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  29 <h2><span class="refentrytitle">Struct template when&lt;Grammar, Fun *&gt;</span></h2>
  30 <p>boost::proto::when&lt;Grammar, Fun *&gt; &#8212; A specialization that treats function pointer <a class="link" href="../../Transform.html" title="Concept Transform">Transform</a>s as if they
  31           were function type <a class="link" href="../../Transform.html" title="Concept Transform">Transform</a>s.</p>
  32 </div>
  33 <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
  34 <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="../../proto/reference.html#header.boost.proto.transform.when_hpp" title="Header &lt;boost/proto/transform/when.hpp&gt;">boost/proto/transform/when.hpp</a>&gt;
  35
  36 </span><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Grammar<span class="special">,</span> <span class="keyword">typename</span> Fun<span class="special">&gt;</span>
  37 <span class="keyword">struct</span> <a class="link" href="when_Grammar__idp705757024.html" title="Struct template when&lt;Grammar, Fun *&gt;">when</a><span class="special">&lt;</span><span class="identifier">Grammar</span><span class="special">,</span> <span class="identifier">Fun</span> <span class="special">*</span><span class="special">&gt;</span> <span class="special">:</span> <span class="keyword"></span> <a class="link" href="when.html" title="Struct template when">proto::when</a>&lt; Grammar, Fun &gt; <span class="special">{</span>
  38 <span class="special">}</span><span class="special">;</span></pre></div>
  39 <div class="refsect1">
  40 <a name="idp484725648"></a><h2>Description</h2>
  41 <p>
  42             This specialization requires that <code class="computeroutput">Fun</code> is actually a function type.
  43           </p>
  44 <p>
  45             This specialization is required for nested transforms such as
  46             <code class="computeroutput">proto::when&lt;G, T0(T1(_))&gt;</code>. In C++, functions that are used
  47             as parameters to other functions automatically decay to funtion pointer types. In other words, the
  48             type <code class="computeroutput">T0(T1(_))</code> is indistinguishable from
  49             <code class="computeroutput">T0(T1(*)(_))</code>. This specialization is required to handle these
  50             nested function pointer type transforms properly.
  51           </p>
  52 </div>
  53 </div>
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  55 <td align="left"></td>
  56 <td align="right"><div class="copyright-footer">Copyright &#169; 2008 Eric Niebler<p>
  57         Distributed under the Boost Software License, Version 1.0. (See accompanying
  58         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>)
  59       </p>
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