path: root/include/type_traits

// -*- C++ -*-
//===------------------------ type_traits ---------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_TYPE_TRAITS
#define _LIBCPP_TYPE_TRAITS

/*
    type_traits synopsis

namespace std
{

    // helper class:
    template <class T, T v> struct integral_constant;
    typedef integral_constant<bool, true>  true_type;
    typedef integral_constant<bool, false> false_type;

    // helper traits
    template <bool, class T = void> struct enable_if;
    template <bool, class T, class F> struct conditional;

    // Primary classification traits:
    template <class T> struct is_void;
    template <class T> struct is_integral;
    template <class T> struct is_floating_point;
    template <class T> struct is_array;
    template <class T> struct is_pointer;
    template <class T> struct is_lvalue_reference;
    template <class T> struct is_rvalue_reference;
    template <class T> struct is_reference;
    template <class T> struct is_member_object_pointer;
    template <class T> struct is_member_function_pointer;
    template <class T> struct is_enum;
    template <class T> struct is_union;
    template <class T> struct is_class;
    template <class T> struct is_function;
    
    // Secondary classification traits:
    template <class T> struct is_reference;
    template <class T> struct is_arithmetic;
    template <class T> struct is_fundamental;
    template <class T> struct is_member_pointer;
    template <class T> struct is_scalar;
    template <class T> struct is_object;
    template <class T> struct is_compound;
    
    // Const-volatile properties and transformations:
    template <class T> struct is_const;
    template <class T> struct is_volatile;
    template <class T> struct remove_const;
    template <class T> struct remove_volatile;
    template <class T> struct remove_cv;
    template <class T> struct add_const;
    template <class T> struct add_volatile;
    template <class T> struct add_cv;
    
    // Reference transformations:
    template <class T> struct remove_reference;
    template <class T> struct add_lvalue_reference;
    template <class T> struct add_rvalue_reference;
    
    // Pointer transformations:
    template <class T> struct remove_pointer;
    template <class T> struct add_pointer;
    
    // Integral properties:
    template <class T> struct is_signed;
    template <class T> struct is_unsigned;
    template <class T> struct make_signed;
    template <class T> struct make_unsigned;
    
    // Array properties and transformations:
    template <class T> struct rank;
    template <class T, unsigned I = 0> struct extent;
    template <class T> struct remove_extent;
    template <class T> struct remove_all_extents;
    
    // Member introspection:
    template <class T> struct is_pod;
    template <class T> struct is_trivial;
    template <class T> struct is_trivially_copyable;
    template <class T> struct is_standard_layout;
    template <class T> struct is_literal_type;
    template <class T> struct is_empty;
    template <class T> struct is_polymorphic;
    template <class T> struct is_abstract;
    template <class T, class... Args> struct is_constructible;
    template <class T, class... Args> struct is_nothrow_constructible;
    template <class T> struct has_default_constructor;
    template <class T> struct has_copy_constructor;
    template <class T> struct has_move_constructor;
    template <class T> struct has_copy_assign;
    template <class T> struct has_move_assign;
    template <class T> struct has_trivial_default_constructor
    template <class T> struct has_trivial_copy_constructor;
    template <class T> struct has_trivial_move_constructor;
    template <class T> struct has_trivial_copy_assign;
    template <class T> struct has_trivial_move_assign;
    template <class T> struct has_trivial_destructor;
    template <class T> struct has_nothrow_default_constructor;
    template <class T> struct has_nothrow_copy_constructor;
    template <class T> struct has_nothrow_move_constructor;
    template <class T> struct has_nothrow_copy_assign;
    template <class T> struct has_nothrow_move_assign;
    template <class T> struct has_virtual_destructor;
    
    // Relationships between types:
    template <class T, class U> struct is_same;
    template <class Base, class Derived> struct is_base_of;
    template <class From, class To> struct is_convertible;
    template <class From, class To> struct is_explicitly_convertible;
    template <class T> struct underlying_type;
    
    // Alignment properties and transformations:
    template <class T> struct alignment_of;
    template <size_t Len, size_t Align = most_stringent_alignment_requirement>
        struct aligned_storage;
    template <std::size_t Len, class... Types> struct aligned_union;

    template <class T> struct decay;
    template <class... T> struct common_type;
    template <class T> struct underlying_type;
    template <class> class result_of; // undefined
    template <class Fn, class... ArgTypes> class result_of<Fn(ArgTypes...)>;

}  // std

*/
#include <__config>
#include <cstddef>

#pragma GCC system_header

_LIBCPP_BEGIN_NAMESPACE_STD

template <bool _B, class _If, class _Then> struct conditional           {typedef _If type;};
template <class _If, class _Then> struct conditional<false, _If, _Then> {typedef _Then type;};

template <bool, class _Tp = void> struct enable_if {};
template <class _Tp> struct enable_if<true, _Tp> {typedef _Tp type;};

struct __two {char _[2];};

// helper class:

template <class _Tp, _Tp __v>
struct integral_constant
{
    static const _Tp          value = __v;
    typedef _Tp               value_type;
    typedef integral_constant type;
};

template <class _Tp, _Tp __v>
const _Tp integral_constant<_Tp, __v>::value;

typedef integral_constant<bool, true>  true_type;
typedef integral_constant<bool, false> false_type;

// is_const

template <class _Tp> struct is_const            : public false_type {};
template <class _Tp> struct is_const<_Tp const> : public true_type {};

// is_volatile

template <class _Tp> struct is_volatile               : public false_type {};
template <class _Tp> struct is_volatile<_Tp volatile> : public true_type {};

// remove_const

template <class _Tp> struct remove_const            {typedef _Tp type;};
template <class _Tp> struct remove_const<const _Tp> {typedef _Tp type;};

// remove_volatile

template <class _Tp> struct remove_volatile               {typedef _Tp type;};
template <class _Tp> struct remove_volatile<volatile _Tp> {typedef _Tp type;};

// remove_cv

template <class _Tp> struct remove_cv
{typedef typename remove_volatile<typename remove_const<_Tp>::type>::type type;};

// is_void

template <class _Tp> struct __is_void       : public false_type {};
template <>          struct __is_void<void> : public true_type {};

template <class _Tp> struct is_void : public __is_void<typename remove_cv<_Tp>::type> {};

