln
+*.tlog
+Testing/Temporary/*.*
+CMakeCache.txt
+*.suo
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..d9229ae
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "tests/unittest-cpp"]
+	path = tests/unittest-cpp
+	url = https://github.com/Microsoft/unittest-cpp.git
diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..5c69187
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,142 @@
+# Based on https://github.com/ldionne/hana/blob/master/.travis.yml
+
+language: cpp
+sudo: false
+
+cache:
+  directories:
+    - ${TRAVIS_BUILD_DIR}/deps/cmake
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.5.2/install
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.6.2/install
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.7.1/install
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.8.1/install
+    - ${TRAVIS_BUILD_DIR}/deps/llvm-3.9.0/install
+
+matrix:
+  include:
+    - env: BUILD_TYPE=Debug
+      os: osx
+      osx_image: xcode8
+      compiler: clang
+    - env: BUILD_TYPE=Release
+      os: osx
+      osx_image: xcode8
+      compiler: clang
+    - env: CLANG_VERSION=3.6 BUILD_TYPE=Debug
+      os: linux
+      addons: &clang36
+        apt:
+          packages:
+            - clang-3.6
+            - g++-5
+          sources: &sources
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-precise-3.6
+    - env: CLANG_VERSION=3.6 BUILD_TYPE=Release
+      os: linux
+      addons: *clang36
+    - env: CLANG_VERSION=3.7 BUILD_TYPE=Debug
+      os: linux
+      addons: &clang37
+        apt:
+          packages:
+            - clang-3.7
+            - g++-5
+          sources: &sources
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-precise-3.7
+    - env: CLANG_VERSION=3.7 BUILD_TYPE=Release
+      os: linux
+      addons: *clang37
+    - env: CLANG_VERSION=3.8 BUILD_TYPE=Debug
+      os: linux
+      addons: &clang38
+        apt:
+          packages:
+            - clang-3.8
+            - g++-5
+          sources: &sources
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-precise-3.8
+    - env: CLANG_VERSION=3.8 BUILD_TYPE=Release
+      os: linux
+      addons: *clang38
+    - env: GCC_VERSION=5 BUILD_TYPE=Debug
+      os: linux
+      addons: &gcc5
+        apt:
+          packages: g++-5
+          sources: *sources
+    - env: GCC_VERSION=5 BUILD_TYPE=Release
+      os: linux
+      addons: *gcc5
+    - env: GCC_VERSION=6 BUILD_TYPE=Debug
+      os: linux
+      addons: &gcc6
+        apt:
+          packages: g++-6
+          sources: *sources
+    - env: GCC_VERSION=6 BUILD_TYPE=Release
+      os: linux
+      addons: *gcc6
+
+install:
+  - if [[ -n "$CLANG_VERSION" ]]; then export CXX=clang++-$CLANG_VERSION CC=clang-$CLANG_VERSION; fi
+  - if [[ -n "$GCC_VERSION" ]]; then export CXX=g++-$GCC_VERSION CC=gcc-$GCC_VERSION; fi
+  - JOBS=2
+  - DEPS_DIR="${TRAVIS_BUILD_DIR}/deps"
+  - mkdir -p "${DEPS_DIR}" && cd "${DEPS_DIR}"
+
+  ############################################################################
+  # Install a recent CMake (unless already installed on OS X)
+  ############################################################################
+  - |
+    if [[ "${TRAVIS_OS_NAME}" == "linux" ]]; then
+      if [[ -z "$(ls -A ${DEPS_DIR}/cmake/bin)" ]]; then
+        CMAKE_URL="https://cmake.org/files/v3.6/cmake-3.6.2-Linux-x86_64.tar.gz"
+        mkdir -p cmake && travis_retry wget --no-check-certificate --quiet -O - "${CMAKE_URL}" | tar --strip-components=1 -xz -C cmake
+      fi
+      export PATH="${DEPS_DIR}/cmake/bin:${PATH}"
+    else
+      if ! brew ls --version cmake &>/dev/null; then brew install cmake; fi
+    fi
+
+  ############################################################################
+  # [linux]: Install the right version of libc++
+  ############################################################################
+  - |
+    if [[ -n "$CLANG_VERSION" && "${TRAVIS_OS_NAME}" == "linux" && "${STDLIB}" != "libstdc++" ]]; then
+      if [[ "$CLANG_VERSION" == "3.5" ]]; then LLVM_VERSION="3.5.2"; fi
+      if [[ "$CLANG_VERSION" == "3.6" ]]; then LLVM_VERSION="3.6.2"; fi
+      if [[ "$CLANG_VERSION" == "3.7" ]]; then LLVM_VERSION="3.7.1"; fi
+      if [[ "$CLANG_VERSION" == "3.8" ]]; then LLVM_VERSION="3.8.1"; fi
+      if [[ "$CLANG_VERSION" == "3.9" ]]; then LLVM_VERSION="3.9.0"; fi
+      LLVM_ROOT="${DEPS_DIR}/llvm-${LLVM_VERSION}"
+      LLVM_URL="http://llvm.org/releases/${LLVM_VERSION}/llvm-${LLVM_VERSION}.src.tar.xz"
+      LIBCXX_URL="http://llvm.org/releases/${LLVM_VERSION}/libcxx-${LLVM_VERSION}.src.tar.xz"
+      LIBCXXABI_URL="http://llvm.org/releases/${LLVM_VERSION}/libcxxabi-${LLVM_VERSION}.src.tar.xz"
+      if [[ -z "$(ls -A ${LLVM_ROOT}/install/include)" ]]; then
+        mkdir -p "${LLVM_ROOT}" "${LLVM_ROOT}/build" "${LLVM_ROOT}/projects/libcxx" "${LLVM_ROOT}/projects/libcxxabi"
+        travis_retry wget --quiet -O - "${LLVM_URL}" | tar --strip-components=1 -xJ -C "${LLVM_ROOT}"
+        travis_retry wget --quiet -O - "${LIBCXX_URL}" | tar --strip-components=1 -xJ -C "${LLVM_ROOT}/projects/libcxx"
+        travis_retry wget --quiet -O - "${LIBCXXABI_URL}" | tar --strip-components=1 -xJ -C "${LLVM_ROOT}/projects/libcxxabi"
+        (cd "${LLVM_ROOT}/build" && cmake .. -DCMAKE_CXX_COMPILER="$CXX" -DCMAKE_C_COMPILER="$CC" -DCMAKE_INSTALL_PREFIX="${LLVM_ROOT}/install" -DCMAKE_BUILD_TYPE=$BUILD_TYPE)
+        (cd "${LLVM_ROOT}/build/projects/libcxx" && make install -j$JOBS)
+        (cd "${LLVM_ROOT}/build/projects/libcxxabi" && make install -j$JOBS)
+      fi
+      export CXXFLAGS="-I ${LLVM_ROOT}/install/include/c++/v1"
+      export LDFLAGS="-L ${LLVM_ROOT}/install/lib -lc++ -lc++abi"
+      export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:${LLVM_ROOT}/install/lib"
+    fi
+
+before_script:
+  - cd "${TRAVIS_BUILD_DIR}"
+  - cmake . -Bbuild -DCMAKE_CXX_COMPILER="$CXX" -DCMAKE_C_COMPILER="$CC" -DCMAKE_BUILD_TYPE=$BUILD_TYPE
+  - cmake --build build -- -j$JOBS
+
+script:
+  - cd build
+  - ctest --output-on-failure -j$JOBS
+
+notifications:
+  email: false
diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..2f1b0f1
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,25 @@
+cmake_minimum_required(VERSION 2.8.7)
+
+project(GSL CXX)
+
+set(GSL_HEADERS
+    "gsl/gsl"
+    "gsl/gsl_assert"
+    "gsl/gsl_byte"
+    "gsl/gsl_util"
+    "gsl/multi_span"
+    "gsl/span"
+    "gsl/string_span"
+)
+
+include_directories(
+    ${CMAKE_CURRENT_BINARY_DIR}
+)
+
+install(FILES ${GSL_HEADERS}
+    DESTINATION include/gsl
+)
+
+enable_testing()
+
+add_subdirectory(tests)
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 0000000..10e6c32
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,29 @@
+## Contributing to the Guideline Support Library
+
+The Guideline Support Library (GSL) contains functions and types that are suggested for use by the
+[C++ Core Guidelines](https://github.com/isocpp/CppCoreGuidelines). GSL design changes are made only as a result of modifications to the Guidelines. 
+
+GSL is accepting contributions that improve or refine any of the types in this library as well as ports to other platforms. Changes should have an issue 
+tracking the suggestion that has been approved by the maintainers. Your pull request should include a link to the bug that you are fixing. If you've submitted 
+a PR, please post a comment in the associated issue to avoid duplication of effort.
+
+## Legal
+You will need to complete a Contributor License Agreement (CLA). Briefly, this agreement testifies that you are granting us and the community permission to 
+use the submitted change according to the terms of the project's license, and that the work being submitted is under appropriate copyright.
+
+Please submit a Contributor License Agreement (CLA) before submitting a pull request. You may visit https://cla.microsoft.com to sign digitally.
+
+## Housekeeping
+Your pull request should: 
+
+* Include a description of what your change intends to do
+* Be a child commit of a reasonably recent commit in the **master** branch 
+    * Requests need not be a single commit, but should be a linear sequence of commits (i.e. no merge commits in your PR)
+* It is desirable, but not necessary, for the tests to pass at each commit. Please see [README.md](./README.md) for instructions to build the test suite. 
+* Have clear commit messages 
+    * e.g. "Fix issue", "Add tests for type", etc.
+* Include appropriate tests 
+    * Tests should include reasonable permutations of the target fix/change
+    * Include baseline changes with your change
+    * All changed code must have 100% code coverage
+* To avoid line ending issues, set `autocrlf = input` and `whitespace = cr-at-eol` in your git configuration
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..aa58667
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+Copyright (c) 2015 Microsoft Corporation. All rights reserved. 
+ 
+This code is licensed under the MIT License (MIT). 
+
+Permission is hereby granted, free of charge, to any person obtaining a copy 
+of this software and associated documentation files (the "Software"), to deal 
+in the Software without restriction, including without limitation the rights 
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies 
+of the Software, and to permit persons to whom the Software is furnished to do 
+so, subject to the following conditions: 
+
+The above copyright notice and this permission notice shall be included in all 
+copies or substantial portions of the Software. 
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 
+THE SOFTWARE. 
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..c3aff66
--- /dev/null
+++ b/README.md
@@ -0,0 +1,86 @@
+# GSL: Guideline Support Library [![Build Status](https://travis-ci.org/Microsoft/GSL.svg?branch=master)](https://travis-ci.org/Microsoft/GSL) [![Build status](https://ci.appveyor.com/api/projects/status/github/Microsoft/GSL?svg=true)](https://ci.appveyor.com/project/neilmacintosh/GSL)
+
+The Guideline Support Library (GSL) contains functions and types that are suggested for use by the
+[C++ Core Guidelines](https://github.com/isocpp/CppCoreGuidelines) maintained by the [Standard C++ Foundation](https://isocpp.org).
+This repo contains Microsoft's implementation of GSL.
+
+The library includes types like `span<T>`, `string_span`, `owner<>` and others.
+
+The entire implementation is provided inline in the headers under the [gsl](./gsl) directory. The implementation generally assumes a platform that implements C++14 support. There are specific workarounds to support MSVC 2013 and 2015.
+
+While some types have been broken out into their own headers (e.g. [gsl/span](./gsl/span)),
+it is simplest to just include [gsl/gsl](./gsl/gsl) and gain access to the entire library.
+
+> NOTE: We encourage contributions that improve or refine any of the types in this library as well as ports to
+other platforms. Please see [CONTRIBUTING.md](./CONTRIBUTING.md) for more information about contributing.
+
+# Project Code of Conduct
+This project has adopted the [Microsoft Open Source Code of Conduct](https://opensource.microsoft.com/codeofconduct/). For more information see the [Code of Conduct FAQ](https://opensource.microsoft.com/codeofconduct/faq/) or contact [opencode@microsoft.com](mailto:opencode@microsoft.com) with any additional questions or comments.
+
+# Quick Start
+## Supported Platforms
+The test suite that exercises GSL has been built and passes successfully on the following platforms:<sup>1)</sup>
+
+* Windows using Visual Studio 2013
+* Windows using Visual Studio 2015
+* Windows using Clang/LLVM 3.6
+* Windows using GCC 5.1
+* GNU/Linux using Clang/LLVM 3.6
+* GNU/Linux using GCC 5.1
+* OS X Yosemite using Xcode with AppleClang 7.0.0.7000072
+* OS X Yosemite using GCC-5.2.0
+* FreeBSD 10.x with Clang/LLVM 3.6
+
+> If you successfully port GSL to another platform, we would love to hear from you. Please submit an issue to let us know. Also please consider
+contributing any changes that were necessary back to this project to benefit the wider community.
+
+<sup>1)</sup> For `gsl::byte` to work correctly with Clang and GCC you might have to use the ` -fno-strict-aliasing` compiler option.
+
+## Building the tests
+To build the tests, you will require the following:
+
+* [CMake](http://cmake.org), version 2.8.7 or later to be installed and in your PATH.
+* [UnitTest-cpp](https://github.com/Microsoft/unittest-cpp), to be cloned under the [tests/unittest-cpp](./tests/unittest-cpp) directory
+of your GSL source.
+
+These steps assume the source code of this repository has been cloned into a directory named `c:\GSL`.
+
+1. Create a directory to contain the build outputs for a particular architecture (we name it c:\GSL\build-x86 in this example).
+
+        cd GSL
+        md build-x86
+        cd build-x86
+
+2. Configure CMake to use the compiler of your choice (you can see a list by running `cmake --help`).
+
+        cmake -G "Visual Studio 14 2015" c:\GSL
+
+3. Build the test suite (in this case, in the Debug configuration, Release is another good choice).    
+
+        cmake --build . --config Debug
+
+4. Run the test suite.    
+
+        ctest -C Debug
+
+All tests should pass - indicating your platform is fully supported and you are ready to use the GSL types!
+
+## Using the libraries
+As the types are entirely implemented inline in headers, there are no linking requirements.
+
+You can copy the [gsl](./gsl) directory into your source tree so it is available
+to your compiler, then include the appropriate headers in your program.
+
+Alternatively set your compiler's *include path* flag to point to the GSL development folder (`c:\GSL` in the example above) or installation folder (after running the install). Eg.
+
+MSVC++
+
+    /I c:\GSL
+
+GCC/clang
+
+    -I$HOME/dev/GSL
+
+Include the library using:
+
+    #include <gsl/gsl>
diff --git a/gsl/gsl b/gsl/gsl
new file mode 100644
index 0000000..12a9676
--- /dev/null
+++ b/gsl/gsl
@@ -0,0 +1,172 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+#ifndef GSL_GSL_H
+#define GSL_GSL_H
+
+#include "gsl_assert"  // Ensures/Expects
+#include "gsl_util"    // finally()/narrow()/narrow_cast()...
+#include "multi_span"  // multi_span, strided_span...
+#include "span"        // span
+#include "string_span" // zstring, string_span, zstring_builder...
+#include <memory>
+
+#ifdef _MSC_VER
+
+// No MSVC does constexpr fully yet
+#pragma push_macro("constexpr")
+#define constexpr /*constexpr*/
+
+// MSVC 2013 workarounds
+#if _MSC_VER <= 1800
+// noexcept is not understood
+#pragma push_macro("noexcept")
+#define noexcept /*noexcept*/
+
+// turn off some misguided warnings
+#pragma warning(push)
+#pragma warning(disable : 4351) // warns about newly introduced aggregate initializer behavior
+
+#endif // _MSC_VER <= 1800
+
+#endif // _MSC_VER
+
+namespace gsl
+{
+
+//
+// GSL.owner: ownership pointers
+//
+using std::unique_ptr;
+using std::shared_ptr;
+
+template <class T>
+using owner = T;
+
+//
+// not_null
+//
+// Restricts a pointer or smart pointer to only hold non-null values.
+//
+// Has zero size overhead over T.
+//
+// If T is a pointer (i.e. T == U*) then
+// - allow construction from U* or U&
+// - disallow construction from nullptr_t
+// - disallow default construction
+// - ensure construction from U* fails with nullptr
+// - allow implicit conversion to U*
+//
+template <class T>
+class not_null
+{
+    static_assert(std::is_assignable<T&, std::nullptr_t>::value, "T cannot be assigned nullptr.");
+
+public:
+    not_null(T t) : ptr_(t) { ensure_invariant(); }
+    not_null& operator=(const T& t)
+    {
+        ptr_ = t;
+        ensure_invariant();
+        return *this;
+    }
+
+    not_null(const not_null& other) = default;
+    not_null& operator=(const not_null& other) = default;
+
+    template <typename U, typename Dummy = std::enable_if_t<std::is_convertible<U, T>::value>>
+    not_null(const not_null<U>& other)
+    {
+        *this = other;
+    }
+
+    template <typename U, typename Dummy = std::enable_if_t<std::is_convertible<U, T>::value>>
+    not_null& operator=(const not_null<U>& other)
+    {
+        ptr_ = other.get();
+        return *this;
+    }
+
+    // prevents compilation when someone attempts to assign a nullptr
+    not_null(std::nullptr_t) = delete;
+    not_null(int) = delete;
+    not_null<T>& operator=(std::nullptr_t) = delete;
+    not_null<T>& operator=(int) = delete;
+
+    T get() const
+    {
+#ifdef _MSC_VER
+        __assume(ptr_ != nullptr);
+#endif
+        return ptr_;
+    } // the assume() should help the optimizer
+
+    operator T() const { return get(); }
+    T operator->() const { return get(); }
+
+    bool operator==(const T& rhs) const { return ptr_ == rhs; }
+    bool operator!=(const T& rhs) const { return !(*this == rhs); }
+private:
+    T ptr_;
+
+    // we assume that the compiler can hoist/prove away most of the checks inlined from this
+    // function
+    // if not, we could make them optional via conditional compilation
+    void ensure_invariant() const { Expects(ptr_ != nullptr); }
+
+    // unwanted operators...pointers only point to single objects!
+    // TODO ensure all arithmetic ops on this type are unavailable
+    not_null<T>& operator++() = delete;
+    not_null<T>& operator--() = delete;
+    not_null<T> operator++(int) = delete;
+    not_null<T> operator--(int) = delete;
+    not_null<T>& operator+(size_t) = delete;
+    not_null<T>& operator+=(size_t) = delete;
+    not_null<T>& operator-(size_t) = delete;
+    not_null<T>& operator-=(size_t) = delete;
+};
+
+} // namespace gsl
+
+namespace std
+{
+template <class T>
+struct hash<gsl::not_null<T>>
+{
+    size_t operator()(const gsl::not_null<T>& value) const { return hash<T>{}(value); }
+};
+
+} // namespace std
+
+#ifdef _MSC_VER
+
+#undef constexpr
+#pragma pop_macro("constexpr")
+
+#if _MSC_VER <= 1800
+
+#undef noexcept
+#pragma pop_macro("noexcept")
+
+#pragma warning(pop)
+
+#endif // _MSC_VER <= 1800
+
+#endif // _MSC_VER
+
+#endif // GSL_GSL_H
diff --git a/gsl/gsl_assert b/gsl/gsl_assert
new file mode 100644
index 0000000..6d8760d
--- /dev/null
+++ b/gsl/gsl_assert
@@ -0,0 +1,85 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+#ifndef GSL_CONTRACTS_H
+#define GSL_CONTRACTS_H
+
+#include <exception>
+#include <stdexcept>
+
+//
+// There are three configuration options for this GSL implementation's behavior
+// when pre/post conditions on the GSL types are violated:
+//
+// 1. GSL_TERMINATE_ON_CONTRACT_VIOLATION: std::terminate will be called (default)
+// 2. GSL_THROW_ON_CONTRACT_VIOLATION: a gsl::fail_fast exception will be thrown
+// 3. GSL_UNENFORCED_ON_CONTRACT_VIOLATION: nothing happens
+//
+#if !(defined(GSL_THROW_ON_CONTRACT_VIOLATION) ^ defined(GSL_TERMINATE_ON_CONTRACT_VIOLATION) ^    \
+      defined(GSL_UNENFORCED_ON_CONTRACT_VIOLATION))
+#define GSL_TERMINATE_ON_CONTRACT_VIOLATION
+#endif
+
+#define GSL_STRINGIFY_DETAIL(x) #x
+#define GSL_STRINGIFY(x) GSL_STRINGIFY_DETAIL(x)
+
+#if defined(__clang__) || defined(__GNUC__)
+#define GSL_LIKELY(x) __builtin_expect (!!(x), 1)
+#define GSL_UNLIKELY(x) __builtin_expect (!!(x), 0)
+#else
+#define GSL_LIKELY(x) (x)
+#define GSL_UNLIKELY(x) (x)
+#endif
+
+//
+// GSL.assert: assertions
+//
+
+namespace gsl
+{
+struct fail_fast : public std::runtime_error
+{
+    explicit fail_fast(char const* const message) : std::runtime_error(message) {}
+};
+}
+
+#if defined(GSL_THROW_ON_CONTRACT_VIOLATION)
+
+#define Expects(cond)                                                                              \
+    if (GSL_UNLIKELY(!(cond)))                                                                     \
+        throw gsl::fail_fast("GSL: Precondition failure at " __FILE__ ": " GSL_STRINGIFY(__LINE__));
+#define Ensures(cond)                                                                              \
+    if (GSL_UNLIKELY(!(cond)))                                                                     \
+        throw gsl::fail_fast("GSL: Postcondition failure at " __FILE__                             \
+                             ": " GSL_STRINGIFY(__LINE__));
+
+#elif defined(GSL_TERMINATE_ON_CONTRACT_VIOLATION)
+
+#define Expects(cond)                                                                              \
+    if (GSL_UNLIKELY(!(cond))) std::terminate();
+#define Ensures(cond)                                                                              \
+    if (GSL_UNLIKELY(!(cond))) std::terminate();
+
+#elif defined(GSL_UNENFORCED_ON_CONTRACT_VIOLATION)
+
+#define Expects(cond)
+#define Ensures(cond)
+
+#endif
+
+#endif // GSL_CONTRACTS_H
diff --git a/gsl/gsl_byte b/gsl/gsl_byte
new file mode 100644
index 0000000..3f77923
--- /dev/null
+++ b/gsl/gsl_byte
@@ -0,0 +1,161 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+#ifndef GSL_BYTE_H
+#define GSL_BYTE_H
+
+#ifdef _MSC_VER
+
+#pragma warning(push)
+
+// don't warn about function style casts in byte related operators
+#pragma warning(disable : 26493)
+
+// MSVC 2013 workarounds
+#if _MSC_VER <= 1800
+
+// constexpr is not understood
+#pragma push_macro("constexpr")
+#define constexpr /*constexpr*/
+
+// noexcept is not understood
+#pragma push_macro("noexcept")
+#define noexcept /*noexcept*/
+
+#endif // _MSC_VER <= 1800
+
+#endif // _MSC_VER
+
+namespace gsl
+{
+// This is a simple definition for now that allows
+// use of byte within span<> to be standards-compliant
+enum class byte : unsigned char
+{
+};
+
+template <class IntegerType, class = std::enable_if_t<std::is_integral<IntegerType>::value>>
+inline constexpr byte& operator<<=(byte& b, IntegerType shift) noexcept
+{
+    return b = byte(static_cast<unsigned char>(b) << shift);
+}
+
+template <class IntegerType, class = std::enable_if_t<std::is_integral<IntegerType>::value>>
+inline constexpr byte operator<<(byte b, IntegerType shift) noexcept
+{
+    return byte(static_cast<unsigned char>(b) << shift);
+}
+
+template <class IntegerType, class = std::enable_if_t<std::is_integral<IntegerType>::value>>
+inline constexpr byte& operator>>=(byte& b, IntegerType shift) noexcept
+{
+    return b = byte(static_cast<unsigned char>(b) >> shift);
+}
+
+template <class IntegerType, class = std::enable_if_t<std::is_integral<IntegerType>::value>>
+inline constexpr byte operator>>(byte b, IntegerType shift) noexcept
+{
+    return byte(static_cast<unsigned char>(b) >> shift);
+}
+
+inline constexpr byte& operator|=(byte& l, byte r) noexcept
+{
+    return l = byte(static_cast<unsigned char>(l) | static_cast<unsigned char>(r));
+}
+
+inline constexpr byte operator|(byte l, byte r) noexcept
+{
+    return byte(static_cast<unsigned char>(l) | static_cast<unsigned char>(r));
+}
+
+inline constexpr byte& operator&=(byte& l, byte r) noexcept
+{
+    return l = byte(static_cast<unsigned char>(l) & static_cast<unsigned char>(r));
+}
+
+inline constexpr byte operator&(byte l, byte r) noexcept
+{
+    return byte(static_cast<unsigned char>(l) & static_cast<unsigned char>(r));
+}
+
+inline constexpr byte& operator^=(byte& l, byte r) noexcept
+{
+    return l = byte(static_cast<unsigned char>(l) ^ static_cast<unsigned char>(r));
+}
+
+inline constexpr byte operator^(byte l, byte r) noexcept
+{
+    return byte(static_cast<unsigned char>(l) ^ static_cast<unsigned char>(r));
+}
+
+inline constexpr byte operator~(byte b) noexcept { return byte(~static_cast<unsigned char>(b)); }
+
+template <class IntegerType, class = std::enable_if_t<std::is_integral<IntegerType>::value>>
+inline constexpr IntegerType to_integer(byte b) noexcept
+{
+    return static_cast<IntegerType>(b);
+}
+
+template<bool E, typename T>
+inline constexpr byte to_byte_impl(T t) noexcept
+{
+    static_assert(
+        E,
+        "gsl::to_byte(t) must be provided an unsigned char, otherwise data loss may occur. "
+        "If you are calling to_byte with an integer contant use: gsl::to_byte<t>() version."
+    );
+    return static_cast<byte>(t);
+}
+template<>
+inline constexpr byte to_byte_impl<true, unsigned char>(unsigned char t) noexcept
+{
+     return byte(t);
+}
+
+template<typename T>
+inline constexpr byte to_byte(T t) noexcept
+{
+     return to_byte_impl<std::is_same<T, unsigned char>::value, T>(t);
+}
+
+template <int I>
+inline constexpr byte to_byte() noexcept
+{
+    static_assert(I >= 0 && I <= 255, "gsl::byte only has 8 bits of storage, values must be in range 0-255");
+    return static_cast<byte>(I);
+}
+
+} // namespace gsl
+
+#ifdef _MSC_VER
+
+#if _MSC_VER <= 1800
+
+#undef constexpr
+#pragma pop_macro("constexpr")
+
+#undef noexcept
+#pragma pop_macro("noexcept")
+
+#endif // _MSC_VER <= 1800
+
+#pragma warning(pop)
+
+#endif // _MSC_VER
+
+#endif // GSL_BYTE_H
diff --git a/gsl/gsl_util b/gsl/gsl_util
new file mode 100644
index 0000000..f0ac964
--- /dev/null
+++ b/gsl/gsl_util
@@ -0,0 +1,185 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+#ifndef GSL_UTIL_H
+#define GSL_UTIL_H
+
+#include "gsl_assert" // Ensures/Expects
+#include <array>
+#include <exception>
+#include <type_traits>
+#include <utility>
+
+#ifdef _MSC_VER
+
+// No MSVC does constexpr fully yet
+#pragma push_macro("constexpr")
+#define constexpr /*constexpr*/
+
+#pragma warning(push)
+#pragma warning(disable : 4127) // conditional expression is constant
+
+// MSVC 2013 workarounds
+#if _MSC_VER <= 1800
+// noexcept is not understood
+#pragma push_macro("noexcept")
+#define noexcept /*noexcept*/
+
+// turn off some misguided warnings
+#pragma warning(push)
+#pragma warning(disable : 4351) // warns about newly introduced aggregate initializer behavior
+
+#endif // _MSC_VER <= 1800
+
+#endif // _MSC_VER
+
+namespace gsl
+{
+//
+// GSL.util: utilities
+//
+
+// final_act allows you to ensure something gets run at the end of a scope
+template <class F>
+class final_act
+{
+public:
+    explicit final_act(F f) noexcept : f_(std::move(f)), invoke_(true) {}
+
+    final_act(final_act&& other) noexcept : f_(std::move(other.f_)), invoke_(other.invoke_)
+    {
+        other.invoke_ = false;
+    }
+
+    final_act(const final_act&) = delete;
+    final_act& operator=(const final_act&) = delete;
+
+    ~final_act() noexcept
+    {
+        if (invoke_) f_();
+    }
+
+private:
+    F f_;
+    bool invoke_;
+};
+
+// finally() - convenience function to generate a final_act
+template <class F>
+inline final_act<F> finally(const F& f) noexcept
+{
+    return final_act<F>(f);
+}
+
+template <class F>
+inline final_act<F> finally(F&& f) noexcept
+{
+    return final_act<F>(std::forward<F>(f));
+}
+
+// narrow_cast(): a searchable way to do narrowing casts of values
+#if _MSC_VER <= 1800
+template <class T, class U>
+inline constexpr T narrow_cast(U u) noexcept
+{
+    return static_cast<T>(u);
+}
+#else
+template <class T, class U>
+inline constexpr T narrow_cast(U&& u) noexcept
+{
+    return static_cast<T>(std::forward<U>(u));
+}
+#endif
+
+struct narrowing_error : public std::exception
+{
+};
+
+namespace details
+{
+    template <class T, class U>
+    struct is_same_signedness
+        : public std::integral_constant<bool, std::is_signed<T>::value == std::is_signed<U>::value>
+    {
+    };
+}
+
+// narrow() : a checked version of narrow_cast() that throws if the cast changed the value
+template <class T, class U>
+inline T narrow(U u)
+{
+    T t = narrow_cast<T>(u);
+    if (static_cast<U>(t) != u) throw narrowing_error();
+    if (!details::is_same_signedness<T, U>::value && ((t < T{}) != (u < U{})))
+        throw narrowing_error();
+    return t;
+}
+
+//
+// at() - Bounds-checked way of accessing static arrays, std::array, std::vector
+//
+template <class T, size_t N>
+constexpr T& at(T (&arr)[N], size_t index)
+{
+    Expects(index < N);
+    return arr[index];
+}
+
+template <class T, size_t N>
+constexpr T& at(std::array<T, N>& arr, size_t index)
+{
+    Expects(index < N);
+    return arr[index];
+}
+
+template <class Cont>
+constexpr typename Cont::value_type& at(Cont& cont, size_t index)
+{
+    Expects(index < cont.size());
+    return cont[index];
+}
+
+template <class T>
+constexpr const T& at(std::initializer_list<T> cont, size_t index)
+{
+    Expects(index < cont.size());
+    return *(cont.begin() + index);
+}
+
+} // namespace gsl
+
+#ifdef _MSC_VER
+
+#pragma warning(pop)
+
+#undef constexpr
+#pragma pop_macro("constexpr")
+
+#if _MSC_VER <= 1800
+
+#undef noexcept
+#pragma pop_macro("noexcept")
+
+#pragma warning(pop)
+
+#endif // _MSC_VER <= 1800
+
+#endif // _MSC_VER
+
+#endif // GSL_UTIL_H
diff --git a/gsl/multi_span b/gsl/multi_span
new file mode 100644
index 0000000..2186c7b
--- /dev/null
+++ b/gsl/multi_span
@@ -0,0 +1,2231 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+#ifndef GSL_MULTI_SPAN_H
+#define GSL_MULTI_SPAN_H
+
+#include "gsl_assert"
+#include "gsl_byte"
+#include "gsl_util"
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <functional>
+#include <iterator>
+#include <limits>
+#include <new>
+#include <numeric>
+#include <stdexcept>
+#include <type_traits>
+#include <utility>
+
+#ifdef _MSC_VER
+
+// turn off some warnings that are noisy about our Expects statements
+#pragma warning(push)
+#pragma warning(disable : 4127) // conditional expression is constant
+
+// No MSVC does constexpr fully yet
+#pragma push_macro("constexpr")
+#define constexpr /*constexpr*/
+
+// VS 2013 workarounds
+#if _MSC_VER <= 1800
+
+#define GSL_MSVC_HAS_VARIADIC_CTOR_BUG
+#define GSL_MSVC_NO_SUPPORT_FOR_MOVE_CTOR_DEFAULT
+
+// noexcept is not understood
+#ifndef GSL_THROW_ON_CONTRACT_VIOLATION
+#pragma push_macro("noexcept")
+#define noexcept /*noexcept*/
+#endif
+
+// turn off some misguided warnings
+#pragma warning(push)
+#pragma warning(disable : 4351) // warns about newly introduced aggregate initializer behavior
+#pragma warning(disable : 4512) // warns that assignment op could not be generated
+
+#endif // _MSC_VER <= 1800
+
+#endif // _MSC_VER
+
+#ifdef GSL_THROW_ON_CONTRACT_VIOLATION
+
+#ifdef _MSC_VER
+#pragma push_macro("noexcept")
+#endif
+
+#define noexcept /*noexcept*/
+
+#endif // GSL_THROW_ON_CONTRACT_VIOLATION
+
+namespace gsl
+{
+
+/*
+** begin definitions of index and bounds
+*/
+namespace details
+{
+    template <typename SizeType>
+    struct SizeTypeTraits
+    {
+        static const SizeType max_value = std::numeric_limits<SizeType>::max();
+    };
+
+    template <typename... Ts>
+    class are_integral : public std::integral_constant<bool, true>
+    {
+    };
+
+    template <typename T, typename... Ts>
+    class are_integral<T, Ts...>
+        : public std::integral_constant<bool,
+                                        std::is_integral<T>::value && are_integral<Ts...>::value>
+    {
+    };
+}
+
+template <size_t Rank>
+class index final
+{
+    static_assert(Rank > 0, "Rank must be greater than 0!");
+
+    template <size_t OtherRank>
+    friend class index;
+
+public:
+    static const size_t rank = Rank;
+    using value_type = std::ptrdiff_t;
+    using size_type = value_type;
+    using reference = std::add_lvalue_reference_t<value_type>;
+    using const_reference = std::add_lvalue_reference_t<std::add_const_t<value_type>>;
+
+    constexpr index() noexcept {}
+
+    constexpr index(const value_type (&values)[Rank]) noexcept
+    {
+        std::copy(values, values + Rank, elems);
+    }
+
+#ifdef GSL_MSVC_HAS_VARIADIC_CTOR_BUG
+    template <
+        typename T, typename... Ts,
+        typename = std::enable_if_t<((sizeof...(Ts) + 1) == Rank) && std::is_integral<T>::value &&
+                                    details::are_integral<Ts...>::value>>
+    constexpr index(T t, Ts... ds)
+        : index({narrow_cast<value_type>(t), narrow_cast<value_type>(ds)...})
+    {
+    }
+#else
+    template <typename... Ts, typename = std::enable_if_t<(sizeof...(Ts) == Rank) &&
+                                                          details::are_integral<Ts...>::value>>
+    constexpr index(Ts... ds) noexcept : elems{narrow_cast<value_type>(ds)...}
+    {
+    }
+#endif
+
+    constexpr index(const index& other) noexcept = default;
+
+    constexpr index& operator=(const index& rhs) noexcept = default;
+
+    // Preconditions: component_idx < rank
+    constexpr reference operator[](size_t component_idx)
+    {
+        Expects(component_idx < Rank); // Component index must be less than rank
+        return elems[component_idx];
+    }
+
+    // Preconditions: component_idx < rank
+    constexpr const_reference operator[](size_t component_idx) const noexcept
+    {
+        Expects(component_idx < Rank); // Component index must be less than rank
+        return elems[component_idx];
+    }
+
+    constexpr bool operator==(const index& rhs) const noexcept
+    {
+        return std::equal(elems, elems + rank, rhs.elems);
+    }
+
+    constexpr bool operator!=(const index& rhs) const noexcept { return !(this == rhs); }
+
+    constexpr index operator+() const noexcept { return *this; }
+
+    constexpr index operator-() const noexcept
+    {
+        index ret = *this;
+        std::transform(ret, ret + rank, ret, std::negate<value_type>{});
+        return ret;
+    }
+
+    constexpr index operator+(const index& rhs) const noexcept
+    {
+        index ret = *this;
+        ret += rhs;
+        return ret;
+    }
+
+    constexpr index operator-(const index& rhs) const noexcept
+    {
+        index ret = *this;
+        ret -= rhs;
+        return ret;
+    }
+
+    constexpr index& operator+=(const index& rhs) noexcept
+    {
+        std::transform(elems, elems + rank, rhs.elems, elems, std::plus<value_type>{});
+        return *this;
+    }
+
+    constexpr index& operator-=(const index& rhs) noexcept
+    {
+        std::transform(elems, elems + rank, rhs.elems, elems, std::minus<value_type>{});
+        return *this;
+    }
+
+    constexpr index operator*(value_type v) const noexcept
+    {
+        index ret = *this;
+        ret *= v;
+        return ret;
+    }
+
+    constexpr index operator/(value_type v) const noexcept
+    {
+        index ret = *this;
+        ret /= v;
+        return ret;
+    }
+
+    friend constexpr index operator*(value_type v, const index& rhs) noexcept { return rhs * v; }
+
+    constexpr index& operator*=(value_type v) noexcept
+    {
+        std::transform(elems, elems + rank, elems,
+                       [v](value_type x) { return std::multiplies<value_type>{}(x, v); });
+        return *this;
+    }
+
+    constexpr index& operator/=(value_type v) noexcept
+    {
+        std::transform(elems, elems + rank, elems,
+                       [v](value_type x) { return std::divides<value_type>{}(x, v); });
+        return *this;
+    }
+
+private:
+    value_type elems[Rank] = {};
+};
+
+#ifndef _MSC_VER
+
+struct static_bounds_dynamic_range_t
+{
+    template <typename T, typename Dummy = std::enable_if_t<std::is_integral<T>::value>>
+    constexpr operator T() const noexcept
+    {
+        return narrow_cast<T>(-1);
+    }
+
+    template <typename T, typename Dummy = std::enable_if_t<std::is_integral<T>::value>>
+    constexpr bool operator==(T other) const noexcept
+    {
+        return narrow_cast<T>(-1) == other;
+    }
+
+    template <typename T, typename Dummy = std::enable_if_t<std::is_integral<T>::value>>
+    constexpr bool operator!=(T other) const noexcept
+    {
+        return narrow_cast<T>(-1) != other;
+    }
+};
+
+template <typename T, typename Dummy = std::enable_if_t<std::is_integral<T>::value>>
+constexpr bool operator==(T left, static_bounds_dynamic_range_t right) noexcept
+{
+    return right == left;
+}
+
+template <typename T, typename Dummy = std::enable_if_t<std::is_integral<T>::value>>
+constexpr bool operator!=(T left, static_bounds_dynamic_range_t right) noexcept
+{
+    return right != left;
+}
+
+constexpr static_bounds_dynamic_range_t dynamic_range{};
+#else
+const std::ptrdiff_t dynamic_range = -1;
+#endif
+
+struct generalized_mapping_tag
+{
+};
+struct contiguous_mapping_tag : generalized_mapping_tag
+{
+};
+
+namespace details
+{
+
+    template <std::ptrdiff_t Left, std::ptrdiff_t Right>
+    struct LessThan
+    {
+        static const bool value = Left < Right;
+    };
+
+    template <std::ptrdiff_t... Ranges>
+    struct BoundsRanges
+    {
+        using size_type = std::ptrdiff_t;
+        static const size_type Depth = 0;
+        static const size_type DynamicNum = 0;
+        static const size_type CurrentRange = 1;
+        static const size_type TotalSize = 1;
+
+        // TODO : following signature is for work around VS bug
+        template <typename OtherRange>
+        BoundsRanges(const OtherRange&, bool /* firstLevel */)
+        {
+        }
+
+        BoundsRanges(const std::ptrdiff_t* const) {}
+        BoundsRanges() = default;
+
+        template <typename T, size_t Dim>
+        void serialize(T&) const
+        {
+        }
+
+        template <typename T, size_t Dim>
+        size_type linearize(const T&) const
+        {
+            return 0;
+        }
+
+        template <typename T, size_t Dim>
+        size_type contains(const T&) const
+        {
+            return -1;
+        }
+
+        size_type elementNum(size_t) const noexcept { return 0; }
+
+        size_type totalSize() const noexcept { return TotalSize; }
+
+        bool operator==(const BoundsRanges&) const noexcept { return true; }
+    };
+
+    template <std::ptrdiff_t... RestRanges>
+    struct BoundsRanges<dynamic_range, RestRanges...> : BoundsRanges<RestRanges...>
+    {
+        using Base = BoundsRanges<RestRanges...>;
+        using size_type = std::ptrdiff_t;
+        static const size_t Depth = Base::Depth + 1;
+        static const size_t DynamicNum = Base::DynamicNum + 1;
+        static const size_type CurrentRange = dynamic_range;
+        static const size_type TotalSize = dynamic_range;
+    private:
+        size_type m_bound;
+    public:
+
+        BoundsRanges(const std::ptrdiff_t* const arr)
+            : Base(arr + 1), m_bound(*arr * this->Base::totalSize())
+        {
+            Expects(0 <= *arr);
+        }
+
+        BoundsRanges() : m_bound(0) {}
+
+        template <std::ptrdiff_t OtherRange, std::ptrdiff_t... RestOtherRanges>
+        BoundsRanges(const BoundsRanges<OtherRange, RestOtherRanges...>& other,
+                     bool /* firstLevel */ = true)
+            : Base(static_cast<const BoundsRanges<RestOtherRanges...>&>(other), false)
+            , m_bound(other.totalSize())
+        {
+        }
+
+        template <typename T, size_t Dim = 0>
+        void serialize(T& arr) const
+        {
+            arr[Dim] = elementNum();
+            this->Base::template serialize<T, Dim + 1>(arr);
+        }
+
+        template <typename T, size_t Dim = 0>
+        size_type linearize(const T& arr) const
+        {
+            const size_type index = this->Base::totalSize() * arr[Dim];
+            Expects(index < m_bound);
+            return index + this->Base::template linearize<T, Dim + 1>(arr);
+        }
+
+        template <typename T, size_t Dim = 0>
+        size_type contains(const T& arr) const
+        {
+            const ptrdiff_t last = this->Base::template contains<T, Dim + 1>(arr);
+            if (last == -1) return -1;
+            const ptrdiff_t cur = this->Base::totalSize() * arr[Dim];
+            return cur < m_bound ? cur + last : -1;
+        }
+
+        size_type totalSize() const noexcept { return m_bound; }
+
+        size_type elementNum() const noexcept { return totalSize() / this->Base::totalSize(); }
+
+        size_type elementNum(size_t dim) const noexcept
+        {
+            if (dim > 0)
+                return this->Base::elementNum(dim - 1);
+            else
+                return elementNum();
+        }
+
+        bool operator==(const BoundsRanges& rhs) const noexcept
+        {
+            return m_bound == rhs.m_bound &&
+                   static_cast<const Base&>(*this) == static_cast<const Base&>(rhs);
+        }
+    };
+
+    template <std::ptrdiff_t CurRange, std::ptrdiff_t... RestRanges>
+    struct BoundsRanges<CurRange, RestRanges...> : BoundsRanges<RestRanges...>
+    {
+        using Base = BoundsRanges<RestRanges...>;
+        using size_type = std::ptrdiff_t;
+        static const size_t Depth = Base::Depth + 1;
+        static const size_t DynamicNum = Base::DynamicNum;
+        static const size_type CurrentRange = CurRange;
+        static const size_type TotalSize =
+            Base::TotalSize == dynamic_range ? dynamic_range : CurrentRange * Base::TotalSize;
+
+        BoundsRanges(const std::ptrdiff_t* const arr) : Base(arr) {}
+        BoundsRanges() = default;
+
+        template <std::ptrdiff_t OtherRange, std::ptrdiff_t... RestOtherRanges>
+        BoundsRanges(const BoundsRanges<OtherRange, RestOtherRanges...>& other,
+                     bool firstLevel = true)
+            : Base(static_cast<const BoundsRanges<RestOtherRanges...>&>(other), false)
+        {
+            (void) firstLevel;
+        }
+
+        template <typename T, size_t Dim = 0>
+        void serialize(T& arr) const
+        {
+            arr[Dim] = elementNum();
+            this->Base::template serialize<T, Dim + 1>(arr);
+        }
+
+        template <typename T, size_t Dim = 0>
+        size_type linearize(const T& arr) const
+        {
+            Expects(arr[Dim] >= 0 && arr[Dim] < CurrentRange); // Index is out of range
+            return this->Base::totalSize() * arr[Dim] +
+                   this->Base::template linearize<T, Dim + 1>(arr);
+        }
+
+        template <typename T, size_t Dim = 0>
+        size_type contains(const T& arr) const
+        {
+            if (arr[Dim] >= CurrentRange) return -1;
+            const size_type last = this->Base::template contains<T, Dim + 1>(arr);
+            if (last == -1) return -1;
+            return this->Base::totalSize() * arr[Dim] + last;
+        }
+
+        size_type totalSize() const noexcept { return CurrentRange * this->Base::totalSize(); }
+
+        size_type elementNum() const noexcept { return CurrentRange; }
+
+        size_type elementNum(size_t dim) const noexcept
+        {
+            if (dim > 0)
+                return this->Base::elementNum(dim - 1);
+            else
+                return elementNum();
+        }
+
+        bool operator==(const BoundsRanges& rhs) const noexcept
+        {
+            return static_cast<const Base&>(*this) == static_cast<const Base&>(rhs);
+        }
+    };
+
+    template <typename SourceType, typename TargetType>
+    struct BoundsRangeConvertible
+        : public std::integral_constant<bool, (SourceType::TotalSize >= TargetType::TotalSize ||
+                                               TargetType::TotalSize == dynamic_range ||
+                                               SourceType::TotalSize == dynamic_range ||
+                                               TargetType::TotalSize == 0)>
+    {
+    };
+
+    template <typename TypeChain>
+    struct TypeListIndexer
+    {
+        const TypeChain& obj_;
+        TypeListIndexer(const TypeChain& obj) : obj_(obj) {}
+
+        template <size_t N>
+        const TypeChain& getObj(std::true_type)
+        {
+            return obj_;
+        }
+
+        template <size_t N, typename MyChain = TypeChain, typename MyBase = typename MyChain::Base>
+        auto getObj(std::false_type)
