]>
Commit | Line | Data |
---|---|---|
7c673cae FG |
1 | <?xml version="1.0" encoding="utf-8" ?> |
2 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> | |
3 | <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> | |
4 | <head> | |
5 | <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> | |
6 | <meta name="generator" content="Docutils 0.7: http://docutils.sourceforge.net/" /> | |
7 | <title>The MPL Reference Manual: front</title> | |
8 | <link rel="stylesheet" href="../style.css" type="text/css" /> | |
9 | </head> | |
10 | <body class="docframe refmanual"> | |
11 | <table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./erase-key.html" class="navigation-link">Prev</a> <a href="./has-key.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./erase-key.html" class="navigation-link">Back</a> <a href="./has-key.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./intrinsic-metafunctions.html" class="navigation-link">Up</a> <a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td> | |
12 | <td class="header-group page-location"><a href="../refmanual.html" class="navigation-link">Front Page</a> / <a href="./sequences.html" class="navigation-link">Sequences</a> / <a href="./intrinsic-metafunctions.html" class="navigation-link">Intrinsic Metafunctions</a> / <a href="./front.html" class="navigation-link">front</a></td> | |
13 | </tr></table><div class="header-separator"></div> | |
14 | <div class="section" id="front"> | |
15 | <h1><a class="toc-backref" href="./intrinsic-metafunctions.html#id1434">front</a></h1> | |
16 | <div class="section" id="id256"> | |
17 | <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> | |
18 | <pre class="literal-block"> | |
19 | template< | |
20 | typename Sequence | |
21 | > | |
22 | struct <a href="./front.html" class="identifier">front</a> | |
23 | { | |
24 | typedef <em>unspecified</em> type; | |
25 | }; | |
26 | </pre> | |
27 | </div> | |
28 | <div class="section" id="id257"> | |
29 | <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> | |
30 | <p>Returns the first element in the sequence.</p> | |
31 | </div> | |
32 | <div class="section" id="id258"> | |
33 | <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> | |
34 | <pre class="literal-block"> | |
35 | #include <<a href="../../../../boost/mpl/front.hpp" class="header">boost/mpl/front.hpp</a>> | |
36 | </pre> | |
37 | </div> | |
38 | <div class="section" id="id259"> | |
39 | <h3><a class="subsection-title" href="#model-of" name="model-of">Model of</a></h3> | |
40 | <p><a class="reference internal" href="./tag-dispatched-metafunction.html">Tag Dispatched Metafunction</a></p> | |
41 | </div> | |
42 | <div class="section" id="id260"> | |
43 | <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> | |
44 | <table border="1" class="docutils table"> | |
45 | <colgroup> | |
46 | <col width="18%" /> | |
47 | <col width="27%" /> | |
48 | <col width="55%" /> | |
49 | </colgroup> | |
50 | <thead valign="bottom"> | |
51 | <tr><th class="head">Parameter</th> | |
52 | <th class="head">Requirement</th> | |
53 | <th class="head">Description</th> | |
54 | </tr> | |
55 | </thead> | |
56 | <tbody valign="top"> | |
57 | <tr><td><tt class="literal"><span class="pre">Sequence</span></tt></td> | |
58 | <td><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a></td> | |
59 | <td>A sequence to be examined.</td> | |
60 | </tr> | |
61 | </tbody> | |
62 | </table> | |
63 | </div> | |
64 | <div class="section" id="id261"> | |
65 | <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> | |
66 | <p>For any <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a> <tt class="literal"><span class="pre">s</span></tt>:</p> | |
67 | <pre class="literal-block"> | |
68 | typedef <a href="./front.html" class="identifier">front</a><s>::type t; | |
69 | </pre> | |
70 | <table class="docutils field-list" frame="void" rules="none"> | |
71 | <col class="field-name" /> | |
72 | <col class="field-body" /> | |
73 | <tbody valign="top"> | |
74 | <tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first">A type.</p> | |
75 | </td> | |
76 | </tr> | |
77 | <tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><p class="first"><tt class="literal"><span class="pre"><a href="./empty.html" class="identifier">empty</a><s>::value</span> <span class="pre">==</span> <span class="pre">false</span></tt>.</p> | |
78 | </td> | |
79 | </tr> | |
80 | <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p> | |
81 | <pre class="last literal-block"> | |
82 | typedef <a href="./deref.html" class="identifier">deref</a>< <a href="./begin.html" class="identifier">begin</a><s>::type >::type t; | |
83 | </pre> | |
84 | </td> | |
85 | </tr> | |
86 | </tbody> | |
87 | </table> | |
88 | </div> | |
89 | <div class="section" id="id262"> | |
90 | <h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3> | |
91 | <p>Amortized constant time.</p> | |
92 | </div> | |
93 | <div class="section" id="id263"> | |
94 | <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> | |
95 | <pre class="literal-block"> | |
96 | typedef <a href="./list.html" class="identifier">list</a><long>::type types1; | |
97 | typedef <a href="./list.html" class="identifier">list</a><int,long>::type types2; | |
98 | typedef <a href="./list.html" class="identifier">list</a><char,int,long>::type types3; | |
99 | ||
100 | <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same< <a href="./front.html" class="identifier">front</a><types1>::type, long > )); | |
101 | <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same< <a href="./front.html" class="identifier">front</a><types2>::type, int> )); | |
102 | <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same< <a href="./front.html" class="identifier">front</a><types3>::type, char> )); | |
103 | </pre> | |
104 | </div> | |
105 | <div class="section" id="id264"> | |
106 | <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> | |
107 | <p><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a>, <a class="reference internal" href="./back.html">back</a>, <a class="reference internal" href="./push-front.html">push_front</a>, <a class="reference internal" href="./begin.html">begin</a>, <a class="reference internal" href="./deref.html">deref</a>, <a class="reference internal" href="./at.html">at</a></p> | |
108 | <!-- Sequences/Intrinsic Metafunctions//has_key --> | |
109 | </div> | |
110 | </div> | |
111 | ||
112 | <div class="footer-separator"></div> | |
113 | <table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./erase-key.html" class="navigation-link">Prev</a> <a href="./has-key.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./erase-key.html" class="navigation-link">Back</a> <a href="./has-key.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./intrinsic-metafunctions.html" class="navigation-link">Up</a> <a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td> | |
114 | <td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div> | |
115 | Distributed under the Boost Software License, Version 1.0. (See accompanying | |
116 | file LICENSE_1_0.txt or copy at <a class="reference external" href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)</div></td></tr></table></body> | |
117 | </html> |