// is_integral

template <class _Tp> struct __is_integral                     : public false_type {};
template <>          struct __is_integral<bool>               : public true_type {};
template <>          struct __is_integral<char>               : public true_type {};
template <>          struct __is_integral<signed char>        : public true_type {};
template <>          struct __is_integral<unsigned char>      : public true_type {};
template <>          struct __is_integral<wchar_t>            : public true_type {};
#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
template <>          struct __is_integral<char16_t>           : public true_type {};
template <>          struct __is_integral<char32_t>           : public true_type {};
#endif
template <>          struct __is_integral<short>              : public true_type {};
template <>          struct __is_integral<unsigned short>     : public true_type {};
template <>          struct __is_integral<int>                : public true_type {};
template <>          struct __is_integral<unsigned int>       : public true_type {};
template <>          struct __is_integral<long>               : public true_type {};
template <>          struct __is_integral<unsigned long>      : public true_type {};
template <>          struct __is_integral<long long>          : public true_type {};
template <>          struct __is_integral<unsigned long long> : public true_type {};

template <class _Tp> struct is_integral : public __is_integral<typename remove_cv<_Tp>::type> {};

// is_floating_point

template <class _Tp> struct __is_floating_point              : public false_type {};
template <>          struct __is_floating_point<float>       : public true_type {};
template <>          struct __is_floating_point<double>      : public true_type {};
template <>          struct __is_floating_point<long double> : public true_type {};

template <class _Tp> struct is_floating_point : public __is_floating_point<typename remove_cv<_Tp>::type> {};

// is_array

template <class _Tp> struct            is_array            : public false_type {};
template <class _Tp> struct            is_array<_Tp[]>     : public true_type {};
template <class _Tp, size_t _Np> struct is_array<_Tp[_Np]> : public true_type {};

// is_pointer

template <class _Tp> struct __is_pointer       : public false_type {};
template <class _Tp> struct __is_pointer<_Tp*> : public true_type {};

template <class _Tp> struct is_pointer : public __is_pointer<typename remove_cv<_Tp>::type> {};

// is_reference

template <class _Tp> struct is_lvalue_reference       : public false_type {};
template <class _Tp> struct is_lvalue_reference<_Tp&> : public true_type {};

template <class _Tp> struct is_rvalue_reference        : public false_type {};
#ifdef _LIBCPP_MOVE
template <class _Tp> struct is_rvalue_reference<_Tp&&> : public true_type {};
#endif

template <class _Tp> struct is_reference        : public false_type {};
template <class _Tp> struct is_reference<_Tp&>  : public true_type {};
#ifdef _LIBCPP_MOVE
template <class _Tp> struct is_reference<_Tp&&> : public true_type {};
#endif

// is_union

#if __GNUC__ >= 4 && __GNUC_MINOR__ >= 3

template <class _Tp> struct is_union : public integral_constant<bool, __is_union(_Tp)> {};

#else

template <class _Tp> struct __libcpp_union : public false_type {};
template <class _Tp> struct is_union : public __libcpp_union<typename remove_cv<_Tp>::type> {};

#endif

// is_class

namespace __is_class_imp
{
template <class _Tp> char  __test(int _Tp::*);
template <class _Tp> __two __test(...);
}

template <class _Tp> struct is_class
    : public integral_constant<bool, sizeof(__is_class_imp::__test<_Tp>(0)) == 1 && !is_union<_Tp>::value> {};

// is_function

namespace __is_function_imp
{
template <class _Tp> char  __test(_Tp*);
template <class _Tp> __two __test(...);
template <class _Tp> _Tp&  __source();
}

template <class _Tp, bool = is_class<_Tp>::value ||
                            is_union<_Tp>::value ||
                            is_void<_Tp>::value  ||
                            is_reference<_Tp>::value>
struct __is_function
    : public integral_constant<bool, sizeof(__is_function_imp::__test<_Tp>(__is_function_imp::__source<_Tp>())) == 1>
    {};
template <class _Tp> struct __is_function<_Tp, true> : public false_type {};

template <class _Tp> struct is_function : public __is_function<_Tp> {};

// is_member_function_pointer

template <class _Tp> struct            __is_member_function_pointer             : public false_type {};
template <class _Tp, class _Up> struct __is_member_function_pointer<_Tp _Up::*> : public is_function<_Tp> {};

template <class _Tp> struct is_member_function_pointer
    : public __is_member_function_pointer<typename remove_cv<_Tp>::type> {};

// is_member_pointer

template <class _Tp>            struct __is_member_pointer             : public false_type {};
template <class _Tp, class _Up> struct __is_member_pointer<_Tp _Up::*> : public true_type {};

template <class _Tp> struct is_member_pointer
    : public __is_member_pointer<typename remove_cv<_Tp>::type> {};

// is_member_object_pointer

template <class _Tp> struct is_member_object_pointer
    : public integral_constant<bool, is_member_pointer<_Tp>::value &&
                                    !is_member_function_pointer<_Tp>::value> {};

// is_enum

template <class _Tp> struct is_enum
    : public integral_constant<bool, !is_void<_Tp>::value             &&
                                     !is_integral<_Tp>::value         &&
                                     !is_floating_point<_Tp>::value   &&
                                     !is_array<_Tp>::value            &&
                                     !is_pointer<_Tp>::value          &&
                                     !is_reference<_Tp>::value        &&
                                     !is_member_pointer<_Tp>::value   &&
                                     !is_union<_Tp>::value            &&
                                     !is_class<_Tp>::value            &&
                                     !is_function<_Tp>::value         > {};

// is_arithmetic

template <class _Tp> struct is_arithmetic
    : public integral_constant<bool, is_integral<_Tp>::value      ||
                                     is_floating_point<_Tp>::value> {};

// is_fundamental

template <class _Tp> struct is_fundamental
    : public integral_constant<bool, is_void<_Tp>::value      ||
                                     is_arithmetic<_Tp>::value> {};

// is_scalar

template <class _Tp> struct is_scalar
    : public integral_constant<bool, is_arithmetic<_Tp>::value     ||
                                     is_member_pointer<_Tp>::value ||
                                     is_pointer<_Tp>::value        ||
                                     is_enum<_Tp>::value           > {};

