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| <title>Iterator Archetype</title> |
| <meta name="author" content="David Abrahams, Jeremy Siek, Thomas Witt" /> |
| <meta name="organization" content="Boost Consulting, Indiana University Open Systems Lab, Zephyr Associates, Inc." /> |
| <meta name="date" content="2006-09-11" /> |
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| <div class="document" id="iterator-archetype"> |
| <h1 class="title">Iterator Archetype</h1> |
| <table class="docinfo" frame="void" rules="none"> |
| <col class="docinfo-name" /> |
| <col class="docinfo-content" /> |
| <tbody valign="top"> |
| <tr><th class="docinfo-name">Author:</th> |
| <td>David Abrahams, Jeremy Siek, Thomas Witt</td></tr> |
| <tr><th class="docinfo-name">Contact:</th> |
| <td><a class="first reference external" href="mailto:dave@boost-consulting.com">dave@boost-consulting.com</a>, <a class="reference external" href="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</a>, <a class="last reference external" href="mailto:witt@styleadvisor.com">witt@styleadvisor.com</a></td></tr> |
| <tr><th class="docinfo-name">Organization:</th> |
| <td><a class="first reference external" href="http://www.boost-consulting.com">Boost Consulting</a>, Indiana University <a class="reference external" href="http://www.osl.iu.edu">Open Systems |
| Lab</a>, <a class="last reference external" href="http://www.styleadvisor.com">Zephyr Associates, Inc.</a></td></tr> |
| <tr><th class="docinfo-name">Date:</th> |
| <td>2006-09-11</td></tr> |
| <tr><th class="docinfo-name">Copyright:</th> |
| <td>Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2004.</td></tr> |
| </tbody> |
| </table> |
| <!-- Distributed under 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) --> |
| <table class="docutils field-list" frame="void" rules="none"> |
| <col class="field-name" /> |
| <col class="field-body" /> |
| <tbody valign="top"> |
| <tr class="field"><th class="field-name">abstract:</th><td class="field-body">The <tt class="docutils literal"><span class="pre">iterator_archetype</span></tt> class constructs a minimal implementation of |
| one of the iterator access concepts and one of the iterator traversal concepts. |
| This is used for doing a compile-time check to see if a the type requirements |
| of a template are really enough to cover the implementation of the template. |
| For further information see the documentation for the <a class="reference external" href="../../concept_check/index.html"><tt class="docutils literal"><span class="pre">boost::concept_check</span></tt></a> library.</td> |
| </tr> |
| </tbody> |
| </table> |
| <div class="contents topic" id="table-of-contents"> |
| <p class="topic-title first">Table of Contents</p> |
| <ul class="simple"> |
| <li><a class="reference internal" href="#reference" id="id1">Reference</a><ul> |
| <li><a class="reference internal" href="#iterator-archetype-synopsis" id="id2"><tt class="docutils literal"><span class="pre">iterator_archetype</span></tt> Synopsis</a></li> |
| <li><a class="reference internal" href="#access-category-tags" id="id3"><tt class="docutils literal"><span class="pre">Access</span> <span class="pre">Category</span> <span class="pre">Tags</span></tt></a></li> |
| <li><a class="reference internal" href="#iterator-archetype-requirements" id="id4"><tt class="docutils literal"><span class="pre">iterator_archetype</span></tt> Requirements</a></li> |
| <li><a class="reference internal" href="#iterator-archetype-models" id="id5"><tt class="docutils literal"><span class="pre">iterator_archetype</span></tt> Models</a></li> |
| <li><a class="reference internal" href="#traits" id="id6"><tt class="docutils literal"><span class="pre">Traits</span></tt></a></li> |
| </ul> |
| </li> |
| </ul> |
| </div> |
| <div class="section" id="reference"> |
| <h1><a class="toc-backref" href="#id1">Reference</a></h1> |
| <div class="section" id="iterator-archetype-synopsis"> |
| <h2><a class="toc-backref" href="#id2"><tt class="docutils literal"><span class="pre">iterator_archetype</span></tt> Synopsis</a></h2> |
| <pre class="literal-block"> |
| namespace iterator_archetypes |
| { |
| // Access categories |
| |
| typedef /*implementation defined*/ readable_iterator_t; |
| typedef /*implementation defined*/ writable_iterator_t; |
| typedef /*implementation defined*/ readable_writable_iterator_t; |
| typedef /*implementation defined*/ readable_lvalue_iterator_t; |
| typedef /*implementation defined*/ writable_lvalue_iterator_t; |
| |
| } |
| |
| template < |
| class Value |
| , class AccessCategory |
| , class TraversalCategory |
| > |
| class iterator_archetype |
| { |
