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  27 <a name="boost.type_erasure.call_idp984806000"></a><div class="titlepage"></div>
  28 <div class="refnamediv">
  29 <h2><span class="refentrytitle">Function call</span></h2>
  30 <p>boost::type_erasure::call</p>
  31 </div>
  32 <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
  33 <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../boost_typeerasure/reference.html#header.boost.type_erasure.call_hpp" title="Header &lt;boost/type_erasure/call.hpp&gt;">boost/type_erasure/call.hpp</a>&gt;
  34
  35 </span>
  36 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Concept<span class="special">,</span> <span class="keyword">typename</span> Op<span class="special">,</span> <span class="keyword">class</span><span class="special">...</span> U<span class="special">&gt;</span>
  37   <span class="emphasis"><em><span class="identifier">unspecified</span></em></span> <span class="identifier">call</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="binding.html" title="Class template binding">binding</a><span class="special">&lt;</span> <span class="identifier">Concept</span> <span class="special">&gt;</span> <span class="special">&amp;</span> binding<span class="special">,</span> <span class="keyword">const</span> <span class="identifier">Op</span> <span class="special">&amp;</span><span class="special">,</span>
  38                    <span class="identifier">U</span> <span class="special">&amp;&amp;</span><span class="special">...</span> args<span class="special">)</span><span class="special">;</span>
  39 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Op<span class="special">,</span> <span class="keyword">class</span><span class="special">...</span> U<span class="special">&gt;</span> <span class="emphasis"><em><span class="identifier">unspecified</span></em></span> <span class="identifier">call</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Op</span> <span class="special">&amp;</span><span class="special">,</span> <span class="identifier">U</span> <span class="special">&amp;&amp;</span><span class="special">...</span> args<span class="special">)</span><span class="special">;</span></pre></div>
  40 <div class="refsect1">
  41 <a name="idp653183552"></a><h2>Description</h2>
  42 <p>Dispatches a type erased function.</p>
  43 <p><code class="computeroutput">Op</code> must be a primitive concept which is present in <code class="computeroutput">Concept</code>. Its signature determines how the arguments of  <code class="computeroutput"><a class="link" href="call_idp984806000.html" title="Function call">call</a></code> are handled. If the argument is a <code class="computeroutput"><a class="link" href="placeholder.html" title="Struct placeholder">placeholder</a></code>,  <code class="computeroutput"><a class="link" href="call_idp984806000.html" title="Function call">call</a></code> expects an <code class="computeroutput"><a class="link" href="any.html" title="Class template any">any</a></code> using that <code class="computeroutput"><a class="link" href="placeholder.html" title="Struct placeholder">placeholder</a></code>. This <code class="computeroutput"><a class="link" href="any.html" title="Class template any">any</a></code> is unwrapped by <code class="computeroutput"><a class="link" href="call_idp984806000.html" title="Function call">call</a></code>. The type that it stores must be the same type specified by <code class="computeroutput">binding</code>. Any arguments that are not placeholders in the signature of <code class="computeroutput">Op</code> are passed through unchanged.</p>
  44 <p>If <code class="computeroutput">binding</code> is not specified, it will be deduced from the arguments. Naturally this requires at least one argument to be an <code class="computeroutput"><a class="link" href="any.html" title="Class template any">any</a></code>. In this case, all <code class="computeroutput"><a class="link" href="any.html" title="Class template any">any</a></code> arguments must have the same <code class="computeroutput"><a class="link" href="binding.html" title="Class template binding">binding</a></code>.</p>
  45 <p>
  46
  47 Example:</p>
  48 <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span>
  49   <span class="identifier">copy_constructible</span><span class="special">&lt;</span><span class="identifier">_b</span><span class="special">&gt;</span><span class="special">,</span>
  50   <span class="identifier">addable</span><span class="special">&lt;</span><span class="identifier">_a</span><span class="special">,</span> <span class="keyword">int</span><span class="special">,</span> <span class="identifier">_b</span><span class="special">&gt;</span> <span class="special">&gt;</span> <span class="identifier">concept</span><span class="special">;</span>
  51 <span class="identifier">any</span><span class="special">&lt;</span><span class="identifier">concept</span><span class="special">,</span> <span class="identifier">_a</span><span class="special">&gt;</span> <span class="identifier">a</span> <span class="special">=</span> <span class="special">...</span><span class="special">;</span>
  52 <span class="identifier">any</span><span class="special">&lt;</span><span class="identifier">concept</span><span class="special">,</span> <span class="identifier">_b</span><span class="special">&gt;</span> <span class="identifier">b</span><span class="special">(</span><span class="identifier">call</span><span class="special">(</span><span class="identifier">addable</span><span class="special">&lt;</span><span class="identifier">_a</span><span class="special">,</span> <span class="keyword">int</span><span class="special">,</span> <span class="identifier">_b</span><span class="special">&gt;</span><span class="special">(</span><span class="special">)</span><span class="special">,</span> <span class="identifier">a</span><span class="special">,</span> <span class="number">10</span><span class="special">)</span><span class="special">)</span><span class="special">;</span>
  53 </pre>
  54 <p>The signature of <code class="computeroutput"><a class="link" href="addable.html" title="Struct template addable">addable</a></code> is <code class="computeroutput">_b(const _a&amp;, const int&amp;)</code> </p>
  55 <div class="variablelist"><table border="0" class="variablelist compact">
  56 <colgroup>
  57 <col align="left" valign="top">
  58 <col>
  59 </colgroup>
  60 <tbody>
  61 <tr>
  62 <td><p><span class="term">Returns:</span></p></td>
  63 <td><p>The result of the operation. If the result type of the signature of <code class="computeroutput">Op</code> is a placeholder, the result will be converted to the appropriate <a class="link" href="any.html" title="Class template any">any</a> type.</p></td>
  64 </tr>
  65 <tr>
  66 <td><p><span class="term">Throws:</span></p></td>
  67 <td>
  68 <a class="link" href="../bad_function_call.html" title="Class bad_function_call">bad_function_call</a> if <a class="link" href="relaxed.html" title="Struct relaxed">relaxed</a> is in <code class="computeroutput">Concept</code> and there is a type mismatch.</td>
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  75 <td align="left"></td>
  76 <td align="right"><div class="copyright-footer">Copyright &#169; 2011-2013 Steven Watanabe<p>
  77         Distributed under the Boost Software License, Version 1.0. (See accompanying
  78         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
  79       </p>
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