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diff --git a/gcc-4.4.3/libstdc++-v3/doc/html/ext/pb_ds/ds_gen.html b/gcc-4.4.3/libstdc++-v3/doc/html/ext/pb_ds/ds_gen.html new file mode 100644 index 000000000..ec99c4d5f --- /dev/null +++ b/gcc-4.4.3/libstdc++-v3/doc/html/ext/pb_ds/ds_gen.html @@ -0,0 +1,344 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> + +<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> +<head> + <meta name="generator" content= + "HTML Tidy for Linux/x86 (vers 12 April 2005), see www.w3.org" /> + + <title>Data-Structure Genericity</title> + <meta http-equiv="Content-Type" content= + "text/html; charset=us-ascii" /> + </head> + +<body> + <div id="page"> + <h1>Data-Structure Genericity</h1> + + <h2><a name="problem" id="problem">The Basic Problem</a></h2> + + <p>The design attempts to address the following problem. When + writing a function manipulating a generic container object, + what is the behavior of the object? <i>E.g.</i>, suppose one + writes</p> + <pre> +<b>template</b><<b>typename</b> Cntnr> +<b>void</b> +some_op_sequence(Cntnr &r_container) +{ + ... +} +</pre>then one needs to address the following questions in the body +of <tt>some_op_sequence</tt>: + + <ol> + <li>Which types and methods does <tt>Cntnr</tt> support? + Containers based on hash tables can be queries for the + hash-functor type and object; this is meaningless for + tree-based containers. Containers based on trees can be + split, joined, or can erase iterators and return the + following iterator; this cannot be done by hash-based + containers.</li> + + <li>What are the guarantees of <tt>Cntnr</tt>? A container + based on a probing hash-table invalidates all iterators when + it is modified; this is not the case for containers based on + node-based trees. Containers based on a node-based tree can + be split or joined without exceptions; this is not the case + for containers based on vector-based trees.</li> + + <li>How does the container maintain its elements? Tree-based + and Trie-based containers store elements by key order; + others, typically, do not. A container based on a splay trees + or lists with update policies "cache" "frequently accessed" + elements; containers based on most other underlying + data structures do not.</li> + </ol> + + <p>The remainder of this section deals with these issues.</p> + + <h2><a name="ds_hierarchy" id="ds_hierarchy">Container + Hierarchy</a></h2> + + <p>Figure <a href="#cd">Container class hierarchy</a> shows the + container hierarchy.</p> + + <h6 class="c1"><a name="cd" id="cd"><img src="container_cd.png" alt= + "no image" /></a></h6> + + <h6 class="c1">Container class hierarchy.</h6> + + <ol> + <li><a href= + "container_base.html"><tt>container_base</tt></a> is an + abstract base class for associative containers.</li> + + <li>Tree-Like-Based Associative-Containers: + + <ol> + <li><a href= + "basic_tree.html"><tt>basic_tree</tt></a> + is an abstract base class for tree-like-based + associative-containers</li> + + <li><a href= + "tree.html"><tt>tree</tt></a> + is a concrete base class for tree-based + associative-containers</li> + + <li><a href= + "trie.html"><tt>trie</tt></a> + is a concrete base class trie-based + associative-containers</li> + </ol> + </li> + + <li>Hash-Based Associative-Containers: + + <ol> + <li><a href= + "basic_hash_table.html"><tt>basic_hash_table</tt></a> + is an abstract base class for hash-based + associative-containers</li> + + <li><a href= + "cc_hash_table.html"><tt>cc_hash_table</tt></a> + is a concrete collision-chaining hash-based + associative-containers</li> + + <li><a href= + "gp_hash_table.html"><tt>gp_hash_table</tt></a> + is a concrete (general) probing hash-based + associative-containers</li> + </ol> + </li> + + <li>List-Based Associative-Containers: + + <ol> + <li><a href= + "list_update.html"><tt>list_update</tt></a> - + list-based update-policy associative container</li> + </ol> + </li> + </ol> + + <p>The hierarchy is composed naturally so that commonality is + captured by base classes. Thus <tt><b>operator[]</b></tt> is + defined <a href= + "container_base.html"><tt>container_base</tt></a>, since + all containers support it. Conversely <tt>split</tt> is defined + in <a href= + "basic_tree.html"><tt>basic_tree</tt></a>, + since only tree-like containers support it. <a href= + "#container_traits">Data-Structure Tags and Traits</a> discusses how + to query which types and methods each container supports.