+            -> decltype(TypeListIndexer<MyBase>(static_cast<const MyBase&>(obj_)).template get<N>())
+        {
+            return TypeListIndexer<MyBase>(static_cast<const MyBase&>(obj_)).template get<N>();
+        }
+
+        template <size_t N>
+        auto get() -> decltype(getObj<N - 1>(std::integral_constant<bool, N == 0>()))
+        {
+            return getObj<N - 1>(std::integral_constant<bool, N == 0>());
+        }
+    };
+
+    template <typename TypeChain>
+    TypeListIndexer<TypeChain> createTypeListIndexer(const TypeChain& obj)
+    {
+        return TypeListIndexer<TypeChain>(obj);
+    }
+
+    template <size_t Rank, bool Enabled = (Rank > 1),
+              typename Ret = std::enable_if_t<Enabled, index<Rank - 1>>>
+    constexpr Ret shift_left(const index<Rank>& other) noexcept
+    {
+        Ret ret{};
+        for (size_t i = 0; i < Rank - 1; ++i) {
+            ret[i] = other[i + 1];
+        }
+        return ret;
+    }
+}
+
+template <typename IndexType>
+class bounds_iterator;
+
+template <std::ptrdiff_t... Ranges>
+class static_bounds
+{
+public:
+    static_bounds(const details::BoundsRanges<Ranges...>&) {}
+};
+
+template <std::ptrdiff_t FirstRange, std::ptrdiff_t... RestRanges>
+class static_bounds<FirstRange, RestRanges...>
+{
+    using MyRanges = details::BoundsRanges<FirstRange, RestRanges...>;
+
+    MyRanges m_ranges;
+    constexpr static_bounds(const MyRanges& range) : m_ranges(range) {}
+
+    template <std::ptrdiff_t... OtherRanges>
+    friend class static_bounds;
+
+public:
+    static const size_t rank = MyRanges::Depth;
+    static const size_t dynamic_rank = MyRanges::DynamicNum;
+    static const std::ptrdiff_t static_size = MyRanges::TotalSize;
+
+    using size_type = std::ptrdiff_t;
+    using index_type = index<rank>;
+    using const_index_type = std::add_const_t<index_type>;
+    using iterator = bounds_iterator<const_index_type>;
+    using const_iterator = bounds_iterator<const_index_type>;
+    using difference_type = std::ptrdiff_t;
+    using sliced_type = static_bounds<RestRanges...>;
+    using mapping_type = contiguous_mapping_tag;
+
+    constexpr static_bounds(const static_bounds&) = default;
+
+    template <typename SourceType, typename TargetType, size_t Rank>
+    struct BoundsRangeConvertible2;
+
+    template <size_t Rank, typename SourceType, typename TargetType,
+              typename Ret = BoundsRangeConvertible2<typename SourceType::Base,
+                                                     typename TargetType::Base, Rank>>
+    static auto helpBoundsRangeConvertible(SourceType, TargetType, std::true_type) -> Ret;
+
+    template <size_t Rank, typename SourceType, typename TargetType>
+    static auto helpBoundsRangeConvertible(SourceType, TargetType, ...) -> std::false_type;
+
+    template <typename SourceType, typename TargetType, size_t Rank>
+    struct BoundsRangeConvertible2
+        : decltype(helpBoundsRangeConvertible<Rank - 1>(
+              SourceType(), TargetType(),
+              std::integral_constant<bool,
+                                     SourceType::Depth == TargetType::Depth &&
+                                         (SourceType::CurrentRange == TargetType::CurrentRange ||
+                                          TargetType::CurrentRange == dynamic_range ||
+                                          SourceType::CurrentRange == dynamic_range)>()))
+    {
+    };
+
+    template <typename SourceType, typename TargetType>
+    struct BoundsRangeConvertible2<SourceType, TargetType, 0> : std::true_type
+    {
+    };
+
+    template <typename SourceType, typename TargetType, std::ptrdiff_t Rank = TargetType::Depth>
+    struct BoundsRangeConvertible
+        : decltype(helpBoundsRangeConvertible<Rank - 1>(
+              SourceType(), TargetType(),
+              std::integral_constant<bool,
+                                     SourceType::Depth == TargetType::Depth &&
+                                         (!details::LessThan<SourceType::CurrentRange,
+                                                             TargetType::CurrentRange>::value ||
+                                          TargetType::CurrentRange == dynamic_range ||
+                                          SourceType::CurrentRange == dynamic_range)>()))
+    {
+    };
+
+    template <typename SourceType, typename TargetType>
+    struct BoundsRangeConvertible<SourceType, TargetType, 0> : std::true_type
+    {
+    };
+
+    template <std::ptrdiff_t... Ranges,
+              typename = std::enable_if_t<details::BoundsRangeConvertible<
+                  details::BoundsRanges<Ranges...>,
+                  details::BoundsRanges<FirstRange, RestRanges...>>::value>>
+    constexpr static_bounds(const static_bounds<Ranges...>& other) : m_ranges(other.m_ranges)
+    {
+        Expects((MyRanges::DynamicNum == 0 && details::BoundsRanges<Ranges...>::DynamicNum == 0) ||
+                MyRanges::DynamicNum > 0 || other.m_ranges.totalSize() >= m_ranges.totalSize());
+    }
+
+    constexpr static_bounds(std::initializer_list<size_type> il)
+        : m_ranges(static_cast<const std::ptrdiff_t*>(il.begin()))
+    {
+        // Size of the initializer list must match the rank of the array
+        Expects((MyRanges::DynamicNum == 0 && il.size() == 1 && *il.begin() == static_size) ||
+                MyRanges::DynamicNum == il.size());
+        // Size of the range must be less than the max element of the size type
+        Expects(m_ranges.totalSize() <= PTRDIFF_MAX);
+    }
+
+    constexpr static_bounds() = default;
+
+    constexpr sliced_type slice() const noexcept
+    {
+        return sliced_type{static_cast<const details::BoundsRanges<RestRanges...>&>(m_ranges)};
+    }
+
+    constexpr size_type stride() const noexcept { return rank > 1 ? slice().size() : 1; }
+
+    constexpr size_type size() const noexcept { return m_ranges.totalSize(); }
+
+    constexpr size_type total_size() const noexcept { return m_ranges.totalSize(); }
+
+    constexpr size_type linearize(const index_type& idx) const { return m_ranges.linearize(idx); }
+
+    constexpr bool contains(const index_type& idx) const noexcept
+    {
+        return m_ranges.contains(idx) != -1;
+    }
+
+    constexpr size_type operator[](size_t index) const noexcept
+    {
+        return m_ranges.elementNum(index);
+    }
+
+    template <size_t Dim = 0>
+    constexpr size_type extent() const noexcept
+    {
+        static_assert(Dim < rank,
+                      "dimension should be less than rank (dimension count starts from 0)");
+        return details::createTypeListIndexer(m_ranges).template get<Dim>().elementNum();
+    }
+
+    template <typename IntType>
+    constexpr size_type extent(IntType dim) const noexcept
+    {
+        static_assert(std::is_integral<IntType>::value,
+                      "Dimension parameter must be supplied as an integral type.");
+        auto real_dim = narrow_cast<size_t>(dim);
+        Expects(real_dim < rank);
+
+        return m_ranges.elementNum(real_dim);
+    }
+
+    constexpr index_type index_bounds() const noexcept
+    {
+        size_type extents[rank] = {};
+        m_ranges.serialize(extents);
+        return {extents};
+    }
+
+    template <std::ptrdiff_t... Ranges>
+    constexpr bool operator==(const static_bounds<Ranges...>& rhs) const noexcept
+    {
+        return this->size() == rhs.size();
+    }
+
+    template <std::ptrdiff_t... Ranges>
+    constexpr bool operator!=(const static_bounds<Ranges...>& rhs) const noexcept
+    {
+        return !(*this == rhs);
+    }
+
+    constexpr const_iterator begin() const noexcept { return const_iterator(*this, index_type{}); }
+
+    constexpr const_iterator end() const noexcept
+    {
+        return const_iterator(*this, this->index_bounds());
+    }
+};
+
+template <size_t Rank>
+class strided_bounds
+{
+    template <size_t OtherRank>
+    friend class strided_bounds;
+
+public:
+    static const size_t rank = Rank;
+    using value_type = std::ptrdiff_t;
+    using reference = std::add_lvalue_reference_t<value_type>;
+    using const_reference = std::add_const_t<reference>;
+    using size_type = value_type;
+    using difference_type = value_type;
+    using index_type = index<rank>;
+    using const_index_type = std::add_const_t<index_type>;
+    using iterator = bounds_iterator<const_index_type>;
+    using const_iterator = bounds_iterator<const_index_type>;
+    static const value_type dynamic_rank = rank;
+    static const value_type static_size = dynamic_range;
+    using sliced_type = std::conditional_t<rank != 0, strided_bounds<rank - 1>, void>;
+    using mapping_type = generalized_mapping_tag;
+
+    constexpr strided_bounds(const strided_bounds&) noexcept = default;
+
+    constexpr strided_bounds& operator=(const strided_bounds&) noexcept = default;
+
+    constexpr strided_bounds(const value_type (&values)[rank], index_type strides)
+        : m_extents(values), m_strides(std::move(strides))
+    {
+    }
+
+    constexpr strided_bounds(const index_type& extents, const index_type& strides) noexcept
+        : m_extents(extents),
+          m_strides(strides)
+    {
+    }
+
+    constexpr index_type strides() const noexcept { return m_strides; }
+
+    constexpr size_type total_size() const noexcept
+    {
+        size_type ret = 0;
+        for (size_t i = 0; i < rank; ++i) {
+            ret += (m_extents[i] - 1) * m_strides[i];
+        }
+        return ret + 1;
+    }
+
+    constexpr size_type size() const noexcept
+    {
+        size_type ret = 1;
+        for (size_t i = 0; i < rank; ++i) {
+            ret *= m_extents[i];
+        }
+        return ret;
+    }
+
+    constexpr bool contains(const index_type& idx) const noexcept
+    {
+        for (size_t i = 0; i < rank; ++i) {
+            if (idx[i] < 0 || idx[i] >= m_extents[i]) return false;
+        }
+        return true;
+    }
+
+    constexpr size_type linearize(const index_type& idx) const noexcept
+    {
+        size_type ret = 0;
+        for (size_t i = 0; i < rank; i++) {
+            Expects(idx[i] < m_extents[i]); // index is out of bounds of the array
+            ret += idx[i] * m_strides[i];
+        }
+        return ret;
+    }
+
+    constexpr size_type stride() const noexcept { return m_strides[0]; }
+
+    template <bool Enabled = (rank > 1), typename Ret = std::enable_if_t<Enabled, sliced_type>>
+    constexpr sliced_type slice() const
+    {
+        return {details::shift_left(m_extents), details::shift_left(m_strides)};
+    }
+
+    template <size_t Dim = 0>
+    constexpr size_type extent() const noexcept
+    {
+        static_assert(Dim < Rank,
+                      "dimension should be less than rank (dimension count starts from 0)");
+        return m_extents[Dim];
+    }
+
+    constexpr index_type index_bounds() const noexcept { return m_extents; }
+    constexpr const_iterator begin() const noexcept { return const_iterator{*this, index_type{}}; }
+
+    constexpr const_iterator end() const noexcept { return const_iterator{*this, index_bounds()}; }
+
+private:
+    index_type m_extents;
+    index_type m_strides;
+};
+
+template <typename T>
+struct is_bounds : std::integral_constant<bool, false>
+{
+};
+template <std::ptrdiff_t... Ranges>
+struct is_bounds<static_bounds<Ranges...>> : std::integral_constant<bool, true>
+{
+};
+template <size_t Rank>
+struct is_bounds<strided_bounds<Rank>> : std::integral_constant<bool, true>
+{
+};
+
+template <typename IndexType>
+class bounds_iterator : public std::iterator<std::random_access_iterator_tag, IndexType>
+{
+private:
+    using Base = std::iterator<std::random_access_iterator_tag, IndexType>;
+
+public:
+    static const size_t rank = IndexType::rank;
+    using typename Base::reference;
+    using typename Base::pointer;
+    using typename Base::difference_type;
+    using typename Base::value_type;
+    using index_type = value_type;
+    using index_size_type = typename IndexType::value_type;
+    template <typename Bounds>
+    explicit bounds_iterator(const Bounds& bnd, value_type curr) noexcept
+        : boundary_(bnd.index_bounds()),
+          curr_(std::move(curr))
+    {
+        static_assert(is_bounds<Bounds>::value, "Bounds type must be provided");
+    }
+
+    constexpr reference operator*() const noexcept { return curr_; }
+
+    constexpr pointer operator->() const noexcept { return &curr_; }
+
+    constexpr bounds_iterator& operator++() noexcept
+    {
+        for (size_t i = rank; i-- > 0;) {
+            if (curr_[i] < boundary_[i] - 1) {
+                curr_[i]++;
+                return *this;
+            }
+            curr_[i] = 0;
+        }
+        // If we're here we've wrapped over - set to past-the-end.
+        curr_ = boundary_;
+        return *this;
+    }
+
+    constexpr bounds_iterator operator++(int) noexcept
+    {
+        auto ret = *this;
+        ++(*this);
+        return ret;
+    }
+
+    constexpr bounds_iterator& operator--() noexcept
+    {
+        if (!less(curr_, boundary_)) {
+            // if at the past-the-end, set to last element
+            for (size_t i = 0; i < rank; ++i) {
+                curr_[i] = boundary_[i] - 1;
+            }
+            return *this;
+        }
+        for (size_t i = rank; i-- > 0;) {
+            if (curr_[i] >= 1) {
+                curr_[i]--;
+                return *this;
+            }
+            curr_[i] = boundary_[i] - 1;
+        }
+        // If we're here the preconditions were violated
+        // "pre: there exists s such that r == ++s"
+        Expects(false);
+        return *this;
+    }
+
+    constexpr bounds_iterator operator--(int) noexcept
+    {
+        auto ret = *this;
+        --(*this);
+        return ret;
+    }
+
+    constexpr bounds_iterator operator+(difference_type n) const noexcept
+    {
+        bounds_iterator ret{*this};
+        return ret += n;
+    }
+
+    constexpr bounds_iterator& operator+=(difference_type n) noexcept
+    {
+        auto linear_idx = linearize(curr_) + n;
+        std::remove_const_t<value_type> stride = 0;
+        stride[rank - 1] = 1;
+        for (size_t i = rank - 1; i-- > 0;) {
+            stride[i] = stride[i + 1] * boundary_[i + 1];
+        }
+        for (size_t i = 0; i < rank; ++i) {
+            curr_[i] = linear_idx / stride[i];
+            linear_idx = linear_idx % stride[i];
+        }
+        // index is out of bounds of the array
+        Expects(!less(curr_, index_type{}) && !less(boundary_, curr_));
+        return *this;
+    }
+
+    constexpr bounds_iterator operator-(difference_type n) const noexcept
+    {
+        bounds_iterator ret{*this};
+        return ret -= n;
+    }
+
+    constexpr bounds_iterator& operator-=(difference_type n) noexcept { return *this += -n; }
+
+    constexpr difference_type operator-(const bounds_iterator& rhs) const noexcept
+    {
+        return linearize(curr_) - linearize(rhs.curr_);
+    }
+
+    constexpr value_type operator[](difference_type n) const noexcept { return *(*this + n); }
+
+    constexpr bool operator==(const bounds_iterator& rhs) const noexcept
+    {
+        return curr_ == rhs.curr_;
+    }
+
+    constexpr bool operator!=(const bounds_iterator& rhs) const noexcept { return !(*this == rhs); }
+
+    constexpr bool operator<(const bounds_iterator& rhs) const noexcept
+    {
+        return less(curr_, rhs.curr_);
+    }
+
+    constexpr bool operator<=(const bounds_iterator& rhs) const noexcept { return !(rhs < *this); }
+
+    constexpr bool operator>(const bounds_iterator& rhs) const noexcept { return rhs < *this; }
+
+    constexpr bool operator>=(const bounds_iterator& rhs) const noexcept { return !(rhs > *this); }
+
+    void swap(bounds_iterator& rhs) noexcept
+    {
+        std::swap(boundary_, rhs.boundary_);
+        std::swap(curr_, rhs.curr_);
+    }
+
+private:
+    constexpr bool less(index_type& one, index_type& other) const noexcept
+    {
+        for (size_t i = 0; i < rank; ++i) {
+            if (one[i] < other[i]) return true;
+        }
+        return false;
+    }
+
+    constexpr index_size_type linearize(const value_type& idx) const noexcept
+    {
+        // TODO: Smarter impl.
+        // Check if past-the-end
+        index_size_type multiplier = 1;
+        index_size_type res = 0;
+        if (!less(idx, boundary_)) {
+            res = 1;
+            for (size_t i = rank; i-- > 0;) {
+                res += (idx[i] - 1) * multiplier;
+                multiplier *= boundary_[i];
+            }
+        }
+        else
+        {
+            for (size_t i = rank; i-- > 0;) {
+                res += idx[i] * multiplier;
+                multiplier *= boundary_[i];
+            }
+        }
+        return res;
+    }
+
+    value_type boundary_;
+    std::remove_const_t<value_type> curr_;
+};
+
+template <typename IndexType>
+bounds_iterator<IndexType> operator+(typename bounds_iterator<IndexType>::difference_type n,
+                                     const bounds_iterator<IndexType>& rhs) noexcept
+{
+    return rhs + n;
+}
+
+namespace details
+{
+    template <typename Bounds>
+    constexpr std::enable_if_t<
+        std::is_same<typename Bounds::mapping_type, generalized_mapping_tag>::value,
+        typename Bounds::index_type>
+    make_stride(const Bounds& bnd) noexcept
+    {
+        return bnd.strides();
+    }
+
+    // Make a stride vector from bounds, assuming contiguous memory.
+    template <typename Bounds>
+    constexpr std::enable_if_t<
+        std::is_same<typename Bounds::mapping_type, contiguous_mapping_tag>::value,
+        typename Bounds::index_type>
+    make_stride(const Bounds& bnd) noexcept
+    {
+        auto extents = bnd.index_bounds();
+        typename Bounds::size_type stride[Bounds::rank] = {};
+
+        stride[Bounds::rank - 1] = 1;
+        for (size_t i = 1; i < Bounds::rank; ++i) {
+            stride[Bounds::rank - i - 1] = stride[Bounds::rank - i] * extents[Bounds::rank - i];
+        }
+        return {stride};
+    }
+
+    template <typename BoundsSrc, typename BoundsDest>
+    void verifyBoundsReshape(const BoundsSrc& src, const BoundsDest& dest)
+    {
+        static_assert(is_bounds<BoundsSrc>::value && is_bounds<BoundsDest>::value,
+                      "The src type and dest type must be bounds");
+        static_assert(std::is_same<typename BoundsSrc::mapping_type, contiguous_mapping_tag>::value,
+                      "The source type must be a contiguous bounds");
+        static_assert(BoundsDest::static_size == dynamic_range ||
+                          BoundsSrc::static_size == dynamic_range ||
+                          BoundsDest::static_size == BoundsSrc::static_size,
+                      "The source bounds must have same size as dest bounds");
+        Expects(src.size() == dest.size());
+    }
+
+} // namespace details
+
+template <typename Span>
+class contiguous_span_iterator;
+template <typename Span>
+class general_span_iterator;
+
+template <std::ptrdiff_t DimSize = dynamic_range>
+struct dim_t
+{
+    static const std::ptrdiff_t value = DimSize;
+};
+template <>
+struct dim_t<dynamic_range>
+{
+    static const std::ptrdiff_t value = dynamic_range;
+    const std::ptrdiff_t dvalue;
+    dim_t(std::ptrdiff_t size) : dvalue(size) {}
+};
+
+template <std::ptrdiff_t N>
+constexpr std::enable_if_t<(N >= 0), dim_t<N>> dim() noexcept
+{
+    return dim_t<N>();
+}
+
+template <std::ptrdiff_t N = dynamic_range>
+constexpr std::enable_if_t<N == dynamic_range, dim_t<N>> dim(std::ptrdiff_t n) noexcept
+{
+    return dim_t<>(n);
+}
+
+template <typename ValueType, std::ptrdiff_t FirstDimension = dynamic_range,
+          std::ptrdiff_t... RestDimensions>
+class multi_span;
+
+template <typename ValueType, size_t Rank>
+class strided_span;
+
+namespace details
+{
+    template <typename T, typename = std::true_type>
+    struct SpanTypeTraits
+    {
+        using value_type = T;
+        using size_type = size_t;
+    };
+
+    template <typename Traits>
+    struct SpanTypeTraits<Traits, typename std::is_reference<typename Traits::span_traits&>::type>
+    {
+        using value_type = typename Traits::span_traits::value_type;
+        using size_type = typename Traits::span_traits::size_type;
+    };
+
+    template <typename T, std::ptrdiff_t... Ranks>
+    struct SpanArrayTraits
+    {
+        using type = multi_span<T, Ranks...>;
+        using value_type = T;
+        using bounds_type = static_bounds<Ranks...>;
+        using pointer = T*;
+        using reference = T&;
+    };
+    template <typename T, std::ptrdiff_t N, std::ptrdiff_t... Ranks>
+    struct SpanArrayTraits<T[N], Ranks...> : SpanArrayTraits<T, Ranks..., N>
+    {
+    };
+
+    template <typename BoundsType>
+    BoundsType newBoundsHelperImpl(std::ptrdiff_t totalSize, std::true_type) // dynamic size
+    {
+        Expects(totalSize >= 0 && totalSize <= PTRDIFF_MAX);
+        return BoundsType{totalSize};
+    }
+    template <typename BoundsType>
+    BoundsType newBoundsHelperImpl(std::ptrdiff_t totalSize, std::false_type) // static size
+    {
+        Expects(BoundsType::static_size <= totalSize);
+        return {};
+    }
+    template <typename BoundsType>
+    BoundsType newBoundsHelper(std::ptrdiff_t totalSize)
+    {
+        static_assert(BoundsType::dynamic_rank <= 1, "dynamic rank must less or equal to 1");
+        return newBoundsHelperImpl<BoundsType>(
+            totalSize, std::integral_constant<bool, BoundsType::dynamic_rank == 1>());
+    }
+
+    struct Sep
+    {
+    };
+
+    template <typename T, typename... Args>
+    T static_as_multi_span_helper(Sep, Args... args)
+    {
+        return T{narrow_cast<typename T::size_type>(args)...};
+    }
+    template <typename T, typename Arg, typename... Args>
+    std::enable_if_t<
+        !std::is_same<Arg, dim_t<dynamic_range>>::value && !std::is_same<Arg, Sep>::value, T>
+        static_as_multi_span_helper(Arg, Args... args)
+    {
+        return static_as_multi_span_helper<T>(args...);
+    }
+    template <typename T, typename... Args>
+    T static_as_multi_span_helper(dim_t<dynamic_range> val, Args... args)
+    {
+        return static_as_multi_span_helper<T>(args..., val.dvalue);
+    }
+
+    template <typename... Dimensions>
+    struct static_as_multi_span_static_bounds_helper
+    {
+        using type = static_bounds<(Dimensions::value)...>;
+    };
+
+    template <typename T>
+    struct is_multi_span_oracle : std::false_type
+    {
+    };
+
+    template <typename ValueType, std::ptrdiff_t FirstDimension, std::ptrdiff_t... RestDimensions>
+    struct is_multi_span_oracle<multi_span<ValueType, FirstDimension, RestDimensions...>>
+        : std::true_type
+    {
+    };
+
+    template <typename ValueType, std::ptrdiff_t Rank>
+    struct is_multi_span_oracle<strided_span<ValueType, Rank>> : std::true_type
+    {
+    };
+
+    template <typename T>
+    struct is_multi_span : is_multi_span_oracle<std::remove_cv_t<T>>
+    {
+    };
+}
+
+template <typename ValueType, std::ptrdiff_t FirstDimension, std::ptrdiff_t... RestDimensions>
+class multi_span
+{
+    // TODO do we still need this?
+    template <typename ValueType2, std::ptrdiff_t FirstDimension2,
+              std::ptrdiff_t... RestDimensions2>
+    friend class multi_span;
+
+public:
+    using bounds_type = static_bounds<FirstDimension, RestDimensions...>;
+    static const size_t Rank = bounds_type::rank;
+    using size_type = typename bounds_type::size_type;
+    using index_type = typename bounds_type::index_type;
+    using value_type = ValueType;
+    using const_value_type = std::add_const_t<value_type>;
+    using pointer = std::add_pointer_t<value_type>;
+    using reference = std::add_lvalue_reference_t<value_type>;
+    using iterator = contiguous_span_iterator<multi_span>;
+    using const_span = multi_span<const_value_type, FirstDimension, RestDimensions...>;
+    using const_iterator = contiguous_span_iterator<const_span>;
+    using reverse_iterator = std::reverse_iterator<iterator>;
+    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+    using sliced_type =
+        std::conditional_t<Rank == 1, value_type, multi_span<value_type, RestDimensions...>>;
+
+private:
+    pointer data_;
+    bounds_type bounds_;
+
+    friend iterator;
+    friend const_iterator;
+
+public:
+    // default constructor - same as constructing from nullptr_t
+    constexpr multi_span() noexcept : multi_span(nullptr, bounds_type{})
+    {
+        static_assert(bounds_type::dynamic_rank != 0 ||
+                          (bounds_type::dynamic_rank == 0 && bounds_type::static_size == 0),
+                      "Default construction of multi_span<T> only possible "
+                      "for dynamic or fixed, zero-length spans.");
+    }
+
+    // construct from nullptr - get an empty multi_span
+    constexpr multi_span(std::nullptr_t) noexcept : multi_span(nullptr, bounds_type{})
+    {
+        static_assert(bounds_type::dynamic_rank != 0 ||
+                          (bounds_type::dynamic_rank == 0 && bounds_type::static_size == 0),
+                      "nullptr_t construction of multi_span<T> only possible "
+                      "for dynamic or fixed, zero-length spans.");
+    }
+
+    // construct from nullptr with size of 0 (helps with template function calls)
+    template <class IntType, typename = std::enable_if_t<std::is_integral<IntType>::value>>
+    constexpr multi_span(std::nullptr_t, IntType size) noexcept : multi_span(nullptr, bounds_type{})
+    {
+        static_assert(bounds_type::dynamic_rank != 0 ||
+                          (bounds_type::dynamic_rank == 0 && bounds_type::static_size == 0),
+                      "nullptr_t construction of multi_span<T> only possible "
+                      "for dynamic or fixed, zero-length spans.");
+        Expects(size == 0);
+    }
+
+    // construct from a single element
+    constexpr multi_span(reference data) noexcept : multi_span(&data, bounds_type{1})
+    {
+        static_assert(bounds_type::dynamic_rank > 0 || bounds_type::static_size == 0 ||
+                          bounds_type::static_size == 1,
+                      "Construction from a single element only possible "
+                      "for dynamic or fixed spans of length 0 or 1.");
+    }
+
+    // prevent constructing from temporaries for single-elements
+    constexpr multi_span(value_type&&) = delete;
+
+    // construct from pointer + length
+    constexpr multi_span(pointer ptr, size_type size) noexcept : multi_span(ptr, bounds_type{size})
+    {
+    }
+
+    // construct from pointer + length - multidimensional
+    constexpr multi_span(pointer data, bounds_type bounds) noexcept : data_(data),
+                                                                      bounds_(std::move(bounds))
+    {
+        Expects((bounds_.size() > 0 && data != nullptr) || bounds_.size() == 0);
+    }
+
+    // construct from begin,end pointer pair
+    template <typename Ptr,
+              typename = std::enable_if_t<std::is_convertible<Ptr, pointer>::value &&
+                                          details::LessThan<bounds_type::dynamic_rank, 2>::value>>
+    constexpr multi_span(pointer begin, Ptr end)
+        : multi_span(begin,
+                     details::newBoundsHelper<bounds_type>(static_cast<pointer>(end) - begin))
+    {
+        Expects(begin != nullptr && end != nullptr && begin <= static_cast<pointer>(end));
+    }
+
+    // construct from n-dimensions static array
+    template <typename T, size_t N, typename Helper = details::SpanArrayTraits<T, N>>
+    constexpr multi_span(T (&arr)[N])
+        : multi_span(reinterpret_cast<pointer>(arr), bounds_type{typename Helper::bounds_type{}})
+    {
+        static_assert(std::is_convertible<typename Helper::value_type(*)[], value_type(*)[]>::value,
+                      "Cannot convert from source type to target multi_span type.");
+        static_assert(std::is_convertible<typename Helper::bounds_type, bounds_type>::value,
+                      "Cannot construct a multi_span from an array with fewer elements.");
+    }
+
+    // construct from n-dimensions dynamic array (e.g. new int[m][4])
+    // (precedence will be lower than the 1-dimension pointer)
+    template <typename T, typename Helper = details::SpanArrayTraits<T, dynamic_range>>
+    constexpr multi_span(T* const& data, size_type size)
+        : multi_span(reinterpret_cast<pointer>(data), typename Helper::bounds_type{size})
+    {
+        static_assert(std::is_convertible<typename Helper::value_type(*)[], value_type(*)[]>::value,
+                      "Cannot convert from source type to target multi_span type.");
+    }
+
+    // construct from std::array
+    template <typename T, size_t N>
+    constexpr multi_span(std::array<T, N>& arr)
+        : multi_span(arr.data(), bounds_type{static_bounds<N>{}})
+    {
+        static_assert(
+            std::is_convertible<T(*)[], typename std::remove_const_t<value_type>(*)[]>::value,
+            "Cannot convert from source type to target multi_span type.");
+        static_assert(std::is_convertible<static_bounds<N>, bounds_type>::value,
+                      "You cannot construct a multi_span from a std::array of smaller size.");
+    }
+
+    // construct from const std::array
+    template <typename T, size_t N>
+    constexpr multi_span(const std::array<std::remove_const_t<value_type>, N>& arr)
+        : multi_span(arr.data(), static_bounds<N>())
+    {
+        static_assert(std::is_convertible<T(*)[], std::remove_const_t<value_type>>::value,
+                      "Cannot convert from source type to target multi_span type.");
+        static_assert(std::is_convertible<static_bounds<N>, bounds_type>::value,
+                      "You cannot construct a multi_span from a std::array of smaller size.");
+    }
+
+    // prevent constructing from temporary std::array
+    template <typename T, size_t N>
+    constexpr multi_span(std::array<T, N>&& arr) = delete;
+
+    // construct from containers
+    // future: could use contiguous_iterator_traits to identify only contiguous containers
+    // type-requirements: container must have .size(), operator[] which are value_type compatible
+    template <typename Cont, typename DataType = typename Cont::value_type,
+              typename = std::enable_if_t<
+                  !details::is_multi_span<Cont>::value &&
+                  std::is_convertible<DataType (*)[], value_type (*)[]>::value &&
+                  std::is_same<std::decay_t<decltype(std::declval<Cont>().size(),
+                                                     *std::declval<Cont>().data())>,
+                               DataType>::value>>
+    constexpr multi_span(Cont& cont)
+        : multi_span(static_cast<pointer>(cont.data()),
+                     details::newBoundsHelper<bounds_type>(narrow_cast<size_type>(cont.size())))
+    {
+    }
+
+    // prevent constructing from temporary containers
+    template <typename Cont, typename DataType = typename Cont::value_type,
+              typename = std::enable_if_t<
+                  !details::is_multi_span<Cont>::value &&
+                  std::is_convertible<DataType (*)[], value_type (*)[]>::value &&
+                  std::is_same<std::decay_t<decltype(std::declval<Cont>().size(),
+                                                     *std::declval<Cont>().data())>,
+                               DataType>::value>>
+    explicit constexpr multi_span(Cont&& cont) = delete;
+
+    // construct from a convertible multi_span
+    template <typename OtherValueType, std::ptrdiff_t... OtherDimensions,
+              typename OtherBounds = static_bounds<OtherDimensions...>,
+              typename = std::enable_if_t<std::is_convertible<OtherValueType, ValueType>::value &&
+                                          std::is_convertible<OtherBounds, bounds_type>::value>>
+    constexpr multi_span(multi_span<OtherValueType, OtherDimensions...> other) noexcept
+        : data_(other.data_),
+          bounds_(other.bounds_)
+    {
+    }
+
+// trivial copy and move
+#ifndef GSL_MSVC_NO_SUPPORT_FOR_MOVE_CTOR_DEFAULT
+    constexpr multi_span(multi_span&&) = default;
+#endif
+    constexpr multi_span(const multi_span&) = default;
+
+// trivial assignment
+#ifndef GSL_MSVC_NO_SUPPORT_FOR_MOVE_CTOR_DEFAULT
+    constexpr multi_span& operator=(multi_span&&) = default;
+#endif
+    constexpr multi_span& operator=(const multi_span&) = default;
+
+    // first() - extract the first Count elements into a new multi_span
+    template <std::ptrdiff_t Count>
+    constexpr multi_span<ValueType, Count> first() const noexcept
+    {
+        static_assert(Count >= 0, "Count must be >= 0.");
+        static_assert(bounds_type::static_size == dynamic_range ||
+                          Count <= bounds_type::static_size,
+                      "Count is out of bounds.");
+
+        Expects(bounds_type::static_size != dynamic_range || Count <= this->size());
+        return {this->data(), Count};
+    }
+
+    // first() - extract the first count elements into a new multi_span
+    constexpr multi_span<ValueType, dynamic_range> first(size_type count) const noexcept
+    {
+        Expects(count >= 0 && count <= this->size());
+        return {this->data(), count};
+    }
+
+    // last() - extract the last Count elements into a new multi_span
+    template <std::ptrdiff_t Count>
+    constexpr multi_span<ValueType, Count> last() const noexcept
+    {
+        static_assert(Count >= 0, "Count must be >= 0.");
+        static_assert(bounds_type::static_size == dynamic_range ||
+                          Count <= bounds_type::static_size,
+                      "Count is out of bounds.");
+
+        Expects(bounds_type::static_size != dynamic_range || Count <= this->size());
+        return {this->data() + this->size() - Count, Count};
+    }
+
+    // last() - extract the last count elements into a new multi_span
+    constexpr multi_span<ValueType, dynamic_range> last(size_type count) const noexcept
+    {
+        Expects(count >= 0 && count <= this->size());
+        return {this->data() + this->size() - count, count};
+    }
+
+    // subspan() - create a subview of Count elements starting at Offset
+    template <std::ptrdiff_t Offset, std::ptrdiff_t Count>
+    constexpr multi_span<ValueType, Count> subspan() const noexcept
+    {
+        static_assert(Count >= 0, "Count must be >= 0.");
+        static_assert(Offset >= 0, "Offset must be >= 0.");
+        static_assert(bounds_type::static_size == dynamic_range ||
+                          ((Offset <= bounds_type::static_size) &&
+                           Count <= bounds_type::static_size - Offset),
+                      "You must describe a sub-range within bounds of the multi_span.");
+
+        Expects(bounds_type::static_size != dynamic_range ||
+                (Offset <= this->size() && Count <= this->size() - Offset));
+        return {this->data() + Offset, Count};
+    }
+
+    // subspan() - create a subview of count elements starting at offset
+    // supplying dynamic_range for count will consume all available elements from offset
+    constexpr multi_span<ValueType, dynamic_range> subspan(size_type offset,
+                                                           size_type count = dynamic_range) const
+        noexcept
+    {
+        Expects((offset >= 0 && offset <= this->size()) &&
+                (count == dynamic_range || (count <= this->size() - offset)));
+        return {this->data() + offset, count == dynamic_range ? this->length() - offset : count};
+    }
+
+    // section - creates a non-contiguous, strided multi_span from a contiguous one
+    constexpr strided_span<ValueType, Rank> section(index_type origin, index_type extents) const
+        noexcept
+    {
+        size_type size = this->bounds().total_size() - this->bounds().linearize(origin);
+        return {&this->operator[](origin), size,
+                strided_bounds<Rank>{extents, details::make_stride(bounds())}};
+    }
+
+    // length of the multi_span in elements
+    constexpr size_type size() const noexcept { return bounds_.size(); }
+
+    // length of the multi_span in elements
+    constexpr size_type length() const noexcept { return this->size(); }
+
+    // length of the multi_span in bytes
+    constexpr size_type size_bytes() const noexcept { return sizeof(value_type) * this->size(); }
+
+    // length of the multi_span in bytes
+    constexpr size_type length_bytes() const noexcept { return this->size_bytes(); }
+
+    constexpr bool empty() const noexcept { return this->size() == 0; }
+
+    static constexpr std::size_t rank() { return Rank; }
+
+    template <size_t Dim = 0>
+    constexpr size_type extent() const noexcept
+    {
+        static_assert(Dim < Rank,
+                      "Dimension should be less than rank (dimension count starts from 0).");
+        return bounds_.template extent<Dim>();
+    }
+
+    template <typename IntType>
+    constexpr size_type extent(IntType dim) const noexcept
+    {
+        return bounds_.extent(dim);
+    }
+
+    constexpr bounds_type bounds() const noexcept { return bounds_; }
+
+    constexpr pointer data() const noexcept { return data_; }
+
+    template <typename FirstIndex>
+    constexpr reference operator()(FirstIndex index)
+    {
+        return this->operator[](narrow_cast<std::ptrdiff_t>(index));
+    }
+
+    template <typename FirstIndex, typename... OtherIndices>
+    constexpr reference operator()(FirstIndex index, OtherIndices... indices)
+    {
+        index_type idx = {narrow_cast<std::ptrdiff_t>(index),
+                          narrow_cast<std::ptrdiff_t>(indices...)};
+        return this->operator[](idx);
+    }
+
+    constexpr reference operator[](const index_type& idx) const noexcept
+    {
+        return data_[bounds_.linearize(idx)];
+    }
+
+    template <bool Enabled = (Rank > 1), typename Ret = std::enable_if_t<Enabled, sliced_type>>
+    constexpr Ret operator[](size_type idx) const noexcept
+    {
+        Expects(idx >= 0 && idx < bounds_.size()); // index is out of bounds of the array
+        const size_type ridx = idx * bounds_.stride();
+
+        // index is out of bounds of the underlying data
+        Expects(ridx < bounds_.total_size());
+        return Ret{data_ + ridx, bounds_.slice()};
+    }
+
+    constexpr iterator begin() const noexcept { return iterator{this, true}; }
+
+    constexpr iterator end() const noexcept { return iterator{this, false}; }
+
+    constexpr const_iterator cbegin() const noexcept
+    {
+        return const_iterator{reinterpret_cast<const const_span*>(this), true};
+    }
+
+    constexpr const_iterator cend() const noexcept
+    {
+        return const_iterator{reinterpret_cast<const const_span*>(this), false};
+    }
+
+    constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator{end()}; }
+
+    constexpr reverse_iterator rend() const noexcept { return reverse_iterator{begin()}; }
+
+    constexpr const_reverse_iterator crbegin() const noexcept
+    {
+        return const_reverse_iterator{cend()};
+    }
+
+    constexpr const_reverse_iterator crend() const noexcept
+    {
+        return const_reverse_iterator{cbegin()};
+    }
+
+    template <typename OtherValueType, std::ptrdiff_t... OtherDimensions,
+              typename Dummy = std::enable_if_t<std::is_same<
+                  std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
+    constexpr bool operator==(const multi_span<OtherValueType, OtherDimensions...>& other) const
+        noexcept
+    {
+        return bounds_.size() == other.bounds_.size() &&
+               (data_ == other.data_ || std::equal(this->begin(), this->end(), other.begin()));
+    }
+
+    template <typename OtherValueType, std::ptrdiff_t... OtherDimensions,
+              typename Dummy = std::enable_if_t<std::is_same<
+                  std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
+    constexpr bool operator!=(const multi_span<OtherValueType, OtherDimensions...>& other) const
+        noexcept
+    {
+        return !(*this == other);
+    }
+
+    template <typename OtherValueType, std::ptrdiff_t... OtherDimensions,
+              typename Dummy = std::enable_if_t<std::is_same<
+                  std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
+    constexpr bool operator<(const multi_span<OtherValueType, OtherDimensions...>& other) const
+        noexcept
+    {
+        return std::lexicographical_compare(this->begin(), this->end(), other.begin(), other.end());
+    }
+
+    template <typename OtherValueType, std::ptrdiff_t... OtherDimensions,
+              typename Dummy = std::enable_if_t<std::is_same<
+                  std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
+    constexpr bool operator<=(const multi_span<OtherValueType, OtherDimensions...>& other) const
+        noexcept
+    {
+        return !(other < *this);
+    }
+
+    template <typename OtherValueType, std::ptrdiff_t... OtherDimensions,
+              typename Dummy = std::enable_if_t<std::is_same<
+                  std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
+    constexpr bool operator>(const multi_span<OtherValueType, OtherDimensions...>& other) const
+        noexcept
+    {
+        return (other < *this);
+    }
+
+    template <typename OtherValueType, std::ptrdiff_t... OtherDimensions,
+              typename Dummy = std::enable_if_t<std::is_same<
+                  std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
+    constexpr bool operator>=(const multi_span<OtherValueType, OtherDimensions...>& other) const
+        noexcept
+    {
+        return !(*this < other);
+    }
+};
+
+//
+// Free functions for manipulating spans
+//
+
+// reshape a multi_span into a different dimensionality
+// DimCount and Enabled here are workarounds for a bug in MSVC 2015
+template <typename SpanType, typename... Dimensions2, size_t DimCount = sizeof...(Dimensions2),
+          bool Enabled = (DimCount > 0), typename = std::enable_if_t<Enabled>>
+constexpr auto as_multi_span(SpanType s, Dimensions2... dims)
+    -> multi_span<typename SpanType::value_type, Dimensions2::value...>
+{
+    static_assert(details::is_multi_span<SpanType>::value,
+                  "Variadic as_multi_span() is for reshaping existing spans.");
+    using BoundsType =
+        typename multi_span<typename SpanType::value_type, (Dimensions2::value)...>::bounds_type;
+    auto tobounds = details::static_as_multi_span_helper<BoundsType>(dims..., details::Sep{});
+    details::verifyBoundsReshape(s.bounds(), tobounds);
+    return {s.data(), tobounds};
+}
+
+// convert a multi_span<T> to a multi_span<const byte>
+template <typename U, std::ptrdiff_t... Dimensions>
+multi_span<const byte, dynamic_range> as_bytes(multi_span<U, Dimensions...> s) noexcept
+{
+    static_assert(std::is_trivial<std::decay_t<U>>::value,
+                  "The value_type of multi_span must be a trivial type.");
+    return {reinterpret_cast<const byte*>(s.data()), s.size_bytes()};
+}
+
+// convert a multi_span<T> to a multi_span<byte> (a writeable byte multi_span)
+// this is not currently a portable function that can be relied upon to work
+// on all implementations. It should be considered an experimental extension
+// to the standard GSL interface.