// is_object

template <class _Tp> struct is_object
    : public integral_constant<bool, is_scalar<_Tp>::value ||
                                     is_array<_Tp>::value  ||
                                     is_union<_Tp>::value  ||
                                     is_class<_Tp>::value  > {};

// is_compound

template <class _Tp> struct is_compound : public integral_constant<bool, !is_fundamental<_Tp>::value> {};

// add_const

template <class _Tp, bool = is_reference<_Tp>::value ||
                            is_function<_Tp>::value  ||
                            is_const<_Tp>::value     >
struct __add_const             {typedef _Tp type;};

template <class _Tp>
struct __add_const<_Tp, false> {typedef const _Tp type;};

template <class _Tp> struct add_const {typedef typename __add_const<_Tp>::type type;};

// add_volatile

template <class _Tp, bool = is_reference<_Tp>::value ||
                            is_function<_Tp>::value  ||
                            is_volatile<_Tp>::value  >
struct __add_volatile             {typedef _Tp type;};

template <class _Tp>
struct __add_volatile<_Tp, false> {typedef volatile _Tp type;};

template <class _Tp> struct add_volatile {typedef typename __add_volatile<_Tp>::type type;};

// add_cv

template <class T> struct add_cv {typedef typename add_const<typename add_volatile<T>::type>::type type;};

// remove_reference

template <class _Tp> struct remove_reference        {typedef _Tp type;};
template <class _Tp> struct remove_reference<_Tp&>  {typedef _Tp type;};
#ifdef _LIBCPP_MOVE
template <class _Tp> struct remove_reference<_Tp&&> {typedef _Tp type;};
#endif

// add_lvalue_reference

template <class _Tp> struct add_lvalue_reference                      {typedef _Tp& type;};
template <class _Tp> struct add_lvalue_reference<_Tp&>                {typedef _Tp& type;};  // for older compiler
template <>          struct add_lvalue_reference<void>                {typedef void type;};
template <>          struct add_lvalue_reference<const void>          {typedef const void type;};
template <>          struct add_lvalue_reference<volatile void>       {typedef volatile void type;};
template <>          struct add_lvalue_reference<const volatile void> {typedef const volatile void type;};

#ifdef _LIBCPP_MOVE

template <class _Tp> struct add_rvalue_reference                      {typedef _Tp&& type;};
template <>          struct add_rvalue_reference<void>                {typedef void type;};
template <>          struct add_rvalue_reference<const void>          {typedef const void type;};
template <>          struct add_rvalue_reference<volatile void>       {typedef volatile void type;};
template <>          struct add_rvalue_reference<const volatile void> {typedef const volatile void type;};

#endif

// remove_pointer

template <class _Tp> struct remove_pointer                      {typedef _Tp type;};
template <class _Tp> struct remove_pointer<_Tp*>                {typedef _Tp type;};
template <class _Tp> struct remove_pointer<_Tp* const>          {typedef _Tp type;};
template <class _Tp> struct remove_pointer<_Tp* volatile>       {typedef _Tp type;};
template <class _Tp> struct remove_pointer<_Tp* const volatile> {typedef _Tp type;};

// add_pointer

template <class _Tp> struct add_pointer {typedef typename remove_reference<_Tp>::type* type;};

// is_signed

template <class _Tp, bool = is_integral<_Tp>::value>
struct ___is_signed : public integral_constant<bool, _Tp(-1) < _Tp(0)> {};

template <class _Tp>
struct ___is_signed<_Tp, false> : public true_type {};  // floating point

template <class _Tp, bool = is_arithmetic<_Tp>::value>
struct __is_signed : public ___is_signed<_Tp> {};

template <class _Tp> struct __is_signed<_Tp, false> : public false_type {};

template <class _Tp> struct is_signed : public __is_signed<_Tp> {};

// is_unsigned

template <class _Tp, bool = is_integral<_Tp>::value>
struct ___is_unsigned : public integral_constant<bool, _Tp(0) < _Tp(-1)> {};

template <class _Tp>
struct ___is_unsigned<_Tp, false> : public false_type {};  // floating point

template <class _Tp, bool = is_arithmetic<_Tp>::value>
struct __is_unsigned : public ___is_unsigned<_Tp> {};

template <class _Tp> struct __is_unsigned<_Tp, false> : public false_type {};

template <class _Tp> struct is_unsigned : public __is_unsigned<_Tp> {};

// rank

template <class _Tp> struct rank                       : public integral_constant<size_t, 0> {};
template <class _Tp> struct rank<_Tp[]>                : public integral_constant<size_t, rank<_Tp>::value + 1> {};
template <class _Tp, size_t _Np> struct rank<_Tp[_Np]> : public integral_constant<size_t, rank<_Tp>::value + 1> {};

// extent

template <class _Tp, unsigned _Ip = 0>         struct extent                : public integral_constant<size_t, 0> {};
template <class _Tp>                           struct extent<_Tp[], 0>      : public integral_constant<size_t, 0> {};
template <class _Tp, unsigned _Ip>             struct extent<_Tp[], _Ip>    : public integral_constant<size_t, extent<_Tp, _Ip-1>::value> {};
template <class _Tp, size_t _Np>               struct extent<_Tp[_Np], 0>   : public integral_constant<size_t, _Np> {};
template <class _Tp, size_t _Np, unsigned _Ip> struct extent<_Tp[_Np], _Ip> : public integral_constant<size_t, extent<_Tp, _Ip-1>::value> {};

// remove_extent

template <class _Tp>             struct remove_extent           {typedef _Tp type;};
template <class _Tp>             struct remove_extent<_Tp[]>    {typedef _Tp type;};
template <class _Tp, size_t _Np> struct remove_extent<_Tp[_Np]> {typedef _Tp type;};

// remove_all_extents

template <class _Tp>             struct remove_all_extents           {typedef _Tp type;};
template <class _Tp>             struct remove_all_extents<_Tp[]>    {typedef typename remove_all_extents<_Tp>::type type;};
template <class _Tp, size_t _Np> struct remove_all_extents<_Tp[_Np]> {typedef typename remove_all_extents<_Tp>::type type;};