</p> + + <h2><a name="container_traits" id="container_traits">Data-Structure Tags and + Traits</a></h2> + + <p>Tags and traits are very useful for manipulating generic + types. For example, if <tt>It</tt> is an iterator class, then + <tt><b>typename</b> It::iterator_category</tt> or + <tt><b>typename</b> + std::iterator_traits<It>::iterator_category</tt> will + yield its category, and <tt><b>typename</b> + std::iterator_traits<It>::value_type</tt> will yield its + value type.</p> + + <p><tt>pb_ds</tt> contains a tag hierarchy corresponding to the + hierarchy in Figure <a href="#cd">Class hierarchy</a>. The tag + hierarchy is shown in Figure <a href= + "#tag_cd">Data-structure tag class hierarchy</a>.</p> + + <h6 class="c1"><a name="tag_cd" id="tag_cd"><img src= + "assoc_container_tag_cd.png" alt="no image" /></a></h6> + + <h6 class="c1">Data-structure tag class hierarchy.</h6> + + <p><a href= + "container_base.html"><tt>container_base</tt></a> + publicly defines <tt>container_category</tt> as one of the classes in + Figure <a href="#tag_cd">Data-structure tag class + hierarchy</a>. Given any container <tt>Cntnr</tt>, the tag of + the underlying data structure can be found via + <tt><b>typename</b> Cntnr::container_category</tt>.</p> + + <p>Additionally, a traits mechanism can be used to query a + container type for its attributes. Given any container + <tt>Cntnr</tt>, then <tt><a href= + "assoc_container_traits.html">__gnu_pbds::container_traits</a><Cntnr></tt> + is a traits class identifying the properties of the + container.</p> + + <p>To find if a container can throw when a key is erased (which + is true for vector-based trees, for example), one can + use</p><a href= + "assoc_container_traits.html"><tt>container_traits</tt></a><tt><Cntnr>::erase_can_throw</tt>, + for example. + + <p>Some of the definitions in <a href= + "assoc_container_traits.html"><tt>container_traits</tt></a> are + dependent on other definitions. <i>E.g.</i>, if <a href= + "assoc_container_traits.html"><tt>container_traits</tt></a><tt><Cntnr>::order_preserving</tt> + is <tt><b>true</b></tt> (which is the case for containers based + on trees and tries), then the container can be split or joined; + in this case, <a href= + "assoc_container_traits.html"><tt>container_traits</tt></a><tt><Cntnr>::split_join_can_throw</tt> + indicates whether splits or joins can throw exceptions (which + is true for vector-based trees); otherwise <a href= + "assoc_container_traits.html"><tt>container_traits</tt></a><tt><Cntnr>::split_join_can_throw</tt> + will yield a compilation error. (This is somewhat similar to a + compile-time version of the COM model [<a href= + "references.html#mscom">mscom</a>]).</p> + + <h2><a name="find_range" id="find_range">Point-Type and + Range-Type Methods and Iterators</a></h2> + + <h3><a name="it_unordered" id="it_unordered">Iterators in + Unordered Container Types</a></h3> + + <p><tt>pb_ds</tt> differentiates between two types of methods + and iterators: point-type methods and iterators, and range-type + methods and iterators (see <a href= + "motivation.html#assoc_diff_it">Motivation::Associative + Containers::Differentiating between Iterator Types</a> and + <a href="tutorial.html#assoc_find_range">Tutorial::Associative + Containers::Point-Type and Range-Type Methods and + Iterators</a>). Each associative container's interface includes + the methods:</p> + <pre> +const_point_iterator +find(const_key_reference r_key) const; + +point_iterator +find(const_key_reference r_key); + +std::pair<point_iterator,<b>bool</b>> +insert(const_reference r_val); +</pre> + + <p>The relationship between these iterator types varies between + container types. Figure <a href= + "#point_iterators_cd">Point-type and range-type iterators</a>-A + shows the most general invariant between point-type and + range-type iterators: <tt>iterator</tt>, <i>e.g.</i>, can + always be converted to <tt>point_iterator</tt>. Figure <a href= + "#point_iterators_cd">Point-type and range-type iterators</a>-B + shows invariants for order-preserving containers: point-type + iterators are synonymous with range-type iterators. + Orthogonally, Figure <a href="#point_iterators_cd">Point-type + and range-type iterators</a>-C shows invariants for "set" + containers: iterators are synonymous with const iterators.</p> + + <h6 class="c1"><a name="point_iterators_cd" id= + "point_iterators_cd"><img src="point_iterators_cd.png" alt= + "no image" /></a></h6> + + <h6 class="c1">Point-type and range-type iterators.</h6> + + <p>Note that point-type iterators in self-organizing containers + (<i>e.g.