+template <typename U, std::ptrdiff_t... Dimensions>
+multi_span<byte> as_writeable_bytes(multi_span<U, Dimensions...> s) noexcept
+{
+    static_assert(std::is_trivial<std::decay_t<U>>::value,
+                  "The value_type of multi_span must be a trivial type.");
+    return {reinterpret_cast<byte*>(s.data()), s.size_bytes()};
+}
+
+// convert a multi_span<const byte> to a multi_span<const T>
+// this is not currently a portable function that can be relied upon to work
+// on all implementations. It should be considered an experimental extension
+// to the standard GSL interface.
+template <typename U, std::ptrdiff_t... Dimensions>
+constexpr auto as_multi_span(multi_span<const byte, Dimensions...> s) noexcept -> multi_span<
+    const U, static_cast<std::ptrdiff_t>(
+                 multi_span<const byte, Dimensions...>::bounds_type::static_size != dynamic_range
+                     ? (static_cast<size_t>(
+                            multi_span<const byte, Dimensions...>::bounds_type::static_size) /
+                        sizeof(U))
+                     : dynamic_range)>
+{
+    using ConstByteSpan = multi_span<const byte, Dimensions...>;
+    static_assert(
+        std::is_trivial<std::decay_t<U>>::value &&
+            (ConstByteSpan::bounds_type::static_size == dynamic_range ||
+             ConstByteSpan::bounds_type::static_size % narrow_cast<std::ptrdiff_t>(sizeof(U)) == 0),
+        "Target type must be a trivial type and its size must match the byte array size");
+
+    Expects((s.size_bytes() % sizeof(U)) == 0 && (s.size_bytes() / sizeof(U)) < PTRDIFF_MAX);
+    return {reinterpret_cast<const U*>(s.data()),
+            s.size_bytes() / narrow_cast<std::ptrdiff_t>(sizeof(U))};
+}
+
+// convert a multi_span<byte> to a multi_span<T>
+// this is not currently a portable function that can be relied upon to work
+// on all implementations. It should be considered an experimental extension
+// to the standard GSL interface.
+template <typename U, std::ptrdiff_t... Dimensions>
+constexpr auto as_multi_span(multi_span<byte, Dimensions...> s) noexcept
+    -> multi_span<U, narrow_cast<std::ptrdiff_t>(
+                         multi_span<byte, Dimensions...>::bounds_type::static_size != dynamic_range
+                             ? static_cast<std::size_t>(
+                                   multi_span<byte, Dimensions...>::bounds_type::static_size) /
+                                   sizeof(U)
+                             : dynamic_range)>
+{
+    using ByteSpan = multi_span<byte, Dimensions...>;
+    static_assert(
+        std::is_trivial<std::decay_t<U>>::value &&
+            (ByteSpan::bounds_type::static_size == dynamic_range ||
+             ByteSpan::bounds_type::static_size % static_cast<std::size_t>(sizeof(U)) == 0),
+        "Target type must be a trivial type and its size must match the byte array size");
+
+    Expects((s.size_bytes() % sizeof(U)) == 0);
+    return {reinterpret_cast<U*>(s.data()),
+            s.size_bytes() / narrow_cast<std::ptrdiff_t>(sizeof(U))};
+}
+
+template <typename T, std::ptrdiff_t... Dimensions>
+constexpr auto as_multi_span(T* const& ptr, dim_t<Dimensions>... args)
+    -> multi_span<std::remove_all_extents_t<T>, Dimensions...>
+{
+    return {reinterpret_cast<std::remove_all_extents_t<T>*>(ptr),
+            details::static_as_multi_span_helper<static_bounds<Dimensions...>>(args...,
+                                                                               details::Sep{})};
+}
+
+template <typename T>
+constexpr auto as_multi_span(T* arr, std::ptrdiff_t len) ->
+    typename details::SpanArrayTraits<T, dynamic_range>::type
+{
+    return {reinterpret_cast<std::remove_all_extents_t<T>*>(arr), len};
+}
+
+template <typename T, size_t N>
+constexpr auto as_multi_span(T (&arr)[N]) -> typename details::SpanArrayTraits<T, N>::type
+{
+    return {arr};
+}
+
+template <typename T, size_t N>
+constexpr multi_span<const T, N> as_multi_span(const std::array<T, N>& arr)
+{
+    return {arr};
+}
+
+template <typename T, size_t N>
+constexpr multi_span<const T, N> as_multi_span(const std::array<T, N>&&) = delete;
+
+template <typename T, size_t N>
+constexpr multi_span<T, N> as_multi_span(std::array<T, N>& arr)
+{
+    return {arr};
+}
+
+template <typename T>
+constexpr multi_span<T, dynamic_range> as_multi_span(T* begin, T* end)
+{
+    return {begin, end};
+}
+
+template <typename Cont>
+constexpr auto as_multi_span(Cont& arr) -> std::enable_if_t<
+    !details::is_multi_span<std::decay_t<Cont>>::value,
+    multi_span<std::remove_reference_t<decltype(arr.size(), *arr.data())>, dynamic_range>>
+{
+    Expects(arr.size() < PTRDIFF_MAX);
+    return {arr.data(), narrow_cast<std::ptrdiff_t>(arr.size())};
+}
+
+template <typename Cont>
+constexpr auto as_multi_span(Cont&& arr) -> std::enable_if_t<
+    !details::is_multi_span<std::decay_t<Cont>>::value,
+    multi_span<std::remove_reference_t<decltype(arr.size(), *arr.data())>, dynamic_range>> = delete;
+
+// from basic_string which doesn't have nonconst .data() member like other contiguous containers
+template <typename CharT, typename Traits, typename Allocator>
+constexpr auto as_multi_span(std::basic_string<CharT, Traits, Allocator>& str)
+    -> multi_span<CharT, dynamic_range>
+{
+    Expects(str.size() < PTRDIFF_MAX);
+    return {&str[0], narrow_cast<std::ptrdiff_t>(str.size())};
+}
+
+// strided_span is an extension that is not strictly part of the GSL at this time.
+// It is kept here while the multidimensional interface is still being defined.
+template <typename ValueType, size_t Rank>
+class strided_span
+{
+public:
+    using bounds_type = strided_bounds<Rank>;
+    using size_type = typename bounds_type::size_type;
+    using index_type = typename bounds_type::index_type;
+    using value_type = ValueType;
+    using const_value_type = std::add_const_t<value_type>;
+    using pointer = std::add_pointer_t<value_type>;
+    using reference = std::add_lvalue_reference_t<value_type>;
+    using iterator = general_span_iterator<strided_span>;
+    using const_strided_span = strided_span<const_value_type, Rank>;
+    using const_iterator = general_span_iterator<const_strided_span>;
+    using reverse_iterator = std::reverse_iterator<iterator>;
+    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+    using sliced_type =
+        std::conditional_t<Rank == 1, value_type, strided_span<value_type, Rank - 1>>;
+
+private:
+    pointer data_;
+    bounds_type bounds_;
+
+    friend iterator;
+    friend const_iterator;
+    template <typename OtherValueType, size_t OtherRank>
+    friend class strided_span;
+
+public:
+    // from raw data
+    constexpr strided_span(pointer ptr, size_type size, bounds_type bounds)
+        : data_(ptr), bounds_(std::move(bounds))
+    {
+        Expects((bounds_.size() > 0 && ptr != nullptr) || bounds_.size() == 0);
+        // Bounds cross data boundaries
+        Expects(this->bounds().total_size() <= size);
+        (void) size;
+    }
+
+    // from static array of size N
+    template <size_type N>
+    constexpr strided_span(value_type (&values)[N], bounds_type bounds)
+        : strided_span(values, N, std::move(bounds))
+    {
+    }
+
+    // from array view
+    template <typename OtherValueType, std::ptrdiff_t... Dimensions,
+              bool Enabled1 = (sizeof...(Dimensions) == Rank),
+              bool Enabled2 = std::is_convertible<OtherValueType*, ValueType*>::value,
+              typename Dummy = std::enable_if_t<Enabled1 && Enabled2>>
+    constexpr strided_span(multi_span<OtherValueType, Dimensions...> av, bounds_type bounds)
+        : strided_span(av.data(), av.bounds().total_size(), std::move(bounds))
+    {
+    }
+
+    // convertible
+    template <typename OtherValueType, typename Dummy = std::enable_if_t<std::is_convertible<
+                                           OtherValueType (*)[], value_type (*)[]>::value>>
+    constexpr strided_span(const strided_span<OtherValueType, Rank>& other)
+        : data_(other.data_), bounds_(other.bounds_)
+    {
+    }
+
+    // convert from bytes
+    template <typename OtherValueType>
+    constexpr strided_span<
+        typename std::enable_if<std::is_same<value_type, const byte>::value, OtherValueType>::type,
+        Rank>
+    as_strided_span() const
+    {
+        static_assert((sizeof(OtherValueType) >= sizeof(value_type)) &&
+                          (sizeof(OtherValueType) % sizeof(value_type) == 0),
+                      "OtherValueType should have a size to contain a multiple of ValueTypes");
+        auto d = narrow_cast<size_type>(sizeof(OtherValueType) / sizeof(value_type));
+
+        size_type size = this->bounds().total_size() / d;
+        return {const_cast<OtherValueType*>(reinterpret_cast<const OtherValueType*>(this->data())),
+                size, bounds_type{resize_extent(this->bounds().index_bounds(), d),
+                                  resize_stride(this->bounds().strides(), d)}};
+    }
+
+    constexpr strided_span section(index_type origin, index_type extents) const
+    {
+        size_type size = this->bounds().total_size() - this->bounds().linearize(origin);
+        return {&this->operator[](origin), size,
+                bounds_type{extents, details::make_stride(bounds())}};
+    }
+
+    constexpr reference operator[](const index_type& idx) const
+    {
+        return data_[bounds_.linearize(idx)];
+    }
+
+    template <bool Enabled = (Rank > 1), typename Ret = std::enable_if_t<Enabled, sliced_type>>
+    constexpr Ret operator[](size_type idx) const
+    {
+        Expects(idx < bounds_.size()); // index is out of bounds of the array
+        const size_type ridx = idx * bounds_.stride();
+
+        // index is out of bounds of the underlying data
+        Expects(ridx < bounds_.total_size());
+        return {data_ + ridx, bounds_.slice().total_size(), bounds_.slice()};
+    }
+
+    constexpr bounds_type bounds() const noexcept { return bounds_; }
+
+    template <size_t Dim = 0>
+    constexpr size_type extent() const noexcept
+    {
+        static_assert(Dim < Rank,
+                      "dimension should be less than Rank (dimension count starts from 0)");
+        return bounds_.template extent<Dim>();
+    }
+
+    constexpr size_type size() const noexcept { return bounds_.size(); }
+
+    constexpr pointer data() const noexcept { return data_; }
+
+    constexpr explicit operator bool() const noexcept { return data_ != nullptr; }
+
+    constexpr iterator begin() const { return iterator{this, true}; }
+
+    constexpr iterator end() const { return iterator{this, false}; }
+
+    constexpr const_iterator cbegin() const
+    {
+        return const_iterator{reinterpret_cast<const const_strided_span*>(this), true};
+    }
+
+    constexpr const_iterator cend() const
+    {
+        return const_iterator{reinterpret_cast<const const_strided_span*>(this), false};
+    }
+
+    constexpr reverse_iterator rbegin() const { return reverse_iterator{end()}; }
+
+    constexpr reverse_iterator rend() const { return reverse_iterator{begin()}; }
+
+    constexpr const_reverse_iterator crbegin() const { return const_reverse_iterator{cend()}; }
+
+    constexpr const_reverse_iterator crend() const { return const_reverse_iterator{cbegin()}; }
+
+    template <typename OtherValueType, std::ptrdiff_t OtherRank,
+              typename Dummy = std::enable_if_t<std::is_same<
+                  std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
+    constexpr bool operator==(const strided_span<OtherValueType, OtherRank>& other) const noexcept
+    {
+        return bounds_.size() == other.bounds_.size() &&
+               (data_ == other.data_ || std::equal(this->begin(), this->end(), other.begin()));
+    }
+
+    template <typename OtherValueType, std::ptrdiff_t OtherRank,
+              typename Dummy = std::enable_if_t<std::is_same<
+                  std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
+    constexpr bool operator!=(const strided_span<OtherValueType, OtherRank>& other) const noexcept
+    {
+        return !(*this == other);
+    }
+
+    template <typename OtherValueType, std::ptrdiff_t OtherRank,
+              typename Dummy = std::enable_if_t<std::is_same<
+                  std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
+    constexpr bool operator<(const strided_span<OtherValueType, OtherRank>& other) const noexcept
+    {
+        return std::lexicographical_compare(this->begin(), this->end(), other.begin(), other.end());
+    }
+
+    template <typename OtherValueType, std::ptrdiff_t OtherRank,
+              typename Dummy = std::enable_if_t<std::is_same<
+                  std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
+    constexpr bool operator<=(const strided_span<OtherValueType, OtherRank>& other) const noexcept
+    {
+        return !(other < *this);
+    }
+
+    template <typename OtherValueType, std::ptrdiff_t OtherRank,
+              typename Dummy = std::enable_if_t<std::is_same<
+                  std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
+    constexpr bool operator>(const strided_span<OtherValueType, OtherRank>& other) const noexcept
+    {
+        return (other < *this);
+    }
+
+    template <typename OtherValueType, std::ptrdiff_t OtherRank,
+              typename Dummy = std::enable_if_t<std::is_same<
+                  std::remove_cv_t<value_type>, std::remove_cv_t<OtherValueType>>::value>>
+    constexpr bool operator>=(const strided_span<OtherValueType, OtherRank>& other) const noexcept
+    {
+        return !(*this < other);
+    }
+
+private:
+    static index_type resize_extent(const index_type& extent, std::ptrdiff_t d)
+    {
+        // The last dimension of the array needs to contain a multiple of new type elements
+        Expects(extent[Rank - 1] >= d && (extent[Rank - 1] % d == 0));
+
+        index_type ret = extent;
+        ret[Rank - 1] /= d;
+
+        return ret;
+    }
+
+    template <bool Enabled = (Rank == 1), typename Dummy = std::enable_if_t<Enabled>>
+    static index_type resize_stride(const index_type& strides, std::ptrdiff_t, void* = 0)
+    {
+        // Only strided arrays with regular strides can be resized
+        Expects(strides[Rank - 1] == 1);
+
+        return strides;
+    }
+
+    template <bool Enabled = (Rank > 1), typename Dummy = std::enable_if_t<Enabled>>
+    static index_type resize_stride(const index_type& strides, std::ptrdiff_t d)
+    {
+        // Only strided arrays with regular strides can be resized
+        Expects(strides[Rank - 1] == 1);
+        // The strides must have contiguous chunks of
+        // memory that can contain a multiple of new type elements
+        Expects(strides[Rank - 2] >= d && (strides[Rank - 2] % d == 0));
+
+        for (size_t i = Rank - 1; i > 0; --i) {
+            // Only strided arrays with regular strides can be resized
+            Expects((strides[i - 1] >= strides[i]) && (strides[i - 1] % strides[i] == 0));
+        }
+
+        index_type ret = strides / d;
+        ret[Rank - 1] = 1;
+
+        return ret;
+    }
+};
+
+template <class Span>
+class contiguous_span_iterator
+    : public std::iterator<std::random_access_iterator_tag, typename Span::value_type>
+{
+    using Base = std::iterator<std::random_access_iterator_tag, typename Span::value_type>;
+
+public:
+    using typename Base::reference;
+    using typename Base::pointer;
+    using typename Base::difference_type;
+
+private:
+    template <typename ValueType, std::ptrdiff_t FirstDimension, std::ptrdiff_t... RestDimensions>
+    friend class multi_span;
+
+    pointer data_;
+    const Span* m_validator;
+    void validateThis() const
+    {
+        // iterator is out of range of the array
+        Expects(data_ >= m_validator->data_ && data_ < m_validator->data_ + m_validator->size());
+    }
+    contiguous_span_iterator(const Span* container, bool isbegin)
+        : data_(isbegin ? container->data_ : container->data_ + container->size())
+        , m_validator(container)
+    {
+    }
+
+public:
+    reference operator*() const noexcept
+    {
+        validateThis();
+        return *data_;
+    }
+    pointer operator->() const noexcept
+    {
+        validateThis();
+        return data_;
+    }
+    contiguous_span_iterator& operator++() noexcept
+    {
+        ++data_;
+        return *this;
+    }
+    contiguous_span_iterator operator++(int) noexcept
+    {
+        auto ret = *this;
+        ++(*this);
+        return ret;
+    }
+    contiguous_span_iterator& operator--() noexcept
+    {
+        --data_;
+        return *this;
+    }
+    contiguous_span_iterator operator--(int) noexcept
+    {
+        auto ret = *this;
+        --(*this);
+        return ret;
+    }
+    contiguous_span_iterator operator+(difference_type n) const noexcept
+    {
+        contiguous_span_iterator ret{*this};
+        return ret += n;
+    }
+    contiguous_span_iterator& operator+=(difference_type n) noexcept
+    {
+        data_ += n;
+        return *this;
+    }
+    contiguous_span_iterator operator-(difference_type n) const noexcept
+    {
+        contiguous_span_iterator ret{*this};
+        return ret -= n;
+    }
+    contiguous_span_iterator& operator-=(difference_type n) noexcept { return *this += -n; }
+    difference_type operator-(const contiguous_span_iterator& rhs) const noexcept
+    {
+        Expects(m_validator == rhs.m_validator);
+        return data_ - rhs.data_;
+    }
+    reference operator[](difference_type n) const noexcept { return *(*this + n); }
+    bool operator==(const contiguous_span_iterator& rhs) const noexcept
+    {
+        Expects(m_validator == rhs.m_validator);
+        return data_ == rhs.data_;
+    }
+    bool operator!=(const contiguous_span_iterator& rhs) const noexcept { return !(*this == rhs); }
+    bool operator<(const contiguous_span_iterator& rhs) const noexcept
+    {
+        Expects(m_validator == rhs.m_validator);
+        return data_ < rhs.data_;
+    }
+    bool operator<=(const contiguous_span_iterator& rhs) const noexcept { return !(rhs < *this); }
+    bool operator>(const contiguous_span_iterator& rhs) const noexcept { return rhs < *this; }
+    bool operator>=(const contiguous_span_iterator& rhs) const noexcept { return !(rhs > *this); }
+    void swap(contiguous_span_iterator& rhs) noexcept
+    {
+        std::swap(data_, rhs.data_);
+        std::swap(m_validator, rhs.m_validator);
+    }
+};
+
+template <typename Span>
+contiguous_span_iterator<Span> operator+(typename contiguous_span_iterator<Span>::difference_type n,
+                                         const contiguous_span_iterator<Span>& rhs) noexcept
+{
+    return rhs + n;
+}
+
+template <typename Span>
+class general_span_iterator
+    : public std::iterator<std::random_access_iterator_tag, typename Span::value_type>
+{
+    using Base = std::iterator<std::random_access_iterator_tag, typename Span::value_type>;
+
+public:
+    using typename Base::reference;
+    using typename Base::pointer;
+    using typename Base::difference_type;
+    using typename Base::value_type;
+
+private:
+    template <typename ValueType, size_t Rank>
+    friend class strided_span;
+
+    const Span* m_container;
+    typename Span::bounds_type::iterator m_itr;
+    general_span_iterator(const Span* container, bool isbegin)
+        : m_container(container)
+        , m_itr(isbegin ? m_container->bounds().begin() : m_container->bounds().end())
+    {
+    }
+
+public:
+    reference operator*() noexcept { return (*m_container)[*m_itr]; }
+    pointer operator->() noexcept { return &(*m_container)[*m_itr]; }
+    general_span_iterator& operator++() noexcept
+    {
+        ++m_itr;
+        return *this;
+    }
+    general_span_iterator operator++(int) noexcept
+    {
+        auto ret = *this;
+        ++(*this);
+        return ret;
+    }
+    general_span_iterator& operator--() noexcept
+    {
+        --m_itr;
+        return *this;
+    }
+    general_span_iterator operator--(int) noexcept
+    {
+        auto ret = *this;
+        --(*this);
+        return ret;
+    }
+    general_span_iterator operator+(difference_type n) const noexcept
+    {
+        general_span_iterator ret{*this};
+        return ret += n;
+    }
+    general_span_iterator& operator+=(difference_type n) noexcept
+    {
+        m_itr += n;
+        return *this;
+    }
+    general_span_iterator operator-(difference_type n) const noexcept
+    {
+        general_span_iterator ret{*this};
+        return ret -= n;
+    }
+    general_span_iterator& operator-=(difference_type n) noexcept { return *this += -n; }
+    difference_type operator-(const general_span_iterator& rhs) const noexcept
+    {
+        Expects(m_container == rhs.m_container);
+        return m_itr - rhs.m_itr;
+    }
+    value_type operator[](difference_type n) const noexcept { return (*m_container)[m_itr[n]]; }
+
+    bool operator==(const general_span_iterator& rhs) const noexcept
+    {
+        Expects(m_container == rhs.m_container);
+        return m_itr == rhs.m_itr;
+    }
+    bool operator!=(const general_span_iterator& rhs) const noexcept { return !(*this == rhs); }
+    bool operator<(const general_span_iterator& rhs) const noexcept
+    {
+        Expects(m_container == rhs.m_container);
+        return m_itr < rhs.m_itr;
+    }
+    bool operator<=(const general_span_iterator& rhs) const noexcept { return !(rhs < *this); }
+    bool operator>(const general_span_iterator& rhs) const noexcept { return rhs < *this; }
+    bool operator>=(const general_span_iterator& rhs) const noexcept { return !(rhs > *this); }
+    void swap(general_span_iterator& rhs) noexcept
+    {
+        std::swap(m_itr, rhs.m_itr);
+        std::swap(m_container, rhs.m_container);
+    }
+};
+
+template <typename Span>
+general_span_iterator<Span> operator+(typename general_span_iterator<Span>::difference_type n,
+                                      const general_span_iterator<Span>& rhs) noexcept
+{
+    return rhs + n;
+}
+
+} // namespace gsl
+
+#ifdef _MSC_VER
+
+#undef constexpr
+#pragma pop_macro("constexpr")
+
+#if _MSC_VER <= 1800
+#pragma warning(pop)
+
+#ifndef GSL_THROW_ON_CONTRACT_VIOLATION
+#undef noexcept
+#pragma pop_macro("noexcept")
+#endif // GSL_THROW_ON_CONTRACT_VIOLATION
+
+#undef GSL_MSVC_HAS_VARIADIC_CTOR_BUG
+
+#endif // _MSC_VER <= 1800
+
+#endif // _MSC_VER
+
+#if defined(GSL_THROW_ON_CONTRACT_VIOLATION)
+
+#undef noexcept
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#pragma pop_macro("noexcept")
+#endif
+
+#endif // GSL_THROW_ON_CONTRACT_VIOLATION
+
+#endif // GSL_MULTI_SPAN_H
diff --git a/gsl/span b/gsl/span
new file mode 100644
index 0000000..cf90e86
--- /dev/null
+++ b/gsl/span
@@ -0,0 +1,673 @@
+
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+#ifndef GSL_SPAN_H
+#define GSL_SPAN_H
+
+#include "gsl_assert"
+#include "gsl_byte"
+#include "gsl_util"
+#include <array>
+#include <iterator>
+#include <limits>
+#include <stdexcept>
+#include <type_traits>
+#include <utility>
+
+#ifdef _MSC_VER
+
+#pragma warning(push)
+
+// turn off some warnings that are noisy about our Expects statements
+#pragma warning(disable : 4127) // conditional expression is constant
+
+// blanket turn off warnings from CppCoreCheck for now
+// so people aren't annoyed by them when running the tool.
+// more targeted suppressions will be added in a future update to the GSL
+#pragma warning(disable : 26481 26482 26483 26485 26490 26491 26492 26493 26495)
+
+// No MSVC does constexpr fully yet
+#pragma push_macro("constexpr")
+#define constexpr /*constexpr*/
+
+// VS 2013 workarounds
+#if _MSC_VER <= 1800
+
+#define GSL_MSVC_HAS_VARIADIC_CTOR_BUG
+#define GSL_MSVC_NO_DEFAULT_MOVE_CTOR
+#define GSL_MSVC_NO_CPP14_STD_EQUAL
+
+// noexcept is not understood
+#ifndef GSL_THROW_ON_CONTRACT_VIOLATION
+#pragma push_macro("noexcept")
+#define noexcept /*noexcept*/
+#endif
+
+#pragma push_macro("alignof")
+#define alignof __alignof
+
+// turn off some misguided warnings
+#pragma warning(push)
+#pragma warning(disable : 4351) // warns about newly introduced aggregate initializer behavior
+#pragma warning(disable : 4512) // warns that assignment op could not be generated
+
+#endif // _MSC_VER <= 1800
+
+#endif // _MSC_VER
+
+#ifdef GSL_THROW_ON_CONTRACT_VIOLATION
+
+#ifdef _MSC_VER
+#pragma push_macro("noexcept")
+#endif
+
+#define noexcept /*noexcept*/
+
+#endif // GSL_THROW_ON_CONTRACT_VIOLATION
+
+namespace gsl
+{
+
+// [views.constants], constants
+constexpr const std::ptrdiff_t dynamic_extent = -1;
+
+template <class ElementType, std::ptrdiff_t Extent = dynamic_extent>
+class span;
+
+// implementation details
+namespace details
+{
+    template <class T>
+    struct is_span_oracle : std::false_type
+    {
+    };
+
+    template <class ElementType, std::ptrdiff_t Extent>
+    struct is_span_oracle<gsl::span<ElementType, Extent>> : std::true_type
+    {
+    };
+
+    template <class T>
+    struct is_span : public is_span_oracle<std::remove_cv_t<T>>
+    {
+    };
+
+    template <class T>
+    struct is_std_array_oracle : std::false_type
+    {
+    };
+
+    template <class ElementType, size_t Extent>
+    struct is_std_array_oracle<std::array<ElementType, Extent>> : std::true_type
+    {
+    };
+
+    template <class T>
+    struct is_std_array : public is_std_array_oracle<std::remove_cv_t<T>>
+    {
+    };
+
+    template <std::ptrdiff_t From, std::ptrdiff_t To>
+    struct is_allowed_extent_conversion
+        : public std::integral_constant<bool, From == To || From == gsl::dynamic_extent ||
+                                                  To == gsl::dynamic_extent>
+    {
+    };
+
+    template <class From, class To>
+    struct is_allowed_element_type_conversion
+        : public std::integral_constant<bool, std::is_convertible<From (*)[], To (*)[]>::value>
+    {
+    };
+
+    template <class Span, bool IsConst>
+    class span_iterator
+    {
+    public:
+        using iterator_category = std::random_access_iterator_tag;
+        using value_type =
+            std::conditional_t<IsConst, std::add_const_t<typename Span::element_type>,
+                               typename Span::element_type>;
+        using difference_type = typename Span::index_type;
+
+        using pointer = std::add_pointer_t<value_type>;
+        using reference = std::add_lvalue_reference_t<value_type>;
+
+        constexpr span_iterator() noexcept : span_iterator(nullptr, 0) {}
+
+        constexpr span_iterator(const Span* span, typename Span::index_type index)
+            : span_(span), index_(index)
+        {
+            Expects(span == nullptr || (index_ >= 0 && index <= span_->length()));
+        }
+
+        friend class span_iterator<Span, true>;
+        constexpr span_iterator(const span_iterator<Span, false>& other) noexcept
+            : span_iterator(other.span_, other.index_)
+        {
+        }
+
+        constexpr span_iterator<Span, IsConst>& operator=(const span_iterator<Span, IsConst>&) noexcept = default;
+
+        constexpr reference operator*() const
+        {
+            Expects(span_);
+            return (*span_)[index_];
+        }
+
+        constexpr pointer operator->() const
+        {
+            Expects(span_);
+            return &((*span_)[index_]);
+        }
+
+        constexpr span_iterator& operator++() noexcept
+        {
+            Expects(span_ && index_ >= 0 && index_ < span_->length());
+            ++index_;
+            return *this;
+        }
+
+        constexpr span_iterator operator++(int) noexcept
+        {
+            auto ret = *this;
+            ++(*this);
+            return ret;
+        }
+
+        constexpr span_iterator& operator--() noexcept
+        {
+            Expects(span_ && index_ > 0 && index_ <= span_->length());
+            --index_;
+            return *this;
+        }
+
+        constexpr span_iterator operator--(int) noexcept
+        {
+            auto ret = *this;
+            --(*this);
+            return ret;
+        }
+
+        constexpr span_iterator operator+(difference_type n) const noexcept
+        {
+            auto ret = *this;
+            return ret += n;
+        }
+
+        constexpr span_iterator& operator+=(difference_type n) noexcept
+        {
+            Expects(span_ && (index_ + n) >= 0 && (index_ + n) <= span_->length());
+            index_ += n;
+            return *this;
+        }
+
+        constexpr span_iterator operator-(difference_type n) const noexcept
+        {
+            auto ret = *this;
+            return ret -= n;
+        }
+
+        constexpr span_iterator& operator-=(difference_type n) noexcept { return *this += -n; }
+
+        constexpr difference_type operator-(const span_iterator& rhs) const noexcept
+        {
+            Expects(span_ == rhs.span_);
+            return index_ - rhs.index_;
+        }
+
+        constexpr reference operator[](difference_type n) const noexcept { return *(*this + n); }
+
+        constexpr friend bool operator==(const span_iterator& lhs,
+                                         const span_iterator& rhs) noexcept
+        {
+            return lhs.span_ == rhs.span_ && lhs.index_ == rhs.index_;
+        }
+
+        constexpr friend bool operator!=(const span_iterator& lhs,
+                                         const span_iterator& rhs) noexcept
+        {
+            return !(lhs == rhs);
+        }
+
+        constexpr friend bool operator<(const span_iterator& lhs, const span_iterator& rhs) noexcept
+        {
+            Expects(lhs.span_ == rhs.span_);
+            return lhs.index_ < rhs.index_;
+        }
+
+        constexpr friend bool operator<=(const span_iterator& lhs,
+                                         const span_iterator& rhs) noexcept
+        {
+            return !(rhs < lhs);
+        }
+
+        constexpr friend bool operator>(const span_iterator& lhs, const span_iterator& rhs) noexcept
+        {
+            return rhs < lhs;
+        }
+
+        constexpr friend bool operator>=(const span_iterator& lhs,
+                                         const span_iterator& rhs) noexcept
+        {
+            return !(rhs > lhs);
+        }
+
+        void swap(span_iterator& rhs) noexcept
+        {
+            std::swap(index_, rhs.index_);
+            std::swap(span_, rhs.span_);
+        }
+
+    protected:
+        const Span* span_;
+        std::ptrdiff_t index_;
+    };
+
+    template <class Span, bool IsConst>
+    constexpr span_iterator<Span, IsConst>
+    operator+(typename span_iterator<Span, IsConst>::difference_type n,
+              const span_iterator<Span, IsConst>& rhs) noexcept
+    {
+        return rhs + n;
+    }
+
+    template <class Span, bool IsConst>
+    constexpr span_iterator<Span, IsConst>
+    operator-(typename span_iterator<Span, IsConst>::difference_type n,
+              const span_iterator<Span, IsConst>& rhs) noexcept
+    {
+        return rhs - n;
+    }
+
+    template <std::ptrdiff_t Ext>
+    class extent_type
+    {
+    public:
+        using index_type = std::ptrdiff_t;
+
+        static_assert(Ext >= 0, "A fixed-size span must be >= 0 in size.");
+
+        constexpr extent_type() noexcept {}
+
+        template <index_type Other>
+        constexpr extent_type(extent_type<Other> ext) noexcept
+        {
+            static_assert(Other == Ext || Other == dynamic_extent,
+                          "Mismatch between fixed-size extent and size of initializing data.");
+            Expects(ext.size() == Ext);
+        }
+
+        constexpr extent_type(index_type size) { Expects(size == Ext); }
+
+        constexpr inline index_type size() const noexcept { return Ext; }
+    };
+
+    template <>
+    class extent_type<dynamic_extent>
+    {
+    public:
+        using index_type = std::ptrdiff_t;
+
+        template <index_type Other>
+        explicit constexpr extent_type(extent_type<Other> ext) : size_(ext.size())
+        {
+        }
+
+        explicit constexpr extent_type(index_type size) : size_(size) { Expects(size >= 0); }
+
+        constexpr inline index_type size() const noexcept { return size_; }
+
+    private:
+        index_type size_;
+    };
+} // namespace details
+
+// [span], class template span
+template <class ElementType, std::ptrdiff_t Extent>
+class span
+{
+public:
+    // constants and types
+    using element_type = ElementType;
+    using index_type = std::ptrdiff_t;
+    using pointer = element_type*;
+    using reference = element_type&;
+
+    using iterator = details::span_iterator<span<ElementType, Extent>, false>;
+    using const_iterator = details::span_iterator<span<ElementType, Extent>, true>;
+    using reverse_iterator = std::reverse_iterator<iterator>;
+    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+
+    constexpr static const index_type extent = Extent;
+
+    // [span.cons], span constructors, copy, assignment, and destructor
+    constexpr span() noexcept : storage_(nullptr, details::extent_type<0>()) {}
+
+    constexpr span(std::nullptr_t) noexcept : span() {}
+
+    constexpr span(pointer ptr, index_type count) : storage_(ptr, count) {}
+
+    constexpr span(pointer firstElem, pointer lastElem)
+        : storage_(firstElem, std::distance(firstElem, lastElem))
+    {
+    }
+
+    template <size_t N>
+    constexpr span(element_type (&arr)[N]) noexcept : storage_(&arr[0], details::extent_type<N>())
+    {
+    }
+
+    template <size_t N, class ArrayElementType = std::remove_const_t<element_type>>
+    constexpr span(std::array<ArrayElementType, N>& arr) noexcept
+        : storage_(&arr[0], details::extent_type<N>())
+    {
+    }
+
+    template <size_t N>
+    constexpr span(const std::array<std::remove_const_t<element_type>, N>& arr) noexcept
+        : storage_(&arr[0], details::extent_type<N>())
+    {
+    }
+
+    // NB: the SFINAE here uses .data() as a incomplete/imperfect proxy for the requirement
+    // on Container to be a contiguous sequence container.
