File: examples.html

package info (click to toggle)
boost1.62 1.62.0%2Bdfsg-4
  • links: PTS, VCS
  • area: main
  • in suites: stretch
  • size: 686,420 kB
  • sloc: cpp: 2,609,004; xml: 972,558; ansic: 53,674; python: 32,437; sh: 8,829; asm: 3,071; cs: 2,121; makefile: 964; perl: 859; yacc: 472; php: 132; ruby: 94; f90: 55; sql: 13; csh: 6
file content (147 lines) | stat: -rw-r--r-- 12,833 bytes parent folder | download | duplicates (2) 
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
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
 
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Examples</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="Chapter&#160;1.&#160;Boost.Optional">
<link rel="up" href="../index.html" title="Chapter&#160;1.&#160;Boost.Optional">
<link rel="prev" href="detailed_semantics.html" title="Detailed Semantics">
<link rel="next" href="optional_references.html" title="Optional references">
</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="detailed_semantics.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.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="optional_references.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
</div>
<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="boost_optional.examples"></a><a class="link" href="examples.html" title="Examples">Examples</a>
</h2></div></div></div>
<div class="toc"><dl class="toc">
<dt><span class="section"><a href="examples.html#boost_optional.examples.optional_return_values">Optional
      return values</a></span></dt>
<dt><span class="section"><a href="examples.html#boost_optional.examples.optional_local_variables">Optional
      local variables</a></span></dt>
<dt><span class="section"><a href="examples.html#boost_optional.examples.optional_data_members">Optional
      data members</a></span></dt>
<dt><span class="section"><a href="examples.html#boost_optional.examples.bypassing_expensive_unnecessary_default_construction">Bypassing
      expensive unnecessary default construction</a></span></dt>
</dl></div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_optional.examples.optional_return_values"></a><a class="link" href="examples.html#boost_optional.examples.optional_return_values" title="Optional return values">Optional
      return values</a>
</h3></div></div></div>
<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">&gt;</span> <span class="identifier">get_async_input</span><span class="special">()</span>
<span class="special">{</span>
    <span class="keyword">if</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">queue</span><span class="special">.</span><span class="identifier">empty</span><span class="special">()</span> <span class="special">)</span>
        <span class="keyword">return</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">&gt;(</span><span class="identifier">queue</span><span class="special">.</span><span class="identifier">top</span><span class="special">());</span>
    <span class="keyword">else</span> <span class="keyword">return</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">&gt;();</span> <span class="comment">// uninitialized</span>
<span class="special">}</span>

<span class="keyword">void</span> <span class="identifier">receive_async_message</span><span class="special">()</span>
<span class="special">{</span>
    <span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">&gt;</span> <span class="identifier">rcv</span> <span class="special">;</span>
    <span class="comment">// The safe boolean conversion from 'rcv' is used here.</span>
    <span class="keyword">while</span> <span class="special">(</span> <span class="special">(</span><span class="identifier">rcv</span> <span class="special">=</span> <span class="identifier">get_async_input</span><span class="special">())</span> <span class="special">&amp;&amp;</span> <span class="special">!</span><span class="identifier">timeout</span><span class="special">()</span> <span class="special">)</span>
        <span class="identifier">output</span><span class="special">(*</span><span class="identifier">rcv</span><span class="special">);</span>
<span class="special">}</span>
</pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_optional.examples.optional_local_variables"></a><a class="link" href="examples.html#boost_optional.examples.optional_local_variables" title="Optional local variables">Optional
      local variables</a>
</h3></div></div></div>
<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">string</span><span class="special">&gt;</span> <span class="identifier">name</span> <span class="special">;</span>
<span class="keyword">if</span> <span class="special">(</span> <span class="identifier">database</span><span class="special">.</span><span class="identifier">open</span><span class="special">()</span> <span class="special">)</span>
<span class="special">{</span>
    <span class="identifier">name</span> <span class="special">=</span> <span class="identifier">database</span><span class="special">.</span><span class="identifier">lookup</span><span class="special">(</span><span class="identifier">employer_name</span><span class="special">)</span> <span class="special">;</span>
<span class="special">}</span>
<span class="keyword">else</span>
<span class="special">{</span>
    <span class="keyword">if</span> <span class="special">(</span> <span class="identifier">can_ask_user</span> <span class="special">)</span>
        <span class="identifier">name</span> <span class="special">=</span> <span class="identifier">user</span><span class="special">.</span><span class="identifier">ask</span><span class="special">(</span><span class="identifier">employer_name</span><span class="special">)</span> <span class="special">;</span>
<span class="special">}</span>

