Planet
navi homePPSaboutscreenshotsdownloaddevelopmentforum

source: downloads/boost_1_33_1/libs/mpl/doc/refmanual/begin.html @ 12

Last change on this file since 12 was 12, checked in by landauf, 18 years ago

added boost
File size: 7.9 KB
Line 
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 0.3.6: http://docutils.sourceforge.net/" />
7<title>The MPL Reference Manual: begin</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="./back.html" class="navigation-link">Prev</a>&nbsp;<a href="./clear.html" class="navigation-link">Next</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./back.html" class="navigation-link">Back</a>&nbsp;<a href="./clear.html" class="navigation-link">Along</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./intrinsic-metafunctions.html" class="navigation-link">Up</a>&nbsp;<a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</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="./begin.html" class="navigation-link">begin</a></td>
13</tr></table><div class="header-separator"></div>
14<div class="section" id="begin">
15<h1><a class="toc-backref" href="./intrinsic-metafunctions.html#id356" name="begin">begin</a></h1>
16<div class="section" id="begin-synopsis">
17<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
18<pre class="literal-block">
19template&lt;
20      typename X
21    &gt;
22struct <a href="./begin.html" class="identifier">begin</a>
23{
24    typedef <em>unspecified</em> type;
25};
26</pre>
27</div>
28<div class="section" id="begin-description">
29<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
30<p>Returns an iterator that points to the first element of the sequence. If
31the argument is not a <a class="reference" href="./forward-sequence.html">Forward Sequence</a>, returns <a class="refentry reference" href="./void.html"><tt class="refentry literal"><span class="pre">void_</span></tt></a>.</p>
32</div>
33<div class="section" id="begin-header">
34<h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
35<pre class="literal-block">
36#include &lt;<a href="../../../../boost/mpl/begin_end.hpp" class="header">boost/mpl/begin_end.hpp</a>&gt;
37</pre>
38</div>
39<div class="section" id="begin-model-of">
40<h3><a class="subsection-title" href="#model-of" name="model-of">Model of</a></h3>
41<p><a class="reference" href="./tag-dispatched.html">Tag Dispatched Metafunction</a></p>
42</div>
43<div class="section" id="begin-parameters">
44<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
45<table border="1" class="table">
46<colgroup>
47<col width="18%" />
48<col width="22%" />
49<col width="60%" />
50</colgroup>
51<thead valign="bottom">
52<tr><th>Parameter</th>
53<th>Requirement</th>
54<th>Description</th>
55</tr>
56</thead>
57<tbody valign="top">
58<tr><td><tt class="literal"><span class="pre">X</span></tt></td>
59<td>Any type</td>
60<td>A type whose begin iterator, if any, will be
61returned.</td>
62</tr>
63</tbody>
64</table>
65</div>
66<div class="section" id="begin-expression-semantics">
67<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
68<p>For any arbitrary type <tt class="literal"><span class="pre">x</span></tt>:</p>
69<pre class="literal-block">
70typedef <a href="./begin.html" class="identifier">begin</a>&lt;x&gt;::type first;
71</pre>
72<table class="field-list" frame="void" rules="none">
73<col class="field-name" />
74<col class="field-body" />
75<tbody valign="top">
76<tr class="field"><th class="field-name">Return type:</th><td class="field-body"><a class="reference" href="./forward-iterator.html">Forward Iterator</a> or <a class="refentry reference" href="./void.html"><tt class="refentry literal"><span class="pre">void_</span></tt></a>.</td>
77</tr>
78<tr class="field"><th class="field-name">Semantics:</th><td class="field-body">If <tt class="literal"><span class="pre">x</span></tt> is a <a class="reference" href="./forward-sequence.html">Forward Sequence</a>, <tt class="literal"><span class="pre">first</span></tt> is an iterator pointing to the
79first element of <tt class="literal"><span class="pre">s</span></tt>; otherwise <tt class="literal"><span class="pre">first</span></tt> is <a class="refentry reference" href="./void.html"><tt class="refentry literal"><span class="pre">void_</span></tt></a>.</td>
80</tr>
81<tr class="field"><th class="field-name">Postcondition:</th><td class="field-body">If <tt class="literal"><span class="pre">first</span></tt> is an iterator, it is either dereferenceable or past-the-end; it
82is past-the-end if and only if <tt class="literal"><span class="pre"><a href="./size.html" class="identifier">size</a>&lt;x&gt;::value</span> <span class="pre">==</span> <span class="pre">0</span></tt>.</td>
83</tr>
84</tbody>
85</table>
86</div>
87<div class="section" id="begin-complexity">
88<h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3>
89<p>Amortized constant time.</p>
90</div>
91<div class="section" id="begin-example">
92<h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
93<pre class="literal-block">
94typedef <a href="./vector.html" class="identifier">vector</a>&lt; unsigned char,unsigned short,
95    unsigned int,unsigned long &gt; unsigned_types;
96
97typedef <a href="./begin.html" class="identifier">begin</a>&lt;unsigned_types&gt;::type iter;
98<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same&lt; <a href="./deref.html" class="identifier">deref</a>&lt;iter&gt;::type, unsigned char &gt; ));
99
100<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same&lt; <a href="./begin.html" class="identifier">begin</a>&lt;int&gt;::type, <a href="./void.html" class="identifier">void_</a> > ));
101</pre>
102</div>
103<div class="section" id="begin-see-also">
104<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
105<p><a class="reference" href="./iterators.html">Iterators</a>, <a class="reference" href="./forward-sequence.html">Forward Sequence</a>, <a class="refentry reference" href="./end.html"><tt class="refentry literal"><span class="pre">end</span></tt></a>, <a class="refentry reference" href="./size.html"><tt class="refentry literal"><span class="pre">size</span></tt></a>, <a class="refentry reference" href="./empty.html"><tt class="refentry literal"><span class="pre">empty</span></tt></a></p>
106<!-- modtime: November 13, 2004 01:25:11 +0000 -->
107<!-- Sequences/Intrinsic Metafunctions//clear -->
108</div>
109</div>
110
111<div class="footer-separator"></div>
112<table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./back.html" class="navigation-link">Prev</a>&nbsp;<a href="./clear.html" class="navigation-link">Next</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./back.html" class="navigation-link">Back</a>&nbsp;<a href="./clear.html" class="navigation-link">Along</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./intrinsic-metafunctions.html" class="navigation-link">Up</a>&nbsp;<a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td>
113</tr></table></body>
114</html>
Note: See TracBrowser for help on using the repository browser.