+    template <class Container,
+              class = std::enable_if_t<
+                  !details::is_span<Container>::value && !details::is_std_array<Container>::value &&
+                  std::is_convertible<typename Container::pointer, pointer>::value &&
+                  std::is_convertible<typename Container::pointer,
+                                      decltype(std::declval<Container>().data())>::value>>
+    constexpr span(Container& cont) : span(cont.data(), narrow<index_type>(cont.size()))
+    {
+    }
+
+    template <class Container,
+              class = std::enable_if_t<
+                  std::is_const<element_type>::value && !details::is_span<Container>::value &&
+                  std::is_convertible<typename Container::pointer, pointer>::value &&
+                  std::is_convertible<typename Container::pointer,
+                                      decltype(std::declval<Container>().data())>::value>>
+    constexpr span(const Container& cont) : span(cont.data(), narrow<index_type>(cont.size()))
+    {
+    }
+
+    constexpr span(const span& other) noexcept = default;
+#ifndef GSL_MSVC_NO_DEFAULT_MOVE_CTOR
+    constexpr span(span&& other) noexcept = default;
+#else
+    constexpr span(span&& other) noexcept : storage_(std::move(other.storage_)) {}
+#endif
+
+    template <
+        class OtherElementType, std::ptrdiff_t OtherExtent,
+        class = std::enable_if_t<
+            details::is_allowed_extent_conversion<OtherExtent, Extent>::value &&
+            details::is_allowed_element_type_conversion<OtherElementType, element_type>::value>>
+    constexpr span(const span<OtherElementType, OtherExtent>& other)
+        : storage_(other.data(), details::extent_type<OtherExtent>(other.size()))
+    {
+    }
+
+    template <
+        class OtherElementType, std::ptrdiff_t OtherExtent,
+        class = std::enable_if_t<
+            details::is_allowed_extent_conversion<OtherExtent, Extent>::value &&
+            details::is_allowed_element_type_conversion<OtherElementType, element_type>::value>>
+    constexpr span(span<OtherElementType, OtherExtent>&& other)
+        : storage_(other.data(), details::extent_type<OtherExtent>(other.size()))
+    {
+    }
+
+    ~span() noexcept = default;
+    constexpr span& operator=(const span& other) noexcept = default;
+
+#ifndef GSL_MSVC_NO_DEFAULT_MOVE_CTOR
+    constexpr span& operator=(span&& other) noexcept = default;
+#else
+    constexpr span& operator=(span&& other) noexcept
+    {
+        storage_ = std::move(other.storage_);
+        return *this;
+    }
+#endif
+    // [span.sub], span subviews
+    template <std::ptrdiff_t Count>
+    constexpr span<element_type, Count> first() const
+    {
+        Expects(Count >= 0 && Count <= size());
+        return {data(), Count};
+    }
+
+    template <std::ptrdiff_t Count>
+    constexpr span<element_type, Count> last() const
+    {
+        Expects(Count >= 0 && Count <= size());
+        return {data() + (size() - Count), Count};
+    }
+
+    template <std::ptrdiff_t Offset, std::ptrdiff_t Count = dynamic_extent>
+    constexpr span<element_type, Count> subspan() const
+    {
+        Expects((Offset == 0 || (Offset > 0 && Offset <= size())) &&
+                (Count == dynamic_extent || (Count >= 0 && Offset + Count <= size())));
+        return {data() + Offset, Count == dynamic_extent ? size() - Offset : Count};
+    }
+
+    constexpr span<element_type, dynamic_extent> first(index_type count) const
+    {
+        Expects(count >= 0 && count <= size());
+        return {data(), count};
+    }
+
+    constexpr span<element_type, dynamic_extent> last(index_type count) const
+    {
+        Expects(count >= 0 && count <= size());
+        return {data() + (size() - count), count};
+    }
+
+    constexpr span<element_type, dynamic_extent> subspan(index_type offset,
+                                                         index_type count = dynamic_extent) const
+    {
+        Expects((offset == 0 || (offset > 0 && offset <= size())) &&
+                (count == dynamic_extent || (count >= 0 && offset + count <= size())));
+        return {data() + offset, count == dynamic_extent ? size() - offset : count};
+    }
+
+    // [span.obs], span observers
+    constexpr index_type length() const noexcept { return size(); }
+    constexpr index_type size() const noexcept { return storage_.size(); }
+    constexpr index_type length_bytes() const noexcept { return size_bytes(); }
+    constexpr index_type size_bytes() const noexcept { return size() * sizeof(element_type); }
+    constexpr bool empty() const noexcept { return size() == 0; }
+
+    // [span.elem], span element access
+    constexpr reference operator[](index_type idx) const
+    {
+        Expects(idx >= 0 && idx < storage_.size());
+        return data()[idx];
+    }
+
+    constexpr reference at(index_type idx) const { return this->operator[](idx); }
+    constexpr reference operator()(index_type idx) const { return this->operator[](idx); }
+    constexpr pointer data() const noexcept { return storage_.data(); }
+
+    // [span.iter], span iterator support
+    iterator begin() const noexcept { return {this, 0}; }
+    iterator end() const noexcept { return {this, length()}; }
+
+    const_iterator cbegin() const noexcept { return {this, 0}; }
+    const_iterator cend() const noexcept { return {this, length()}; }
+
+    reverse_iterator rbegin() const noexcept { return reverse_iterator{end()}; }
+    reverse_iterator rend() const noexcept { return reverse_iterator{begin()}; }
+
+    const_reverse_iterator crbegin() const noexcept { return const_reverse_iterator{cend()}; }
+    const_reverse_iterator crend() const noexcept { return const_reverse_iterator{cbegin()}; }
+
+private:
+    // this implementation detail class lets us take advantage of the
+    // empty base class optimization to pay for only storage of a single
+    // pointer in the case of fixed-size spans
+    template <class ExtentType>
+    class storage_type : public ExtentType
+    {
+    public:
+        template <class OtherExtentType>
+        constexpr storage_type(pointer data, OtherExtentType ext) : ExtentType(ext), data_(data)
+        {
+            Expects((!data && ExtentType::size() == 0) || (data && ExtentType::size() >= 0));
+        }
+
+        constexpr inline pointer data() const noexcept { return data_; }
+
+    private:
+        pointer data_;
+    };
+
+    storage_type<details::extent_type<Extent>> storage_;
+};
+
+// [span.comparison], span comparison operators
+template <class ElementType, std::ptrdiff_t FirstExtent, std::ptrdiff_t SecondExtent>
+constexpr bool operator==(const span<ElementType, FirstExtent>& l,
+                          const span<ElementType, SecondExtent>& r)
+{
+#ifdef GSL_MSVC_NO_CPP14_STD_EQUAL
+    return (l.size() == r.size()) && std::equal(l.begin(), l.end(), r.begin());
+#else
+    return std::equal(l.begin(), l.end(), r.begin(), r.end());
+#endif
+}
+
+template <class ElementType, std::ptrdiff_t Extent>
+constexpr bool operator!=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r)
+{
+    return !(l == r);
+}
+
+template <class ElementType, std::ptrdiff_t Extent>
+constexpr bool operator<(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r)
+{
+    return std::lexicographical_compare(l.begin(), l.end(), r.begin(), r.end());
+}
+
+template <class ElementType, std::ptrdiff_t Extent>
+constexpr bool operator<=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r)
+{
+    return !(l > r);
+}
+
+template <class ElementType, std::ptrdiff_t Extent>
+constexpr bool operator>(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r)
+{
+    return r < l;
+}
+
+template <class ElementType, std::ptrdiff_t Extent>
+constexpr bool operator>=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r)
+{
+    return !(l < r);
+}
+
+namespace details
+{
+    // if we only supported compilers with good constexpr support then
+    // this pair of classes could collapse down to a constexpr function
+
+    // we should use a narrow_cast<> to go to size_t, but older compilers may not see it as
+    // constexpr
+    // and so will fail compilation of the template
+    template <class ElementType, std::ptrdiff_t Extent>
+    struct calculate_byte_size
+        : std::integral_constant<std::ptrdiff_t,
+                                 static_cast<std::ptrdiff_t>(sizeof(ElementType) *
+                                                             static_cast<std::size_t>(Extent))>
+    {
+    };
+
+    template <class ElementType>
+    struct calculate_byte_size<ElementType, dynamic_extent>
+        : std::integral_constant<std::ptrdiff_t, dynamic_extent>
+    {
+    };
+}
+
+// [span.objectrep], views of object representation
+template <class ElementType, std::ptrdiff_t Extent>
+span<const byte, details::calculate_byte_size<ElementType, Extent>::value>
+as_bytes(span<ElementType, Extent> s) noexcept
+{
+    return {reinterpret_cast<const byte*>(s.data()), s.size_bytes()};
+}
+
+template <class ElementType, std::ptrdiff_t Extent,
+          class = std::enable_if_t<!std::is_const<ElementType>::value>>
+span<byte, details::calculate_byte_size<ElementType, Extent>::value>
+as_writeable_bytes(span<ElementType, Extent> s) noexcept
+{
+    return {reinterpret_cast<byte*>(s.data()), s.size_bytes()};
+}
+
+// Specialization of gsl::at for span
+template <class ElementType, std::ptrdiff_t Extent>
+constexpr ElementType& at(const span<ElementType, Extent>& s, size_t index)
+{
+    // No bounds checking here because it is done in span::operator[] called below
+    return s[index];
+}
+
+} // namespace gsl
+
+#ifdef _MSC_VER
+
+#undef constexpr
+#pragma pop_macro("constexpr")
+
+#if _MSC_VER <= 1800
+#pragma warning(pop)
+
+#ifndef GSL_THROW_ON_CONTRACT_VIOLATION
+#undef noexcept
+#pragma pop_macro("noexcept")
+#endif // GSL_THROW_ON_CONTRACT_VIOLATION
+
+#pragma pop_macro("alignof")
+
+#undef GSL_MSVC_HAS_VARIADIC_CTOR_BUG
+
+#endif // _MSC_VER <= 1800
+
+#endif // _MSC_VER
+
+#if defined(GSL_THROW_ON_CONTRACT_VIOLATION)
+
+#undef noexcept
+
+#ifdef _MSC_VER
+#pragma pop_macro("noexcept")
+#endif
+
+#endif // GSL_THROW_ON_CONTRACT_VIOLATION
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+#endif // GSL_SPAN_H
diff --git a/gsl/string_span b/gsl/string_span
new file mode 100644
index 0000000..703bc01
--- /dev/null
+++ b/gsl/string_span
@@ -0,0 +1,870 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+#ifndef GSL_STRING_SPAN_H
+#define GSL_STRING_SPAN_H
+
+#include "gsl_assert"
+#include "gsl_util"
+#include "span"
+#include <cstdint>
+#include <cstring>
+#include <string>
+
+#ifdef _MSC_VER
+
+// No MSVC does constexpr fully yet
+#pragma push_macro("constexpr")
+#define constexpr /*constexpr*/
+
+#pragma warning(push)
+
+// blanket turn off warnings from CppCoreCheck for now
+// so people aren't annoyed by them when running the tool.
+// more targeted suppressions will be added in a future update to the GSL
+#pragma warning(disable : 26481 26482 26483 26485 26490 26491 26492 26493 26495)
+
+// VS 2013 workarounds
+#if _MSC_VER <= 1800
+
+#define GSL_MSVC_HAS_TYPE_DEDUCTION_BUG
+#define GSL_MSVC_HAS_SFINAE_SUBSTITUTION_ICE
+#define GSL_MSVC_NO_CPP14_STD_EQUAL
+#define GSL_MSVC_NO_DEFAULT_MOVE_CTOR
+
+// noexcept is not understood
+#ifndef GSL_THROW_ON_CONTRACT_VIOLATION
+#pragma push_macro("noexcept")
+#define noexcept /*noexcept*/
+#endif
+
+#endif // _MSC_VER <= 1800
+#endif // _MSC_VER
+
+// In order to test the library, we need it to throw exceptions that we can catch
+#ifdef GSL_THROW_ON_CONTRACT_VIOLATION
+
+#ifdef _MSC_VER
+#pragma push_macro("noexcept")
+#endif
+
+#define noexcept /*noexcept*/
+
+#endif // GSL_THROW_ON_CONTRACT_VIOLATION
+
+namespace gsl
+{
+//
+// czstring and wzstring
+//
+// These are "tag" typedef's for C-style strings (i.e. null-terminated character arrays)
+// that allow static analysis to help find bugs.
+//
+// There are no additional features/semantics that we can find a way to add inside the
+// type system for these types that will not either incur significant runtime costs or
+// (sometimes needlessly) break existing programs when introduced.
+//
+
+template <typename CharT, std::ptrdiff_t Extent = dynamic_extent>
+using basic_zstring = CharT*;
+
+template <std::ptrdiff_t Extent = dynamic_extent>
+using czstring = basic_zstring<const char, Extent>;
+
+template <std::ptrdiff_t Extent = dynamic_extent>
+using cwzstring = basic_zstring<const wchar_t, Extent>;
+
+template <std::ptrdiff_t Extent = dynamic_extent>
+using zstring = basic_zstring<char, Extent>;
+
+template <std::ptrdiff_t Extent = dynamic_extent>
+using wzstring = basic_zstring<wchar_t, Extent>;
+
+namespace details
+{
+    inline std::ptrdiff_t string_length(const char *str, std::ptrdiff_t n)
+    {
+        if (str == nullptr || n <= 0)
+            return 0;
+
+        span<const char> str_span{str, n};
+
+        std::ptrdiff_t len = 0;
+        while (len < n && str_span[len])
+            len++;
+
+        return len;
+    }
+
+    inline std::ptrdiff_t wstring_length(const wchar_t *str, std::ptrdiff_t n)
+    {
+        if (str == nullptr || n <= 0)
+            return 0;
+
+        span<const wchar_t> str_span{str, n};
+
+        std::ptrdiff_t len = 0;
+        while (len < n && str_span[len])
+            len++;
+
+        return len;
+    }
+}
+
+//
+// ensure_sentinel()
+//
+// Provides a way to obtain an span from a contiguous sequence
+// that ends with a (non-inclusive) sentinel value.
+//
+// Will fail-fast if sentinel cannot be found before max elements are examined.
+//
+template <typename T, const T Sentinel>
+span<T, dynamic_extent> ensure_sentinel(T* seq, std::ptrdiff_t max = PTRDIFF_MAX)
+{
+    auto cur = seq;
+    while ((cur - seq) < max && *cur != Sentinel) ++cur;
+    Ensures(*cur == Sentinel);
+    return {seq, cur - seq};
+}
+
+//
+// ensure_z - creates a span for a czstring or cwzstring.
+// Will fail fast if a null-terminator cannot be found before
+// the limit of size_type.
+//
+template <typename T>
+inline span<T, dynamic_extent> ensure_z(T* const& sz, std::ptrdiff_t max = PTRDIFF_MAX)
+{
+    return ensure_sentinel<T, 0>(sz, max);
+}
+
+// TODO (neilmac) there is probably a better template-magic way to get the const and non-const
+// overloads to share an implementation
+inline span<char, dynamic_extent> ensure_z(char* const& sz, std::ptrdiff_t max)
+{
+    auto len = details::string_length(sz, max);
+    Ensures(sz[len] == 0);
+    return {sz, len};
+}
+
+inline span<const char, dynamic_extent> ensure_z(const char* const& sz, std::ptrdiff_t max)
+{
+    auto len = details::string_length(sz, max);
+    Ensures(sz[len] == 0);
+    return {sz, len};
+}
+
+inline span<wchar_t, dynamic_extent> ensure_z(wchar_t* const& sz, std::ptrdiff_t max)
+{
+    auto len = details::wstring_length(sz, max);
+    Ensures(sz[len] == 0);
+    return {sz, len};
+}
+
+inline span<const wchar_t, dynamic_extent> ensure_z(const wchar_t* const& sz, std::ptrdiff_t max)
+{
+    auto len = details::wstring_length(sz, max);
+    Ensures(sz[len] == 0);
+    return {sz, len};
+}
+
+template <typename T, size_t N>
+span<T, dynamic_extent> ensure_z(T (&sz)[N])
+{
+    return ensure_z(&sz[0], static_cast<std::ptrdiff_t>(N));
+}
+
+template <class Cont>
+span<typename std::remove_pointer<typename Cont::pointer>::type, dynamic_extent>
+ensure_z(Cont& cont)
+{
+    return ensure_z(cont.data(), static_cast<std::ptrdiff_t>(cont.length()));
+}
+
+template <typename CharT, std::ptrdiff_t>
+class basic_string_span;
+
+namespace details
+{
+    template <typename T>
+    struct is_basic_string_span_oracle : std::false_type
+    {
+    };
+
+    template <typename CharT, std::ptrdiff_t Extent>
+    struct is_basic_string_span_oracle<basic_string_span<CharT, Extent>> : std::true_type
+    {
+    };
+
+    template <typename T>
+    struct is_basic_string_span : is_basic_string_span_oracle<std::remove_cv_t<T>>
+    {
+    };
+
+    template <typename T>
+    struct length_func
+    {
+    };
+
+    template <>
+    struct length_func<char>
+    {
+        std::ptrdiff_t operator()(char* const ptr, std::ptrdiff_t length) noexcept
+        {
+            return details::string_length(ptr, length);
+        }
+    };
+
+    template <>
+    struct length_func<wchar_t>
+    {
+        std::ptrdiff_t operator()(wchar_t* const ptr, std::ptrdiff_t length) noexcept
+        {
+            return details::wstring_length(ptr, length);
+        }
+    };
+
+    template <>
+    struct length_func<const char>
+    {
+        std::ptrdiff_t operator()(const char* const ptr, std::ptrdiff_t length) noexcept
+        {
+            return details::string_length(ptr, length);
+        }
+    };
+
+    template <>
+    struct length_func<const wchar_t>
+    {
+        std::ptrdiff_t operator()(const wchar_t* const ptr, std::ptrdiff_t length) noexcept
+        {
+            return details::wstring_length(ptr, length);
+        }
+    };
+}
+
+//
+// string_span and relatives
+//
+template <typename CharT, std::ptrdiff_t Extent = dynamic_extent>
+class basic_string_span
+{
+public:
+    using element_type = CharT;
+    using pointer = std::add_pointer_t<element_type>;
+    using reference = std::add_lvalue_reference_t<element_type>;
+    using const_reference = std::add_lvalue_reference_t<std::add_const_t<element_type>>;
+    using impl_type = span<element_type, Extent>;
+
+    using index_type = typename impl_type::index_type;
+    using iterator = typename impl_type::iterator;
+    using const_iterator = typename impl_type::const_iterator;
+    using reverse_iterator = typename impl_type::reverse_iterator;
+    using const_reverse_iterator = typename impl_type::const_reverse_iterator;
+
+    // default (empty)
+    constexpr basic_string_span() noexcept = default;
+
+    // copy
+    constexpr basic_string_span(const basic_string_span& other) noexcept = default;
+
+// move
+#ifndef GSL_MSVC_NO_DEFAULT_MOVE_CTOR
+    constexpr basic_string_span(basic_string_span&& other) noexcept = default;
+#else
+    constexpr basic_string_span(basic_string_span&& other) : span_(std::move(other.span_)) {}
+#endif
+
+    // assign
+    constexpr basic_string_span& operator=(const basic_string_span& other) noexcept = default;
+
+// move assign
+#ifndef GSL_MSVC_NO_DEFAULT_MOVE_CTOR
+    constexpr basic_string_span& operator=(basic_string_span&& other) noexcept = default;
+#else
+    constexpr basic_string_span& operator=(basic_string_span&& other) noexcept
+    {
+        span_ = std::move(other.span_);
+        return *this;
+    }
+#endif
+
+    // from nullptr
+    constexpr basic_string_span(std::nullptr_t ptr) noexcept : span_(ptr) {}
+
+    constexpr basic_string_span(pointer ptr, index_type length) : span_(ptr, length) {}
+    constexpr basic_string_span(pointer firstElem, pointer lastElem) : span_(firstElem, lastElem) {}
+
+    // From static arrays - if 0-terminated, remove 0 from the view
+    // All other containers allow 0s within the length, so we do not remove them
+    template <size_t N>
+    constexpr basic_string_span(element_type (&arr)[N]) : span_(remove_z(arr))
+    {
+    }
+
+    template <size_t N, class ArrayElementType = std::remove_const_t<element_type>>
+    constexpr basic_string_span(std::array<ArrayElementType, N>& arr) noexcept : span_(arr)
+    {
+    }
+
+    template <size_t N, class ArrayElementType = std::remove_const_t<element_type>>
+    constexpr basic_string_span(const std::array<ArrayElementType, N>& arr) noexcept : span_(arr)
+    {
+    }
+
+    // Container signature should work for basic_string after C++17 version exists
+    template <class Traits, class Allocator>
+    constexpr basic_string_span(std::basic_string<element_type, Traits, Allocator>& str)
+        : span_(&str[0], str.length())
+    {
+    }
+
+    template <class Traits, class Allocator>
+    constexpr basic_string_span(const std::basic_string<element_type, Traits, Allocator>& str)
+        : span_(&str[0], str.length())
+    {
+    }
+
+    // from containers. Containers must have a pointer type and data() function signatures
+    template <class Container,
+              class = std::enable_if_t<
+                  !details::is_basic_string_span<Container>::value &&
+                  std::is_convertible<typename Container::pointer, pointer>::value &&
+                  std::is_convertible<typename Container::pointer,
+                                      decltype(std::declval<Container>().data())>::value>>
+    constexpr basic_string_span(Container& cont) : span_(cont)
+    {
+    }
+
+    template <class Container,
+              class = std::enable_if_t<
+                  !details::is_basic_string_span<Container>::value &&
+                  std::is_convertible<typename Container::pointer, pointer>::value &&
+                  std::is_convertible<typename Container::pointer,
+                                      decltype(std::declval<Container>().data())>::value>>
+    constexpr basic_string_span(const Container& cont) : span_(cont)
+    {
+    }
+
+    // from string_span
+    template <
+        class OtherValueType, std::ptrdiff_t OtherExtent,
+        class = std::enable_if_t<std::is_convertible<
+            typename basic_string_span<OtherValueType, OtherExtent>::impl_type, impl_type>::value>>
+    constexpr basic_string_span(basic_string_span<OtherValueType, OtherExtent> other)
+        : span_(other.data(), other.length())
+    {
+    }
+
+    template <index_type Count>
+    constexpr basic_string_span<element_type, Count> first() const
+    {
+        return {span_.template first<Count>()};
+    }
+
+    constexpr basic_string_span<element_type, dynamic_extent> first(index_type count) const
+    {
+        return {span_.first(count)};
+    }
+
+    template <index_type Count>
+    constexpr basic_string_span<element_type, Count> last() const
+    {
+        return {span_.template last<Count>()};
+    }
+
+    constexpr basic_string_span<element_type, dynamic_extent> last(index_type count) const
+    {
+        return {span_.last(count)};
+    }
+
+    template <index_type Offset, index_type Count>
+    constexpr basic_string_span<element_type, Count> subspan() const
+    {
+        return {span_.template subspan<Offset, Count>()};
+    }
+
+    constexpr basic_string_span<element_type, dynamic_extent>
+    subspan(index_type offset, index_type count = dynamic_extent) const
+    {
+        return {span_.subspan(offset, count)};
+    }
+
+    constexpr reference operator[](index_type idx) const { return span_[idx]; }
+    constexpr reference operator()(index_type idx) const { return span_[idx]; }
+
+    constexpr pointer data() const { return span_.data(); }
+
+    constexpr index_type length() const noexcept { return span_.size(); }
+    constexpr index_type size() const noexcept { return span_.size(); }
+    constexpr index_type size_bytes() const noexcept { return span_.size_bytes(); }
+    constexpr index_type length_bytes() const noexcept { return span_.length_bytes(); }
+    constexpr bool empty() const noexcept { return size() == 0; }
+
+    constexpr iterator begin() const noexcept { return span_.begin(); }
+    constexpr iterator end() const noexcept { return span_.end(); }
+
+    constexpr const_iterator cbegin() const noexcept { return span_.cbegin(); }
+    constexpr const_iterator cend() const noexcept { return span_.cend(); }
+
+    constexpr reverse_iterator rbegin() const noexcept { return span_.rbegin(); }
+    constexpr reverse_iterator rend() const noexcept { return span_.rend(); }
+
+    constexpr const_reverse_iterator crbegin() const noexcept { return span_.crbegin(); }
+    constexpr const_reverse_iterator crend() const noexcept { return span_.crend(); }
+
+private:
+    static impl_type remove_z(pointer const& sz, std::ptrdiff_t max)
+    {
+        return {sz, details::length_func<element_type>()(sz, max)};
+    }
+
+    template <size_t N>
+    static impl_type remove_z(element_type (&sz)[N])
+    {
+        return remove_z(&sz[0], narrow_cast<std::ptrdiff_t>(N));
+    }
+
+    impl_type span_;
+};
+
+template <std::ptrdiff_t Extent = dynamic_extent>
+using string_span = basic_string_span<char, Extent>;
+
+template <std::ptrdiff_t Extent = dynamic_extent>
+using cstring_span = basic_string_span<const char, Extent>;
+
+template <std::ptrdiff_t Extent = dynamic_extent>
+using wstring_span = basic_string_span<wchar_t, Extent>;
+
+template <std::ptrdiff_t Extent = dynamic_extent>
+using cwstring_span = basic_string_span<const wchar_t, Extent>;
+
+//
+// to_string() allow (explicit) conversions from string_span to string
+//
+#ifndef GSL_MSVC_HAS_TYPE_DEDUCTION_BUG
+
+template <typename CharT, std::ptrdiff_t Extent>
+std::basic_string<typename std::remove_const<CharT>::type>
+to_string(basic_string_span<CharT, Extent> view)
+{
+    return {view.data(), static_cast<size_t>(view.length())};
+}
+
+#else
+
+inline std::string to_string(cstring_span<> view)
+{
+    return {view.data(), static_cast<size_t>(view.length())};
+}
+
+inline std::string to_string(string_span<> view)
+{
+    return {view.data(), static_cast<size_t>(view.length())};
+}
+
+inline std::wstring to_string(cwstring_span<> view)
+{
+    return {view.data(), static_cast<size_t>(view.length())};
+}
+
+inline std::wstring to_string(wstring_span<> view)
+{
+    return {view.data(), static_cast<size_t>(view.length())};
+}
+
+#endif
+
+template <typename CharT,
+	  typename Traits = typename std::char_traits<CharT>,
+	  typename Allocator = std::allocator<CharT>,
+	  typename gCharT,
+	  std::ptrdiff_t Extent>
+std::basic_string<CharT, Traits, Allocator> to_basic_string(basic_string_span<gCharT, Extent> view)
+{
+  return {view.data(), static_cast<size_t>(view.length())};
+}
+  
+// zero-terminated string span, used to convert
+// zero-terminated spans to legacy strings
+template <typename CharT, std::ptrdiff_t Extent = dynamic_extent>
+class basic_zstring_span
+{
+public:
+    using value_type = CharT;
+    using const_value_type = std::add_const_t<CharT>;
+
+    using pointer = std::add_pointer_t<value_type>;
+    using const_pointer = std::add_pointer_t<const_value_type>;
+
+    using zstring_type = basic_zstring<value_type, Extent>;
+    using const_zstring_type = basic_zstring<const_value_type, Extent>;
+
+    using impl_type = span<value_type, Extent>;
+    using string_span_type = basic_string_span<value_type, Extent>;
+
+    constexpr basic_zstring_span(impl_type s) noexcept : span_(s)
+    {
+        // expects a zero-terminated span
+        Expects(s[s.size() - 1] == '\0');
+    }
+
+    // copy
+    constexpr basic_zstring_span(const basic_zstring_span& other) = default;
+
+// move
+#ifndef GSL_MSVC_NO_DEFAULT_MOVE_CTOR
+    constexpr basic_zstring_span(basic_zstring_span&& other) = default;
+#else
+    constexpr basic_zstring_span(basic_zstring_span&& other) : span_(std::move(other.span_)) {}
+#endif
+
+    // assign
+    constexpr basic_zstring_span& operator=(const basic_zstring_span& other) = default;
+
+// move assign
+#ifndef GSL_MSVC_NO_DEFAULT_MOVE_CTOR
+    constexpr basic_zstring_span& operator=(basic_zstring_span&& other) = default;
+#else
+    constexpr basic_zstring_span& operator=(basic_zstring_span&& other)
+    {
+        span_ = std::move(other.span_);
+        return *this;
+    }
+#endif
+
+    constexpr bool empty() const noexcept { return span_.size() == 0; }
+
+    constexpr string_span_type as_string_span() const noexcept
+    {
+        auto sz = span_.size();
+        return span_.first(sz <= 0 ? 0 : sz - 1);
+    }
+
+    constexpr string_span_type ensure_z() const noexcept { return gsl::ensure_z(span_); }
+
+    constexpr const_zstring_type assume_z() const noexcept { return span_.data(); }
+
+private:
+    impl_type span_;
+};
+
+template <std::ptrdiff_t Max = dynamic_extent>
+using zstring_span = basic_zstring_span<char, Max>;
+
+template <std::ptrdiff_t Max = dynamic_extent>
+using wzstring_span = basic_zstring_span<wchar_t, Max>;
+
+template <std::ptrdiff_t Max = dynamic_extent>
+using czstring_span = basic_zstring_span<const char, Max>;
+
+template <std::ptrdiff_t Max = dynamic_extent>
+using cwzstring_span = basic_zstring_span<const wchar_t, Max>;
+
+// operator ==
+template <class CharT, std::ptrdiff_t Extent, class T,
+          class = std::enable_if_t<
+              details::is_basic_string_span<T>::value ||
+              std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>>>::value>>
+bool operator==(const gsl::basic_string_span<CharT, Extent>& one, const T& other) noexcept
+{
+    gsl::basic_string_span<std::add_const_t<CharT>> tmp(other);
+#ifdef GSL_MSVC_NO_CPP14_STD_EQUAL
+    return (one.size() == tmp.size()) && std::equal(one.begin(), one.end(), tmp.begin());
+#else
+    return std::equal(one.begin(), one.end(), tmp.begin(), tmp.end());
+#endif
+}
+
+template <class CharT, std::ptrdiff_t Extent, class T,
+          class = std::enable_if_t<
+              !details::is_basic_string_span<T>::value &&
+              std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>>>::value>>
+bool operator==(const T& one, const gsl::basic_string_span<CharT, Extent>& other) noexcept
+{
+    gsl::basic_string_span<std::add_const_t<CharT>> tmp(one);
+#ifdef GSL_MSVC_NO_CPP14_STD_EQUAL
+    return (tmp.size() == other.size()) && std::equal(tmp.begin(), tmp.end(), other.begin());
+#else
+    return std::equal(tmp.begin(), tmp.end(), other.begin(), other.end());
+#endif
+}
+
+// operator !=
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+          typename = std::enable_if_t<std::is_convertible<
+              T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value>>
+bool operator!=(gsl::basic_string_span<CharT, Extent> one, const T& other) noexcept
+{
+    return !(one == other);
+}
+
+template <
+    typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+    typename Dummy = std::enable_if_t<
+        std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value &&
+        !gsl::details::is_basic_string_span<T>::value>>
+bool operator!=(const T& one, gsl::basic_string_span<CharT, Extent> other) noexcept
+{
+    return !(one == other);
+}
+
+// operator<
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+          typename = std::enable_if_t<std::is_convertible<
+              T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value>>
+bool operator<(gsl::basic_string_span<CharT, Extent> one, const T& other) noexcept
+{
+    gsl::basic_string_span<std::add_const_t<CharT>, Extent> tmp(other);
+    return std::lexicographical_compare(one.begin(), one.end(), tmp.begin(), tmp.end());
+}
+
+template <
+    typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+    typename Dummy = std::enable_if_t<
+        std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value &&
+        !gsl::details::is_basic_string_span<T>::value>>
+bool operator<(const T& one, gsl::basic_string_span<CharT, Extent> other) noexcept
+{
+    gsl::basic_string_span<std::add_const_t<CharT>, Extent> tmp(one);
+    return std::lexicographical_compare(tmp.begin(), tmp.end(), other.begin(), other.end());
+}
+
+#ifndef _MSC_VER
+
+// VS treats temp and const containers as convertible to basic_string_span,
+// so the cases below are already covered by the previous operators
+
+template <
+    typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+    typename DataType = typename T::value_type,
+    typename Dummy = std::enable_if_t<
+        !gsl::details::is_span<T>::value && !gsl::details::is_basic_string_span<T>::value &&
+        std::is_convertible<DataType*, CharT*>::value &&
+        std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>,
+                     DataType>::value>>
+bool operator<(gsl::basic_string_span<CharT, Extent> one, const T& other) noexcept
+{
+    gsl::basic_string_span<std::add_const_t<CharT>, Extent> tmp(other);
+    return std::lexicographical_compare(one.begin(), one.end(), tmp.begin(), tmp.end());
+}
+
+template <
+    typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+    typename DataType = typename T::value_type,
+    typename Dummy = std::enable_if_t<
+        !gsl::details::is_span<T>::value && !gsl::details::is_basic_string_span<T>::value &&
+        std::is_convertible<DataType*, CharT*>::value &&
+        std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>,
+                     DataType>::value>>
+bool operator<(const T& one, gsl::basic_string_span<CharT, Extent> other) noexcept
+{
+    gsl::basic_string_span<std::add_const_t<CharT>, Extent> tmp(one);
+    return std::lexicographical_compare(tmp.begin(), tmp.end(), other.begin(), other.end());
+}
+#endif
+
+// operator <=
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+          typename = std::enable_if_t<std::is_convertible<
+              T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value>>
+bool operator<=(gsl::basic_string_span<CharT, Extent> one, const T& other) noexcept
+{
+    return !(other < one);
+}
+
+template <
+    typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+    typename Dummy = std::enable_if_t<
+        std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value &&
+        !gsl::details::is_basic_string_span<T>::value>>
+bool operator<=(const T& one, gsl::basic_string_span<CharT, Extent> other) noexcept
+{
+    return !(other < one);
+}
+
+#ifndef _MSC_VER
+
+// VS treats temp and const containers as convertible to basic_string_span,
+// so the cases below are already covered by the previous operators
+
+template <
+    typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+    typename DataType = typename T::value_type,
+    typename Dummy = std::enable_if_t<
+        !gsl::details::is_span<T>::value && !gsl::details::is_basic_string_span<T>::value &&
+        std::is_convertible<DataType*, CharT*>::value &&
+        std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>,
+                     DataType>::value>>
+bool operator<=(gsl::basic_string_span<CharT, Extent> one, const T& other) noexcept
+{
+    return !(other < one);
+}
+
+template <
+    typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+    typename DataType = typename T::value_type,
+    typename Dummy = std::enable_if_t<
+        !gsl::details::is_span<T>::value && !gsl::details::is_basic_string_span<T>::value &&
+        std::is_convertible<DataType*, CharT*>::value &&
+        std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>,
+                     DataType>::value>>
+bool operator<=(const T& one, gsl::basic_string_span<CharT, Extent> other) noexcept
+{
+    return !(other < one);
+}
+#endif
+
+// operator>
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+          typename = std::enable_if_t<std::is_convertible<
+              T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value>>
+bool operator>(gsl::basic_string_span<CharT, Extent> one, const T& other) noexcept
+{
+    return other < one;
+}
+
+template <
+    typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+    typename Dummy = std::enable_if_t<
+        std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value &&
+        !gsl::details::is_basic_string_span<T>::value>>
+bool operator>(const T& one, gsl::basic_string_span<CharT, Extent> other) noexcept
+{
+    return other < one;
+}
+
+#ifndef _MSC_VER
+
+// VS treats temp and const containers as convertible to basic_string_span,
+// so the cases below are already covered by the previous operators
+
+template <
+    typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+    typename DataType = typename T::value_type,
+    typename Dummy = std::enable_if_t<
+        !gsl::details::is_span<T>::value && !gsl::details::is_basic_string_span<T>::value &&
+        std::is_convertible<DataType*, CharT*>::value &&
+        std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>,
+                     DataType>::value>>
+bool operator>(gsl::basic_string_span<CharT, Extent> one, const T& other) noexcept
+{
+    return other < one;
+}
+
+template <
+    typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+    typename DataType = typename T::value_type,
+    typename Dummy = std::enable_if_t<
+        !gsl::details::is_span<T>::value && !gsl::details::is_basic_string_span<T>::value &&
+        std::is_convertible<DataType*, CharT*>::value &&
+        std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>,
+                     DataType>::value>>
+bool operator>(const T& one, gsl::basic_string_span<CharT, Extent> other) noexcept
+{
+    return other < one;
+}
+#endif
+
+// operator >=
+template <typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+          typename = std::enable_if_t<std::is_convertible<
+              T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value>>
+bool operator>=(gsl::basic_string_span<CharT, Extent> one, const T& other) noexcept
+{
+    return !(one < other);
+}
+
+template <
+    typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+    typename Dummy = std::enable_if_t<
+        std::is_convertible<T, gsl::basic_string_span<std::add_const_t<CharT>, Extent>>::value &&
+        !gsl::details::is_basic_string_span<T>::value>>
+bool operator>=(const T& one, gsl::basic_string_span<CharT, Extent> other) noexcept
+{
+    return !(one < other);
+}
+
+#ifndef _MSC_VER
+
+// VS treats temp and const containers as convertible to basic_string_span,
+// so the cases below are already covered by the previous operators
+
+template <
+    typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+    typename DataType = typename T::value_type,
+    typename Dummy = std::enable_if_t<
+        !gsl::details::is_span<T>::value && !gsl::details::is_basic_string_span<T>::value &&
+        std::is_convertible<DataType*, CharT*>::value &&
+        std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>,
+                     DataType>::value>>
+bool operator>=(gsl::basic_string_span<CharT, Extent> one, const T& other) noexcept
+{
+    return !(one < other);
+}
+
+template <
+    typename CharT, std::ptrdiff_t Extent = gsl::dynamic_extent, typename T,
+    typename DataType = typename T::value_type,
+    typename Dummy = std::enable_if_t<
+        !gsl::details::is_span<T>::value && !gsl::details::is_basic_string_span<T>::value &&
+        std::is_convertible<DataType*, CharT*>::value &&
+        std::is_same<std::decay_t<decltype(std::declval<T>().size(), *std::declval<T>().data())>,
+                     DataType>::value>>
+bool operator>=(const T& one, gsl::basic_string_span<CharT, Extent> other) noexcept
+{
+    return !(one < other);
+}
+#endif
+} // namespace GSL
+
+#ifdef _MSC_VER
+
+#pragma warning(pop)
+
+#undef constexpr
+#pragma pop_macro("constexpr")
+
+// VS 2013 workarounds
+#if _MSC_VER <= 1800
+
+#ifndef GSL_THROW_ON_CONTRACT_VIOLATION
+#undef noexcept
+#pragma pop_macro("noexcept")
+#endif // GSL_THROW_ON_CONTRACT_VIOLATION
+
+#undef GSL_MSVC_HAS_TYPE_DEDUCTION_BUG
+#undef GSL_MSVC_HAS_SFINAE_SUBSTITUTION_ICE
+#undef GSL_MSVC_NO_CPP14_STD_EQUAL
+#undef GSL_MSVC_NO_DEFAULT_MOVE_CTOR
+
+#endif // _MSC_VER <= 1800
+#endif // _MSC_VER
+
+#if defined(GSL_THROW_ON_CONTRACT_VIOLATION)
+
+#undef noexcept
+
+#ifdef _MSC_VER
+#pragma pop_macro("noexcept")
+#endif
+
+#endif // GSL_THROW_ON_CONTRACT_VIOLATION
+#endif // GSL_STRING_SPAN_H
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
new file mode 100644
index 0000000..44db32d
--- /dev/null
+++ b/tests/CMakeLists.txt
@@ -0,0 +1,54 @@
+cmake_minimum_required(VERSION 2.8.7)
+
+project(GSLTests CXX)
+
+if (NOT EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/unittest-cpp/tests)
+    execute_process(COMMAND git submodule update --init WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")
+endif()
+
+add_subdirectory(unittest-cpp)
+
+include_directories(
+    ..
