1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> 4<title>Macro BOOST_TTI_TRAIT_MEMBER_TYPE</title> 5<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="index.html" title="Chapter 1. The Type Traits Introspection Library"> 8<link rel="up" href="header/boost/tti/member_type_hpp.html" title="Header <boost/tti/member_type.hpp>"> 9<link rel="prev" href="boost/tti/valid_member_type.html" title="Struct template valid_member_type"> 10<link rel="next" href="BOOST_TTI_MEMBER_TYPE.html" title="Macro BOOST_TTI_MEMBER_TYPE"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td> 15<td align="center"><a href="../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="boost/tti/valid_member_type.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="header/boost/tti/member_type_hpp.html"><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="BOOST_TTI_MEMBER_TYPE.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="refentry"> 26<a name="BOOST_TT_idm46187185643920"></a><div class="titlepage"></div> 27<div class="refnamediv"> 28<h2><span class="refentrytitle">Macro BOOST_TTI_TRAIT_MEMBER_TYPE</span></h2> 29<p>BOOST_TTI_TRAIT_MEMBER_TYPE — Expands to a metafunction whose typedef 'type' is either the named type or a marker type. </p> 30</div> 31<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 32<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="header/boost/tti/member_type_hpp.html" title="Header <boost/tti/member_type.hpp>">boost/tti/member_type.hpp</a>> 33 34</span>BOOST_TTI_TRAIT_MEMBER_TYPE(trait, name)</pre></div> 35<div class="refsect1"> 36<a name="idm45456560311936"></a><h2>Description</h2> 37<p>trait = the name of the metafunction within the tti namespace.</p> 38<p>name = the name of the inner type.</p> 39<p>generates a metafunction called "trait" where 'trait' is the macro parameter. template<class BOOST_TTI_TP_T,class BOOST_TTI_TP_MARKER_TYPE = boost::tti::detail::notype> 40 struct trait 41 { 42 typedef unspecified type; 43 44 typedef BOOST_TTI_TP_MARKER_TYPE boost_tti_marker_type; 45 }; 46 47 The metafunction types and return: 48 49 BOOST_TTI_TP_T = the enclosing type. 50 BOOST_TTI_TP_MARKER_TYPE = (optional) a type to use as the marker type. 51 defaults to the internal boost::tti::detail::notype. 52 53 returns = 'type' is the inner type of 'name' if the inner type exists 54 within the enclosing type, else 'type' is a marker type. 55 if the end-user does not specify a marker type then 56 an internal boost::tti::detail::notype marker type is used. 57 58 The metafunction also encapsulates the type of the marker type as 59 a nested 'boost_tti_marker_type'. 60</p> 61<p>The purpose of this macro is to encapsulate the 'name' type as the typedef 'type' of a metafunction, but only if it exists within the enclosing type. This allows for an evaluation of inner type existence, without generating a compiler error, which can be used by other metafunctions in this library. </p> 62</div> 63</div> 64<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 65<td align="left"></td> 66<td align="right"><div class="copyright-footer">Copyright © 2011-2013 Tropic Software 67 East Inc<p> 68 Distributed under the Boost Software License, Version 1.0. (See accompanying 69 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>) 70 </p> 71</div></td> 72</tr></table> 73<hr> 74<div class="spirit-nav"> 75<a accesskey="p" href="boost/tti/valid_member_type.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="header/boost/tti/member_type_hpp.html"><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="BOOST_TTI_MEMBER_TYPE.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 76</div> 77</body> 78</html> 79