| typedef /* see below */ value_type; |
| typedef /* see below */ reference; |
| typedef /* see below */ pointer; |
| typedef /* see below */ difference_type; |
| typedef /* see below */ iterator_category; |
| }; |
| </pre> |
| </div> |
| <div class="section" id="access-category-tags"> |
| <h2><a class="toc-backref" href="#id3"><tt class="docutils literal"><span class="pre">Access</span> <span class="pre">Category</span> <span class="pre">Tags</span></tt></a></h2> |
| <p>The access category types provided correspond to the following |
| standard iterator access concept combinations:</p> |
| <pre class="literal-block"> |
| readable_iterator_t := |
| |
| Readable Iterator |
| |
| writable_iterator_t := |
| |
| Writeable Iterator |
| |
| readable_writable_iterator_t := |
| |
| Readable Iterator & Writeable Iterator & Swappable Iterator |
| |
| readable_lvalue_iterator_t := |
| |
| Readable Iterator & Lvalue Iterator |
| |
| writeable_lvalue_iterator_t := |
| |
| Readable Iterator & Writeable Iterator & Swappable Iterator & Lvalue Iterator |
| </pre> |
| </div> |
| <div class="section" id="iterator-archetype-requirements"> |
| <h2><a class="toc-backref" href="#id4"><tt class="docutils literal"><span class="pre">iterator_archetype</span></tt> Requirements</a></h2> |
| <p>The <tt class="docutils literal"><span class="pre">AccessCategory</span></tt> argument must be one of the predefined access |
| category tags. The <tt class="docutils literal"><span class="pre">TraversalCategory</span></tt> must be one of the standard |
| traversal tags. The <tt class="docutils literal"><span class="pre">Value</span></tt> type must satisfy the requirements of |
| the iterator concept specified by <tt class="docutils literal"><span class="pre">AccessCategory</span></tt> and |
| <tt class="docutils literal"><span class="pre">TraversalCategory</span></tt> as implied by the nested traits types.</p> |
| </div> |
| <div class="section" id="iterator-archetype-models"> |
| <h2><a class="toc-backref" href="#id5"><tt class="docutils literal"><span class="pre">iterator_archetype</span></tt> Models</a></h2> |
| <p><tt class="docutils literal"><span class="pre">iterator_archetype</span></tt> models the iterator concepts specified by the |
| <tt class="docutils literal"><span class="pre">AccessCategory</span></tt> and <tt class="docutils literal"><span class="pre">TraversalCategory</span></tt> |
| arguments. <tt class="docutils literal"><span class="pre">iterator_archetype</span></tt> does not model any other access |
| concepts or any more derived traversal concepts.</p> |
| </div> |
| <div class="section" id="traits"> |
| <h2><a class="toc-backref" href="#id6"><tt class="docutils literal"><span class="pre">Traits</span></tt></a></h2> |
| <p>The nested trait types are defined as follows:</p> |
| <pre class="literal-block"> |
| if (AccessCategory == readable_iterator_t) |
| |
| value_type = Value |
| reference = Value |
| pointer = Value* |
| |
| else if (AccessCategory == writable_iterator_t) |
| |
| value_type = void |
| reference = void |
| pointer = void |
| |
| else if (AccessCategory == readable_writable_iterator_t) |
| |
| value_type = Value |
| |
| reference := |
| |
| A type X that is convertible to Value for which the following |
| expression is valid. Given an object x of type X and v of type |
| Value. |
| |
| x = v |
| |
| pointer = Value* |
| |
| else if (AccessCategory == readable_lvalue_iterator_t) |
| |
| value_type = Value |
| reference = Value const& |
| pointer = Value const* |
| |
| else if (AccessCategory == writable_lvalue_iterator_t) |
| |
| value_type = Value |
| reference = Value& |
| pointer = Value* |
| |
| if ( TraversalCategory is convertible to forward_traversal_tag ) |
| |
| difference_type := ptrdiff_t |
| |
| else |
| |
| difference_type := unspecified type |
| |
| |
| iterator_category := |
| |
| A type X satisfying the following two constraints: |
| |
| 1. X is convertible to X1, and not to any more-derived |
| type, where X1 is defined by: |
| |
| if (reference is a reference type |
| && TraversalCategory is convertible to forward_traversal_tag) |
| { |
| if (TraversalCategory is convertible to random_access_traversal_tag) |
| X1 = random_access_iterator_tag |
| else if (TraversalCategory is convertible to bidirectional_traversal_tag) |
| X1 = bidirectional_iterator_tag |
| else |
| X1 = forward_iterator_tag |
| } |
| else |
| { |
| if (TraversalCategory is convertible to single_pass_traversal_tag |
| && reference != void) |
| X1 = input_iterator_tag |
| else |
| X1 = output_iterator_tag |
| } |
| |
| 2. X is convertible to TraversalCategory |
| </pre> |
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