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<div class="section" id="distance">
<h1><a class="toc-backref" href="./iterator-metafunctions.html#id1455">distance</a></h1>
<div class="section" id="id412">
<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
<pre class="literal-block">
template&lt;
      typename First
    , typename Last
    &gt;
struct <a href="./distance.html" class="identifier">distance</a>
{
    typedef <em>unspecified</em> type;
};
</pre>
</div>
<div class="section" id="id413">
<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
<p>Returns the distance between <tt class="literal"><span class="pre">First</span></tt> and <tt class="literal"><span class="pre">Last</span></tt> iterators, that is, an
<a class="reference internal" href="./integral-constant.html">Integral Constant</a> <tt class="literal"><span class="pre">n</span></tt> such that <tt class="literal"><span class="pre"><a href="./advance.html" class="identifier">advance</a>&lt;First,n&gt;::type</span></tt> is
identical to <tt class="literal"><span class="pre">Last</span></tt>.</p>
</div>
<div class="section" id="id414">
<h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
<pre class="literal-block">
#include &lt;<a href="../../../../boost/mpl/distance.hpp" class="header">boost/mpl/distance.hpp</a>&gt;
</pre>
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<div class="section" id="id415">
<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
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<tr><th class="head">Parameter</th>
<th class="head">Requirement</th>
<th class="head">Description</th>
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<tbody valign="top">
<tr><td><tt class="literal"><span class="pre">First</span></tt>,
<tt class="literal"><span class="pre">Last</span></tt></td>
<td><a class="reference internal" href="./forward-iterator.html">Forward Iterator</a></td>
<td>Iterators to compute a
distance between.</td>
</tr>
</tbody>
</table>
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<div class="section" id="id416">
<h3><a class="subsection-title" href="#model-of" name="model-of">Model Of</a></h3>
<p><a class="reference internal" href="./tag-dispatched-metafunction.html">Tag Dispatched Metafunction</a></p>
</div>
<div class="section" id="id417">
<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
<p>For any <a class="reference internal" href="./forward-iterator.html">Forward Iterator</a>s <tt class="literal"><span class="pre">first</span></tt> and <tt class="literal"><span class="pre">last</span></tt>:</p>
<pre class="literal-block">
typedef <a href="./distance.html" class="identifier">distance</a>&lt;first,last&gt;::type n;
</pre>
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<tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first"><a class="reference internal" href="./integral-constant.html">Integral Constant</a>.</p>
</td>
</tr>
<tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><p class="first">[<tt class="literal"><span class="pre">first</span></tt>, <tt class="literal"><span class="pre">last</span></tt>) is a valid range.</p>
</td>
</tr>
<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p>
<pre class="literal-block">
typedef <a href="./iter-fold.html" class="identifier">iter_fold</a>&lt;
      <a href="./iterator-range.html" class="identifier">iterator_range</a>&lt;first,last&gt;
    , <a href="./long.html" class="identifier">long_</a>&lt;0&gt;
    , <a href="./next.html" class="identifier">next</a>&lt;<a href="./placeholders.html" class="identifier">_1</a>&gt;
    &gt;::type n;
</pre>
</td>
</tr>
<tr class="field"><th class="field-name">Postcondition:</th><td class="field-body"><p class="first last"><tt class="literal"><span class="pre">is_same&lt;</span> <span class="pre"><a href="./advance.html" class="identifier">advance</a>&lt;first,n&gt;::type,</span> <span class="pre">last</span> <span class="pre">&gt;::value</span> <span class="pre">==</span> <span class="pre">true</span></tt>.</p>
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<div class="section" id="id418">
<h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3>
<p>Amortized constant time if <tt class="literal"><span class="pre">first</span></tt> and <tt class="literal"><span class="pre">last</span></tt> are <a class="reference internal" href="./random-access-iterator.html">Random Access Iterator</a>s,
otherwise linear time.</p>
</div>
<div class="section" id="id419">
<h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
<pre class="literal-block">
typedef <a href="./range-c.html" class="identifier">range_c</a>&lt;int,0,10&gt;::type range;
typedef <a href="./begin.html" class="identifier">begin</a>&lt;range&gt;::type first;
typedef <a href="./end.html" class="identifier">end</a>&lt;range&gt;::type last;

<a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( (<a href="./distance.html" class="identifier">distance</a>&lt;first,last&gt;::value), ==, 10);
</pre>
</div>
<div class="section" id="id420">
<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
<p><a class="reference internal" href="./iterators.html">Iterators</a>, <a class="reference internal" href="./tag-dispatched-metafunction.html">Tag Dispatched Metafunction</a>, <a class="reference internal" href="./advance.html">advance</a>, <a class="reference internal" href="./next.html">next</a>, <a class="reference internal" href="./prior.html">prior</a></p>
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