</i>, hash-based associative containers) lack movement + operators, such as <tt><b>operator++</b></tt> - in fact, this + is the reason why <tt>pb_ds</tt> differentiates from the STL's + design on this point.</p> + + <p>Typically, one can determine an iterator's movement + capabilities in the STL using + <tt>std::iterator_traits<It>iterator_category</tt>, which + is a <tt><b>struct</b></tt> indicating the iterator's movement + capabilities. Unfortunately, none of the STL's predefined + categories reflect a pointer's <u>not</u> having any movement + capabilities whatsoever. Consequently, <tt>pb_ds</tt> adds a + type <a href= + "trivial_iterator_tag.html"><tt>trivial_iterator_tag</tt></a> + (whose name is taken from a concept in [<a href= + "references.html#sgi_stl">sgi_stl</a>]), which is the category + of iterators with no movement capabilities. All other STL tags, + such as <tt>forward_iterator_tag</tt> retain their common + use.</p> + + <h3><a name="inv_guar" id="inv_guar">Invalidation + Guarantees</a></h3> + + <p><a href= + "motivation.html#assoc_inv_guar">Motivation::Associative + Containers::Differentiating between Iterator + Types::Invalidation Guarantees</a> posed a problem. Given three + different types of associative containers, a modifying + operation (in that example, <tt>erase</tt>) invalidated + iterators in three different ways: the iterator of one + container remained completely valid - it could be de-referenced + and incremented; the iterator of a different container could + not even be de-referenced; the iterator of the third container + could be de-referenced, but its "next" iterator changed + unpredictably.</p> + + <p>Distinguishing between find and range types allows + fine-grained invalidation guarantees, because these questions + correspond exactly to the question of whether point-type + iterators and range-type iterators are valid. <a href= + "#invalidation_guarantee_cd">Invalidation guarantees class + hierarchy</a> shows tags corresponding to different types of + invalidation guarantees.</p> + + <h6 class="c1"><a name="invalidation_guarantee_cd" id= + "invalidation_guarantee_cd"><img src= + "invalidation_guarantee_cd.png" alt="no image" /></a></h6> + + <h6 class="c1">Invalidation guarantees class hierarchy.</h6> + + <ol> + <li><a href= + "basic_invalidation_guarantee.html"><tt>basic_invalidation_guarantee</tt></a> + corresponds to a basic guarantee that a point-type iterator, + a found pointer, or a found reference, remains valid as long + as the container object is not modified.</li> + + <li><a href= + "point_invalidation_guarantee.html"><tt>point_invalidation_guarantee</tt></a> + corresponds to a guarantee that a point-type iterator, a + found pointer, or a found reference, remains valid even if + the container object is modified.</li> + + <li><a href= + "range_invalidation_guarantee.html"><tt>range_invalidation_guarantee</tt></a> + corresponds to a guarantee that a range-type iterator remains + valid even if the container object is modified.</li> + </ol> + + <p>As shown in <a href= + "tutorial.html#assoc_find_range">Tutorial::Associative + Containers::Point-Type and Range-Type Methods and + Iterators</a>, to find the invalidation guarantee of a + container, one can use</p> + <pre> +<b>typename</b> <a href= +"assoc_container_traits.html">container_traits</a><Cntnr>::invalidation_guarantee +</pre> + + <p>which is one of the classes in Figure <a href= + "#invalidation_guarantee_cd">Invalidation guarantees class + hierarchy</a>.</p> + + <p>Note that this hierarchy corresponds to the logic it + represents: if a container has range-invalidation guarantees, + then it must also have find invalidation guarantees; + correspondingly, its invalidation guarantee (in this case + <a href= + "range_invalidation_guarantee.html"><tt>range_invalidation_guarantee</tt></a>) + can be cast to its base class (in this case <a href= + "point_invalidation_guarantee.html"><tt>point_invalidation_guarantee</tt></a>). + This means that this this hierarchy can be used easily using + standard metaprogramming techniques, by specializing on the + type of <tt>invalidation_guarantee</tt>.</p> + + <p>(These types of problems were addressed, in a more general + setting, in [<a href= + "references.html#meyers96more">meyers96more</a>] - Item 2. In + our opinion, an invalidation-guarantee hierarchy would solve + these problems in all container types - not just associative + containers.)</p> + </div> +</body> +</html> |