// is_same

template <class _Tp, class _Up> struct is_same           : public false_type {};
template <class _Tp>            struct is_same<_Tp, _Tp> : public true_type {};

// is_abstract

namespace __is_abstract_imp
{
template <class _Tp> char  __test(_Tp (*)[1]);
template <class _Tp> __two __test(...);
}

template <class _Tp, bool = is_class<_Tp>::value>
struct __libcpp_abstract : public integral_constant<bool, sizeof(__is_abstract_imp::__test<_Tp>(0)) != 1> {};

template <class _Tp> struct __libcpp_abstract<_Tp, false> : public false_type {};

template <class _Tp> struct is_abstract : public __libcpp_abstract<_Tp> {};

// is_convertible

namespace __is_convertible_imp
{
#ifdef _LIBCPP_MOVE
template <class _Tp> char  __test(const volatile typename remove_reference<_Tp>::type&&);
#else
template <class _Tp> char  __test(_Tp);
#endif
template <class _Tp> __two __test(...);
#ifdef _LIBCPP_MOVE
template <class _Tp> _Tp&& __source();
#else
template <class _Tp> typename remove_reference<_Tp>::type& __source();
#endif

template <class _Tp, bool _IsArray =    is_array<_Tp>::value,
                     bool _IsFunction = is_function<_Tp>::value,
                     bool _IsVoid =     is_void<_Tp>::value>
                     struct __is_array_function_or_void                          {enum {value = 0};};
template <class _Tp> struct __is_array_function_or_void<_Tp, true, false, false> {enum {value = 1};};
template <class _Tp> struct __is_array_function_or_void<_Tp, false, true, false> {enum {value = 2};};
template <class _Tp> struct __is_array_function_or_void<_Tp, false, false, true> {enum {value = 3};};
}

template <class _Tp,
    unsigned = __is_convertible_imp::__is_array_function_or_void<typename remove_reference<_Tp>::type>::value>
struct __is_convertible_check
{
    static const size_t __v = 0;
};

template <class _Tp>
struct __is_convertible_check<_Tp, 0>
{
    static const size_t __v = sizeof(_Tp);
};

template <class _T1, class _T2,
    unsigned _T1_is_array_function_or_void = __is_convertible_imp::__is_array_function_or_void<_T1>::value,
    unsigned _T2_is_array_function_or_void = __is_convertible_imp::__is_array_function_or_void<_T2>::value>
struct __is_convertible
    : public integral_constant<bool,
        sizeof(__is_convertible_imp::__test<_T2>(__is_convertible_imp::__source<_T1>())) == 1
    >
{};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 1, 0> : false_type {};

template <class _T1> struct __is_convertible<_T1, const _T1&, 1, 0> : true_type {};
#ifdef _LIBCPP_MOVE
template <class _T1> struct __is_convertible<_T1, _T1&&, 1, 0> : true_type {};
template <class _T1> struct __is_convertible<_T1, const _T1&&, 1, 0> : true_type {};
template <class _T1> struct __is_convertible<_T1, volatile _T1&&, 1, 0> : true_type {};
template <class _T1> struct __is_convertible<_T1, const volatile _T1&&, 1, 0> : true_type {};
#endif

template <class _T1, class _T2> struct __is_convertible<_T1, _T2*, 1, 0>
    : public integral_constant<bool, __is_convertible<typename remove_all_extents<_T1>::type*, _T2*>::value> {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2* const, 1, 0>
    : public integral_constant<bool, __is_convertible<typename remove_all_extents<_T1>::type*, _T2*const>::value> {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2* volatile, 1, 0>
    : public integral_constant<bool, __is_convertible<typename remove_all_extents<_T1>::type*, _T2*volatile>::value> {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2* const volatile, 1, 0>
    : public integral_constant<bool, __is_convertible<typename remove_all_extents<_T1>::type*, _T2*const volatile>::value> {};


template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 2, 0>                : public false_type {};
#ifdef _LIBCPP_MOVE
template <class _T1>            struct __is_convertible<_T1, _T1&&, 2, 0>               : public true_type {};
#endif
template <class _T1>            struct __is_convertible<_T1, _T1*, 2, 0>               : public true_type {};
template <class _T1>            struct __is_convertible<_T1, _T1*const, 2, 0>          : public true_type {};
template <class _T1>            struct __is_convertible<_T1, _T1*volatile, 2, 0>       : public true_type {};
template <class _T1>            struct __is_convertible<_T1, _T1*const volatile, 2, 0> : public true_type {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 3, 0> : public false_type {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 0, 1> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 1, 1> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 2, 1> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 3, 1> : public false_type {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 0, 2> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 1, 2> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 2, 2> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 3, 2> : public false_type {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 0, 3> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 1, 3> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 2, 3> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 3, 3> : public true_type {};

template <class _T1, class _T2> struct is_convertible : public __is_convertible<_T1, _T2>
{
    static const size_t __complete_check1 = __is_convertible_check<_T1>::__v;
    static const size_t __complete_check2 = __is_convertible_check<_T2>::__v;
};

// is_base_of

//  (C) Copyright Rani Sharoni 2003.
//  Use, modification and distribution are subject to the Boost Software License,
//  Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
//  http://www.boost.org/LICENSE_1_0.txt).
//
//  See http://www.boost.org/libs/type_traits for most recent version including documentation.

template <class _Bp, class _Dp>
struct __is_base_of_tests
{
    template <class _Tp>
    static char  __test(const volatile _Dp*, _Tp);
    static __two __test(const volatile _Bp*, int);
};

template <class _Bp, class _Dp>
struct __is_base_of_imp
{
    struct __host
    {
        operator const volatile _Bp*() const;
        operator const volatile _Dp*();
    };

    static const size_t __complete_check = sizeof(_Dp);
    static const bool value = sizeof(__is_base_of_tests<_Bp, _Dp>::__test(__host(), 0)) == 1;
};

template <class _Bp, class _Dp, bool = is_class<_Bp>::value,
                                bool = is_class<_Dp>::value,
                                bool = is_same<_Bp, _Dp>::value>
struct __libcpp_base_of : public false_type {};

template <class _Bp, class _Dp>
struct __libcpp_base_of<_Bp, _Dp, true, true, true> : public true_type {};

template <class _Bp, class _Dp>
struct __libcpp_base_of<_Bp, _Dp, true, true, false>
    : public integral_constant<bool, __is_base_of_imp<_Bp, _Dp>::value> {};

template <class _Bp, class _Dp>
struct is_base_of
    : public __libcpp_base_of<typename remove_cv<_Bp>::type, typename remove_cv<_Dp>::type>
{
};

