1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 5<title>Struct template is_transform</title> 6<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> 7<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 8<link rel="home" href="../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> 9<link rel="up" href="../../proto/reference.html#header.boost.proto.traits_hpp" title="Header <boost/proto/traits.hpp>"> 10<link rel="prev" href="is_callable.html" title="Struct template is_callable"> 11<link rel="next" href="is_aggregate.html" title="Struct template is_aggregate"> 12</head> 13<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 14<table cellpadding="2" width="100%"><tr> 15<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td> 16<td align="center"><a href="../../../../index.html">Home</a></td> 17<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td> 18<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 19<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 20<td align="center"><a href="../../../../more/index.htm">More</a></td> 21</tr></table> 22<hr> 23<div class="spirit-nav"> 24<a accesskey="p" href="is_callable.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.traits_hpp"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="is_aggregate.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="refentry"> 27<a name="boost.proto.is_transform"></a><div class="titlepage"></div> 28<div class="refnamediv"> 29<h2><span class="refentrytitle">Struct template is_transform</span></h2> 30<p>boost::proto::is_transform — Boolean metafunction which tells whether a type is a 31 <a class="link" href="../../PrimitiveTransform.html" title="Concept PrimitiveTransform">PrimitiveTransform</a> or not.</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: <<a class="link" href="../../proto/reference.html#header.boost.proto.traits_hpp" title="Header <boost/proto/traits.hpp>">boost/proto/traits.hpp</a>> 35 36</span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></span> 37<span class="keyword">struct</span> <a class="link" href="is_transform.html" title="Struct template is_transform">is_transform</a> <span class="special">:</span> <span class="keyword"></span> mpl::bool_<<em class="replaceable"><code>true-or-false</code></em>> <span class="special">{</span> 38<span class="special">}</span><span class="special">;</span></pre></div> 39<div class="refsect1"> 40<a name="id-1.3.33.5.41.19.4"></a><h2>Description</h2> 41<p> 42 <code class="computeroutput">proto::is_transform<></code> is used by the 43 <code class="computeroutput"><a class="link" href="make.html" title="Struct template make">proto::make<></a></code> 44 transform to determine whether a type <code class="computeroutput">R</code> represents a 45 <a class="link" href="../../PrimitiveTransform.html" title="Concept PrimitiveTransform">PrimitiveTransform</a> to apply, or whether it merely represents itself. 46 </p> 47<p> 48 It is also used by the 49 <code class="computeroutput"><a class="link" href="call.html" title="Struct template call">proto::call<></a></code> 50 transform to determine whether the function types <code class="computeroutput">R()</code>, 51 <code class="computeroutput">R(A1)</code>, and <code class="computeroutput">R(A1, A2)</code> should 52 be passed the expression, state and data parameters (as needed). 53 </p> 54<p> 55 Unless specialized for a type 56 <code class="computeroutput">T</code>, <code class="computeroutput">proto::is_transform<T>::value</code> 57 is computed as follows: 58 </p> 59<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 60<li class="listitem"><p> 61 If <code class="computeroutput">T</code> is a class type that inherits directly or indirectly from 62 an instantiation of 63 <code class="computeroutput"><a class="link" href="transform.html" title="Struct template transform">proto::transform<></a></code>, 64 <code class="computeroutput">proto::is_transform<T>::value</code> is <code class="computeroutput">true</code>. 65 </p></li> 66<li class="listitem"><p> 67 Otherwise, <code class="computeroutput">proto::is_transform<T>::value</code> 68 is <code class="computeroutput">false</code>. 69 </p></li> 70</ul></div> 71<p> 72 </p> 73</div> 74</div> 75<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 76<td align="left"></td> 77<td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<p> 78 Distributed under the Boost Software License, Version 1.0. (See accompanying 79 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>) 80 </p> 81</div></td> 82</tr></table> 83<hr> 84<div class="spirit-nav"> 85<a accesskey="p" href="is_callable.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.traits_hpp"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="is_aggregate.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 86</div> 87</body> 88</html> 89