+    ./unittest-cpp
+)
+
+add_definitions(-DGSL_THROW_ON_CONTRACT_VIOLATION)
+
+if(MSVC14 OR MSVC12) # has the support we need
+    # remove unnecessary warnings about unchecked iterators
+    add_definitions(-D_SCL_SECURE_NO_WARNINGS)
+    add_compile_options(/W4)
+else()
+    include(CheckCXXCompilerFlag)
+    CHECK_CXX_COMPILER_FLAG("-std=c++14" COMPILER_SUPPORTS_CXX14)
+    CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
+    if(COMPILER_SUPPORTS_CXX14)
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-strict-aliasing -std=c++14 -O3 -Wall -Wno-missing-braces")
+    elseif(COMPILER_SUPPORTS_CXX11)
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-strict-aliasing -std=c++11 -O3 -Wall -Wno-missing-braces")
+    else()
+      message(STATUS "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.")
+    endif()
+endif()
+
+function(add_gsl_test name)
+    add_executable(${name} ${name}.cpp ../gsl/gsl ../gsl/gsl_assert ../gsl/gsl_util ../gsl/multi_span ../gsl/span ../gsl/string_span)
+    target_link_libraries(${name} UnitTest++)
+    add_test(
+      ${name}
+      ${name}
+    )
+endfunction()
+
+add_gsl_test(span_tests)
+add_gsl_test(multi_span_tests)
+add_gsl_test(strided_span_tests)
+add_gsl_test(string_span_tests)
+add_gsl_test(at_tests)
+add_gsl_test(bounds_tests)
+add_gsl_test(notnull_tests)
+add_gsl_test(assertion_tests)
+add_gsl_test(utils_tests)
+add_gsl_test(owner_tests)
+add_gsl_test(byte_tests)
diff --git a/tests/assertion_tests.cpp b/tests/assertion_tests.cpp
new file mode 100644
index 0000000..a251200
--- /dev/null
+++ b/tests/assertion_tests.cpp
@@ -0,0 +1,53 @@
+/////////////////////////////////////////////////////////////////////////////// 
+// 
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved. 
+// 
+// This code is licensed under the MIT License (MIT). 
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 
+// THE SOFTWARE. 
+// 
+///////////////////////////////////////////////////////////////////////////////
+
+#include <UnitTest++/UnitTest++.h> 
+#include <gsl/gsl>
+
+using namespace gsl;
+
+SUITE(assertion_tests)
+{
+    int f(int i)
+    {
+        Expects(i > 0 && i < 10);
+        return i;
+    }
+
+    TEST(expects)
+    {
+        CHECK(f(2) == 2);
+        CHECK_THROW(f(10), fail_fast);
+    }
+
+    int g(int i)
+    {        
+        i++;
+        Ensures(i > 0 && i < 10);
+        return i;
+    }
+
+    TEST(ensures)
+    {
+        CHECK(g(2) == 3);
+        CHECK_THROW(g(9), fail_fast);
+    }
+}
+
+int main(int, const char *[])
+{
+    return UnitTest::RunAllTests();
+}
diff --git a/tests/at_tests.cpp b/tests/at_tests.cpp
new file mode 100644
index 0000000..008fddf
--- /dev/null
+++ b/tests/at_tests.cpp
@@ -0,0 +1,71 @@
+/////////////////////////////////////////////////////////////////////////////// 
+// 
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved. 
+// 
+// This code is licensed under the MIT License (MIT). 
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 
+// THE SOFTWARE. 
+// 
+///////////////////////////////////////////////////////////////////////////////
+
+#include <UnitTest++/UnitTest++.h> 
+#include <gsl/gsl>
+#include <vector>
+#include <initializer_list>
+
+using namespace std;
+using namespace gsl;
+
+SUITE(at_tests)
+{
+    TEST(static_array)
+    {
+        int a[] = { 1, 2, 3, 4 };
+
+        for (int i = 0; i < 4; ++i)
+            CHECK(at(a, i) == i+1);
+
+        CHECK_THROW(at(a, 4), fail_fast);
+    }
+
+    TEST(std_array)
+    {
+        std::array<int,4> a = { 1, 2, 3, 4 };
+
+        for (int i = 0; i < 4; ++i)
+            CHECK(at(a, i) == i+1);
+
+        CHECK_THROW(at(a, 4), fail_fast);
+    }
+
+    TEST(StdVector)
+    {
+        std::vector<int> a = { 1, 2, 3, 4 };
+
+        for (int i = 0; i < 4; ++i)
+            CHECK(at(a, i) == i+1);
+
+        CHECK_THROW(at(a, 4), fail_fast);
+    }
+
+    TEST(InitializerList)
+    {
+        std::initializer_list<int> a = { 1, 2, 3, 4 };
+
+        for (int i = 0; i < 4; ++i)
+            CHECK(at(a, i) == i+1);
+
+        CHECK_THROW(at(a, 4), fail_fast);
+    }
+}
+
+int main(int, const char *[])
+{
+    return UnitTest::RunAllTests();
+}
diff --git a/tests/bounds_tests.cpp b/tests/bounds_tests.cpp
new file mode 100644
index 0000000..d10bf6d
--- /dev/null
+++ b/tests/bounds_tests.cpp
@@ -0,0 +1,103 @@
+/////////////////////////////////////////////////////////////////////////////// 
+// 
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved. 
+// 
+// This code is licensed under the MIT License (MIT). 
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 
+// THE SOFTWARE. 
+// 
+///////////////////////////////////////////////////////////////////////////////
+
+#include <UnitTest++/UnitTest++.h> 
+#include <gsl/multi_span>
+#include <vector>
+
+using namespace std;
+using namespace gsl;;
+
+namespace 
+{
+    void use(std::ptrdiff_t&) {}
+}
+
+SUITE(bounds_test)
+{
+	TEST(basic_bounds)
+	{
+		for (auto point : static_bounds<dynamic_range, 3, 4 > { 2 })
+		{
+			for (decltype(point)::size_type j = 0;
+			     j < static_cast<decltype(point)::size_type>(decltype(point)::rank);
+			     j++)
+			{
+				use(j);
+				use(point[j]);
+			}
+		}
+	}
+	
+	TEST(bounds_basic)
+	{
+		static_bounds<3, 4, 5> b;
+		auto a = b.slice();
+		(void)a;           
+		static_bounds<4, dynamic_range, 2> x{ 4 };
+		x.slice().slice();
+	}
+	
+	TEST (arrayview_iterator)
+	{
+		static_bounds<4, dynamic_range, 2> bounds{ 3 };
+		
+		auto itr = bounds.begin();
+		(void)itr;	
+#ifdef CONFIRM_COMPILATION_ERRORS
+		multi_span<int, 4, dynamic_range, 2> av(nullptr, bounds);
+	
+		auto itr2 = av.cbegin();
+	
+		for (auto& v : av) {
+			v = 4;
+		}
+		fill(av.begin(), av.end(), 0);
+#endif			
+	}
+	
+	TEST (bounds_convertible)
+	{
+		static_bounds<7, 4, 2> b1;
+		static_bounds<7, dynamic_range, 2> b2 = b1;
+		(void)b2;	
+#ifdef CONFIRM_COMPILATION_ERRORS
+		static_bounds<7, dynamic_range, 1> b4 = b2; 
+#endif
+	
+		static_bounds<dynamic_range, dynamic_range, dynamic_range> b3 = b1;
+		static_bounds<7, 4, 2> b4 = b3; 
+		(void)b4;
+
+		static_bounds<dynamic_range> b11;
+	
+		static_bounds<dynamic_range> b5;
+		static_bounds<34> b6;
+		
+		b5 = static_bounds<20>();
+		CHECK_THROW(b6 = b5, fail_fast);
+		b5 = static_bounds<34>();
+		b6 = b5;
+
+		CHECK(b5 == b6);
+		CHECK(b5.size() == b6.size());
+	}                                 
+}
+
+int main(int, const char *[])
+{
+	return UnitTest::RunAllTests();
+}
diff --git a/tests/byte_tests.cpp b/tests/byte_tests.cpp
new file mode 100644
index 0000000..8cb0da8
--- /dev/null
+++ b/tests/byte_tests.cpp
@@ -0,0 +1,135 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <UnitTest++/UnitTest++.h>
+#include <gsl/gsl_byte>
+
+#include <iostream>
+#include <list>
+#include <map>
+#include <memory>
+#include <string>
+#include <vector>
+
+using namespace std;
+using namespace gsl;
+
+namespace
+{
+
+SUITE(byte_tests)
+{
+    TEST(construction)
+    {
+        {
+            byte b = static_cast<byte>(4);
+            CHECK(static_cast<unsigned char>(b) == 4);
+        }
+
+        {
+            byte b = byte(12);
+            CHECK(static_cast<unsigned char>(b) == 12);
+        }
+
+        {
+            byte b = to_byte<12>();
+            CHECK(static_cast<unsigned char>(b) == 12);
+        }
+        {
+            unsigned char uc = 12;
+            byte b = to_byte(uc);
+            CHECK(static_cast<unsigned char>(b) == 12);
+        }
+
+        // waiting for C++17 enum class direct initializer support
+        //{
+        //    byte b { 14 };
+        //    CHECK(static_cast<unsigned char>(b) == 14);
+        //}
+    }
+
+    TEST(bitwise_operations)
+    {
+        byte b = to_byte<0xFF>();
+
+        byte a = to_byte<0x00>();
+        CHECK((b | a) == to_byte<0xFF>());
+        CHECK(a == to_byte<0x00>());
+
+        a |= b;
+        CHECK(a == to_byte<0xFF>());
+
+        a = to_byte<0x01>();
+        CHECK((b & a) == to_byte<0x01>());
+
+        a &= b;
+        CHECK(a == to_byte<0x01>());
+
+        CHECK((b ^ a) == to_byte<0xFE>());
+        
+        CHECK(a == to_byte<0x01>());
+        a ^= b;
+        CHECK(a == to_byte<0xFE>());
+
+        a = to_byte<0x01>();
+        CHECK(~a == to_byte<0xFE>());
+
+        a = to_byte<0xFF>();
+        CHECK((a << 4) == to_byte<0xF0>());
+        CHECK((a >> 4) == to_byte<0x0F>());
+
+        a <<= 4;
+        CHECK(a == to_byte<0xF0>());
+        a >>= 4;
+        CHECK(a == to_byte<0x0F>());
+    }
+
+    TEST(to_integer)
+    {
+        byte b = to_byte<0x12>();
+
+        CHECK(0x12 == gsl::to_integer<char>(b));
+        CHECK(0x12 == gsl::to_integer<short>(b));
+        CHECK(0x12 == gsl::to_integer<long>(b));
+        CHECK(0x12 == gsl::to_integer<long long>(b));
+
+        CHECK(0x12 == gsl::to_integer<unsigned char>(b));
+        CHECK(0x12 == gsl::to_integer<unsigned short>(b));
+        CHECK(0x12 == gsl::to_integer<unsigned long>(b));
+        CHECK(0x12 == gsl::to_integer<unsigned long long>(b));
+
+//      CHECK(0x12 == gsl::to_integer<float>(b));   // expect compile-time error
+//      CHECK(0x12 == gsl::to_integer<double>(b));  // expect compile-time error
+    }
+
+    int modify_both(gsl::byte& b, int& i)
+    {
+        i = 10;
+        b = to_byte<5>();
+        return i;
+    }
+
+    TEST(aliasing)
+    {
+        int i{ 0 };
+        int res = modify_both(reinterpret_cast<byte&>(i), i);
+        CHECK(res == i);
+    }
+}
+
+}
+
+int main(int, const char* []) { return UnitTest::RunAllTests(); }
diff --git a/tests/multi_span_tests.cpp b/tests/multi_span_tests.cpp
new file mode 100644
index 0000000..c0240ea
--- /dev/null
+++ b/tests/multi_span_tests.cpp
@@ -0,0 +1,1685 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <UnitTest++/UnitTest++.h>
+#include <gsl/multi_span>
+
+#include <iostream>
+#include <list>
+#include <map>
+#include <memory>
+#include <string>
+#include <vector>
+
+using namespace std;
+using namespace gsl;
+
+namespace
+{
+struct BaseClass
+{
+};
+struct DerivedClass : BaseClass
+{
+};
+}
+
+SUITE(multi_span_tests)
+{
+
+    TEST(default_constructor)
+    {
+        {
+            multi_span<int> s;
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            multi_span<const int> cs;
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+
+        {
+            multi_span<int, 0> s;
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            multi_span<const int, 0> cs;
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<int, 1> s;
+            CHECK(s.length() == 1 && s.data() == nullptr); // explains why it can't compile
+#endif
+        }
+
+        {
+            multi_span<int> s{};
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            multi_span<const int> cs{};
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+    }
+
+    TEST(from_nullptr_constructor)
+    {
+        {
+            multi_span<int> s = nullptr;
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            multi_span<const int> cs = nullptr;
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+
+        {
+            multi_span<int, 0> s = nullptr;
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            multi_span<const int, 0> cs = nullptr;
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<int, 1> s = nullptr;
+            CHECK(s.length() == 1 && s.data() == nullptr); // explains why it can't compile
+#endif
+        }
+
+        {
+            multi_span<int> s{nullptr};
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            multi_span<const int> cs{nullptr};
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+
+        {
+            multi_span<int*> s{nullptr};
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            multi_span<const int*> cs{nullptr};
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+    }
+
+    TEST(from_nullptr_length_constructor)
+    {
+        {
+            multi_span<int> s{nullptr, 0};
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            multi_span<const int> cs{nullptr, 0};
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+
+        {
+            multi_span<int, 0> s{nullptr, 0};
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            multi_span<const int, 0> cs{nullptr, 0};
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<int, 1> s{nullptr, 0};
+            CHECK(s.length() == 1 && s.data() == nullptr); // explains why it can't compile
+#endif
+        }
+
+        {
+            auto workaround_macro = []() { multi_span<int> s{nullptr, 1}; };
+            CHECK_THROW(workaround_macro(), fail_fast);
+
+            auto const_workaround_macro = []() { multi_span<const int> cs{nullptr, 1}; };
+            CHECK_THROW(const_workaround_macro(), fail_fast);
+        }
+
+        {
+            auto workaround_macro = []() { multi_span<int, 0> s{nullptr, 1}; };
+            CHECK_THROW(workaround_macro(), fail_fast);
+
+            auto const_workaround_macro = []() { multi_span<const int, 0> s{nullptr, 1}; };
+            CHECK_THROW(const_workaround_macro(), fail_fast);
+        }
+
+        {
+            multi_span<int*> s{nullptr, 0};
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            multi_span<const int*> cs{nullptr, 0};
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+    }
+
+    TEST(from_element_constructor)
+    {
+        int i = 5;
+
+        {
+            multi_span<int> s = i;
+            CHECK(s.length() == 1 && s.data() == &i);
+            CHECK(s[0] == 5);
+
+            multi_span<const int> cs = i;
+            CHECK(cs.length() == 1 && cs.data() == &i);
+            CHECK(cs[0] == 5);
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            const j = 1;
+            multi_span<int, 0> s = j;
+#endif
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<int, 0> s = i;
+            CHECK(s.length() == 0 && s.data() == &i);
+#endif
+        }
+
+        {
+            multi_span<int, 1> s = i;
+            CHECK(s.length() == 1 && s.data() == &i);
+            CHECK(s[0] == 5);
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<int, 2> s = i;
+            CHECK(s.length() == 2 && s.data() == &i);
+#endif
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            auto get_a_temp = []() -> int { return 4; };
+            auto use_a_span = [](multi_span<int> s) { (void) s; };
+            use_a_span(get_a_temp());
+#endif
+        }
+    }
+
+    TEST(from_pointer_length_constructor)
+    {
+        int arr[4] = {1, 2, 3, 4};
+
+        {
+            multi_span<int> s{&arr[0], 2};
+            CHECK(s.length() == 2 && s.data() == &arr[0]);
+            CHECK(s[0] == 1 && s[1] == 2);
+        }
+
+        {
+            multi_span<int, 2> s{&arr[0], 2};
+            CHECK(s.length() == 2 && s.data() == &arr[0]);
+            CHECK(s[0] == 1 && s[1] == 2);
+        }
+
+        {
+            int* p = nullptr;
+            multi_span<int> s{p, 0};
+            CHECK(s.length() == 0 && s.data() == nullptr);
+        }
+
+        {
+            int* p = nullptr;
+            auto workaround_macro = [=]() { multi_span<int> s{p, 2}; };
+            CHECK_THROW(workaround_macro(), fail_fast);
+        }
+    }
+
+    TEST(from_pointer_pointer_constructor)
+    {
+        int arr[4] = {1, 2, 3, 4};
+
+        {
+            multi_span<int> s{&arr[0], &arr[2]};
+            CHECK(s.length() == 2 && s.data() == &arr[0]);
+            CHECK(s[0] == 1 && s[1] == 2);
+        }
+
+        {
+            multi_span<int, 2> s{&arr[0], &arr[2]};
+            CHECK(s.length() == 2 && s.data() == &arr[0]);
+            CHECK(s[0] == 1 && s[1] == 2);
+        }
+
+        {
+            multi_span<int> s{&arr[0], &arr[0]};
+            CHECK(s.length() == 0 && s.data() == &arr[0]);
+        }
+
+        {
+            multi_span<int, 0> s{&arr[0], &arr[0]};
+            CHECK(s.length() == 0 && s.data() == &arr[0]);
+        }
+
+        {
+            auto workaround_macro = [&]() { multi_span<int> s{&arr[1], &arr[0]}; };
+            CHECK_THROW(workaround_macro(), fail_fast);
+        }
+
+        {
+            int* p = nullptr;
+            auto workaround_macro = [&]() { multi_span<int> s{&arr[0], p}; };
+            CHECK_THROW(workaround_macro(), fail_fast);
+        }
+
+        {
+            int* p = nullptr;
+            auto workaround_macro = [&]() { multi_span<int> s{p, p}; };
+            CHECK_THROW(workaround_macro(), fail_fast);
+        }
+
+        {
+            int* p = nullptr;
+            auto workaround_macro = [&]() { multi_span<int> s{&arr[0], p}; };
+            CHECK_THROW(workaround_macro(), fail_fast);
+        }
+    }
+
+    TEST(from_array_constructor)
+    {
+        int arr[5] = {1, 2, 3, 4, 5};
+
+        {
+            multi_span<int> s{arr};
+            CHECK(s.length() == 5 && s.data() == &arr[0]);
+        }
+
+        {
+            multi_span<int, 5> s{arr};
+            CHECK(s.length() == 5 && s.data() == &arr[0]);
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<int, 6> s{arr};
+#endif
+        }
+
+        {
+            multi_span<int, 0> s{arr};
+            CHECK(s.length() == 0 && s.data() == &arr[0]);
+        }
+
+        int arr2d[2][3] = {1, 2, 3, 4, 5, 6};
+
+        {
+            multi_span<int> s{arr2d};
+            CHECK(s.length() == 6 && s.data() == &arr2d[0][0]);
+            CHECK(s[0] == 1 && s[5] == 6);
+        }
+
+        {
+            multi_span<int, 0> s{arr2d};
+            CHECK(s.length() == 0 && s.data() == &arr2d[0][0]);
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<int, 5> s{arr2d};
+#endif
+        }
+
+        {
+            multi_span<int, 6> s{arr2d};
+            CHECK(s.length() == 6 && s.data() == &arr2d[0][0]);
+            CHECK(s[0] == 1 && s[5] == 6);
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<int, 7> s{arr2d};
+#endif
+        }
+
+        {
+            multi_span<int[3]> s{arr2d[0]};
+            CHECK(s.length() == 1 && s.data() == &arr2d[0]);
+        }
+
+        {
+            multi_span<int, 2, 3> s{arr2d};
+            CHECK(s.length() == 6 && s.data() == &arr2d[0][0]);
+            auto workaround_macro = [&]() { return s[{1, 2}] == 6; };
+            CHECK(workaround_macro());
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<int, 3, 3> s{arr2d};
+#endif
+        }
+
+        int arr3d[2][3][2] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
+
+        {
+            multi_span<int> s{arr3d};
+            CHECK(s.length() == 12 && s.data() == &arr3d[0][0][0]);
+            CHECK(s[0] == 1 && s[11] == 12);
+        }
+
+        {
+            multi_span<int, 0> s{arr3d};
+            CHECK(s.length() == 0 && s.data() == &arr3d[0][0][0]);
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<int, 11> s{arr3d};
+#endif
+        }
+
+        {
+            multi_span<int, 12> s{arr3d};
+            CHECK(s.length() == 12 && s.data() == &arr3d[0][0][0]);
+            CHECK(s[0] == 1 && s[5] == 6);
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<int, 13> s{arr3d};
+#endif
+        }
+
+        {
+            multi_span<int[3][2]> s{arr3d[0]};
+            CHECK(s.length() == 1 && s.data() == &arr3d[0]);
+        }
+
+        {
+            multi_span<int, 3, 2, 2> s{arr3d};
+            CHECK(s.length() == 12 && s.data() == &arr3d[0][0][0]);
+            auto workaround_macro = [&]() { return s[{2, 1, 0}] == 11; };
+            CHECK(workaround_macro());
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<int, 3, 3, 3> s{arr3d};
+#endif
+        }
+    }
+
+    TEST(from_dynamic_array_constructor)
+    {
+        double(*arr)[3][4] = new double[100][3][4];
+
+        {
+            multi_span<double, dynamic_range, 3, 4> s(arr, 10);
+            CHECK(s.length() == 120 && s.data() == &arr[0][0][0]);
+            CHECK_THROW(s[10][3][4], fail_fast);
+        }
+
+        {
+            multi_span<double, dynamic_range, 4, 3> s(arr, 10);
+            CHECK(s.length() == 120 && s.data() == &arr[0][0][0]);
+        }
+
+        {
+            multi_span<double> s(arr, 10);
+            CHECK(s.length() == 120 && s.data() == &arr[0][0][0]);
+        }
+
+        {
+            multi_span<double, dynamic_range, 3, 4> s(arr, 0);
+            CHECK(s.length() == 0 && s.data() == &arr[0][0][0]);
+        }
+
+        delete[] arr;
+    }
+
+    TEST(from_std_array_constructor)
+    {
+        std::array<int, 4> arr = {1, 2, 3, 4};
+
+        {
+            multi_span<int> s{arr};
+            CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
+
+            multi_span<const int> cs{arr};
+            CHECK(cs.size() == narrow_cast<ptrdiff_t>(arr.size()) && cs.data() == arr.data());
+        }
+
+        {
+            multi_span<int, 4> s{arr};
+            CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
+
+            multi_span<const int, 4> cs{arr};
+            CHECK(cs.size() == narrow_cast<ptrdiff_t>(arr.size()) && cs.data() == arr.data());
+        }
+
+        {
+            multi_span<int, 2> s{arr};
+            CHECK(s.size() == 2 && s.data() == arr.data());
+
+            multi_span<const int, 2> cs{arr};
+            CHECK(cs.size() == 2 && cs.data() == arr.data());
+        }
+
+        {
+            multi_span<int, 0> s{arr};
+            CHECK(s.size() == 0 && s.data() == arr.data());
+
+            multi_span<const int, 0> cs{arr};
+            CHECK(cs.size() == 0 && cs.data() == arr.data());
+        }
+
+        // TODO This is currently an unsupported scenario. We will come back to it as we revise
+        // the multidimensional interface and what transformations between dimensionality look like
+        //{
+        //    multi_span<int, 2, 2> s{arr};
+        //    CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
+        //}
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<int, 5> s{arr};
+#endif
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            auto get_an_array = []() { return std::array<int, 4>{1, 2, 3, 4}; };
+            auto take_a_span = [](multi_span<int> s) { (void) s; };
+            // try to take a temporary std::array
+            take_a_span(get_an_array());
+#endif
+        }
+    }
+
+    TEST(from_const_std_array_constructor)
+    {
+        const std::array<int, 4> arr = {1, 2, 3, 4};
+
+        {
+            multi_span<const int> s{arr};
+            CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
+        }
+
+        {
+            multi_span<const int, 4> s{arr};
+            CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
+        }
+
+        {
+            multi_span<const int, 2> s{arr};
+            CHECK(s.size() == 2 && s.data() == arr.data());
+        }
+
+        {
+            multi_span<const int, 0> s{arr};
+            CHECK(s.size() == 0 && s.data() == arr.data());
+        }
+
+        // TODO This is currently an unsupported scenario. We will come back to it as we revise
+        // the multidimensional interface and what transformations between dimensionality look like
+        //{
+        //    multi_span<int, 2, 2> s{arr};
+        //    CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
+        //}
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<const int, 5> s{arr};
+#endif
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            auto get_an_array = []() -> const std::array<int, 4> { return {1, 2, 3, 4}; };
+            auto take_a_span = [](multi_span<const int> s) { (void) s; };
+            // try to take a temporary std::array
+            take_a_span(get_an_array());
+#endif
+        }
+    }
+
+    TEST(from_container_constructor)
+    {
+        std::vector<int> v = {1, 2, 3};
+        const std::vector<int> cv = v;
+
+        {
+            multi_span<int> s{v};
+            CHECK(s.size() == narrow_cast<std::ptrdiff_t>(v.size()) && s.data() == v.data());
+
+            multi_span<const int> cs{v};
+            CHECK(cs.size() == narrow_cast<std::ptrdiff_t>(v.size()) && cs.data() == v.data());
+        }
+
+        std::string str = "hello";
+        const std::string cstr = "hello";
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<char> s{str};
+            CHECK(s.size() == narrow_cast<std::ptrdiff_t>(str.size()) && s.data() == str.data());
+#endif
+            multi_span<const char> cs{str};
+            CHECK(cs.size() == narrow_cast<std::ptrdiff_t>(str.size()) && cs.data() == str.data());
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            multi_span<char> s{cstr};
+#endif
+            multi_span<const char> cs{cstr};
+            CHECK(cs.size() == narrow_cast<std::ptrdiff_t>(cstr.size()) &&
+                  cs.data() == cstr.data());
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            auto get_temp_vector = []() -> std::vector<int> { return {}; };
+            auto use_span = [](multi_span<int> s) { (void) s; };
+            use_span(get_temp_vector());
+#endif
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            auto get_temp_string = []() -> std::string { return {}; };
+            auto use_span = [](multi_span<char> s) { (void) s; };
+            use_span(get_temp_string());
+#endif
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            auto get_temp_vector = []() -> const std::vector<int> { return {}; };
+            auto use_span = [](multi_span<const char> s) { (void) s; };
+            use_span(get_temp_vector());
+#endif
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            auto get_temp_string = []() -> const std::string { return {}; };
+            auto use_span = [](multi_span<const char> s) { (void) s; };
+            use_span(get_temp_string());
+#endif
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            std::map<int, int> m;
+            multi_span<int> s{m};
+#endif
+        }
+    }
+
+    TEST(from_convertible_span_constructor)
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<int, 7, 4, 2> av1(nullptr, b1);
+
+        auto f = [&]() { multi_span<int, 7, 4, 2> av1(nullptr); };
+        CHECK_THROW(f(), fail_fast);
+#endif
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+        static_bounds<size_t, 7, dynamic_range, 2> b12(b11);
+        b12 = b11;
+        b11 = b12;
+
+        multi_span<int, dynamic_range> av1 = nullptr;
+        multi_span<int, 7, dynamic_range, 2> av2(av1);
+        multi_span<int, 7, 4, 2> av2(av1);
+#endif
+
+        multi_span<DerivedClass> avd;
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<BaseClass> avb = avd;
+#endif
+        multi_span<const DerivedClass> avcd = avd;
+        (void) avcd;
+    }
+
+    TEST(copy_move_and_assignment)
+    {
+        multi_span<int> s1;
+        CHECK(s1.empty());
+
+        int arr[] = {3, 4, 5};
+
+        multi_span<const int> s2 = arr;
+        CHECK(s2.length() == 3 && s2.data() == &arr[0]);
+
+        s2 = s1;
+        CHECK(s2.empty());
+
+        auto get_temp_span = [&]() -> multi_span<int> { return {&arr[1], 2}; };
+        auto use_span = [&](multi_span<const int> s) { CHECK(s.length() == 2 && s.data() == &arr[1]); };
+        use_span(get_temp_span());
+
+        s1 = get_temp_span();
+        CHECK(s1.length() == 2 && s1.data() == &arr[1]);
+    }
+
+    template <class Bounds>
+    void fn(const Bounds&)
+    {
+        static_assert(Bounds::static_size == 60, "static bounds is wrong size");
+    }
+    TEST(as_multi_span_reshape)
+    {
+        int a[3][4][5];
+        auto av = as_multi_span(a);
+        fn(av.bounds());
+        auto av2 = as_multi_span(av, dim<60>());
+        auto av3 = as_multi_span(av2, dim<3>(), dim<4>(), dim<5>());
+        auto av4 = as_multi_span(av3, dim<4>(), dim(3), dim<5>());
+        auto av5 = as_multi_span(av4, dim<3>(), dim<4>(), dim<5>());
+        auto av6 = as_multi_span(av5, dim<12>(), dim(5));
+
+        fill(av6.begin(), av6.end(), 1);
+
+        auto av7 = as_bytes(av6);
+
+        auto av8 = as_multi_span<int>(av7);
+
+        CHECK(av8.size() == av6.size());
+        for (auto i = 0; i < av8.size(); i++) {
+            CHECK(av8[i] == 1);
+        }
+    }
+
+    TEST(first)
+    {
+        int arr[5] = {1, 2, 3, 4, 5};
+
+        {
+            multi_span<int, 5> av = arr;
+            CHECK((av.first<2>().bounds() == static_bounds<2>()));
+            CHECK(av.first<2>().length() == 2);
+            CHECK(av.first(2).length() == 2);
+        }
+
+        {
+            multi_span<int, 5> av = arr;
+            CHECK((av.first<0>().bounds() == static_bounds<0>()));
+            CHECK(av.first<0>().length() == 0);
+            CHECK(av.first(0).length() == 0);
+        }
+
+        {
+            multi_span<int, 5> av = arr;
+            CHECK((av.first<5>().bounds() == static_bounds<5>()));
+            CHECK(av.first<5>().length() == 5);
+            CHECK(av.first(5).length() == 5);
+        }
+
+        {
+            multi_span<int, 5> av = arr;
+#ifdef CONFIRM_COMPILATION_ERRORS
+            CHECK(av.first<6>().bounds() == static_bounds<6>());
+            CHECK(av.first<6>().length() == 6);
+            CHECK(av.first<-1>().length() == -1);
+#endif
+            CHECK_THROW(av.first(6).length(), fail_fast);
+        }
+
+        {
+            multi_span<int, dynamic_range> av;
+            CHECK((av.first<0>().bounds() == static_bounds<0>()));
+            CHECK(av.first<0>().length() == 0);
+            CHECK(av.first(0).length() == 0);
+        }
+    }
+
+    TEST(last)
+    {
+        int arr[5] = {1, 2, 3, 4, 5};
+
+        {
+            multi_span<int, 5> av = arr;
+            CHECK((av.last<2>().bounds() == static_bounds<2>()));
+            CHECK(av.last<2>().length() == 2);
+            CHECK(av.last(2).length() == 2);
+        }
+
+        {
+            multi_span<int, 5> av = arr;
+            CHECK((av.last<0>().bounds() == static_bounds<0>()));
+            CHECK(av.last<0>().length() == 0);
+            CHECK(av.last(0).length() == 0);
+        }
+
+        {
+            multi_span<int, 5> av = arr;
+            CHECK((av.last<5>().bounds() == static_bounds<5>()));
+            CHECK(av.last<5>().length() == 5);
+            CHECK(av.last(5).length() == 5);
+        }
+
+        {
+            multi_span<int, 5> av = arr;
+#ifdef CONFIRM_COMPILATION_ERRORS
+            CHECK((av.last<6>().bounds() == static_bounds<6>()));
+            CHECK(av.last<6>().length() == 6);
+#endif
+            CHECK_THROW(av.last(6).length(), fail_fast);
+        }
+
+        {
+            multi_span<int, dynamic_range> av;
+            CHECK((av.last<0>().bounds() == static_bounds<0>()));
+            CHECK(av.last<0>().length() == 0);
+            CHECK(av.last(0).length() == 0);
+        }
+    }
+
+    TEST(subspan)
+    {
+        int arr[5] = {1, 2, 3, 4, 5};
+
+        {
+            multi_span<int, 5> av = arr;
+            CHECK((av.subspan<2, 2>().bounds() == static_bounds<2>()));
+            CHECK((av.subspan<2, 2>().length() == 2));
+            CHECK(av.subspan(2, 2).length() == 2);
+            CHECK(av.subspan(2, 3).length() == 3);
+        }
+
+        {
+            multi_span<int, 5> av = arr;
+            CHECK((av.subspan<0, 0>().bounds() == static_bounds<0>()));
+            CHECK((av.subspan<0, 0>().length() == 0));
+            CHECK(av.subspan(0, 0).length() == 0);
+        }
+
+        {
+            multi_span<int, 5> av = arr;
+            CHECK((av.subspan<0, 5>().bounds() == static_bounds<5>()));
+            CHECK((av.subspan<0, 5>().length() == 5));
+            CHECK(av.subspan(0, 5).length() == 5);
+            CHECK_THROW(av.subspan(0, 6).length(), fail_fast);
+            CHECK_THROW(av.subspan(1, 5).length(), fail_fast);
+        }
+
+        {
+            multi_span<int, 5> av = arr;
+            CHECK((av.subspan<5, 0>().bounds() == static_bounds<0>()));
+            CHECK((av.subspan<5, 0>().length() == 0));
+            CHECK(av.subspan(5, 0).length() == 0);
+            CHECK_THROW(av.subspan(6, 0).length(), fail_fast);
+        }
+
+        {
+            multi_span<int, dynamic_range> av;
+            CHECK((av.subspan<0, 0>().bounds() == static_bounds<0>()));
+            CHECK((av.subspan<0, 0>().length() == 0));
+            CHECK(av.subspan(0, 0).length() == 0);
+            CHECK_THROW((av.subspan<1, 0>().length()), fail_fast);
+        }
+
+        {
+            multi_span<int> av;
+            CHECK(av.subspan(0).length() == 0);
+            CHECK_THROW(av.subspan(1).length(), fail_fast);
+        }
+
+        {
+            multi_span<int> av = arr;
+            CHECK(av.subspan(0).length() == 5);
+            CHECK(av.subspan(1).length() == 4);
+            CHECK(av.subspan(4).length() == 1);
+            CHECK(av.subspan(5).length() == 0);
+            CHECK_THROW(av.subspan(6).length(), fail_fast);
+            auto av2 = av.subspan(1);
+            for (int i = 0; i < 4; ++i) CHECK(av2[i] == i + 2);
+        }
+
+        {
+            multi_span<int, 5> av = arr;
+            CHECK(av.subspan(0).length() == 5);
+            CHECK(av.subspan(1).length() == 4);
+            CHECK(av.subspan(4).length() == 1);
+            CHECK(av.subspan(5).length() == 0);
+            CHECK_THROW(av.subspan(6).length(), fail_fast);
+            auto av2 = av.subspan(1);
+            for (int i = 0; i < 4; ++i) CHECK(av2[i] == i + 2);
+        }
+    }
+
+    TEST(rank)
+    {
+        int arr[2] = {1, 2};
+
+        {
+            multi_span<int> s;
+            CHECK(s.rank() == 1);
+        }
+
+        {
+            multi_span<int, 2> s = arr;
+            CHECK(s.rank() == 1);
+        }
+
+        int arr2d[1][1] = {};
+        {
+            multi_span<int, 1, 1> s = arr2d;
+            CHECK(s.rank() == 2);
+        }
+    }
+
+    TEST(extent)
+    {
+        {
+            multi_span<int> s;
+            CHECK(s.extent() == 0);
+            CHECK(s.extent(0) == 0);
+            CHECK_THROW(s.extent(1), fail_fast);
+#ifdef CONFIRM_COMPILATION_ERRORS
+            CHECK(s.extent<1>() == 0);
+#endif
+        }
+
+        {
+            multi_span<int, 0> s;
+            CHECK(s.extent() == 0);
+            CHECK(s.extent(0) == 0);
+            CHECK_THROW(s.extent(1), fail_fast);
+        }
+
+        {
+            int arr2d[1][2] = {};
+
+            multi_span<int, 1, 2> s = arr2d;
+            CHECK(s.extent() == 1);
+            CHECK(s.extent<0>() == 1);
+            CHECK(s.extent<1>() == 2);
+            CHECK(s.extent(0) == 1);
+            CHECK(s.extent(1) == 2);
+            CHECK_THROW(s.extent(3), fail_fast);
+        }
+
+        {
+            int arr2d[1][2] = {};
+
+            multi_span<int, 0, 2> s = arr2d;
+            CHECK(s.extent() == 0);
+            CHECK(s.extent<0>() == 0);
+            CHECK(s.extent<1>() == 2);
+            CHECK(s.extent(0) == 0);
+            CHECK(s.extent(1) == 2);
+            CHECK_THROW(s.extent(3), fail_fast);
+        }
+    }
+
+    TEST(operator_function_call)
+    {
+        int arr[4] = {1, 2, 3, 4};
+
+        {
+            multi_span<int> s = arr;
+            CHECK(s(0) == 1);
+            CHECK_THROW(s(5), fail_fast);
+        }