// is_empty

template <class _Tp>
struct __is_empty1
    : public _Tp
{
    double _;
};

struct __is_empty2
{
    double _;
};

template <class _Tp, bool = is_class<_Tp>::value>
struct __libcpp_empty : public integral_constant<bool, sizeof(__is_empty1<_Tp>) == sizeof(__is_empty2)> {};

template <class _Tp> struct __libcpp_empty<_Tp, false> : public false_type {};

template <class _Tp> struct is_empty : public __libcpp_empty<_Tp> {};

// is_polymorphic

template <class _Tp> struct __is_polymorphic1 : public _Tp {};
template <class _Tp> struct __is_polymorphic2 : public _Tp {virtual ~__is_polymorphic2() throw();};

template <class _Tp, bool = is_class<_Tp>::value>
struct __libcpp_polymorphic
    : public integral_constant<bool, sizeof(__is_polymorphic1<_Tp>) == sizeof(__is_polymorphic2<_Tp>)> {};

template <class _Tp> struct __libcpp_polymorphic<_Tp, false> : public false_type {};

template <class _Tp> struct is_polymorphic : public __libcpp_polymorphic<_Tp> {};

// has_trivial_default_constructor

template <class _Tp> struct __has_trivial_default_constructor : public integral_constant<bool, is_scalar<_Tp>::value> {};

template <class _Tp> struct has_trivial_default_constructor
    : public __has_trivial_default_constructor<typename remove_all_extents<_Tp>::type> {};

// has_nothrow_default_constructor

template <class _Tp> struct has_nothrow_default_constructor : public has_trivial_default_constructor<_Tp> {};

// has_trivial_copy_constructor

template <class _Tp> struct __has_trivial_copy_constructor : public integral_constant<bool, is_scalar<_Tp>::value ||
                                                                                is_reference<_Tp>::value> {};

template <class _Tp> struct has_trivial_copy_constructor
    : public __has_trivial_copy_constructor<typename remove_all_extents<_Tp>::type> {};

// has_nothrow_copy_constructor

template <class _Tp> struct has_nothrow_copy_constructor : public has_trivial_copy_constructor<_Tp> {};

// has_nothrow_move_constructor

template <class _Tp> struct has_nothrow_move_constructor : public has_nothrow_copy_constructor<_Tp> {};

// has_copy_constructor

template <class _Tp> struct has_copy_constructor : public true_type {};

// has_trivial_copy_assign

template <class _Tp> struct __libcpp_trivial_copy_assign : public integral_constant<bool, !is_const<_Tp>::value &&
                                                                                   is_scalar<_Tp>::value> {};

template <class _Tp> struct has_trivial_copy_assign
    : public __libcpp_trivial_copy_assign<typename remove_all_extents<_Tp>::type> {};

// has_nothrow_copy_assign

template <class _Tp> struct has_nothrow_copy_assign: public has_trivial_copy_assign<_Tp> {};

// has_trivial_destructor

template <class _Tp> struct __libcpp_trivial_destructor : public integral_constant<bool, is_scalar<_Tp>::value ||
                                                                                      is_reference<_Tp>::value> {};

template <class _Tp> struct has_trivial_destructor
    : public __libcpp_trivial_destructor<typename remove_all_extents<_Tp>::type> {};

// has_virtual_destructor

template <class _Tp> struct has_virtual_destructor : public false_type {};

// is_pod

template <class _Tp> struct is_pod : public integral_constant<bool, has_trivial_default_constructor<_Tp>::value   &&
                                                                    has_trivial_copy_constructor<_Tp>::value      &&
                                                                    has_trivial_copy_assign<_Tp>::value    &&
                                                                    has_trivial_destructor<_Tp>::value> {};

// alignment_of

template <class _Tp> struct __alignment_of {_Tp _;};

template <class _Tp> struct alignment_of
    : public integral_constant<size_t, __alignof__(__alignment_of<typename remove_all_extents<_Tp>::type>)> {};

// aligned_storage

template <class _Hp, class _Tp>
struct __type_list
{
    typedef _Hp _Head;
    typedef _Tp _Tail;
};

struct __nat {};

template <class _Tp>
struct __align_type
{
    static const size_t value = alignment_of<_Tp>::value;
    typedef _Tp type;
};

struct __struct_double {long double _;};
struct __struct_double4 {double _[4];};

typedef
    __type_list<__align_type<unsigned char>,
    __type_list<__align_type<unsigned short>,
    __type_list<__align_type<unsigned int>,
    __type_list<__align_type<unsigned long>,
    __type_list<__align_type<unsigned long long>,
    __type_list<__align_type<double>,
    __type_list<__align_type<long double>,
    __type_list<__align_type<__struct_double>,
    __type_list<__align_type<__struct_double4>,
    __type_list<__align_type<int*>,
    __nat
    > > > > > > > > > > __all_types;

template <class _TL, size_t _Align> struct __find_pod;

template <class _Hp, size_t _Align>
struct __find_pod<__type_list<_Hp, __nat>, _Align>
{
    typedef typename conditional<
                             _Align == _Hp::value,
                             typename _Hp::type,
                             void
                         >::type type;
};

template <class _Hp, class _Tp, size_t _Align>
struct __find_pod<__type_list<_Hp, _Tp>, _Align>
{
    typedef typename conditional<
                             _Align == _Hp::value,
                             typename _Hp::type,
                             typename __find_pod<_Tp, _Align>::type
                         >::type type;
};

template <class _TL, size_t _Len> struct __find_max_align;

template <class _Hp, size_t _Len>
struct __find_max_align<__type_list<_Hp, __nat>, _Len> : public integral_constant<size_t, _Hp::value> {};

