blob: 36a668f2ac8037a0ef82654de6ed9572d0195e00 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Struct template is_callable</title>
<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
<link rel="home" href="../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset">
<link rel="up" href="../../proto/reference.html#header.boost.proto.traits_hpp" title="Header <boost/proto/traits.hpp>">
<link rel="prev" href="result_of/child_c.html" title="Struct template child_c">
<link rel="next" href="is_transform.html" title="Struct template is_transform">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr>
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td>
<td align="center"><a href="../../../../index.html">Home</a></td>
<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td>
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
<td align="center"><a href="../../../../more/index.htm">More</a></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="result_of/child_c.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_transform.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
</div>
<div class="refentry">
<a name="boost.proto.is_callable"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2><span class="refentrytitle">Struct template is_callable</span></h2>
<p>boost::proto::is_callable — Boolean metafunction which tells whether a type is a callable
<a class="link" href="../../PolymorphicFunctionObject.html" title="Concept PolymorphicFunctionObject">PolymorphicFunctionObject</a> or not.</p>
</div>
<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
<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>>
</span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></span>
<span class="keyword">struct</span> <a class="link" href="is_callable.html" title="Struct template is_callable">is_callable</a> <span class="special">:</span> <span class="keyword"></span> mpl::bool_<<em class="replaceable"><code>true-or-false</code></em>> <span class="special">{</span>
<span class="special">}</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="idp381762976"></a><h2>Description</h2>
<p>
<code class="computeroutput">proto::is_callable<></code> is used by the
<code class="computeroutput"><a class="link" href="when.html" title="Struct template when">proto::when<></a></code>
transform to determine whether a function type <code class="computeroutput">R(A<sub>1</sub>,...A<sub>n</sub>)</code>
is a <a class="link" href="../../CallableTransform.html" title="Concept CallableTransform">CallableTransform</a> or an <a class="link" href="../../ObjectTransform.html" title="Concept ObjectTransform">ObjectTransform</a>.
The former are evaluated using <code class="computeroutput"><a class="link" href="call.html" title="Struct template call">proto::call<></a></code>
and the later with <code class="computeroutput"><a class="link" href="make.html" title="Struct template make">proto::make<></a></code>.
If <code class="computeroutput">proto::is_callable<R>::value</code> is <code class="computeroutput">true</code>,
the function type is a <a class="link" href="../../CallableTransform.html" title="Concept CallableTransform">CallableTransform</a>; otherwise, it is an <a class="link" href="../../ObjectTransform.html" title="Concept ObjectTransform">ObjectTransform</a>.
</p>
<p>
Unless specialized for a type
<code class="computeroutput">T</code>, <code class="computeroutput">proto::is_callable<T>::value</code>
is computed as follows:
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem"><p>
If <code class="computeroutput">T</code> is a template type
<code class="computeroutput">X<Y<sub>0</sub>,...Y<sub>n</sub>></code>,
where all <code class="computeroutput">Y<sub>x</sub></code> are types for
<code class="computeroutput">x</code> in <code class="computeroutput">[0,n]</code>,
<code class="computeroutput">proto::is_callable<T>::value</code> is
<code class="computeroutput">boost::is_same<Y<sub>n</sub>, <a class="link" href="callable.html" title="Struct callable">proto::callable</a>>::value</code>.
</p></li>
<li class="listitem"><p>
If <code class="computeroutput">T</code> is derived from <code class="computeroutput"><a class="link" href="callable.html" title="Struct callable">proto::callable</a></code>,
<code class="computeroutput">proto::is_callable<T>::value</code> is <code class="computeroutput">true</code>.
</p></li>
<li class="listitem"><p>
Otherwise, <code class="computeroutput">proto::is_callable<T>::value</code>
is <code class="computeroutput">false</code>.
</p></li>
</ul></div>
<p>
</p>
</div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
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>)
</p>
</div></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="result_of/child_c.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_transform.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>
|