+
+        int arr2d[2][3] = {1, 2, 3, 4, 5, 6};
+
+        {
+            multi_span<int, 2, 3> s = arr2d;
+            CHECK(s(0, 0) == 1);
+            CHECK(s(1, 2) == 6);
+        }
+    }
+
+    TEST(comparison_operators)
+    {
+        {
+            int arr[10][2];
+            auto s1 = as_multi_span(arr);
+            multi_span<const int, dynamic_range, 2> s2 = s1;
+
+            CHECK(s1 == s2);
+
+            multi_span<int, 20> s3 = as_multi_span(s1, dim(20));
+            CHECK(s3 == s2 && s3 == s1);
+        }
+
+        {
+            multi_span<int> s1 = nullptr;
+            multi_span<int> s2 = nullptr;
+            CHECK(s1 == s2);
+            CHECK(!(s1 != s2));
+            CHECK(!(s1 < s2));
+            CHECK(s1 <= s2);
+            CHECK(!(s1 > s2));
+            CHECK(s1 >= s2);
+            CHECK(s2 == s1);
+            CHECK(!(s2 != s1));
+            CHECK(!(s2 < s1));
+            CHECK(s2 <= s1);
+            CHECK(!(s2 > s1));
+            CHECK(s2 >= s1);
+        }
+
+        {
+            int arr[] = {2, 1}; // bigger
+
+            multi_span<int> s1 = nullptr;
+            multi_span<int> s2 = arr;
+
+            CHECK(s1 != s2);
+            CHECK(s2 != s1);
+            CHECK(!(s1 == s2));
+            CHECK(!(s2 == s1));
+            CHECK(s1 < s2);
+            CHECK(!(s2 < s1));
+            CHECK(s1 <= s2);
+            CHECK(!(s2 <= s1));
+            CHECK(s2 > s1);
+            CHECK(!(s1 > s2));
+            CHECK(s2 >= s1);
+            CHECK(!(s1 >= s2));
+        }
+
+        {
+            int arr1[] = {1, 2};
+            int arr2[] = {1, 2};
+            multi_span<int> s1 = arr1;
+            multi_span<int> s2 = arr2;
+
+            CHECK(s1 == s2);
+            CHECK(!(s1 != s2));
+            CHECK(!(s1 < s2));
+            CHECK(s1 <= s2);
+            CHECK(!(s1 > s2));
+            CHECK(s1 >= s2);
+            CHECK(s2 == s1);
+            CHECK(!(s2 != s1));
+            CHECK(!(s2 < s1));
+            CHECK(s2 <= s1);
+            CHECK(!(s2 > s1));
+            CHECK(s2 >= s1);
+        }
+
+        {
+            int arr[] = {1, 2, 3};
+
+            multi_span<int> s1 = {&arr[0], 2}; // shorter
+            multi_span<int> s2 = arr; // longer
+
+            CHECK(s1 != s2);
+            CHECK(s2 != s1);
+            CHECK(!(s1 == s2));
+            CHECK(!(s2 == s1));
+            CHECK(s1 < s2);
+            CHECK(!(s2 < s1));
+            CHECK(s1 <= s2);
+            CHECK(!(s2 <= s1));
+            CHECK(s2 > s1);
+            CHECK(!(s1 > s2));
+            CHECK(s2 >= s1);
+            CHECK(!(s1 >= s2));
+        }
+
+        {
+            int arr1[] = {1, 2}; // smaller
+            int arr2[] = {2, 1}; // bigger
+
+            multi_span<int> s1 = arr1;
+            multi_span<int> s2 = arr2;
+
+            CHECK(s1 != s2);
+            CHECK(s2 != s1);
+            CHECK(!(s1 == s2));
+            CHECK(!(s2 == s1));
+            CHECK(s1 < s2);
+            CHECK(!(s2 < s1));
+            CHECK(s1 <= s2);
+            CHECK(!(s2 <= s1));
+            CHECK(s2 > s1);
+            CHECK(!(s1 > s2));
+            CHECK(s2 >= s1);
+            CHECK(!(s1 >= s2));
+        }
+    }
+
+    TEST(basics)
+    {
+        auto ptr = as_multi_span(new int[10], 10);
+        fill(ptr.begin(), ptr.end(), 99);
+        for (int num : ptr) {
+            CHECK(num == 99);
+        }
+
+        delete[] ptr.data();
+    }
+
+    TEST(bounds_checks)
+    {
+        int arr[10][2];
+        auto av = as_multi_span(arr);
+
+        fill(begin(av), end(av), 0);
+
+        av[2][0] = 1;
+        av[1][1] = 3;
+
+        // out of bounds
+        CHECK_THROW(av[1][3] = 3, fail_fast);
+        CHECK_THROW((av[{1, 3}] = 3), fail_fast);
+
+        CHECK_THROW(av[10][2], fail_fast);
+        CHECK_THROW((av[{10, 2}]), fail_fast);
+
+        CHECK_THROW(av[-1][0], fail_fast);
+        CHECK_THROW((av[{-1, 0}]), fail_fast);
+
+        CHECK_THROW(av[0][-1], fail_fast);
+        CHECK_THROW((av[{0, -1}]), fail_fast);
+    }
+
+    void overloaded_func(multi_span<const int, dynamic_range, 3, 5> exp, int expected_value)
+    {
+        for (auto val : exp) {
+            CHECK(val == expected_value);
+        }
+    }
+
+    void overloaded_func(multi_span<const char, dynamic_range, 3, 5> exp, char expected_value)
+    {
+        for (auto val : exp) {
+            CHECK(val == expected_value);
+        }
+    }
+
+    void fixed_func(multi_span<int, 3, 3, 5> exp, int expected_value)
+    {
+        for (auto val : exp) {
+            CHECK(val == expected_value);
+        }
+    }
+
+    TEST(span_parameter_test)
+    {
+        auto data = new int[4][3][5];
+
+        auto av = as_multi_span(data, 4);
+
+        CHECK(av.size() == 60);
+
+        fill(av.begin(), av.end(), 34);
+
+        int count = 0;
+        for_each(av.rbegin(), av.rend(), [&](int val) { count += val; });
+        CHECK(count == 34 * 60);
+        overloaded_func(av, 34);
+
+        overloaded_func(as_multi_span(av, dim(4), dim(3), dim(5)), 34);
+
+        // fixed_func(av, 34);
+        delete[] data;
+    }
+
+    TEST(md_access)
+    {
+        auto width = 5, height = 20;
+
+        auto imgSize = width * height;
+        auto image_ptr = new int[imgSize][3];
+
+        // size check will be done
+        auto image_view =
+            as_multi_span(as_multi_span(image_ptr, imgSize), dim(height), dim(width), dim<3>());
+
+        iota(image_view.begin(), image_view.end(), 1);
+
+        int expected = 0;
+        for (auto i = 0; i < height; i++) {
+            for (auto j = 0; j < width; j++) {
+                CHECK(expected + 1 == image_view[i][j][0]);
+                CHECK(expected + 2 == image_view[i][j][1]);
+                CHECK(expected + 3 == image_view[i][j][2]);
+
+                auto val = image_view[{i, j, 0}];
+                CHECK(expected + 1 == val);
+                val = image_view[{i, j, 1}];
+                CHECK(expected + 2 == val);
+                val = image_view[{i, j, 2}];
+                CHECK(expected + 3 == val);
+
+                expected += 3;
+            }
+        }
+    }
+
+    TEST(as_multi_span)
+    {
+        {
+            int* arr = new int[150];
+
+            auto av = as_multi_span(arr, dim<10>(), dim(3), dim<5>());
+
+            fill(av.begin(), av.end(), 24);
+            overloaded_func(av, 24);
+
+            delete[] arr;
+
+            array<int, 15> stdarr{0};
+            auto av2 = as_multi_span(stdarr);
+            overloaded_func(as_multi_span(av2, dim(1), dim<3>(), dim<5>()), 0);
+
+            string str = "ttttttttttttttt"; // size = 15
+            auto t = str.data();
+            (void) t;
+            auto av3 = as_multi_span(str);
+            overloaded_func(as_multi_span(av3, dim(1), dim<3>(), dim<5>()), 't');
+        }
+
+        {
+            string str;
+            multi_span<char> strspan = as_multi_span(str);
+            (void) strspan;
+            const string cstr;
+            multi_span<const char> cstrspan = as_multi_span(cstr);
+            (void) cstrspan;
+        }
+
+        {
+            int a[3][4][5];
+            auto av = as_multi_span(a);
+            const int(*b)[4][5];
+            b = a;
+            auto bv = as_multi_span(b, 3);
+
+            CHECK(av == bv);
+
+            const std::array<double, 3> arr = {0.0, 0.0, 0.0};
+            auto cv = as_multi_span(arr);
+            (void) cv;
+
+            vector<float> vec(3);
+            auto dv = as_multi_span(vec);
+            (void) dv;
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+            auto dv2 = as_multi_span(std::move(vec));
+#endif
+        }
+    }
+
+    TEST(empty_spans)
+    {
+        {
+            multi_span<int, 0> empty_av(nullptr);
+
+            CHECK(empty_av.bounds().index_bounds() == index<1>{0});
+            CHECK_THROW(empty_av[0], fail_fast);
+            CHECK_THROW(empty_av.begin()[0], fail_fast);
+            CHECK_THROW(empty_av.cbegin()[0], fail_fast);
+            for (auto& v : empty_av) {
+                (void) v;
+                CHECK(false);
+            }
+        }
+
+        {
+            multi_span<int> empty_av = {};
+            CHECK(empty_av.bounds().index_bounds() == index<1>{0});
+            CHECK_THROW(empty_av[0], fail_fast);
+            CHECK_THROW(empty_av.begin()[0], fail_fast);
+            CHECK_THROW(empty_av.cbegin()[0], fail_fast);
+            for (auto& v : empty_av) {
+                (void) v;
+                CHECK(false);
+            }
+        }
+    }
+
+    TEST(index_constructor)
+    {
+        auto arr = new int[8];
+        for (int i = 0; i < 4; ++i) {
+            arr[2 * i] = 4 + i;
+            arr[2 * i + 1] = i;
+        }
+
+        multi_span<int, dynamic_range> av(arr, 8);
+
+        ptrdiff_t a[1] = {0};
+        index<1> i = a;
+
+        CHECK(av[i] == 4);
+
+        auto av2 = as_multi_span(av, dim<4>(), dim(2));
+        ptrdiff_t a2[2] = {0, 1};
+        index<2> i2 = a2;
+
+        CHECK(av2[i2] == 0);
+        CHECK(av2[0][i] == 4);
+
+        delete[] arr;
+    }
+
+    TEST(index_constructors)
+    {
+        {
+            // components of the same type
+            index<3> i1(0, 1, 2);
+            CHECK(i1[0] == 0);
+
+            // components of different types
+            size_t c0 = 0;
+            size_t c1 = 1;
+            index<3> i2(c0, c1, 2);
+            CHECK(i2[0] == 0);
+
+            // from array
+            index<3> i3 = {0, 1, 2};
+            CHECK(i3[0] == 0);
+
+            // from other index of the same size type
+            index<3> i4 = i3;
+            CHECK(i4[0] == 0);
+
+            // default
+            index<3> i7;
+            CHECK(i7[0] == 0);
+
+            // default
+            index<3> i9 = {};
+            CHECK(i9[0] == 0);
+        }
+
+        {
+            // components of the same type
+            index<1> i1(0);
+            CHECK(i1[0] == 0);
+
+            // components of different types
+            size_t c0 = 0;
+            index<1> i2(c0);
+            CHECK(i2[0] == 0);
+
+            // from array
+            index<1> i3 = {0};
+            CHECK(i3[0] == 0);
+
+            // from int
+            index<1> i4 = 0;
+            CHECK(i4[0] == 0);
+
+            // from other index of the same size type
+            index<1> i5 = i3;
+            CHECK(i5[0] == 0);
+
+            // default
+            index<1> i8;
+            CHECK(i8[0] == 0);
+
+            // default
+            index<1> i9 = {};
+            CHECK(i9[0] == 0);
+        }
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            index<3> i1(0, 1);
+            index<3> i2(0, 1, 2, 3);
+            index<3> i3 = {0};
+            index<3> i4 = {0, 1, 2, 3};
+            index<1> i5 = {0, 1};
+        }
+#endif
+    }
+
+    TEST(index_operations)
+    {
+        ptrdiff_t a[3] = {0, 1, 2};
+        ptrdiff_t b[3] = {3, 4, 5};
+        index<3> i = a;
+        index<3> j = b;
+
+        CHECK(i[0] == 0);
+        CHECK(i[1] == 1);
+        CHECK(i[2] == 2);
+
+        {
+            index<3> k = i + j;
+
+            CHECK(i[0] == 0);
+            CHECK(i[1] == 1);
+            CHECK(i[2] == 2);
+            CHECK(k[0] == 3);
+            CHECK(k[1] == 5);
+            CHECK(k[2] == 7);
+        }
+
+        {
+            index<3> k = i * 3;
+
+            CHECK(i[0] == 0);
+            CHECK(i[1] == 1);
+            CHECK(i[2] == 2);
+            CHECK(k[0] == 0);
+            CHECK(k[1] == 3);
+            CHECK(k[2] == 6);
+        }
+
+        {
+            index<3> k = 3 * i;
+
+            CHECK(i[0] == 0);
+            CHECK(i[1] == 1);
+            CHECK(i[2] == 2);
+            CHECK(k[0] == 0);
+            CHECK(k[1] == 3);
+            CHECK(k[2] == 6);
+        }
+
+        {
+            index<2> k = details::shift_left(i);
+
+            CHECK(i[0] == 0);
+            CHECK(i[1] == 1);
+            CHECK(i[2] == 2);
+            CHECK(k[0] == 1);
+            CHECK(k[1] == 2);
+        }
+    }
+
+    void iterate_second_column(multi_span<int, dynamic_range, dynamic_range> av)
+    {
+        auto length = av.size() / 2;
+
+        // view to the second column
+        auto section = av.section({0, 1}, {length, 1});
+
+        CHECK(section.size() == length);
+        for (auto i = 0; i < section.size(); ++i) {
+            CHECK(section[i][0] == av[i][1]);
+        }
+
+        for (auto i = 0; i < section.size(); ++i) {
+            auto idx = index<2>{i, 0}; // avoid braces inside the CHECK macro
+            CHECK(section[idx] == av[i][1]);
+        }
+
+        CHECK(section.bounds().index_bounds()[0] == length);
+        CHECK(section.bounds().index_bounds()[1] == 1);
+        for (auto i = 0; i < section.bounds().index_bounds()[0]; ++i) {
+            for (auto j = 0; j < section.bounds().index_bounds()[1]; ++j) {
+                auto idx = index<2>{i, j}; // avoid braces inside the CHECK macro
+                CHECK(section[idx] == av[i][1]);
+            }
+        }
+
+        size_t check_sum = 0;
+        for (auto i = 0; i < length; ++i) {
+            check_sum += av[i][1];
+        }
+
+        {
+            auto idx = 0;
+            size_t sum = 0;
+            for (auto num : section) {
+                CHECK(num == av[idx][1]);
+                sum += num;
+                idx++;
+            }
+
+            CHECK(sum == check_sum);
+        }
+        {
+            size_t idx = length - 1;
+            size_t sum = 0;
+            for (auto iter = section.rbegin(); iter != section.rend(); ++iter) {
+                CHECK(*iter == av[idx][1]);
+                sum += *iter;
+                idx--;
+            }
+
+            CHECK(sum == check_sum);
+        }
+    }
+
+    TEST(span_section_iteration)
+    {
+        int arr[4][2] = {{4, 0}, {5, 1}, {6, 2}, {7, 3}};
+
+        // static bounds
+        {
+            multi_span<int, 4, 2> av = arr;
+            iterate_second_column(av);
+        }
+        // first bound is dynamic
+        {
+            multi_span<int, dynamic_range, 2> av = arr;
+            iterate_second_column(av);
+        }
+        // second bound is dynamic
+        {
+            multi_span<int, 4, dynamic_range> av = arr;
+            iterate_second_column(av);
+        }
+        // both bounds are dynamic
+        {
+            multi_span<int, dynamic_range, dynamic_range> av = arr;
+            iterate_second_column(av);
+        }
+    }
+
+    TEST(dynamic_span_section_iteration)
+    {
+        auto height = 4, width = 2;
+        auto size = height * width;
+
+        auto arr = new int[size];
+        for (auto i = 0; i < size; ++i) {
+            arr[i] = i;
+        }
+
+        auto av = as_multi_span(arr, size);
+
+        // first bound is dynamic
+        {
+            multi_span<int, dynamic_range, 2> av2 = as_multi_span(av, dim(height), dim(width));
+            iterate_second_column(av2);
+        }
+        // second bound is dynamic
+        {
+            multi_span<int, 4, dynamic_range> av2 = as_multi_span(av, dim(height), dim(width));
+            iterate_second_column(av2);
+        }
+        // both bounds are dynamic
+        {
+            multi_span<int, dynamic_range, dynamic_range> av2 = as_multi_span(av, dim(height), dim(width));
+            iterate_second_column(av2);
+        }
+
+        delete[] arr;
+    }
+
+    TEST(span_structure_size)
+    {
+        double(*arr)[3][4] = new double[100][3][4];
+        multi_span<double, dynamic_range, 3, 4> av1(arr, 10);
+
+        struct EffectiveStructure
+        {
+            double* v1;
+            ptrdiff_t v2;
+        };
+        CHECK(sizeof(av1) == sizeof(EffectiveStructure));
+
+        CHECK_THROW(av1[10][3][4], fail_fast);
+
+        multi_span<const double, dynamic_range, 6, 4> av2 = as_multi_span(av1, dim(5), dim<6>(), dim<4>());
+        (void) av2;
+    }
+
+    TEST(fixed_size_conversions)
+    {
+        int arr[] = {1, 2, 3, 4};
+
+        // converting to an multi_span from an equal size array is ok
+        multi_span<int, 4> av4 = arr;
+        CHECK(av4.length() == 4);
+
+        // converting to dynamic_range a_v is always ok
+        {
+            multi_span<int, dynamic_range> av = av4;
+            (void) av;
+        }
+        {
+            multi_span<int, dynamic_range> av = arr;
+            (void) av;
+        }
+
+// initialization or assignment to static multi_span that REDUCES size is NOT ok
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            multi_span<int, 2> av2 = arr;
+        }
+        {
+            multi_span<int, 2> av2 = av4;
+        }
+#endif
+
+        {
+            multi_span<int, dynamic_range> av = arr;
+            multi_span<int, 2> av2 = av;
+            (void) av2;
+        }
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            multi_span<int, dynamic_range> av = arr;
+            multi_span<int, 2, 1> av2 = av.as_multi_span(dim<2>(), dim<2>());
+        }
+#endif
+
+        {
+            multi_span<int, dynamic_range> av = arr;
+            multi_span<int, 2, 1> av2 = as_multi_span(av, dim(2), dim(2));
+            auto workaround_macro = [&]() { return av2[{1, 0}] == 2; };
+            CHECK(workaround_macro());
+        }
+
+        // but doing so explicitly is ok
+
+        // you can convert statically
+        {
+            multi_span<int, 2> av2 = {arr, 2};
+            (void) av2;
+        }
+        {
+            multi_span<int, 1> av2 = av4.first<1>();
+            (void) av2;
+        }
+
+        // ...or dynamically
+        {
+            // NB: implicit conversion to multi_span<int,2> from multi_span<int,dynamic_range>
+            multi_span<int, 1> av2 = av4.first(1);
+            (void) av2;
+        }
+
+        // initialization or assignment to static multi_span that requires size INCREASE is not ok.
+        int arr2[2] = {1, 2};
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            multi_span<int, 4> av4 = arr2;
+        }
+        {
+            multi_span<int, 2> av2 = arr2;
+            multi_span<int, 4> av4 = av2;
+        }
+#endif
+        {
+            auto f = [&]() {
+                multi_span<int, 4> av9 = {arr2, 2};
+                (void) av9;
+            };
+            CHECK_THROW(f(), fail_fast);
+        }
+
+        // this should fail - we are trying to assign a small dynamic a_v to a fixed_size larger one
+        multi_span<int, dynamic_range> av = arr2;
+        auto f = [&]() {
+            multi_span<int, 4> av2 = av;
+            (void) av2;
+        };
+        CHECK_THROW(f(), fail_fast);
+    }
+
+    TEST(as_writeable_bytes)
+    {
+        int a[] = {1, 2, 3, 4};
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            // you should not be able to get writeable bytes for const objects
+            multi_span<const int, dynamic_range> av = a;
+            auto wav = av.as_writeable_bytes();
+#endif
+        }
+
+        {
+            multi_span<int, dynamic_range> av;
+            auto wav = as_writeable_bytes(av);
+            CHECK(wav.length() == av.length());
+            CHECK(wav.length() == 0);
+            CHECK(wav.size_bytes() == 0);
+        }
+
+        {
+            multi_span<int, dynamic_range> av = a;
+            auto wav = as_writeable_bytes(av);
+            CHECK(wav.data() == (byte*) &a[0]);
+            CHECK(wav.length() == sizeof(a));
+        }
+    }
+
+    TEST(iterator)
+    {
+        int a[] = {1, 2, 3, 4};
+
+        {
+            multi_span<int, dynamic_range> av = a;
+            auto wav = as_writeable_bytes(av);
+            for (auto& b : wav) {
+                b = byte(0);
+            }
+            for (size_t i = 0; i < 4; ++i) {
+                CHECK(a[i] == 0);
+            }
+        }
+
+        {
+            multi_span<int, dynamic_range> av = a;
+            for (auto& n : av) {
+                n = 1;
+            }
+            for (size_t i = 0; i < 4; ++i) {
+                CHECK(a[i] == 1);
+            }
+        }
+    }
+}
+
+int main(int, const char* []) { return UnitTest::RunAllTests(); }
diff --git a/tests/notnull_tests.cpp b/tests/notnull_tests.cpp
new file mode 100644
index 0000000..526b074
--- /dev/null
+++ b/tests/notnull_tests.cpp
@@ -0,0 +1,103 @@
+/////////////////////////////////////////////////////////////////////////////// 
+// 
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved. 
+// 
+// This code is licensed under the MIT License (MIT). 
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 
+// THE SOFTWARE. 
+// 
+///////////////////////////////////////////////////////////////////////////////
+
+#include <UnitTest++/UnitTest++.h> 
+#include <gsl/gsl>
+#include <vector>
+
+using namespace gsl;
+
+struct MyBase {};
+struct MyDerived : public MyBase {};
+struct Unrelated {};
+
+// stand-in for a user-defined ref-counted class
+template<typename T>
+struct RefCounted
+{
+    RefCounted(T* p) : p_(p) {}
+    operator T*() { return p_; }
+    T* p_;
+};
+
+SUITE(NotNullTests)
+{
+
+    bool helper(not_null<int*> p)
+    {
+        return *p == 12;
+    }
+
+    TEST(TestNotNullConstructors)
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        not_null<int*> p = nullptr; // yay...does not compile!
+        not_null<std::vector<char>*> p = 0; // yay...does not compile!
+        not_null<int*> p; // yay...does not compile!
+        std::unique_ptr<int> up = std::make_unique<int>(120);
+        not_null<int*> p = up;
+
+        // Forbid non-nullptr assignable types
+        not_null<std::vector<int>> f(std::vector<int>{1});
+        not_null<int> z(10);
+        not_null<std::vector<int>> y({1,2});
+#endif
+      int i = 12; 
+      auto rp = RefCounted<int>(&i);
+      not_null<int*> p(rp);
+      CHECK(p.get() == &i);
+
+      not_null<std::shared_ptr<int>> x(std::make_shared<int>(10)); // shared_ptr<int> is nullptr assignable
+    }
+
+    TEST(TestNotNullCasting)
+    {
+        MyBase base;
+	MyDerived derived;
+	Unrelated unrelated;
+	not_null<Unrelated*> u = &unrelated;
+        (void)u;
+	not_null<MyDerived*> p = &derived;
+        not_null<MyBase*> q = &base;
+	q = p; // allowed with heterogeneous copy ctor
+        CHECK(q == p);
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+	q = u; // no viable conversion possible between MyBase* and Unrelated*
+	p = q; // not possible to implicitly convert MyBase* to MyDerived*
+
+        not_null<Unrelated*> r = p;
+        not_null<Unrelated*> s = reinterpret_cast<Unrelated*>(p);
+#endif
+        not_null<Unrelated*> t = reinterpret_cast<Unrelated*>(p.get());
+        CHECK((void*)p.get() == (void*)t.get());
+    }
+
+    TEST(TestNotNullAssignment)
+    {
+        int i = 12;
+        not_null<int*> p = &i; 
+        CHECK(helper(p));
+
+        int* q = nullptr;
+        CHECK_THROW(p = q, fail_fast);
+    }
+}
+
+int main(int, const char *[])
+{
+    return UnitTest::RunAllTests();
+}
diff --git a/tests/owner_tests.cpp b/tests/owner_tests.cpp
new file mode 100644
index 0000000..6680981
--- /dev/null
+++ b/tests/owner_tests.cpp
@@ -0,0 +1,43 @@
+/////////////////////////////////////////////////////////////////////////////// 
+// 
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved. 
+// 
+// This code is licensed under the MIT License (MIT). 
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 
+// THE SOFTWARE. 
+// 
+///////////////////////////////////////////////////////////////////////////////
+
+#include <UnitTest++/UnitTest++.h> 
+#include <gsl/gsl>
+#include <functional>
+
+using namespace gsl;
+
+SUITE(owner_tests)
+{
+    void f(int* i)
+    {
+        *i += 1;
+    }
+
+    TEST(basic_test)
+    {
+        owner<int*> p = new int(120);
+        CHECK(*p == 120);
+        f(p);
+        CHECK(*p == 121);
+        delete p;
+    }
+}
+
+int main(int, const char *[])
+{
+    return UnitTest::RunAllTests();
+}
diff --git a/tests/span_tests.cpp b/tests/span_tests.cpp
new file mode 100644
index 0000000..35e6b03
--- /dev/null
+++ b/tests/span_tests.cpp
@@ -0,0 +1,1385 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <UnitTest++/UnitTest++.h>
+#include <gsl/span>
+
+#include <iostream>
+#include <list>
+#include <map>
+#include <memory>
+#include <string>
+#include <vector>
+#include <regex>
+
+using namespace std;
+using namespace gsl;
+
+namespace
+{
+struct BaseClass
+{
+};
+struct DerivedClass : BaseClass
+{
+};
+}
+
+SUITE(span_tests)
+{
+    TEST(default_constructor)
+    {
+        {
+            span<int> s;
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            span<const int> cs;
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+
+        {
+            span<int, 0> s;
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            span<const int, 0> cs;
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            span<int, 1> s;
+            CHECK(s.length() == 1 && s.data() == nullptr); // explains why it can't compile
+#endif
+        }
+
+        {
+            span<int> s{};
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            span<const int> cs{};
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+    }
+
+    TEST(size_optimization)
+    {
+        {
+            span<int> s;
+            CHECK(sizeof(s) == sizeof(int*) + sizeof(ptrdiff_t));
+        }
+
+        {
+            span<int, 0> s;
+            CHECK(sizeof(s) == sizeof(int*));
+        }
+    }
+
+    TEST(from_nullptr_constructor)
+    {
+        {
+            span<int> s = nullptr;
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            span<const int> cs = nullptr;
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+
+        {
+            span<int, 0> s = nullptr;
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            span<const int, 0> cs = nullptr;
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            span<int, 1> s = nullptr;
+            CHECK(s.length() == 1 && s.data() == nullptr); // explains why it can't compile
+#endif
+        }
+
+        {
+            span<int> s{nullptr};
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            span<const int> cs{nullptr};
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+
+        {
+            span<int*> s{nullptr};
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            span<const int*> cs{nullptr};
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+    }
+
+    TEST(from_nullptr_length_constructor)
+    {
+        {
+            span<int> s{nullptr, static_cast<span<int>::index_type>(0)};
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            span<const int> cs{nullptr, static_cast<span<int>::index_type>(0)};
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+
+        {
+            span<int, 0> s{nullptr, static_cast<span<int>::index_type>(0)};
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            span<const int, 0> cs{nullptr, static_cast<span<int>::index_type>(0)};
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+
+        {
+            auto workaround_macro = []() { span<int, 1> s{ nullptr, static_cast<span<int>::index_type>(0) }; };
+            CHECK_THROW(workaround_macro(), fail_fast); 
+        }
+
+        {
+            auto workaround_macro = []() { span<int> s{nullptr, 1}; };
+            CHECK_THROW(workaround_macro(), fail_fast);
+
+            auto const_workaround_macro = []() { span<const int> cs{nullptr, 1}; };
+            CHECK_THROW(const_workaround_macro(), fail_fast);
+        }
+
+        {
+            auto workaround_macro = []() { span<int, 0> s{nullptr, 1}; };
+            CHECK_THROW(workaround_macro(), fail_fast);
+
+            auto const_workaround_macro = []() { span<const int, 0> s{nullptr, 1}; };
+            CHECK_THROW(const_workaround_macro(), fail_fast);
+        }
+
+        {
+            span<int*> s{nullptr, static_cast<span<int>::index_type>(0)};
+            CHECK(s.length() == 0 && s.data() == nullptr);
+
+            span<const int*> cs{nullptr, static_cast<span<int>::index_type>(0)};
+            CHECK(cs.length() == 0 && cs.data() == nullptr);
+        }
+    }
+
+    TEST(from_pointer_length_constructor)
+    {
+        int arr[4] = {1, 2, 3, 4};
+
+        {
+            span<int> s{&arr[0], 2};
+            CHECK(s.length() == 2 && s.data() == &arr[0]);
+            CHECK(s[0] == 1 && s[1] == 2);
+        }
+
+        {
+            span<int, 2> s{&arr[0], 2};
+            CHECK(s.length() == 2 && s.data() == &arr[0]);
+            CHECK(s[0] == 1 && s[1] == 2);
+        }
+
+        {
+            int* p = nullptr;
+            span<int> s{p, static_cast<span<int>::index_type>(0)};
+            CHECK(s.length() == 0 && s.data() == nullptr);
+        }
+
+        {
+            int* p = nullptr;
+            auto workaround_macro = [=]() { span<int> s{p, 2}; };
+            CHECK_THROW(workaround_macro(), fail_fast);
+        }
+    }
+
+    TEST(from_pointer_pointer_constructor)
+    {
+        int arr[4] = {1, 2, 3, 4};
+
+        {
+            span<int> s{&arr[0], &arr[2]};
+            CHECK(s.length() == 2 && s.data() == &arr[0]);
+            CHECK(s[0] == 1 && s[1] == 2);
+        }
+
+        {
+            span<int, 2> s{&arr[0], &arr[2]};
+            CHECK(s.length() == 2 && s.data() == &arr[0]);
+            CHECK(s[0] == 1 && s[1] == 2);
+        }
+
+        {
+            span<int> s{&arr[0], &arr[0]};
+            CHECK(s.length() == 0 && s.data() == &arr[0]);
+        }
+
+        {
+            span<int, 0> s{&arr[0], &arr[0]};
+            CHECK(s.length() == 0 && s.data() == &arr[0]);
+        }
+
+        // this will fail the std::distance() precondition, which asserts on MSVC debug builds
+        //{
+        //    auto workaround_macro = [&]() { span<int> s{&arr[1], &arr[0]}; };
+        //    CHECK_THROW(workaround_macro(), fail_fast);
+        //}
+
+        // this will fail the std::distance() precondition, which asserts on MSVC debug builds
+        //{
+        //    int* p = nullptr;
+        //    auto workaround_macro = [&]() { span<int> s{&arr[0], p}; };
+        //    CHECK_THROW(workaround_macro(), fail_fast);
+        //}
+
+        {
+            int* p = nullptr;
+            span<int> s{ p, p };
+            CHECK(s.length() == 0 && s.data() == nullptr);
+        }
+
+        {
+            int* p = nullptr;
+            span<int, 0> s{ p, p };
+            CHECK(s.length() == 0 && s.data() == nullptr);
+        }
+
+        // this will fail the std::distance() precondition, which asserts on MSVC debug builds
+        //{
+        //    int* p = nullptr;
+        //    auto workaround_macro = [&]() { span<int> s{&arr[0], p}; };
+        //    CHECK_THROW(workaround_macro(), fail_fast);
+        //}
+    }
+
+    TEST(from_array_constructor)
+    {
+        int arr[5] = {1, 2, 3, 4, 5};
+
+        {
+            span<int> s{arr};
+            CHECK(s.length() == 5 && s.data() == &arr[0]);
+        }
+
+        {
+            span<int, 5> s{arr};
+            CHECK(s.length() == 5 && s.data() == &arr[0]);
+        }
+
+        int arr2d[2][3] = { 1, 2, 3, 4, 5, 6 };
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            span<int, 6> s{arr};
+        }
+
+        {
+            span<int, 0> s{arr};
+            CHECK(s.length() == 0 && s.data() == &arr[0]);
+        }
+
+        {
+            span<int> s{arr2d};
+            CHECK(s.length() == 6 && s.data() == &arr2d[0][0]);
+            CHECK(s[0] == 1 && s[5] == 6);
+        }
+
+        {
+            span<int, 0> s{arr2d};
+            CHECK(s.length() == 0 && s.data() == &arr2d[0][0]);
+        }
+
+        {
+            span<int, 6> s{ arr2d };
+        }
+#endif
+        {
+            span<int[3]> s{ &(arr2d[0]), 1 };
+            CHECK(s.length() == 1 && s.data() == &arr2d[0]);
+        }
+
+        int arr3d[2][3][2] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            span<int> s{arr3d};
+            CHECK(s.length() == 12 && s.data() == &arr3d[0][0][0]);
+            CHECK(s[0] == 1 && s[11] == 12);
+        }
+
+        {
+            span<int, 0> s{arr3d};
+            CHECK(s.length() == 0 && s.data() == &arr3d[0][0][0]);
+        }
+
+        {
+            span<int, 11> s{arr3d};
+        }
+
+        {
+            span<int, 12> s{arr3d};
+            CHECK(s.length() == 12 && s.data() == &arr3d[0][0][0]);
+            CHECK(s[0] == 1 && s[5] == 6);
+        }
+#endif
+        {
+            span<int[3][2]> s{&arr3d[0], 1};
+            CHECK(s.length() == 1 && s.data() == &arr3d[0]);
+        }
+    }
+
+    TEST(from_dynamic_array_constructor)
+    {
+        double(*arr)[3][4] = new double[100][3][4];
+
+        {
+            span<double> s(&arr[0][0][0], 10);
+            CHECK(s.length() == 10 && s.data() == &arr[0][0][0]);
+        }
+
+        delete[] arr;
+    }
+
+    TEST(from_std_array_constructor)
+    {
+        std::array<int, 4> arr = {1, 2, 3, 4};
+
+        {
+            span<int> s{arr};
+            CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
+
+            span<const int> cs{arr};
+            CHECK(cs.size() == narrow_cast<ptrdiff_t>(arr.size()) && cs.data() == arr.data());
+        }
+
+        {
+            span<int, 4> s{arr};
+            CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
+
+            span<const int, 4> cs{arr};
+            CHECK(cs.size() == narrow_cast<ptrdiff_t>(arr.size()) && cs.data() == arr.data());
+        }
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            span<int, 2> s{arr};
+            CHECK(s.size() == 2 && s.data() == arr.data());
+
+            span<const int, 2> cs{arr};
+            CHECK(cs.size() == 2 && cs.data() == arr.data());
+        }
+
+        {
+            span<int, 0> s{arr};
+            CHECK(s.size() == 0 && s.data() == arr.data());
+
+            span<const int, 0> cs{arr};
+            CHECK(cs.size() == 0 && cs.data() == arr.data());
+        }
+
+        {
+            span<int, 5> s{arr};
+        }
+
+        {
+            auto get_an_array = []()->std::array<int, 4> { return{1, 2, 3, 4}; };
+            auto take_a_span = [](span<int> s) { static_cast<void>(s); };
+            // try to take a temporary std::array
+            take_a_span(get_an_array());
+        }
+#endif
+
+        {
+            auto get_an_array = []() -> std::array<int, 4> { return { 1, 2, 3, 4 }; };
+            auto take_a_span = [](span<const int> s) { static_cast<void>(s); };
+            // try to take a temporary std::array
+            take_a_span(get_an_array());
+        }
+    }
+
+    TEST(from_const_std_array_constructor)
+    {
+        const std::array<int, 4> arr = {1, 2, 3, 4};
+
+        {
+            span<const int> s{arr};
+            CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
+        }
+
+        {
+            span<const int, 4> s{arr};
+            CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
+        }
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            span<const int, 2> s{arr};