template <size_t _Len, size_t _A1, size_t _A2>
struct __select_align
{
private:
    static const size_t __min = _A2 < _A1 ? _A2 : _A1;
    static const size_t __max = _A1 < _A2 ? _A2 : _A1;
public:
    static const size_t value = _Len < __max ? __min : __max;
};

template <class _Hp, class _Tp, size_t _Len>
struct __find_max_align<__type_list<_Hp, _Tp>, _Len>
    : public integral_constant<size_t, __select_align<_Len, _Hp::value, __find_max_align<_Tp, _Len>::value>::value> {};

template <size_t _Len, const size_t _Align = __find_max_align<__all_types, _Len>::value>
struct aligned_storage
{
    typedef typename __find_pod<__all_types, _Align>::type _Aligner;
    static_assert(!is_void<_Aligner>::value, "");
    union type
    {
        _Aligner __align;
        unsigned char __data[_Len];
    };
};

#define _CREATE_ALIGNED_STORAGE_SPECIALIZATION(n) \
template <size_t _Len>\
struct aligned_storage<_Len, n>\
{\
    struct type\
    {\
        unsigned char _[_Len];\
    } __attribute__((__aligned__(n)));\
}

_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x1);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x2);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x4);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x8);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x10);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x20);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x40);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x80);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x100);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x200);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x400);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x800);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x1000);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x2000);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x4000);

#undef _CREATE_ALIGNED_STORAGE_SPECIALIZATION

// __promote

template <class _A1, class _A2 = void, class _A3 = void,
          bool = (is_arithmetic<_A1>::value || is_void<_A1>::value) &&
                 (is_arithmetic<_A2>::value || is_void<_A2>::value) &&
                 (is_arithmetic<_A3>::value || is_void<_A3>::value)>
class __promote {};


template <class _A1, class _A2, class _A3>
class __promote<_A1, _A2, _A3, true>
{
private:
    typedef typename __promote<_A1>::type __type1;
    typedef typename __promote<_A2>::type __type2;
    typedef typename __promote<_A3>::type __type3;
public:
    typedef __typeof__(__type1() + __type2() + __type3()) type;
};

template <class _A1, class _A2>
class __promote<_A1, _A2, void, true>
{
private:
    typedef typename __promote<_A1>::type __type1;
    typedef typename __promote<_A2>::type __type2;
public:
    typedef __typeof__(__type1() + __type2()) type;
};

template <class _A1>
class __promote<_A1, void, void, true>
{
public:
    typedef typename conditional<is_arithmetic<_A1>::value,
                     typename conditional<is_integral<_A1>::value, double, _A1>::type,
                     void
            >::type type;
};

#ifdef _LIBCPP_STORE_AS_OPTIMIZATION

// __transform

template <class _Tp, size_t = sizeof(_Tp), bool = is_scalar<_Tp>::value> struct __transform {typedef _Tp type;};
template <class _Tp> struct __transform<_Tp, 1, true> {typedef unsigned char      type;};
template <class _Tp> struct __transform<_Tp, 2, true> {typedef unsigned short     type;};
template <class _Tp> struct __transform<_Tp, 4, true> {typedef unsigned int       type;};
template <class _Tp> struct __transform<_Tp, 8, true> {typedef unsigned long long type;};

#endif  // _LIBCPP_STORE_AS_OPTIMIZATION

// make_signed / make_unsigned

typedef
    __type_list<signed char,
    __type_list<signed short,
    __type_list<signed int,
    __type_list<signed long,
    __type_list<signed long long,
    __nat
    > > > > > __signed_types;

typedef
    __type_list<unsigned char,
    __type_list<unsigned short,
    __type_list<unsigned int,
    __type_list<unsigned long,
    __type_list<unsigned long long,
    __nat
    > > > > > __unsigned_types;

template <class _TypeList, size_t _Size, bool = _Size <= sizeof(typename _TypeList::_Head)> struct __find_first;

template <class _Hp, class _Tp, size_t _Size>
struct __find_first<__type_list<_Hp, _Tp>, _Size, true>
{
    typedef _Hp type;
};

template <class _Hp, class _Tp, size_t _Size>
struct __find_first<__type_list<_Hp, _Tp>, _Size, false>
{
    typedef typename __find_first<_Tp, _Size>::type type;
};

template <class _Tp, class _Up, bool = is_const<typename remove_reference<_Tp>::type>::value,
                             bool = is_volatile<typename remove_reference<_Tp>::type>::value>
struct __apply_cv
{
    typedef _Up type;
};

template <class _Tp, class _Up>
struct __apply_cv<_Tp, _Up, true, false>
{
    typedef const _Up type;
};

template <class _Tp, class _Up>
struct __apply_cv<_Tp, _Up, false, true>
{
    typedef volatile _Up type;
};

template <class _Tp, class _Up>
struct __apply_cv<_Tp, _Up, true, true>
{
    typedef const volatile _Up type;
};

template <class _Tp, class _Up>
struct __apply_cv<_Tp&, _Up, false, false>
{
    typedef _Up& type;
};

template <class _Tp, class _Up>
struct __apply_cv<_Tp&, _Up, true, false>
{
    typedef const _Up& type;
};

template <class _Tp, class _Up>
struct __apply_cv<_Tp&, _Up, false, true>
{
    typedef volatile _Up& type;
};

template <class _Tp, class _Up>
struct __apply_cv<_Tp&, _Up, true, true>
{
    typedef const volatile _Up& type;
};

template <class _Tp, bool = is_integral<_Tp>::value || is_enum<_Tp>::value>
struct __make_signed {};

template <class _Tp>
struct __make_signed<_Tp, true>
{
    typedef typename __find_first<__signed_types, sizeof(_Tp)>::type type;
};

template <> struct __make_signed<bool,               true> {};
template <> struct __make_signed<  signed short,     true> {typedef short     type;};
template <> struct __make_signed<unsigned short,     true> {typedef short     type;};
template <> struct __make_signed<  signed int,       true> {typedef int       type;};
template <> struct __make_signed<unsigned int,       true> {typedef int       type;};
template <> struct __make_signed<  signed long,      true> {typedef long      type;};
template <> struct __make_signed<unsigned long,      true> {typedef long      type;};
template <> struct __make_signed<  signed long long, true> {typedef long long type;};
template <> struct __make_signed<unsigned long long, true> {typedef long long type;};