<span class="keyword">if</span> <span class="special">(</span> <span class="identifier">name</span> <span class="special">)</span>
    <span class="identifier">print</span><span class="special">(*</span><span class="identifier">name</span><span class="special">);</span>
<span class="keyword">else</span> <span class="identifier">print</span><span class="special">(</span><span class="string">"employer's name not found!"</span><span class="special">);</span>
</pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_optional.examples.optional_data_members"></a><a class="link" href="examples.html#boost_optional.examples.optional_data_members" title="Optional data members">Optional
      data members</a>
</h3></div></div></div>
<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">figure</span>
<span class="special">{</span>
    <span class="keyword">public</span><span class="special">:</span>

    <span class="identifier">figure</span><span class="special">()</span>
    <span class="special">{</span>
        <span class="comment">// data member 'm_clipping_rect' is uninitialized at this point.</span>
    <span class="special">}</span>

    <span class="keyword">void</span> <span class="identifier">clip_in_rect</span> <span class="special">(</span> <span class="identifier">rect</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rect</span> <span class="special">)</span>
    <span class="special">{</span>
        <span class="special">....</span>
        <span class="identifier">m_clipping_rect</span> <span class="special">=</span> <span class="identifier">rect</span> <span class="special">;</span> <span class="comment">// initialized here.</span>
    <span class="special">}</span>

    <span class="keyword">void</span> <span class="identifier">draw</span> <span class="special">(</span> <span class="identifier">canvas</span><span class="special">&amp;</span> <span class="identifier">cvs</span> <span class="special">)</span>
    <span class="special">{</span>
        <span class="keyword">if</span> <span class="special">(</span> <span class="identifier">m_clipping_rect</span> <span class="special">)</span>
            <span class="identifier">do_clipping</span><span class="special">(*</span><span class="identifier">m_clipping_rect</span><span class="special">);</span>

        <span class="identifier">cvs</span><span class="special">.</span><span class="identifier">drawXXX</span><span class="special">(..);</span>
    <span class="special">}</span>

    <span class="comment">// this can return NULL.</span>
    <span class="identifier">rect</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">get_clipping_rect</span><span class="special">()</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">get_pointer</span><span class="special">(</span><span class="identifier">m_clipping_rect</span><span class="special">);</span> <span class="special">}</span>

    <span class="keyword">private</span> <span class="special">:</span>

    <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">rect</span><span class="special">&gt;</span> <span class="identifier">m_clipping_rect</span> <span class="special">;</span>

<span class="special">};</span>
</pre>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_optional.examples.bypassing_expensive_unnecessary_default_construction"></a><a class="link" href="examples.html#boost_optional.examples.bypassing_expensive_unnecessary_default_construction" title="Bypassing expensive unnecessary default construction">Bypassing
      expensive unnecessary default construction</a>
</h3></div></div></div>
<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">ExpensiveCtor</span> <span class="special">{</span> <span class="special">...</span> <span class="special">}</span> <span class="special">;</span>
<span class="keyword">class</span> <span class="identifier">Fred</span>
<span class="special">{</span>
    <span class="identifier">Fred</span><span class="special">()</span> <span class="special">:</span> <span class="identifier">mLargeVector</span><span class="special">(</span><span class="number">10000</span><span class="special">)</span> <span class="special">{}</span>

    <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">ExpensiveCtor</span><span class="special">&gt;</span> <span class="special">&gt;</span> <span class="identifier">mLargeVector</span> <span class="special">;</span>
<span class="special">}</span> <span class="special">;</span>
</pre>
</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 &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014 Andrzej Krzemie&#324;ski<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="detailed_semantics.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.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="optional_references.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>