+            CHECK(s.size() == 2 && s.data() == arr.data());
+        }
+
+        {
+            span<const int, 0> s{arr};
+            CHECK(s.size() == 0 && s.data() == arr.data());
+        }
+
+        {
+            span<const int, 5> s{arr};
+        }
+#endif
+
+        {
+            auto get_an_array = []() -> const std::array<int, 4> { return {1, 2, 3, 4}; };
+            auto take_a_span = [](span<const int> s) { static_cast<void>(s); };
+            // try to take a temporary std::array
+            take_a_span(get_an_array());
+        }
+    }
+
+    TEST(from_std_array_const_constructor)
+    {
+        std::array<const int, 4> arr = {1, 2, 3, 4};
+
+        {
+            span<const int> s{arr};
+            CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
+        }
+
+        {
+            span<const int, 4> s{arr};
+            CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
+        }
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            span<const int, 2> s{arr};
+            CHECK(s.size() == 2 && s.data() == arr.data());
+        }
+
+        {
+            span<const int, 0> s{arr};
+            CHECK(s.size() == 0 && s.data() == arr.data());
+        }
+
+        {
+            span<const int, 5> s{arr};
+        }
+
+        {
+            span<int, 4> s{arr};
+        }
+#endif
+    }
+
+    TEST(from_container_constructor)
+    {
+        std::vector<int> v = {1, 2, 3};
+        const std::vector<int> cv = v;
+
+        {
+            span<int> s{v};
+            CHECK(s.size() == narrow_cast<std::ptrdiff_t>(v.size()) && s.data() == v.data());
+
+            span<const int> cs{v};
+            CHECK(cs.size() == narrow_cast<std::ptrdiff_t>(v.size()) && cs.data() == v.data());
+        }
+
+        std::string str = "hello";
+        const std::string cstr = "hello";
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            span<char> s{str};
+            CHECK(s.size() == narrow_cast<std::ptrdiff_t>(str.size()) && s.data() == str.data());
+#endif
+            span<const char> cs{str};
+            CHECK(cs.size() == narrow_cast<std::ptrdiff_t>(str.size()) && cs.data() == str.data());
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            span<char> s{cstr};
+#endif                                                          
+            span<const char> cs{cstr};
+            CHECK(cs.size() == narrow_cast<std::ptrdiff_t>(cstr.size()) &&
+                  cs.data() == cstr.data());
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            auto get_temp_vector = []() -> std::vector<int> { return {}; };
+            auto use_span = [](span<int> s) { static_cast<void>(s); };
+            use_span(get_temp_vector());
+#endif                      
+        }
+
+        {
+            auto get_temp_vector = []() -> std::vector<int> { return{}; };
+            auto use_span = [](span<const int> s) { static_cast<void>(s); };
+            use_span(get_temp_vector());
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            auto get_temp_string = []() -> std::string { return{}; };
+            auto use_span = [](span<char> s) { static_cast<void>(s); };
+            use_span(get_temp_string());
+#endif                         
+        }
+
+        {
+            auto get_temp_string = []() -> std::string { return {}; };
+            auto use_span = [](span<const char> s) { static_cast<void>(s); };
+            use_span(get_temp_string());
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            auto get_temp_vector = []() -> const std::vector<int> { return {}; };
+            auto use_span = [](span<const char> s) { static_cast<void>(s); };
+            use_span(get_temp_vector());
+#endif
+        }
+
+        {
+            auto get_temp_string = []() -> const std::string { return {}; };
+            auto use_span = [](span<const char> s) { static_cast<void>(s); };
+            use_span(get_temp_string());
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            std::map<int, int> m;
+            span<int> s{m};
+#endif
+        }
+    }
+
+    TEST(from_convertible_span_constructor)
+    {
+        {
+            span<DerivedClass> avd;
+            span<const DerivedClass> avcd = avd;
+            static_cast<void>(avcd);
+        }
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            span<DerivedClass> avd;
+            span<BaseClass> avb = avd;
+            static_cast<void>(avb);
+#endif
+        }
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            span<int> s;
+            span<unsigned int> s2 = s;
+            static_cast<void>(s2);
+        }
+
+        {
+            span<int> s;
+            span<const unsigned int> s2 = s;
+            static_cast<void>(s2);
+        }
+
+        {
+            span<int> s;
+            span<short> s2 = s;
+            static_cast<void>(s2);
+        }
+#endif
+    }
+
+    TEST(copy_move_and_assignment)
+    {
+        span<int> s1;
+        CHECK(s1.empty());
+
+        int arr[] = {3, 4, 5};
+
+        span<const int> s2 = arr;
+        CHECK(s2.length() == 3 && s2.data() == &arr[0]);
+
+        s2 = s1;
+        CHECK(s2.empty());
+
+        auto get_temp_span = [&]() -> span<int> { return {&arr[1], 2}; };
+        auto use_span = [&](span<const int> s) { CHECK(s.length() == 2 && s.data() == &arr[1]); };
+        use_span(get_temp_span());
+
+        s1 = get_temp_span();
+        CHECK(s1.length() == 2 && s1.data() == &arr[1]);
+    }
+
+    TEST(first)
+    {
+        int arr[5] = {1, 2, 3, 4, 5};
+
+        {
+            span<int, 5> av = arr;
+            CHECK(av.first<2>().length() == 2);
+            CHECK(av.first(2).length() == 2);
+        }
+
+        {
+            span<int, 5> av = arr;
+            CHECK(av.first<0>().length() == 0);
+            CHECK(av.first(0).length() == 0);
+        }
+
+        {
+            span<int, 5> av = arr;
+            CHECK(av.first<5>().length() == 5);
+            CHECK(av.first(5).length() == 5);
+        }
+
+        {
+            span<int, 5> av = arr;
+#ifdef CONFIRM_COMPILATION_ERRORS
+            CHECK(av.first<6>().length() == 6);
+            CHECK(av.first<-1>().length() == -1);
+#endif
+            CHECK_THROW(av.first(6).length(), fail_fast);
+        }
+
+        {
+            span<int> av;
+            CHECK(av.first<0>().length() == 0);
+            CHECK(av.first(0).length() == 0);
+        }
+    }
+
+    TEST(last)
+    {
+        int arr[5] = {1, 2, 3, 4, 5};
+
+        {
+            span<int, 5> av = arr;
+            CHECK(av.last<2>().length() == 2);
+            CHECK(av.last(2).length() == 2);
+        }
+
+        {
+            span<int, 5> av = arr;
+            CHECK(av.last<0>().length() == 0);
+            CHECK(av.last(0).length() == 0);
+        }
+
+        {
+            span<int, 5> av = arr;
+            CHECK(av.last<5>().length() == 5);
+            CHECK(av.last(5).length() == 5);
+        }
+
+        {
+            span<int, 5> av = arr;
+#ifdef CONFIRM_COMPILATION_ERRORS
+            CHECK(av.last<6>().length() == 6);
+#endif    
+            CHECK_THROW(av.last(6).length(), fail_fast);
+        }
+
+        {
+            span<int> av;
+            CHECK(av.last<0>().length() == 0);
+            CHECK(av.last(0).length() == 0);
+        }
+    }
+
+    TEST(subspan)
+    {
+        int arr[5] = {1, 2, 3, 4, 5};
+
+        {
+            span<int, 5> av = arr;
+            CHECK((av.subspan<2, 2>().length() == 2));
+            CHECK(av.subspan(2, 2).length() == 2);
+            CHECK(av.subspan(2, 3).length() == 3);
+        }
+
+        {
+            span<int, 5> av = arr;
+            CHECK((av.subspan<0, 0>().length() == 0));
+            CHECK(av.subspan(0, 0).length() == 0);
+        }
+
+        {
+            span<int, 5> av = arr;
+            CHECK((av.subspan<0, 5>().length() == 5));
+            CHECK(av.subspan(0, 5).length() == 5);
+            CHECK_THROW(av.subspan(0, 6).length(), fail_fast);
+            CHECK_THROW(av.subspan(1, 5).length(), fail_fast);
+        }
+
+        {
+            span<int, 5> av = arr;
+            CHECK((av.subspan<4, 0>().length() == 0));
+            CHECK(av.subspan(4, 0).length() == 0);
+            CHECK(av.subspan(5, 0).length() == 0);
+            CHECK_THROW(av.subspan(6, 0).length(), fail_fast);
+        }
+
+        {
+            span<int> av;
+            CHECK((av.subspan<0, 0>().length() == 0));
+            CHECK(av.subspan(0, 0).length() == 0);
+            CHECK_THROW((av.subspan<1, 0>().length()), fail_fast);
+        }
+
+        {
+            span<int> av;
+            CHECK(av.subspan(0).length() == 0);
+            CHECK_THROW(av.subspan(1).length(), fail_fast);
+        }
+
+        {
+            span<int> av = arr;
+            CHECK(av.subspan(0).length() == 5);
+            CHECK(av.subspan(1).length() == 4);
+            CHECK(av.subspan(4).length() == 1);
+            CHECK(av.subspan(5).length() == 0);
+            CHECK_THROW(av.subspan(6).length(), fail_fast);
+            auto av2 = av.subspan(1);
+            for (int i = 0; i < 4; ++i) CHECK(av2[i] == i + 2);
+        }
+
+        {
+            span<int, 5> av = arr;
+            CHECK(av.subspan(0).length() == 5);
+            CHECK(av.subspan(1).length() == 4);
+            CHECK(av.subspan(4).length() == 1);
+            CHECK(av.subspan(5).length() == 0);
+            CHECK_THROW(av.subspan(6).length(), fail_fast);
+            auto av2 = av.subspan(1);
+            for (int i = 0; i < 4; ++i) CHECK(av2[i] == i + 2);
+        }
+    }
+
+    TEST(at_call)
+    {
+        int arr[4] = {1, 2, 3, 4};
+
+        {
+            span<int> s = arr;
+            CHECK(s.at(0) == 1);
+            CHECK_THROW(s.at(5), fail_fast);
+        }
+
+        {
+            int arr2d[2] = {1, 6};
+            span<int, 2> s = arr2d;
+            CHECK(s.at(0) == 1);
+            CHECK(s.at(1) == 6);
+            CHECK_THROW(s.at(2) ,fail_fast);
+        }
+    }
+
+    TEST(operator_function_call)
+    {
+        int arr[4] = {1, 2, 3, 4};
+
+        {
+            span<int> s = arr;
+            CHECK(s(0) == 1);
+            CHECK_THROW(s(5), fail_fast);
+        }
+
+        {
+            int arr2d[2] = {1, 6};
+            span<int, 2> s = arr2d;
+            CHECK(s(0) == 1);
+            CHECK(s(1) == 6);
+            CHECK_THROW(s(2) ,fail_fast);
+        }
+    }
+
+    TEST(iterator_default_init)
+    {
+        span<int>::iterator it1;
+        span<int>::iterator it2;
+        CHECK(it1 == it2);
+    }
+
+    TEST(const_iterator_default_init)
+    {
+        span<int>::const_iterator it1;
+        span<int>::const_iterator it2;
+        CHECK(it1 == it2);
+    }
+
+    TEST(iterator_conversions)
+    {
+        span<int>::iterator badIt;
+        span<int>::const_iterator badConstIt;
+        CHECK(badIt == badConstIt);
+
+        int a[] = { 1, 2, 3, 4 };
+        span<int> s = a;
+
+        auto it = s.begin();
+        auto cit = s.cbegin();
+
+        CHECK(it == cit);
+        CHECK(cit == it);
+
+        span<int>::const_iterator cit2 = it;
+        CHECK(cit2 == cit);
+
+        span<int>::const_iterator cit3 = it + 4;
+        CHECK(cit3 == s.cend());
+    }
+
+    TEST(iterator_comparisons)
+    {
+        int a[] = { 1, 2, 3, 4 };
+        {
+            span<int> s = a;
+            span<int>::iterator it = s.begin();
+            auto it2 = it + 1;
+            span<int>::const_iterator cit = s.cbegin();
+
+            CHECK(it == cit);
+            CHECK(cit == it);
+            CHECK(it == it);
+            CHECK(cit == cit);
+            CHECK(cit == s.begin());
+            CHECK(s.begin() == cit);
+            CHECK(s.cbegin() == cit);
+            CHECK(it == s.begin());
+            CHECK(s.begin() == it);
+
+            CHECK(it != it2);
+            CHECK(it2 != it);
+            CHECK(it != s.end());
+            CHECK(it2 != s.end());
+            CHECK(s.end() != it);
+            CHECK(it2 != cit);
+            CHECK(cit != it2);
+
+            CHECK(it < it2);
+            CHECK(it <= it2);
+            CHECK(it2 <= s.end());
+            CHECK(it < s.end());
+            CHECK(it <= cit);
+            CHECK(cit <= it);
+            CHECK(cit < it2);
+            CHECK(cit <= it2);
+            CHECK(cit < s.end());
+            CHECK(cit <= s.end());
+
+            CHECK(it2 > it);
+            CHECK(it2 >= it);
+            CHECK(s.end() > it2);
+            CHECK(s.end() >= it2);
+            CHECK(it2 > cit);
+            CHECK(it2 >= cit);
+        }
+    }
+
+    TEST(begin_end)
+    {
+        {
+            int a[] = { 1, 2, 3, 4 };
+            span<int> s = a;
+
+            span<int>::iterator it = s.begin();
+            span<int>::iterator it2 = std::begin(s);
+            CHECK(it == it2);
+
+            it = s.end();
+            it2 = std::end(s);
+            CHECK(it == it2);
+        }
+
+        {
+            int a[] = { 1, 2, 3, 4 };
+            span<int> s = a;
+
+            auto it = s.begin();
+            auto first = it;
+            CHECK(it == first);
+            CHECK(*it == 1);
+
+            auto beyond = s.end();
+            CHECK(it != beyond);
+            CHECK_THROW(*beyond, fail_fast);
+
+            CHECK(beyond - first == 4);
+            CHECK(first - first == 0);
+            CHECK(beyond - beyond == 0);
+            
+            ++it;
+            CHECK(it - first == 1);
+            CHECK(*it == 2);
+            *it = 22;
+            CHECK(*it == 22);
+            CHECK(beyond - it == 3);
+
+            it = first;
+            CHECK(it == first);
+            while (it != s.end())
+            {
+                *it = 5;
+                ++it;
+            }
+
+            CHECK(it == beyond);
+            CHECK(it - beyond == 0);
+
+            for (auto& n : s)
+            {
+                CHECK(n == 5);
+            }
+        }
+    }
+
+    TEST(cbegin_cend)
+    {
+        {
+            int a[] = { 1, 2, 3, 4 };
+            span<int> s = a;
+
+            span<int>::const_iterator cit = s.cbegin();
+            span<int>::const_iterator cit2 = std::cbegin(s);
+            CHECK(cit == cit2);
+
+            cit = s.cend();
+            cit2 = std::cend(s);
+            CHECK(cit == cit2);
+        }
+
+        {
+            int a[] = {1, 2, 3, 4};
+            span<int> s = a;
+
+            auto it = s.cbegin();
+            auto first = it;
+            CHECK(it == first);
+            CHECK(*it == 1);
+
+            auto beyond = s.cend();
+            CHECK(it != beyond);
+            CHECK_THROW(*beyond, fail_fast);
+
+            CHECK(beyond - first == 4);
+            CHECK(first - first == 0);
+            CHECK(beyond - beyond == 0);
+
+            ++it;
+            CHECK(it - first == 1);
+            CHECK(*it == 2);
+            CHECK(beyond - it == 3);
+
+            int last = 0;
+            it = first;
+            CHECK(it == first);
+            while (it != s.cend())
+            {
+                CHECK(*it == last + 1);
+
+                last = *it;
+                ++it;
+            }
+
+            CHECK(it == beyond);
+            CHECK(it - beyond == 0);
+        }
+    }
+
+    TEST(rbegin_rend)
+    {
+        {
+            int a[] = {1, 2, 3, 4};
+            span<int> s = a;
+
+            auto it = s.rbegin();
+            auto first = it;
+            CHECK(it == first);
+            CHECK(*it == 4);
+
+            auto beyond = s.rend();
+            CHECK(it != beyond);
+            CHECK_THROW(*beyond, fail_fast);
+
+            CHECK(beyond - first == 4);
+            CHECK(first - first == 0);
+            CHECK(beyond - beyond == 0);
+
+            ++it;
+            CHECK(it - first == 1);
+            CHECK(*it == 3);
+            *it = 22;
+            CHECK(*it == 22);
+            CHECK(beyond - it == 3);
+
+            it = first;
+            CHECK(it == first);
+            while (it != s.rend())
+            {
+                *it = 5;
+                ++it;
+            }
+
+            CHECK(it == beyond);
+            CHECK(it - beyond == 0);
+
+            for (auto& n : s)
+            {
+                CHECK(n == 5);
+            }
+        }
+    }
+
+    TEST(crbegin_crend)
+    {
+        {
+            int a[] = {1, 2, 3, 4};
+            span<int> s = a;
+
+            auto it = s.crbegin();
+            auto first = it;
+            CHECK(it == first);
+            CHECK(*it == 4);
+
+            auto beyond = s.crend();
+            CHECK(it != beyond);
+            CHECK_THROW(*beyond, fail_fast);
+
+            CHECK(beyond - first == 4);
+            CHECK(first - first == 0);
+            CHECK(beyond - beyond == 0);
+
+            ++it;
+            CHECK(it - first == 1);
+            CHECK(*it == 3);
+            CHECK(beyond - it == 3);
+
+            it = first;
+            CHECK(it == first);
+            int last = 5;
+            while (it != s.crend())
+            {
+                CHECK(*it == last - 1);
+                last = *it;
+
+                ++it;
+            }
+
+            CHECK(it == beyond);
+            CHECK(it - beyond == 0);
+        }
+    }
+
+    TEST(comparison_operators)
+    {
+        {
+            span<int> s1 = nullptr;
+            span<int> s2 = nullptr;
+            CHECK(s1 == s2);
+            CHECK(!(s1 != s2));
+            CHECK(!(s1 < s2));
+            CHECK(s1 <= s2);
+            CHECK(!(s1 > s2));
+            CHECK(s1 >= s2);
+            CHECK(s2 == s1);
+            CHECK(!(s2 != s1));
+            CHECK(!(s2 < s1));
+            CHECK(s2 <= s1);
+            CHECK(!(s2 > s1));
+            CHECK(s2 >= s1);
+        }
+
+        {
+            int arr[] = {2, 1};
+            span<int> s1 = arr;
+            span<int> s2 = arr;
+
+            CHECK(s1 == s2);
+            CHECK(!(s1 != s2));
+            CHECK(!(s1 < s2));
+            CHECK(s1 <= s2);
+            CHECK(!(s1 > s2));
+            CHECK(s1 >= s2);
+            CHECK(s2 == s1);
+            CHECK(!(s2 != s1));
+            CHECK(!(s2 < s1));
+            CHECK(s2 <= s1);
+            CHECK(!(s2 > s1));
+            CHECK(s2 >= s1);
+        }
+
+        {
+            int arr[] = {2, 1}; // bigger
+
+            span<int> s1 = nullptr;
+            span<int> s2 = arr;
+
+            CHECK(s1 != s2);
+            CHECK(s2 != s1);
+            CHECK(!(s1 == s2));
+            CHECK(!(s2 == s1));
+            CHECK(s1 < s2);
+            CHECK(!(s2 < s1));
+            CHECK(s1 <= s2);
+            CHECK(!(s2 <= s1));
+            CHECK(s2 > s1);
+            CHECK(!(s1 > s2));
+            CHECK(s2 >= s1);
+            CHECK(!(s1 >= s2));
+        }
+
+        {
+            int arr1[] = {1, 2};
+            int arr2[] = {1, 2};
+            span<int> s1 = arr1;
+            span<int> s2 = arr2;
+
+            CHECK(s1 == s2);
+            CHECK(!(s1 != s2));
+            CHECK(!(s1 < s2));
+            CHECK(s1 <= s2);
+            CHECK(!(s1 > s2));
+            CHECK(s1 >= s2);
+            CHECK(s2 == s1);
+            CHECK(!(s2 != s1));
+            CHECK(!(s2 < s1));
+            CHECK(s2 <= s1);
+            CHECK(!(s2 > s1));
+            CHECK(s2 >= s1);
+        }
+
+        {
+            int arr[] = {1, 2, 3};
+
+            span<int> s1 = {&arr[0], 2}; // shorter
+            span<int> s2 = arr; // longer
+
+            CHECK(s1 != s2);
+            CHECK(s2 != s1);
+            CHECK(!(s1 == s2));
+            CHECK(!(s2 == s1));
+            CHECK(s1 < s2);
+            CHECK(!(s2 < s1));
+            CHECK(s1 <= s2);
+            CHECK(!(s2 <= s1));
+            CHECK(s2 > s1);
+            CHECK(!(s1 > s2));
+            CHECK(s2 >= s1);
+            CHECK(!(s1 >= s2));
+        }
+
+        {
+            int arr1[] = {1, 2}; // smaller
+            int arr2[] = {2, 1}; // bigger
+
+            span<int> s1 = arr1;
+            span<int> s2 = arr2;
+
+            CHECK(s1 != s2);
+            CHECK(s2 != s1);
+            CHECK(!(s1 == s2));
+            CHECK(!(s2 == s1));
+            CHECK(s1 < s2);
+            CHECK(!(s2 < s1));
+            CHECK(s1 <= s2);
+            CHECK(!(s2 <= s1));
+            CHECK(s2 > s1);
+            CHECK(!(s1 > s2));
+            CHECK(s2 >= s1);
+            CHECK(!(s1 >= s2));
+        }
+    }
+
+    TEST(as_bytes)
+    {
+        int a[] = {1, 2, 3, 4};
+
+        {
+            span<const int> s = a;
+            CHECK(s.length() == 4);
+            span<const byte> bs = as_bytes(s);
+            CHECK(static_cast<const void*>(bs.data()) == static_cast<const void*>(s.data()));
+            CHECK(bs.length() == s.length_bytes());
+        }
+
+        {
+            span<int> s;
+            auto bs = as_bytes(s);
+            CHECK(bs.length() == s.length());
+            CHECK(bs.length() == 0);
+            CHECK(bs.size_bytes() == 0);
+            CHECK(static_cast<const void*>(bs.data()) == static_cast<const void*>(s.data()));
+            CHECK(bs.data() == nullptr);
+        }
+
+        {
+            span<int> s = a;
+            auto bs = as_bytes(s);
+            CHECK(static_cast<const void*>(bs.data()) == static_cast<const void*>(s.data()));
+            CHECK(bs.length() == s.length_bytes());
+        }
+    }
+
+    TEST(as_writeable_bytes)
+    {
+        int a[] = {1, 2, 3, 4};
+
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            // you should not be able to get writeable bytes for const objects
+            span<const int> s = a;
+            CHECK(s.length() == 4);
+            span<const byte> bs = as_writeable_bytes(s);
+            CHECK(static_cast<void*>(bs.data()) == static_cast<void*>(s.data()));
+            CHECK(bs.length() == s.length_bytes());
+#endif
+        }
+
+        {
+            span<int> s;
+            auto bs = as_writeable_bytes(s);
+            CHECK(bs.length() == s.length());
+            CHECK(bs.length() == 0);
+            CHECK(bs.size_bytes() == 0);
+            CHECK(static_cast<void*>(bs.data()) == static_cast<void*>(s.data()));
+            CHECK(bs.data() == nullptr);
+        }
+
+        {
+            span<int> s = a;
+            auto bs = as_writeable_bytes(s);
+            CHECK(static_cast<void*>(bs.data()) == static_cast<void*>(s.data()));
+            CHECK(bs.length() == s.length_bytes());
+        }
+    }
+
+    TEST(fixed_size_conversions)
+    {
+        int arr[] = {1, 2, 3, 4};
+
+        // converting to an span from an equal size array is ok
+        span<int, 4> s4 = arr;
+        CHECK(s4.length() == 4);
+
+        // converting to dynamic_range is always ok
+        {
+            span<int> s = s4;
+            CHECK(s.length() == s4.length());
+            static_cast<void>(s);
+        }
+
+// initialization or assignment to static span that REDUCES size is NOT ok
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            span<int, 2> s = arr;
+        }
+        {
+            span<int, 2> s2 = s4;
+            static_cast<void>(s2);
+        }
+#endif
+
+        // even when done dynamically
+        {
+            span<int> s = arr;
+            auto f = [&]() {
+                span<int, 2> s2 = s;
+                static_cast<void>(s2);
+            };
+            CHECK_THROW(f(), fail_fast);
+        }
+
+        // but doing so explicitly is ok
+
+        // you can convert statically
+        {
+            span<int, 2> s2 = {arr, 2};
+            static_cast<void>(s2);
+        }
+        {
+            span<int, 1> s1 = s4.first<1>();
+            static_cast<void>(s1);
+        }
+
+        // ...or dynamically
+        {
+            // NB: implicit conversion to span<int,1> from span<int>
+            span<int, 1> s1 = s4.first(1);
+            static_cast<void>(s1);
+        }
+
+        // initialization or assignment to static span that requires size INCREASE is not ok.
+        int arr2[2] = {1, 2};
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            span<int, 4> s3 = arr2;
+        }
+        {
+            span<int, 2> s2 = arr2;
+            span<int, 4> s4a = s2;
+        }
+#endif
+        {
+            auto f = [&]() {
+                span<int, 4> s4 = {arr2, 2};
+                static_cast<void>(s4);
+            };                     
+            CHECK_THROW(f(), fail_fast);
+        }
+
+        // this should fail - we are trying to assign a small dynamic span to a fixed_size larger one
+        span<int> av = arr2;
+        auto f = [&]() {
+            span<int, 4> s4 = av;
+            static_cast<void>(s4);            
+        };
+        CHECK_THROW(f(), fail_fast);
+    }
+
+    TEST(interop_with_std_regex)
+    {
+        char lat[] = { '1', '2', '3', '4', '5', '6', 'E', 'F', 'G' };
+        span<char> s = lat;
+        auto f_it = s.begin() + 7;
+
+        std::match_results<span<char>::iterator> match;
+
+        std::regex_match(s.begin(), s.end(), match, std::regex(".*"));
+        CHECK(match.ready());
+        CHECK(!match.empty());
+        CHECK(match[0].matched);
+        CHECK(match[0].first == s.begin());
+        CHECK(match[0].second == s.end());
+
+        std::regex_search(s.begin(), s.end(), match, std::regex("F"));
+        CHECK(match.ready());
+        CHECK(!match.empty());
+        CHECK(match[0].matched);
+        CHECK(match[0].first == f_it);
+        CHECK(match[0].second == (f_it + 1));
+    }
+
+    TEST(interop_with_gsl_at)
+    {
+        int arr[5] = {1, 2, 3, 4, 5};
+        span<int> s{arr};
+        CHECK(at(s,0) == 1 && at(s,1) == 2);
+    }
+}
+
+int main(int, const char* []) { return UnitTest::RunAllTests(); }
diff --git a/tests/strided_span_tests.cpp b/tests/strided_span_tests.cpp
new file mode 100644
index 0000000..86666d1
--- /dev/null
+++ b/tests/strided_span_tests.cpp
@@ -0,0 +1,748 @@
+/////////////////////////////////////////////////////////////////////////////// 
+// 
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved. 
+// 
+// This code is licensed under the MIT License (MIT). 
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 
+// THE SOFTWARE. 
+// 
+///////////////////////////////////////////////////////////////////////////////
+
+#include <UnitTest++/UnitTest++.h> 
+#include <gsl/multi_span>
+
+#include <string>
+#include <vector>
+#include <list>
+#include <iostream>
+#include <memory>
+#include <map>
+
+using namespace std;
+using namespace gsl;
+
+namespace 
+{
+	struct BaseClass {};
+	struct DerivedClass : BaseClass {};
+}
+
+SUITE(strided_span_tests)
+{
+	TEST (span_section_test)
+	{
+		int a[30][4][5];
+		
+		auto av = as_multi_span(a);
+		auto sub = av.section({15, 0, 0}, gsl::index<3>{2, 2, 2});
+		auto subsub = sub.section({1, 0, 0}, gsl::index<3>{1, 1, 1});
+		(void)subsub;
+	}
+
+	TEST(span_section)
+	{
+		std::vector<int> data(5 * 10);
+		std::iota(begin(data), end(data), 0);
+        const multi_span<int, 5, 10> av = as_multi_span(multi_span<int>{data}, dim<5>(), dim<10>());
+
+		strided_span<int, 2> av_section_1 = av.section({ 1, 2 }, { 3, 4 });
+		CHECK((av_section_1[{0, 0}] == 12));
+		CHECK((av_section_1[{0, 1}] == 13));
+		CHECK((av_section_1[{1, 0}] == 22));
+		CHECK((av_section_1[{2, 3}] == 35));
+
+		strided_span<int, 2> av_section_2 = av_section_1.section({ 1, 2 }, { 2,2 });
+		CHECK((av_section_2[{0, 0}] == 24));
+		CHECK((av_section_2[{0, 1}] == 25));
+		CHECK((av_section_2[{1, 0}] == 34));
+	}
+
+	TEST(strided_span_constructors)
+	{
+		// Check stride constructor
+		{
+			int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
+			const int carr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
+
+			strided_span<int, 1> sav1{ arr, {{9}, {1}} }; // T -> T
+			CHECK(sav1.bounds().index_bounds() == index<1>{ 9 });
+			CHECK(sav1.bounds().stride() == 1);
+			CHECK(sav1[0] == 1 && sav1[8] == 9);
+
+
+			strided_span<const int, 1> sav2{ carr, {{ 4 }, { 2 }} }; // const T -> const T
+			CHECK(sav2.bounds().index_bounds() == index<1>{ 4 });
+			CHECK(sav2.bounds().strides() == index<1>{2});
+			CHECK(sav2[0] == 1 && sav2[3] == 7);
+
+			strided_span<int, 2> sav3{ arr, {{ 2, 2 },{ 6, 2 }} }; // T -> const T
+			CHECK((sav3.bounds().index_bounds() == index<2>{ 2, 2 }));
+			CHECK((sav3.bounds().strides() == index<2>{ 6, 2 }));
+			CHECK((sav3[{0, 0}] == 1 && sav3[{0, 1}] == 3 && sav3[{1, 0}] == 7));
+		}
+
+		// Check multi_span constructor
+		{
+			int arr[] = { 1, 2 };
+
+			// From non-cv-qualified source
+			{
+				const multi_span<int> src = arr;
+
+				strided_span<int, 1> sav{ src, {2, 1} };
+				CHECK(sav.bounds().index_bounds() == index<1>{ 2 });
+				CHECK(sav.bounds().strides() == index<1>{ 1 });
+				CHECK(sav[1] == 2);
+
+#if _MSC_VER > 1800
+				//strided_span<const int, 1> sav_c{ {src}, {2, 1} };
+				strided_span<const int, 1> sav_c{ multi_span<const int>{src}, strided_bounds<1>{2, 1} };
+#else
+				strided_span<const int, 1> sav_c{ multi_span<const int>{src}, strided_bounds<1>{2, 1} };
+#endif
+				CHECK(sav_c.bounds().index_bounds() == index<1>{ 2 });
+				CHECK(sav_c.bounds().strides() == index<1>{ 1 });
+				CHECK(sav_c[1] == 2);
+
+#if _MSC_VER > 1800
+				strided_span<volatile int, 1> sav_v{ src, {2, 1} };
+#else
+				strided_span<volatile int, 1> sav_v{ multi_span<volatile int>{src}, strided_bounds<1>{2, 1} };
+#endif
+				CHECK(sav_v.bounds().index_bounds() == index<1>{ 2 });
+				CHECK(sav_v.bounds().strides() == index<1>{ 1 });
+				CHECK(sav_v[1] == 2);
+
+#if _MSC_VER > 1800
+				strided_span<const volatile int, 1> sav_cv{ src, {2, 1} };
+#else
+				strided_span<const volatile int, 1> sav_cv{ multi_span<const volatile int>{src}, strided_bounds<1>{2, 1} };
+#endif
+				CHECK(sav_cv.bounds().index_bounds() == index<1>{ 2 });
+				CHECK(sav_cv.bounds().strides() == index<1>{ 1 });
+				CHECK(sav_cv[1] == 2);
+			}
+
+			// From const-qualified source
+			{
+				const multi_span<const int> src{ arr };
+
+				strided_span<const int, 1> sav_c{ src, {2, 1} };
+				CHECK(sav_c.bounds().index_bounds() == index<1>{ 2 });
+				CHECK(sav_c.bounds().strides() == index<1>{ 1 });
+				CHECK(sav_c[1] == 2);
+
+#if _MSC_VER > 1800
+				strided_span<const volatile int, 1> sav_cv{ src, {2, 1} };
+#else
+				strided_span<const volatile int, 1> sav_cv{ multi_span<const volatile int>{src}, strided_bounds<1>{2, 1} };
+#endif
+				
+				CHECK(sav_cv.bounds().index_bounds() == index<1>{ 2 });
+				CHECK(sav_cv.bounds().strides() == index<1>{ 1 });
+				CHECK(sav_cv[1] == 2);
+			}
+
+			// From volatile-qualified source
+			{
+				const multi_span<volatile int> src{ arr };
+
+				strided_span<volatile int, 1> sav_v{ src, {2, 1} };
+				CHECK(sav_v.bounds().index_bounds() == index<1>{ 2 });
+				CHECK(sav_v.bounds().strides() == index<1>{ 1 });
+				CHECK(sav_v[1] == 2);
+
+#if _MSC_VER > 1800
+				strided_span<const volatile int, 1> sav_cv{ src, {2, 1} };
+#else
+				strided_span<const volatile int, 1> sav_cv{ multi_span<const volatile int>{src}, strided_bounds<1>{2, 1} };
+#endif
+				CHECK(sav_cv.bounds().index_bounds() == index<1>{ 2 });
+				CHECK(sav_cv.bounds().strides() == index<1>{ 1 });
+				CHECK(sav_cv[1] == 2);
+			}
+
+			// From cv-qualified source
+			{
+				const multi_span<const volatile int> src{ arr };
+
+				strided_span<const volatile int, 1> sav_cv{ src, {2, 1} };
+				CHECK(sav_cv.bounds().index_bounds() == index<1>{ 2 });
+				CHECK(sav_cv.bounds().strides() == index<1>{ 1 });
+				CHECK(sav_cv[1] == 2);
+			}
+		}
+
+		// Check const-casting constructor
+		{
+			int arr[2] = { 4, 5 };
+
+			const multi_span<int, 2> av(arr, 2);
+			multi_span<const int, 2> av2{ av };
+			CHECK(av2[1] == 5);
+
+			static_assert(std::is_convertible<const multi_span<int, 2>, multi_span<const int, 2>>::value, "ctor is not implicit!");
+		
+			const strided_span<int, 1> src{ arr, {2, 1} };
+			strided_span<const int, 1> sav{ src };
+			CHECK(sav.bounds().index_bounds() == index<1>{ 2 });
+			CHECK(sav.bounds().stride() == 1);
+			CHECK(sav[1] == 5);
+			
+			static_assert(std::is_convertible<const strided_span<int, 1>, strided_span<const int, 1>>::value, "ctor is not implicit!");
+		}
+
+		// Check copy constructor
+		{
+			int arr1[2] = { 3, 4 };
+			const strided_span<int, 1> src1{ arr1, {2, 1} };
+			strided_span<int, 1> sav1{ src1 };
+ 
+			CHECK(sav1.bounds().index_bounds() == index<1>{ 2 });
+			CHECK(sav1.bounds().stride() == 1);
+			CHECK(sav1[0] == 3);
+
+			int arr2[6] = { 1, 2, 3, 4, 5, 6 };
+			const strided_span<const int, 2> src2{ arr2, {{ 3, 2 }, { 2, 1 }} };
+			strided_span<const int, 2> sav2{ src2 };
+			CHECK((sav2.bounds().index_bounds() == index<2>{ 3, 2 }));
+			CHECK((sav2.bounds().strides() == index<2>{ 2, 1 }));
+			CHECK((sav2[{0, 0}] == 1 && sav2[{2, 0}] == 5));
+		}
+
+		// Check const-casting assignment operator
+		{
+			int arr1[2] = { 1, 2 };
+			int arr2[6] = { 3, 4, 5, 6, 7, 8 };
+
+			const strided_span<int, 1> src{ arr1, {{2}, {1}} };
+			strided_span<const int, 1> sav{ arr2, {{3}, {2}} };
+			strided_span<const int, 1>& sav_ref = (sav = src);
+			CHECK(sav.bounds().index_bounds() == index<1>{ 2 });
+			CHECK(sav.bounds().strides() == index<1>{ 1 });
+			CHECK(sav[0] == 1);
+			CHECK(&sav_ref == &sav);
+		}
+		
+		// Check copy assignment operator
+		{
+			int arr1[2] = { 3, 4 };
+			int arr1b[1] = { 0 };
+			const strided_span<int, 1> src1{ arr1, {2, 1} };
+			strided_span<int, 1> sav1{ arr1b, {1, 1} };
+			strided_span<int, 1>& sav1_ref = (sav1 = src1);
+			CHECK(sav1.bounds().index_bounds() == index<1>{ 2 });
+			CHECK(sav1.bounds().strides() == index<1>{ 1 });
+			CHECK(sav1[0] == 3);
+			CHECK(&sav1_ref == &sav1);
+
+			const int arr2[6] = { 1, 2, 3, 4, 5, 6 };
+			const int arr2b[1] = { 0 };
+			const strided_span<const int, 2> src2{ arr2, {{ 3, 2 },{ 2, 1 }} };
+			strided_span<const int, 2> sav2{ arr2b, {{ 1, 1 },{ 1, 1 }} };
+			strided_span<const int, 2>& sav2_ref = (sav2 = src2);
+			CHECK((sav2.bounds().index_bounds() == index<2>{ 3, 2 }));
+			CHECK((sav2.bounds().strides() == index<2>{ 2, 1 }));
+			CHECK((sav2[{0, 0}] == 1 && sav2[{2, 0}] == 5));
+			CHECK(&sav2_ref == &sav2);
+		}
+	}
+
+	TEST(strided_span_slice)
+	{
+		std::vector<int> data(5 * 10);
+		std::iota(begin(data), end(data), 0);
+        const multi_span<int, 5, 10> src = as_multi_span(multi_span<int>{data}, dim<5>(), dim<10>());
+
+		const strided_span<int, 2> sav{ src, {{5, 10}, {10, 1}} };
+#ifdef CONFIRM_COMPILATION_ERRORS
+		const strided_span<const int, 2> csav{ {src},{ { 5, 10 },{ 10, 1 } } };
+#endif
+		const strided_span<const int, 2> csav{ multi_span<const int, 5, 10>{ src }, { { 5, 10 },{ 10, 1 } } };
+
+		strided_span<int, 1> sav_sl = sav[2];
+		CHECK(sav_sl[0] == 20);
+		CHECK(sav_sl[9] == 29);
+
+		strided_span<const int, 1> csav_sl = sav[3];
+		CHECK(csav_sl[0] == 30);
+		CHECK(csav_sl[9] == 39);
+
+		CHECK(sav[4][0] == 40);
+		CHECK(sav[4][9] == 49);
+	}
+
+	TEST(strided_span_column_major)
+	{
+		// strided_span may be used to accomodate more peculiar
+		// use cases, such as column-major multidimensional array
+		// (aka. "FORTRAN" layout).