template <class _Tp>
struct make_signed
{
    typedef typename __apply_cv<_Tp, typename __make_signed<typename remove_cv<_Tp>::type>::type>::type type;
};

template <class _Tp, bool = is_integral<_Tp>::value || is_enum<_Tp>::value>
struct __make_unsigned {};

template <class _Tp>
struct __make_unsigned<_Tp, true>
{
    typedef typename __find_first<__unsigned_types, sizeof(_Tp)>::type type;
};

template <> struct __make_unsigned<bool,               true> {};
template <> struct __make_unsigned<  signed short,     true> {typedef unsigned short     type;};
template <> struct __make_unsigned<unsigned short,     true> {typedef unsigned short     type;};
template <> struct __make_unsigned<  signed int,       true> {typedef unsigned int       type;};
template <> struct __make_unsigned<unsigned int,       true> {typedef unsigned int       type;};
template <> struct __make_unsigned<  signed long,      true> {typedef unsigned long      type;};
template <> struct __make_unsigned<unsigned long,      true> {typedef unsigned long      type;};
template <> struct __make_unsigned<  signed long long, true> {typedef unsigned long long type;};
template <> struct __make_unsigned<unsigned long long, true> {typedef unsigned long long type;};

template <class _Tp>
struct make_unsigned
{
    typedef typename __apply_cv<_Tp, typename __make_unsigned<typename remove_cv<_Tp>::type>::type>::type type;
};

#ifdef _LIBCPP_HAS_NO_VARIADICS

template <class _Tp, class _Up = void, class V = void>
struct common_type
{
public:
    typedef typename common_type<typename common_type<_Tp, _Up>::type, V>::type type;
};


template <class _Tp>
struct common_type<_Tp, void, void>
{
public:
    typedef _Tp type;
};

template <class _Tp, class _Up>
struct common_type<_Tp, _Up, void>
{
private:
#ifdef _LIBCPP_MOVE
    static _Tp&& __t();
    static _Up&& __u();
#else
    static _Tp __t();
    static _Up __u();
    static bool __f();
#endif
public:
    typedef __typeof__(__f() ? __t() : __u()) type;
};

#else

template <class ..._Tp> struct common_type;

template <class _Tp>
struct common_type<_Tp>
{
    typedef _Tp type;
};

template <class _Tp, class _Up>
struct common_type<_Tp, _Up>
{
private:
    static _Tp&& __t();
    static _Up&& __u();
    static bool __f();
public:
    typedef decltype(__f() ? __t() : __u()) type;
};

template <class _Tp, class _Up, class ..._Vp>
struct common_type<_Tp, _Up, _Vp...>
{
    typedef typename common_type<typename common_type<_Tp, _Up>::type, _Vp...>::type type;
};

#endif

// move

#ifdef _LIBCPP_MOVE

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
typename remove_reference<_Tp>::type&&
move(_Tp&& __t) {return __t;}

template <class _Tp, class _Up,
    class = typename _STD::enable_if<
         is_lvalue_reference<_Tp>::value ? is_lvalue_reference<_Up>::value : true
                     >::type,
    class = typename _STD::enable_if<
         is_convertible<typename remove_reference<_Up>::type*,
                        typename remove_reference<_Tp>::type*>::value>::type>
inline _LIBCPP_INLINE_VISIBILITY
_Tp&&
forward(_Up&& __t)
{
    return __t;  // to quiet spurious warning
//    return static_cast<_Tp&&>(__t);
}

#else  // _LIBCPP_MOVE

template <class T>
class __rv
{
    typedef typename remove_reference<T>::type Trr;
    Trr& t_;
public:
    Trr* operator->() {return &t_;}
    explicit __rv(Trr& t) : t_(t) {}
};

template <class T>
inline
typename enable_if
<
    !is_convertible<T, __rv<T> >::value,
    T&
>::type
move(T& t)
{
    return t;
}

template <class T>
inline
typename enable_if
<
    is_convertible<T, __rv<T> >::value,
    T
>::type
move(T& t)
{
    return T(__rv<T>(t));
}

template <class T, class U>
inline
typename enable_if
<
    !is_convertible<T, __rv<T> >::value,
    typename add_lvalue_reference<T>::type
>::type
forward(U& t)
{
    return t;
}

template <class T, class U>
inline
typename enable_if
<
    !is_convertible<T, __rv<T> >::value,
    typename add_lvalue_reference<T>::type
>::type
forward(const U& t)
{
    return t;
}

template <class T, class U>
inline
typename enable_if
<
    is_convertible<T, __rv<T> >::value,
    T
>::type
forward(U& t)
{
    return T(__rv<T>(t));
}

template <class T, class U>
inline
typename enable_if
<
    is_convertible<T, __rv<T> >::value,
    T
>::type
forward(const U& t)
{
    return T(__rv<T>(t));
}

#endif  // _LIBCPP_MOVE

#ifdef _LIBCPP_MOVE

template <class _Tp>
typename add_rvalue_reference<_Tp>::type
declval();

#else

template <class _Tp>
typename add_lvalue_reference<_Tp>::type
declval();

#endif

template <class _Tp>
struct decay
{
private:
    typedef typename remove_reference<_Tp>::type _Up;
public:
    typedef typename conditional
                     <
                         is_array<_Up>::value,
                         typename remove_extent<_Up>::type*,
                         typename conditional
                         <
                              is_function<_Up>::value,
                              typename add_pointer<_Up>::type,
                              typename remove_cv<_Up>::type
                         >::type
                     >::type type;
};

// result_of

template <class> class result_of;

template <class _Fn, bool>
class __result_of
{
};

