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| <div class="document" id="iterator-traits"> |
| <h1 class="title">Iterator Traits</h1> |
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| <tr><th class="docinfo-name">Author:</th> |
| <td>David Abrahams</td></tr> |
| <tr><th class="docinfo-name">Contact:</th> |
| <td><a class="first last reference external" href="mailto:dave@boost-consulting.com">dave@boost-consulting.com</a></td></tr> |
| <tr><th class="docinfo-name">Organization:</th> |
| <td><a class="first last reference external" href="http://www.boost-consulting.com">Boost Consulting</a></td></tr> |
| <tr><th class="docinfo-name">Date:</th> |
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| <tr><th class="docinfo-name">Copyright:</th> |
| <td>Copyright David Abrahams 2004.</td></tr> |
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| <tr class="field"><th class="field-name">abstract:</th><td class="field-body">Header <tt class="docutils literal"><boost/iterator/iterator_traits.hpp></tt> provides |
| the ability to access an iterator's associated types using |
| MPL-compatible <a class="reference external" href="../../mpl/doc/index.html#metafunctions">metafunctions</a>.</td> |
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| <div class="section" id="overview"> |
| <h1>Overview</h1> |
| <p><tt class="docutils literal"><span class="pre">std::iterator_traits</span></tt> provides access to five associated types |
| of any iterator: its <tt class="docutils literal">value_type</tt>, <tt class="docutils literal">reference</tt>, <tt class="docutils literal">pointer</tt>, |
| <tt class="docutils literal">iterator_category</tt>, and <tt class="docutils literal">difference_type</tt>. Unfortunately, |
| such a "multi-valued" traits template can be difficult to use in a |
| metaprogramming context. <tt class="docutils literal"><boost/iterator/iterator_traits.hpp></tt> |
| provides access to these types using a standard <a class="reference external" href="../../mpl/doc/index.html#metafunctions">metafunctions</a>.</p> |
| </div> |
| <div class="section" id="summary"> |
| <h1>Summary</h1> |
| <p>Header <tt class="docutils literal"><boost/iterator/iterator_traits.hpp></tt>:</p> |
| <pre class="literal-block"> |
| template <class Iterator> |
| struct iterator_value |
| { |
| typedef typename |
| std::iterator_traits<Iterator>::value_type |
| type; |
| }; |
| |
| template <class Iterator> |
| struct iterator_reference |
| { |
| typedef typename |
| std::iterator_traits<Iterator>::reference |
| type; |
| }; |
| |
| |
| template <class Iterator> |
| struct iterator_pointer |
| { |
| typedef typename |
| std::iterator_traits<Iterator>::pointer |
| type; |
| }; |
| |
| template <class Iterator> |
| struct iterator_difference |
| { |
| typedef typename |
| detail::iterator_traits<Iterator>::difference_type |
| type; |
| }; |
| |
| template <class Iterator> |
| struct iterator_category |
| { |
| typedef typename |
| detail::iterator_traits<Iterator>::iterator_category |
| type; |
| }; |
| </pre> |
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