+
+		int cm_array[3 * 5] = {
+			1, 4, 7, 10, 13,
+			2, 5, 8, 11, 14,
+			3, 6, 9, 12, 15
+		};
+		strided_span<int, 2> cm_sav{ cm_array, {{ 5, 3 },{ 1, 5 }} };
+
+		// Accessing elements
+		CHECK((cm_sav[{0, 0}] == 1));
+		CHECK((cm_sav[{0, 1}] == 2));
+		CHECK((cm_sav[{1, 0}] == 4));
+		CHECK((cm_sav[{4, 2}] == 15));
+
+		// Slice
+		strided_span<int, 1> cm_sl = cm_sav[3];
+
+		CHECK(cm_sl[0] == 10);
+		CHECK(cm_sl[1] == 11);
+		CHECK(cm_sl[2] == 12);
+
+		// Section 
+		strided_span<int, 2> cm_sec = cm_sav.section( { 2, 1 }, { 3, 2 });
+
+		CHECK((cm_sec.bounds().index_bounds() == index<2>{3, 2}));
+		CHECK((cm_sec[{0, 0}] == 8));
+		CHECK((cm_sec[{0, 1}] == 9));
+		CHECK((cm_sec[{1, 0}] == 11));
+		CHECK((cm_sec[{2, 1}] == 15));
+	}
+
+	TEST(strided_span_bounds)
+	{
+		int arr[] = { 0, 1, 2, 3 };
+		multi_span<int> av(arr);
+
+		{
+			// incorrect sections
+			
+			CHECK_THROW(av.section(0, 0)[0], fail_fast);
+			CHECK_THROW(av.section(1, 0)[0], fail_fast);
+			CHECK_THROW(av.section(1, 1)[1], fail_fast);
+			
+			CHECK_THROW(av.section(2, 5), fail_fast);
+			CHECK_THROW(av.section(5, 2), fail_fast);
+			CHECK_THROW(av.section(5, 0), fail_fast);
+			CHECK_THROW(av.section(0, 5), fail_fast);
+			CHECK_THROW(av.section(5, 5), fail_fast);
+		}
+
+		{
+			// zero stride
+			strided_span<int, 1> sav{ av,{ { 4 },{} } };
+			CHECK(sav[0] == 0);
+			CHECK(sav[3] == 0);
+			CHECK_THROW(sav[4], fail_fast);
+		}
+
+		{
+			// zero extent
+			strided_span<int, 1> sav{ av,{ {},{ 1 } } };
+			CHECK_THROW(sav[0], fail_fast);
+		}
+
+		{
+			// zero extent and stride
+			strided_span<int, 1> sav{ av,{ {},{} } };
+			CHECK_THROW(sav[0], fail_fast);
+		}
+
+		{
+			// strided array ctor with matching strided bounds 
+			strided_span<int, 1> sav{ arr,{ 4, 1 } };
+			CHECK(sav.bounds().index_bounds() == index<1>{ 4 });
+			CHECK(sav[3] == 3);
+			CHECK_THROW(sav[4], fail_fast);
+		}
+
+		{
+			// strided array ctor with smaller strided bounds 
+			strided_span<int, 1> sav{ arr,{ 2, 1 } };
+			CHECK(sav.bounds().index_bounds() == index<1>{ 2 });
+			CHECK(sav[1] == 1);
+			CHECK_THROW(sav[2], fail_fast);
+		}
+
+		{
+			// strided array ctor with fitting irregular bounds 
+			strided_span<int, 1> sav{ arr,{ 2, 3 } };
+			CHECK(sav.bounds().index_bounds() == index<1>{ 2 });
+			CHECK(sav[0] == 0);
+			CHECK(sav[1] == 3);
+			CHECK_THROW(sav[2], fail_fast);
+		}
+
+		{
+			// bounds cross data boundaries - from static arrays
+			CHECK_THROW((strided_span<int, 1> { arr, { 3, 2 } }), fail_fast);
+			CHECK_THROW((strided_span<int, 1> { arr, { 3, 3 } }), fail_fast);
+			CHECK_THROW((strided_span<int, 1> { arr, { 4, 5 } }), fail_fast);
+			CHECK_THROW((strided_span<int, 1> { arr, { 5, 1 } }), fail_fast);
+			CHECK_THROW((strided_span<int, 1> { arr, { 5, 5 } }), fail_fast);
+		}
+
+		{
+			// bounds cross data boundaries - from array view
+			CHECK_THROW((strided_span<int, 1> { av, { 3, 2 } }), fail_fast);
+			CHECK_THROW((strided_span<int, 1> { av, { 3, 3 } }), fail_fast);
+			CHECK_THROW((strided_span<int, 1> { av, { 4, 5 } }), fail_fast);
+			CHECK_THROW((strided_span<int, 1> { av, { 5, 1 } }), fail_fast);
+			CHECK_THROW((strided_span<int, 1> { av, { 5, 5 } }), fail_fast);
+		}
+
+		{
+			// bounds cross data boundaries - from dynamic arrays
+			CHECK_THROW((strided_span<int, 1> { av.data(), 4, { 3, 2 } }), fail_fast);
+			CHECK_THROW((strided_span<int, 1> { av.data(), 4, { 3, 3 } }), fail_fast);
+			CHECK_THROW((strided_span<int, 1> { av.data(), 4, { 4, 5 } }), fail_fast);
+			CHECK_THROW((strided_span<int, 1> { av.data(), 4, { 5, 1 } }), fail_fast);
+			CHECK_THROW((strided_span<int, 1> { av.data(), 4, { 5, 5 } }), fail_fast);
+			CHECK_THROW((strided_span<int, 1> { av.data(), 2, { 2, 2 } }), fail_fast);
+		}
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+		{
+			strided_span<int, 1> sav0{ av.data(), { 3, 2 } };
+			strided_span<int, 1> sav1{ arr, { 1 } };
+			strided_span<int, 1> sav2{ arr, { 1,1,1 } };
+			strided_span<int, 1> sav3{ av, { 1 } };
+			strided_span<int, 1> sav4{ av, { 1,1,1 } };
+			strided_span<int, 2> sav5{ av.as_multi_span(dim<2>(), dim<2>()), { 1 } };
+			strided_span<int, 2> sav6{ av.as_multi_span(dim<2>(), dim<2>()), { 1,1,1 } };
+			strided_span<int, 2> sav7{ av.as_multi_span(dim<2>(), dim<2>()), { { 1,1 },{ 1,1 },{ 1,1 } } };
+
+			index<1> index{ 0, 1 };
+			strided_span<int, 1> sav8{ arr,{ 1,{ 1,1 } } };
+			strided_span<int, 1> sav9{ arr,{ { 1,1 },{ 1,1 } } };
+			strided_span<int, 1> sav10{ av,{ 1,{ 1,1 } } };
+			strided_span<int, 1> sav11{ av,{ { 1,1 },{ 1,1 } } };
+			strided_span<int, 2> sav12{ av.as_multi_span(dim<2>(), dim<2>()),{ { 1 },{ 1 } } };
+			strided_span<int, 2> sav13{ av.as_multi_span(dim<2>(), dim<2>()),{ { 1 },{ 1,1,1 } } };
+			strided_span<int, 2> sav14{ av.as_multi_span(dim<2>(), dim<2>()),{ { 1,1,1 },{ 1 } } };
+		}
+#endif
+	}
+
+	TEST(strided_span_type_conversion)
+	{
+		int arr[] = { 0, 1, 2, 3 };
+		multi_span<int> av(arr);
+
+		{
+			strided_span<int, 1> sav{ av.data(), av.size(), { av.size() / 2, 2 } };
+#ifdef CONFIRM_COMPILATION_ERRORS
+			strided_span<long, 1> lsav1 = sav.as_strided_span<long, 1>();
+#endif
+		}
+		{
+			strided_span<int, 1> sav{ av, { av.size() / 2, 2 } };
+#ifdef CONFIRM_COMPILATION_ERRORS
+			strided_span<long, 1> lsav1 = sav.as_strided_span<long, 1>();
+#endif
+		}
+
+		multi_span<const byte, dynamic_range> bytes = as_bytes(av);
+
+		// retype strided array with regular strides - from raw data
+		{
+			strided_bounds<2> bounds{ { 2, bytes.size() / 4 }, { bytes.size() / 2, 1 } };
+			strided_span<const byte, 2> sav2{ bytes.data(), bytes.size(), bounds };
+			strided_span<const int, 2> sav3 = sav2.as_strided_span<const int>();
+			CHECK(sav3[0][0] == 0);
+			CHECK(sav3[1][0] == 2);
+			CHECK_THROW(sav3[1][1], fail_fast);
+			CHECK_THROW(sav3[0][1], fail_fast);
+		}
+
+		// retype strided array with regular strides - from multi_span
+		{
+			strided_bounds<2> bounds{ { 2, bytes.size() / 4 }, { bytes.size() / 2, 1 } };
+			multi_span<const byte, 2, dynamic_range> bytes2 = as_multi_span(bytes, dim<2>(), dim(bytes.size() / 2));
+			strided_span<const byte, 2> sav2{ bytes2, bounds };
+			strided_span<int, 2> sav3 = sav2.as_strided_span<int>();
+			CHECK(sav3[0][0] == 0);
+			CHECK(sav3[1][0] == 2);
+			CHECK_THROW(sav3[1][1], fail_fast);
+			CHECK_THROW(sav3[0][1], fail_fast);
+		}
+
+		// retype strided array with not enough elements - last dimension of the array is too small
+		{
+			strided_bounds<2> bounds{ { 4,2 },{ 4, 1 } };
+			multi_span<const byte, 2, dynamic_range> bytes2 = as_multi_span(bytes, dim<2>(), dim(bytes.size() / 2));
+			strided_span<const byte, 2> sav2{ bytes2, bounds };
+			CHECK_THROW(sav2.as_strided_span<int>(), fail_fast);
+		}
+
+		// retype strided array with not enough elements - strides are too small
+		{
+			strided_bounds<2> bounds{ { 4,2 },{ 2, 1 } };
+			multi_span<const byte, 2, dynamic_range> bytes2 = as_multi_span(bytes, dim<2>(), dim(bytes.size() / 2));
+			strided_span<const byte, 2> sav2{ bytes2, bounds };
+			CHECK_THROW(sav2.as_strided_span<int>(), fail_fast);
+		}
+
+		// retype strided array with not enough elements - last dimension does not divide by the new typesize
+		{
+			strided_bounds<2> bounds{ { 2,6 },{ 4, 1 } };
+			multi_span<const byte, 2, dynamic_range> bytes2 = as_multi_span(bytes, dim<2>(), dim(bytes.size() / 2));
+			strided_span<const byte, 2> sav2{ bytes2, bounds };
+			CHECK_THROW(sav2.as_strided_span<int>(), fail_fast);
+		}
+
+		// retype strided array with not enough elements - strides does not divide by the new typesize
+		{
+			strided_bounds<2> bounds{ { 2, 1 },{ 6, 1 } };
+			multi_span<const byte, 2, dynamic_range> bytes2 = as_multi_span(bytes, dim<2>(), dim(bytes.size() / 2));
+			strided_span<const byte, 2> sav2{ bytes2, bounds };
+			CHECK_THROW(sav2.as_strided_span<int>(), fail_fast);
+		}
+
+		// retype strided array with irregular strides - from raw data
+		{
+			strided_bounds<1> bounds{ bytes.size() / 2, 2 };
+			strided_span<const byte, 1> sav2{ bytes.data(), bytes.size(), bounds };
+			CHECK_THROW(sav2.as_strided_span<int>(), fail_fast);
+		}
+
+		// retype strided array with irregular strides - from multi_span
+		{
+			strided_bounds<1> bounds{ bytes.size() / 2, 2 };
+			strided_span<const byte, 1> sav2{ bytes, bounds };
+			CHECK_THROW(sav2.as_strided_span<int>(), fail_fast);
+		}
+	}
+
+	TEST(empty_strided_spans)
+	{
+		{
+			multi_span<int, 0> empty_av(nullptr);
+			strided_span<int, 1> empty_sav{ empty_av, { 0, 1 } };
+
+			CHECK(empty_sav.bounds().index_bounds() == index<1>{ 0 });
+			CHECK_THROW(empty_sav[0], fail_fast);
+			CHECK_THROW(empty_sav.begin()[0], fail_fast);
+			CHECK_THROW(empty_sav.cbegin()[0], fail_fast);
+
+			for (auto& v : empty_sav)
+			{
+                (void)v;
+				CHECK(false);
+			}
+		}
+
+		{
+			strided_span<int, 1> empty_sav{ nullptr, 0, { 0, 1 } };
+
+			CHECK(empty_sav.bounds().index_bounds() == index<1>{ 0 });
+			CHECK_THROW(empty_sav[0], fail_fast);
+			CHECK_THROW(empty_sav.begin()[0], fail_fast);
+			CHECK_THROW(empty_sav.cbegin()[0], fail_fast);
+
+			for (auto& v : empty_sav)
+			{
+                (void)v;
+				CHECK(false);
+			}
+		}
+	}
+
+    void iterate_every_other_element(multi_span<int, dynamic_range> av)
+    {
+        // pick every other element
+
+        auto length = av.size() / 2;
+#if _MSC_VER > 1800
+        auto bounds = strided_bounds<1>({length}, {2});
+#else
+        auto bounds = strided_bounds<1>(index<1>{ length }, index<1>{ 2 });
+#endif
+        strided_span<int, 1> strided(&av.data()[1], av.size() - 1, bounds);
+
+        CHECK(strided.size() == length);
+        CHECK(strided.bounds().index_bounds()[0] == length);
+        for (auto i = 0; i < strided.size(); ++i)
+        {
+            CHECK(strided[i] == av[2 * i + 1]);
+        }
+
+        int idx = 0;
+        for (auto num : strided)
+        {
+            CHECK(num == av[2 * idx + 1]);
+            idx++;
+        }
+    }
+
+    TEST(strided_span_section_iteration)
+    {
+        int arr[8] = {4,0,5,1,6,2,7,3};
+
+        // static bounds
+        {
+            multi_span<int, 8> av(arr, 8);
+            iterate_every_other_element(av);
+        }
+
+        // dynamic bounds
+        {
+            multi_span<int, dynamic_range> av(arr, 8);
+            iterate_every_other_element(av);
+        }
+    }
+
+    TEST(dynamic_strided_span_section_iteration)
+    {
+        auto arr = new int[8];
+        for (int i = 0; i < 4; ++i)
+        {
+            arr[2 * i] = 4 + i;
+            arr[2 * i + 1] = i;
+        }
+
+        auto av = as_multi_span(arr, 8);
+        iterate_every_other_element(av);
+
+        delete[] arr;
+    }
+
+    void iterate_second_slice(multi_span<int, dynamic_range, dynamic_range, dynamic_range> av)
+    {
+        int expected[6] = {2,3,10,11,18,19};
+        auto section = av.section({0,1,0}, {3,1,2});
+
+        for (auto i = 0; i < section.extent<0>(); ++i)
+        {
+            for (auto j = 0; j < section.extent<1>(); ++j)
+                for (auto k = 0; k < section.extent<2>(); ++k)
+                {
+                    auto idx = index<3>{i,j,k}; // avoid braces in the CHECK macro
+                    CHECK(section[idx] == expected[2 * i + 2 * j + k]);
+                }
+        }
+
+        for (auto i = 0; i < section.extent<0>(); ++i)
+        {
+            for (auto j = 0; j < section.extent<1>(); ++j)
+                for (auto k = 0; k < section.extent<2>(); ++k)
+                    CHECK(section[i][j][k] == expected[2 * i + 2 * j + k]);
+        }
+
+        int i = 0;
+        for (auto num : section)
+        {
+            CHECK(num == expected[i]);
+            i++;
+        }
+    }
+
+    TEST(strided_span_section_iteration_3d)
+    {
+        int arr[3][4][2];
+        for (auto i = 0; i < 3; ++i)
+        {
+            for (auto j = 0; j < 4; ++j)
+                for (auto k = 0; k < 2; ++k)
+                    arr[i][j][k] = 8 * i + 2 * j + k;
+        }
+
+        {
+            multi_span<int, 3, 4, 2> av = arr;
+            iterate_second_slice(av);
+        }
+    }
+
+    TEST(dynamic_strided_span_section_iteration_3d)
+    {
+        auto height = 12, width = 2;
+        auto size = height * width;
+
+        auto arr = new int[size];
+        for (auto i = 0; i < size; ++i)
+        {
+            arr[i] = i;
+        }
+
+        {
+            auto av = as_multi_span(as_multi_span(arr, 24), dim<3>(), dim<4>(), dim<2>());
+            iterate_second_slice(av);
+        }
+
+        {
+            auto av = as_multi_span(as_multi_span(arr, 24), dim(3), dim<4>(), dim<2>());
+            iterate_second_slice(av);
+        }
+
+        {
+            auto av = as_multi_span(as_multi_span(arr, 24), dim<3>(), dim(4), dim<2>());
+            iterate_second_slice(av);
+        }
+
+        {
+            auto av = as_multi_span(as_multi_span(arr, 24), dim<3>(), dim<4>(), dim(2));
+            iterate_second_slice(av);
+        }
+        delete[] arr;
+    }
+
+    TEST(strided_span_conversion)
+    {
+        // get an multi_span of 'c' values from the list of X's
+
+        struct X { int a; int b; int c; };
+
+        X arr[4] = {{0,1,2},{3,4,5},{6,7,8},{9,10,11}};
+
+        int s = sizeof(int) / sizeof(byte);
+        auto d2 = 3 * s;
+        auto d1 = sizeof(int) * 12 / d2;
+
+        // convert to 4x12 array of bytes
+        auto av = as_multi_span(as_bytes(as_multi_span(arr, 4)), dim(d1), dim(d2));
+
+        CHECK(av.bounds().index_bounds()[0] == 4);
+        CHECK(av.bounds().index_bounds()[1] == 12);
+
+        // get the last 4 columns
+        auto section = av.section({0, 2 * s}, {4, s}); // { { arr[0].c[0], arr[0].c[1], arr[0].c[2], arr[0].c[3] } , { arr[1].c[0], ... } , ... }
+
+                                                       // convert to array 4x1 array of integers
+        auto cs = section.as_strided_span<int>(); // { { arr[0].c }, {arr[1].c } , ... } 
+
+        CHECK(cs.bounds().index_bounds()[0] == 4);
+        CHECK(cs.bounds().index_bounds()[1] == 1);
+
+        // transpose to 1x4 array 
+        strided_bounds<2> reverse_bounds{
+            {cs.bounds().index_bounds()[1] , cs.bounds().index_bounds()[0]},
+            {cs.bounds().strides()[1], cs.bounds().strides()[0]}
+        };
+
+        strided_span<int, 2> transposed{cs.data(), cs.bounds().total_size(), reverse_bounds};
+
+        // slice to get a one-dimensional array of c's
+        strided_span<int, 1> result = transposed[0];
+
+        CHECK(result.bounds().index_bounds()[0] == 4);
+        CHECK_THROW(result.bounds().index_bounds()[1], fail_fast);
+
+        int i = 0;
+        for (auto& num : result)
+        {
+            CHECK(num == arr[i].c);
+            i++;
+        }
+
+    }
+}
+
+int main(int, const char *[])
+{
+	return UnitTest::RunAllTests();
+}
diff --git a/tests/string_span_tests.cpp b/tests/string_span_tests.cpp
new file mode 100644
index 0000000..a1cfe79
--- /dev/null
+++ b/tests/string_span_tests.cpp
@@ -0,0 +1,971 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <UnitTest++/UnitTest++.h>
+#include <cstdlib>
+#include <gsl/string_span>
+#include <vector>
+#include <map>
+
+using namespace std;
+using namespace gsl;
+
+
+SUITE(string_span_tests)
+{
+
+    TEST(TestLiteralConstruction)
+    {
+        cwstring_span<> v = ensure_z(L"Hello");
+        CHECK(5 == v.length());
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+        wstring_span<> v2 = ensure0(L"Hello");
+#endif
+    }
+
+    TEST(TestConstructFromStdString)
+    {
+        std::string s = "Hello there world";
+        cstring_span<> v = s;
+        CHECK(v.length() == static_cast<cstring_span<>::index_type>(s.length()));
+    }
+
+    TEST(TestConstructFromStdVector)
+    {
+        std::vector<char> vec(5, 'h');
+        string_span<> v {vec};
+        CHECK(v.length() == static_cast<string_span<>::index_type>(vec.size()));
+    }
+
+    TEST(TestStackArrayConstruction)
+    {
+        wchar_t stack_string[] = L"Hello";
+
+        {
+            cwstring_span<> v = ensure_z(stack_string);
+            CHECK(v.length() == 5);
+        }
+
+        {
+            cwstring_span<> v = stack_string;
+            CHECK(v.length() == 5);
+        }
+
+        {
+            wstring_span<> v = ensure_z(stack_string);
+            CHECK(v.length() == 5);
+        }
+
+        {
+            wstring_span<> v = stack_string;
+            CHECK(v.length() == 5);
+        }
+    }
+
+    TEST(TestConstructFromConstCharPointer)
+    {
+        const char* s = "Hello";
+        cstring_span<> v = ensure_z(s);
+        CHECK(v.length() == 5);
+    }
+
+    TEST(TestConversionToConst)
+    {
+        char stack_string[] = "Hello";
+        string_span<> v = ensure_z(stack_string);
+        cstring_span<> v2 = v;
+        CHECK(v.length() == v2.length());
+    }
+
+    TEST(TestConversionFromConst)
+    {
+        char stack_string[] = "Hello";
+        cstring_span<> v = ensure_z(stack_string);
+        (void)v;
+#ifdef CONFIRM_COMPILATION_ERRORS
+        string_span<> v2 = v;
+        string_span<> v3 = "Hello";
+#endif
+    }
+
+    TEST(TestToString)
+    {
+        auto s = gsl::to_string(cstring_span<>{});
+        CHECK(s.length() == 0);
+
+        char stack_string[] = "Hello";
+        cstring_span<> v = ensure_z(stack_string);
+        auto s2 = gsl::to_string(v);
+        CHECK(static_cast<cstring_span<>::index_type>(s2.length()) == v.length());
+        CHECK(s2.length() == 5);
+    }
+
+    TEST(TestToBasicString)
+    {
+        auto s = gsl::to_basic_string<char,std::char_traits<char>,::std::allocator<char>>(cstring_span<>{});
+        CHECK(s.length() == 0);
+
+        char stack_string[] = "Hello";
+        cstring_span<> v = ensure_z(stack_string);
+        auto s2 = gsl::to_basic_string<char,std::char_traits<char>,::std::allocator<char>>(v);
+        CHECK(static_cast<cstring_span<>::index_type>(s2.length()) == v.length());
+        CHECK(s2.length() == 5);
+    }
+    
+    TEST(EqualityAndImplicitConstructors)
+    {
+        {
+            cstring_span<> span = "Hello";
+            cstring_span<> span1;
+
+            // comparison to empty span
+            CHECK(span1 != span);
+            CHECK(span != span1);      
+        }
+
+        {
+            cstring_span<> span = "Hello";
+            cstring_span<> span1 = "Hello1";
+
+            // comparison to different span
+            CHECK(span1 != span);
+            CHECK(span != span1);
+        }
+
+        {
+            cstring_span<> span = "Hello";
+
+            const char ar[] = { 'H', 'e', 'l', 'l', 'o' };
+            const char ar1[] = "Hello";
+            const char ar2[10] = "Hello";
+            const char* ptr = "Hello";
+            const std::string str = "Hello";
+            const std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            gsl::span<const char> sp = ensure_z("Hello");
+
+            // comparison to  literal
+            CHECK(span == cstring_span<>("Hello"));
+
+            // comparison to static array with no null termination
+            CHECK(span == cstring_span<>(ar));
+
+            // comparison to static array with null at the end
+            CHECK(span == cstring_span<>(ar1));
+
+            // comparison to static array with null in the middle
+            CHECK(span == cstring_span<>(ar2));
+
+            // comparison to null-terminated c string
+            CHECK(span == cstring_span<>(ptr, 5));
+
+            // comparison to string
+            CHECK(span == cstring_span<>(str));
+
+            // comparison to vector of charaters with no null termination
+            CHECK(span == cstring_span<>(vec));
+
+            // comparison to span
+            CHECK(span == cstring_span<>(sp));
+
+            // comparison to string_span
+            CHECK(span == span);
+        }
+
+        {
+            char ar[] = { 'H', 'e', 'l', 'l', 'o' };
+
+            string_span<> span = ar;
+
+            char ar1[] = "Hello";
+            char ar2[10] = "Hello";
+            char* ptr = ar;
+            std::string str = "Hello";
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            gsl::span<char> sp = ensure_z(ar1);
+
+            // comparison to static array with no null termination
+            CHECK(span == string_span<>(ar));
+
+            // comparison to static array with null at the end
+            CHECK(span == string_span<>(ar1));
+
+            // comparison to static array with null in the middle
+            CHECK(span == string_span<>(ar2));
+
+            // comparison to null-terminated c string
+            CHECK(span == string_span<>(ptr, 5));
+
+            // comparison to string
+            CHECK(span == string_span<>(str));
+
+            // comparison to vector of charaters with no null termination
+            CHECK(span == string_span<>(vec));
+
+            // comparison to span
+            CHECK(span == string_span<>(sp));
+
+            // comparison to string_span
+            CHECK(span == span);
+        }
+
+
+        {
+            const char ar[] = { 'H', 'e', 'l', 'l', 'o' };
+            const char ar1[] = "Hello";
+            const char ar2[10] = "Hello";
+            const std::string str = "Hello";
+            const std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            gsl::span<const char> sp = ensure_z("Hello");
+
+            cstring_span<> span = "Hello";
+
+            // const span, const other type
+
+            CHECK(span == "Hello");
+            CHECK(span == ar);
+            CHECK(span == ar1);
+            CHECK(span == ar2);
+#ifdef CONFIRM_COMPILATION_ERRORS
+            const char* ptr = "Hello";
+            CHECK(span == ptr);
+#endif
+            CHECK(span == str);
+            CHECK(span == vec);
+            CHECK(span == sp);
+
+            CHECK("Hello" == span);
+            CHECK(ar == span);
+            CHECK(ar1 == span);
+            CHECK(ar2 == span);
+#ifdef CONFIRM_COMPILATION_ERRORS
+            CHECK(ptr == span);
+#endif
+            CHECK(str == span);
+            CHECK(vec == span);
+            CHECK(sp == span);
+
+            // const span, non-const other type
+
+            char _ar[] = { 'H', 'e', 'l', 'l', 'o' };
+            char _ar1[] = "Hello";
+            char _ar2[10] = "Hello";
+            char* _ptr = _ar;
+            std::string _str = "Hello";
+            std::vector<char> _vec = { 'H', 'e', 'l', 'l', 'o' };
+            gsl::span<char> _sp{ _ar, 5 };
+
+            CHECK(span == _ar);
+            CHECK(span == _ar1);
+            CHECK(span == _ar2);
+#ifdef CONFIRM_COMPILATION_ERRORS
+            CHECK(span == _ptr);
+#endif
+            CHECK(span == _str);
+            CHECK(span == _vec);
+            CHECK(span == _sp);
+
+            CHECK(_ar == span);
+            CHECK(_ar1 == span);
+            CHECK(_ar2 == span);
+#ifdef CONFIRM_COMPILATION_ERRORS
+            CHECK(_ptr == span);
+#endif
+            CHECK(_str == span);
+            CHECK(_vec == span);
+            CHECK(_sp == span);
+
+            string_span<> _span{ _ptr, 5 };
+
+            // non-const span, non-const other type
+            
+            CHECK(_span == _ar);
+            CHECK(_span == _ar1);
+            CHECK(_span == _ar2);
+#ifdef CONFIRM_COMPILATION_ERRORS
+            CHECK(_span == _ptr);
+#endif
+            CHECK(_span == _str);
+            CHECK(_span == _vec);
+            CHECK(_span == _sp);
+
+            CHECK(_ar == _span);
+            CHECK(_ar1 == _span);
+            CHECK(_ar2 == _span);
+#ifdef CONFIRM_COMPILATION_ERRORS
+            CHECK(_ptr == _span);
+#endif
+            CHECK(_str == _span);
+            CHECK(_vec == _span);
+            CHECK(_sp == _span);
+
+            // non-const span, const other type
+
+            CHECK(_span == "Hello");
+            CHECK(_span == ar);
+            CHECK(_span == ar1);
+            CHECK(_span == ar2);
+#ifdef CONFIRM_COMPILATION_ERRORS
+            CHECK(_span == ptr);
+#endif
+            CHECK(_span == str);
+            CHECK(_span == vec);
+            CHECK(_span == sp);
+
+            CHECK("Hello" == _span);
+            CHECK(ar == _span);
+            CHECK(ar1 == _span);
+            CHECK(ar2 == _span);
+#ifdef CONFIRM_COMPILATION_ERRORS
+            CHECK(ptr == _span);
+#endif
+            CHECK(str == _span);
+            CHECK(vec == _span);
+            CHECK(sp == _span);
+
+            // two spans
+
+            CHECK(_span == span);
+            CHECK(span == _span);
+        }
+
+        {
+            std::vector<char> str1 = { 'H', 'e', 'l', 'l', 'o' };
+            cstring_span<> span1 = str1;
+            std::vector<char> str2 = std::move(str1);
+            cstring_span<> span2 = str2;
+
+            // comparison of spans from the same vector before and after move (ok)
+            CHECK(span1 == span2);
+        }
+    }
+
+    TEST(ComparisonAndImplicitConstructors)
+    {
+        {
+            cstring_span<> span = "Hello";
+
+            const char ar[] = { 'H', 'e', 'l', 'l', 'o' };
+            const char ar1[] = "Hello";
+            const char ar2[10] = "Hello";
+            const char* ptr = "Hello";
+            const std::string str = "Hello";
+            const std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+
+            // comparison to  literal
+            CHECK(span < cstring_span<>("Helloo"));
+            CHECK(span > cstring_span<>("Hell"));
+
+            // comparison to static array with no null termination
+            CHECK(span >= cstring_span<>(ar));
+
+            // comparison to static array with null at the end
+            CHECK(span <= cstring_span<>(ar1));
+
+            // comparison to static array with null in the middle
+            CHECK(span >= cstring_span<>(ar2));
+
+            // comparison to null-terminated c string
+            CHECK(span <= cstring_span<>(ptr, 5));
+
+            // comparison to string
+            CHECK(span >= cstring_span<>(str));
+
+            // comparison to vector of charaters with no null termination
+            CHECK(span <= cstring_span<>(vec));
+        }
+
+        {
+            char ar[] = { 'H', 'e', 'l', 'l', 'o' };
+
+            string_span<> span = ar;
+
+            char larr[] = "Hell";
+            char rarr[] = "Helloo";
+
+            char ar1[] = "Hello";
+            char ar2[10] = "Hello";
+            char* ptr = ar;
+            std::string str = "Hello";
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+
+
+            // comparison to static array with no null termination
+            CHECK(span <= string_span<>(ar));
+            CHECK(span < string_span<>(rarr));
+            CHECK(span > string_span<>(larr));
+
+            // comparison to static array with null at the end
+            CHECK(span >= string_span<>(ar1));
+
+            // comparison to static array with null in the middle
+            CHECK(span <= string_span<>(ar2));
+
+            // comparison to null-terminated c string
+            CHECK(span >= string_span<>(ptr, 5));
+
+            // comparison to string
+            CHECK(span <= string_span<>(str));
+
+            // comparison to vector of charaters with no null termination
+            CHECK(span >= string_span<>(vec));
+        }
+    }
+    TEST(ConstrutorsEnsureZ)
+    {
+        // remove z from literals
+        {
+            cstring_span<> sp = "hello";
+            CHECK((sp.length() == 5));
+        }
+
+        // take the string as is
+        {
+            auto str = std::string("hello");
+            cstring_span<> sp = str;
+            CHECK((sp.length() == 5));
+        }
+
+        // ensure z on c strings
+        {
+            char* ptr = new char[3];
+
+            ptr[0] = 'a';
+            ptr[1] = 'b';
+            ptr[2] = '\0';
+
+            string_span<> span = ensure_z(ptr);
+            CHECK(span.length() == 2);
+
+            delete[] ptr;
+        }
+    }
+
+    TEST(Constructors)
+    {
+        // creating cstring_span
+
+        // from span of a final extent
+        {
+            span<const char, 6> sp = "Hello";
+            cstring_span<> span = sp;
+            CHECK(span.length() == 6);
+        }
+
+        // from const span of a final extent to non-const string_span
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            span<const char, 6> sp = "Hello";
+            string_span<> span = sp;
+            CHECK(span.length() == 6);
+        }
+#endif
+
+        // from string temporary
+#ifdef CONFIRM_COMPILATION_ERRORS
+        {
+            cstring_span<> span = std::string("Hello");
+        }
+#endif
+
+        // default
+        {
+            cstring_span<> span;
+            CHECK(span.length() == 0);
+        }
+
+        // from nullptr
+        {
+            cstring_span<> span(nullptr);
+            CHECK(span.length() == 0);
+        }
+
+        // from string literal
+        {
+            cstring_span<> span = "Hello";
+            CHECK(span.length() == 5);
+        }
+
+        // from const static array
+        {
+            const char ar[] = { 'H', 'e', 'l', 'l', 'o' };
+            cstring_span<> span = ar;
+            CHECK(span.length() == 5);
+        }
+
+        // from non-const static array
+        {
+            char ar[] = { 'H', 'e', 'l', 'l', 'o' };
+            cstring_span<> span = ar;
+            CHECK(span.length() == 5);
+        }
+
+        // from const ptr and length
+        {
+            const char* ptr = "Hello";
+            cstring_span<> span{ ptr, 5 };
+            CHECK(span.length() == 5);
+        }
+
+        // from const ptr and length, include 0
+        {
+            const char* ptr = "Hello";
+            cstring_span<> span{ ptr, 6 };
+            CHECK(span.length() == 6);
+        }
+
+        // from const ptr and length, 0 inside
+        {
+            const char* ptr = "He\0lo";
+            cstring_span<> span{ ptr, 5 };
+            CHECK(span.length() == 5);
+        }
+
+        // from non-const ptr and length
+        {
+            char ar[] = { 'H', 'e', 'l', 'l', 'o' };
+            char* ptr = ar;
+            cstring_span<> span{ ptr, 5 };
+            CHECK(span.length() == 5);
+        }
+
+        // from non-const ptr and length, 0 inside
+        {
+            char ar[] = { 'H', 'e', '\0', 'l', 'o' };
+            char* ptr = ar;
+            cstring_span<> span{ ptr, 5 };
+            CHECK(span.length() == 5);
+        }
+
+        // from const string
+        {
+            const std::string str = "Hello";
+            cstring_span<> span = str;
+            CHECK(span.length() == 5);
+        }
+
+        // from non-const string
+        {
+            std::string str = "Hello";
+            cstring_span<> span = str;
+            CHECK(span.length() == 5);
+        }
+
+        // from const vector
+        {
+            const std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            cstring_span<> span = vec;
+            CHECK(span.length() == 5);
+        }
+
+        // from non-const vector
+        {
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            cstring_span<> span = vec;
+            CHECK(span.length() == 5);
+        }
+
+        // from const span
+        {
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            const span<const char> inner = vec;
+            cstring_span<> span = inner;
+            CHECK(span.length() == 5);
+        }
+
+        // from non-const span
+        {
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            span<char> inner = vec;
+            cstring_span<> span = inner;
+            CHECK(span.length() == 5);
+        }
+
+        // from const string_span
+        {
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            cstring_span<> tmp = vec;
+            cstring_span<> span = tmp;
+            CHECK(span.length() == 5);
+        }
+
+        // from non-const string_span
+        {
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            string_span<> tmp = vec;
+            cstring_span<> span = tmp;
+            CHECK(span.length() == 5);
+        }
+
+        // creating string_span
+
+        // from string literal
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            string_span<> span = "Hello";
+#endif
+        }
+
+        // from const static array
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            const char ar[] = { 'H', 'e', 'l', 'l', 'o' };
+            string_span<> span = ar;
+            CHECK(span.length() == 5);
+#endif
+        }
+
+        // from non-const static array
+        {
+            char ar[] = { 'H', 'e', 'l', 'l', 'o' };
+            string_span<> span = ar;
+            CHECK(span.length() == 5);
+        }
+
+        // from const ptr and length
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            const char* ptr = "Hello";
+            string_span<> span{ ptr, 5 };
+            CHECK(span.length() == 5);
+#endif
+        }
+
+        // from non-const ptr and length
+        {
+            char ar[] = { 'H', 'e', 'l', 'l', 'o' };
+            char* ptr = ar;
+            string_span<> span{ ptr, 5 };
+            CHECK(span.length() == 5);
+        }
+
+        // from const string
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            const std::string str = "Hello";
+            string_span<> span = str;
+            CHECK(span.length() == 5);
+#endif
+        }
+
+        // from non-const string
+        {
+            std::string str = "Hello";
+            string_span<> span = str;
+            CHECK(span.length() == 5);
+        }
+
+        // from const vector
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            const std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            string_span<> span = vec;
+            CHECK(span.length() == 5);
+#endif
+        }
+
+        // from non-const vector
+        {
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            string_span<> span = vec;
+            CHECK(span.length() == 5);
+        }
+
+        // from const span
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            const span<const char> inner = vec;
+            string_span<> span = inner;
+            CHECK(span.length() == 5);
+#endif
+        }
+
+        // from non-const span
+        {
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            span<char> inner = vec;
+            string_span<> span = inner;
+            CHECK(span.length() == 5);
+        }
+
+        // from non-const span of non-const data from const vector
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            const std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            const span<char> inner = vec;
+            string_span<> span = inner;
+            CHECK(span.length() == 5);
+#endif
+        }
+
+        // from const string_span
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            cstring_span<> tmp = vec;
+            string_span<> span = tmp;
+            CHECK(span.length() == 5);
+#endif
+        }
+
+        // from non-const string_span
+        {
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            string_span<> tmp = vec;
+            string_span<> span = tmp;
+            CHECK(span.length() == 5);
+        }
+
+        // from non-const string_span from const vector
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            const std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            string_span<> tmp = vec;
+            string_span<> span = tmp;
+            CHECK(span.length() == 5);
+#endif
+        }
+
+        // from const string_span of non-const data
+        {
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            const string_span<> tmp = vec;
+            string_span<> span = tmp;
+            CHECK(span.length() == 5);
+        }
+    }
+
+    template<typename T>
+    T move_wrapper(T&& t)
+    {
+        return std::move(t);
+    }
+
+    template <class T>
+    T create() { return T{}; }
+
+    template <class T>
+    void use(basic_string_span<T, gsl::dynamic_extent> s) {}
+
+    TEST(MoveConstructors)
+    {
+        // move string_span
+        {
+            cstring_span<> span = "Hello";
+            auto span1 = std::move(span);
+            CHECK(span1.length() == 5);
+        }
+        {
+            cstring_span<> span = "Hello";
+            auto span1 = move_wrapper(std::move(span));
+            CHECK(span1.length() == 5);
+        }
+        {
+            cstring_span<> span = "Hello";
+            auto span1 = move_wrapper(std::move(span));
+            CHECK(span1.length() == 5);
+        }
+
+        // move span
+        {
+            span<const char> span = ensure_z("Hello");
+            cstring_span<> span1 = std::move(span);
+            CHECK(span1.length() == 5);
+        }
+        {
+            span<const char> span = ensure_z("Hello");
+            cstring_span<> span2 = move_wrapper(std::move(span));
+            CHECK(span2.length() == 5);
+        }
+
+        // move string
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            std::string str = "Hello";
+            string_span<> span = std::move(str);
+            CHECK(span.length() == 5);
+#endif
+        }
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            std::string str = "Hello";
+            string_span<> span = move_wrapper<std::string>(std::move(str));
+            CHECK(span.length() == 5);
+#endif
+        }
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            use<char>(create<string>());
+#endif
+        }
+
+        // move container
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            string_span<> span = std::move(vec);
+            CHECK(span.length() == 5);
+#endif
+        }
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            std::vector<char> vec = { 'H', 'e', 'l', 'l', 'o' };
+            string_span<> span = move_wrapper<std::vector<char>>(std::move(vec));
+            CHECK(span.length() == 5);
+#endif
+        }
+        {
+#ifdef CONFIRM_COMPILATION_ERRORS
+            use<char>(create<std::vector<char>>());
+#endif
+        }
+    }
+
+    TEST(Conversion)
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        cstring_span<> span = "Hello";
+        cwstring_span<> wspan{ span };
+        CHECK(wspan.length() == 5);
+#endif
+    }
+
+    czstring_span<> CreateTempName(string_span<> span)
+    {
+        Expects(span.size() > 1);
+
+        int last = 0;
+        if (span.size() > 4)
+        {
+            span[0] = 't';
+            span[1] = 'm';
+            span[2] = 'p';
+            last = 3;
+        }
+        span[last] = '\0';
+
+        auto ret = span.subspan(0, 4);
+        return{ ret };
+    }
+
+    TEST(zstring)
+    {
+
+        // create zspan from zero terminated string
+        {
+            char buf[1];
+            buf[0] = '\0';
+
+            zstring_span<> zspan({ buf, 1 });
+
+            CHECK(strlen(zspan.assume_z()) == 0);
+            CHECK(zspan.as_string_span().size() == 0);
+            CHECK(zspan.ensure_z().size() == 0);
+        }
+
+        // create zspan from non-zero terminated string
+        {
+            char buf[1];
+            buf[0] = 'a';
+
+            auto workaround_macro = [&]() { zstring_span<> zspan({ buf, 1 }); };
+            CHECK_THROW(workaround_macro(), fail_fast);
+        }
+
+        // usage scenario: create zero-terminated temp file name and pass to a legacy API
+        {
+            char buf[10];
+
+            auto name = CreateTempName({ buf, 10 });
+            if (!name.empty())
+            {
+                czstring<> str = name.assume_z();
+                CHECK(strlen(str) == 3);
+                CHECK(*(str+3) == '\0');
+            }
+        }
+
+    }
+
+    cwzstring_span<> CreateTempNameW(wstring_span<> span)
+    {
+        Expects(span.size() > 1);
+
+        int last = 0;
+        if (span.size() > 4)
+        {
+            span[0] = L't';
+            span[1] = L'm';
+            span[2] = L'p';
+            last = 3;
+        }
+        span[last] = L'\0';
+
+        auto ret = span.subspan(0, 4);
+        return{ ret };
+    }
+
+    TEST(wzstring)
+    {
+
+        // create zspan from zero terminated string
+        {
+            wchar_t buf[1];
+            buf[0] = L'\0';
+
+            wzstring_span<> zspan({ buf, 1 });
+
+            CHECK(wcsnlen(zspan.assume_z(), 1) == 0);
+            CHECK(zspan.as_string_span().size() == 0);
+            CHECK(zspan.ensure_z().size() == 0);
+        }
+
+        // create zspan from non-zero terminated string
+        {
+            wchar_t buf[1];
+            buf[0] = L'a';
+
+            auto workaround_macro = [&]() { wzstring_span<> zspan({ buf, 1 }); };
+            CHECK_THROW(workaround_macro(), fail_fast);
+        }
+
+        // usage scenario: create zero-terminated temp file name and pass to a legacy API
+        {
+            wchar_t buf[10];
+
+            auto name = CreateTempNameW({ buf, 10 });
+            if (!name.empty())
+            {
+                cwzstring<> str = name.assume_z();
+                CHECK(wcsnlen(str, 10) == 3);
+                CHECK(*(str + 3) == L'\0');
+            }
+        }
+    }
+
+    TEST(Issue305)
+    {
+        std::map<gsl::cstring_span<>, int> foo = { { "foo", 0 },{ "bar", 1 } };
+        CHECK(foo["foo"] == 0);
+        CHECK(foo["bar"] == 1);
+    }
+}
+
+int main(int, const char *[])
+{
+    return UnitTest::RunAllTests();
+}
diff --git a/tests/unittest-cpp b/tests/unittest-cpp
new file mode 160000
+Subproject dc6b90838014ab985bf3cd74ac17ad9d00e1fbc
diff --git a/tests/utils_tests.cpp b/tests/utils_tests.cpp
new file mode 100644
index 0000000..9f4ba02
--- /dev/null
+++ b/tests/utils_tests.cpp
@@ -0,0 +1,119 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <UnitTest++/UnitTest++.h>
+#include <gsl/gsl>
+#include <functional>
+
+using namespace gsl;
+
+SUITE(utils_tests)
+{
+    void f(int& i)
+    {
+        i += 1;
+    }
+
+    TEST(finally_lambda)
+    {
+        int i = 0;
+        {
+            auto _ = finally([&]() {f(i);});
+            CHECK(i == 0);
+        }
+        CHECK(i == 1);
+    }
+
+    TEST(finally_lambda_move)
+    {
+        int i = 0;
+        {
+            auto _1 = finally([&]() {f(i);});
+            {
+                auto _2 = std::move(_1);
+                CHECK(i == 0);
+            }
+            CHECK(i == 1);
+            {
+                auto _2 = std::move(_1);
+                CHECK(i == 1);
+            }
+            CHECK(i == 1);
+        }
+        CHECK(i == 1);
+    }
+
+    TEST(finally_function_with_bind)
+    {
+        int i = 0;
+        {
+            auto _ = finally(std::bind(&f, std::ref(i)));
+            CHECK(i == 0);
+        }
+        CHECK(i == 1);
+    }
+
+    int j = 0;
+    void g() { j += 1; };
+    TEST(finally_function_ptr)
+    {
+        j = 0;
+        {
+            auto _ = finally(&g);
+            CHECK(j == 0);
+        }
+        CHECK(j == 1);
+    }
+
+    TEST(narrow_cast)
+    {
+        int n = 120;
+        char c = narrow_cast<char>(n);
+        CHECK(c == 120);
+
+        n = 300;
+        unsigned char uc = narrow_cast<unsigned char>(n);
+        CHECK(uc == 44);
+    }
+
+    TEST(narrow)
+    {
+        int n = 120;
+        char c = narrow<char>(n);
+        CHECK(c == 120);
+
+        n = 300;
+        CHECK_THROW(narrow<char>(n), narrowing_error);
+
+        const auto int32_max = std::numeric_limits<int32_t>::max();
+        const auto int32_min = std::numeric_limits<int32_t>::min();
+
+        CHECK(narrow<uint32_t>(int32_t(0)) == 0);
+        CHECK(narrow<uint32_t>(int32_t(1)) == 1);
+        CHECK(narrow<uint32_t>(int32_max) == static_cast<uint32_t>(int32_max));
+
+        CHECK_THROW(narrow<uint32_t>(int32_t(-1)), narrowing_error);
+        CHECK_THROW(narrow<uint32_t>(int32_min), narrowing_error);
+
+        n = -42;
+        CHECK_THROW(narrow<unsigned>(n), narrowing_error);
+    }
+}
+
+int main(int, const char *[])
+{
+    return UnitTest::RunAllTests();
+}