#ifndef _LIBCPP_HAS_NO_VARIADICS

template <class _Fn, class ..._ArgTypes>
class __result_of<_Fn(_ArgTypes...), true>
{
public:
    typedef decltype(declval<_Fn>()(declval<_ArgTypes>()...)) type;
};

template <class _Fn, class ..._ArgTypes>
class result_of<_Fn(_ArgTypes...)>
    : public __result_of<_Fn(_ArgTypes...),
                         is_class<typename remove_reference<_Fn>::type>::value ||
                         is_function<typename remove_pointer<
                                        typename remove_reference<_Fn>::type
                                                            >::type
                                    >::value
                        >
{
};

#else

template <class _Fn>
class __result_of<_Fn(), true>
{
public:
    typedef decltype(declval<_Fn>()()) type;
};

template <class _Fn, class _A0>
class __result_of<_Fn(_A0), true>
{
public:
    typedef decltype(declval<_Fn>()(declval<_A0>())) type;
};

template <class _Fn, class _A0, class _A1>
class __result_of<_Fn(_A0, _A1), true>
{
public:
    typedef decltype(declval<_Fn>()(declval<_A0>(), declval<_A1>())) type;
};

template <class _Fn, class _A0, class _A1, class _A2>
class __result_of<_Fn(_A0, _A1, _A2), true>
{
public:
    typedef decltype(declval<_Fn>()(declval<_A0>(), declval<_A1>(), declval<_A2>())) type;
};

template <class _Fn>
class result_of<_Fn()>
    : public __result_of<_Fn(),
                         is_class<typename remove_reference<_Fn>::type>::value ||
                         is_function<typename remove_pointer<
                                        typename remove_reference<_Fn>::type
                                                            >::type
                                    >::value
                        >
{
};

template <class _Fn, class _A0>
class result_of<_Fn(_A0)>
    : public __result_of<_Fn(_A0),
                         is_class<typename remove_reference<_Fn>::type>::value ||
                         is_function<typename remove_pointer<
                                        typename remove_reference<_Fn>::type
                                                            >::type
                                    >::value
                        >
{
};

template <class _Fn, class _A0, class _A1>
class result_of<_Fn(_A0, _A1)>
    : public __result_of<_Fn(_A0, _A1),
                         is_class<typename remove_reference<_Fn>::type>::value ||
                         is_function<typename remove_pointer<
                                        typename remove_reference<_Fn>::type
                                                            >::type
                                    >::value
                        >
{
};

template <class _Fn, class _A0, class _A1, class _A2>
class result_of<_Fn(_A0, _A1, _A2)>
    : public __result_of<_Fn(_A0, _A1, _A2),
                         is_class<typename remove_reference<_Fn>::type>::value ||
                         is_function<typename remove_pointer<
                                        typename remove_reference<_Fn>::type
                                                            >::type
                                    >::value
                        >
{
};

#endif

#ifndef _LIBCPP_HAS_NO_ADVANCED_SFINAE

// template <class T, class... Args> struct is_constructible;

//      main is_constructible test

template <class _Tp, class ..._Args>
decltype(_STD::move(_Tp(_STD::declval<_Args>()...)), true_type())
__is_constructible_test(_Tp&&, _Args&& ...);

struct __any
{
    __any(...);
};

template <class ..._Args>
false_type
__is_constructible_test(__any, _Args&& ...);

template <bool, class _Tp, class... _Args>
struct __is_constructible // false, _Tp is not a scalar
    : public common_type
             <
                 decltype(__is_constructible_test(declval<_Tp>(), declval<_Args>()...))
             >::type
    {};

//      function types are not constructible

template <class _R, class... _A1, class... _A2>
struct __is_constructible<false, _R(_A1...), _A2...>
    : public false_type
    {};

//      handle scalars and reference types

//      Scalars are default constructible, references are not

template <class _Tp>
struct __is_constructible<true, _Tp> 
    : public is_scalar<_Tp>
    {};

//      Scalars and references are constructible from one arg if that arg is
//          implicitly convertible to the scalar or reference.

template <class _Tp>
struct __is_constructible_ref
{
    true_type static __(_Tp);
    false_type static __(...);
};

template <class _Tp, class _A0>
struct __is_constructible<true, _Tp, _A0> 
    : public common_type
             <
                 decltype(__is_constructible_ref<_Tp>::__(declval<_A0>()))
             >::type
    {};

//      Scalars and references are not constructible from multiple args.

template <class _Tp, class _A0, class ..._Args>
struct __is_constructible<true, _Tp, _A0, _Args...> 
    : public false_type
    {};

//      Treat scalars and reference types separately

template <bool, class _Tp, class... _Args>
struct __is_constructible_void_check
    : public __is_constructible<is_scalar<_Tp>::value || is_reference<_Tp>::value,
                                _Tp, _Args...>
    {};

//      If any of T or Args is void, is_constructible should be false

template <class _Tp, class... _Args>
struct __is_constructible_void_check<true, _Tp, _Args...>
    : public false_type
    {};

template <class ..._Args> struct __constains_void;

template <> struct __constains_void<> : false_type {};

template <class _A0, class ..._Args>
struct __constains_void<_A0, _Args...>
{
    static const bool value = is_void<_A0>::value ||
                              __constains_void<_Args...>::value;
};

//      is_constructible entry point

template <class _Tp, class... _Args>
struct is_constructible
    : public __is_constructible_void_check<__constains_void<_Tp, _Args...>::value,
                                           _Tp, _Args...>
    {};

//      Array types are default constructible if their element type
//      is default constructible

template <class _A, size_t _N>
struct __is_constructible<false, _A[_N]>
    : public is_constructible<typename remove_all_extents<_A>::type>
    {};

//      Otherwise array types are not constructible by this syntax

template <class _A, size_t _N, class ..._Args>
struct __is_constructible<false, _A[_N], _Args...>
    : public false_type
    {};

//      Incomplete array types are not constructible

template <class _A, class ..._Args>
struct __is_constructible<false, _A[], _Args...>
    : public false_type
    {};

#endif

template <class _Tp> struct __is_zero_default_constructible
    : public integral_constant<bool, is_scalar<_Tp>::value || is_empty<_Tp>::value> {};

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(_Tp& __x, _Tp& __y)
{
    _Tp __t(_STD::move(__x));
    __x = _STD::move(__y);
    __y = _STD::move(__t);
}

_LIBCPP_END_NAMESPACE_STD

#endif  // _LIBCPP_TYPE_TRAITS