File: tuto.html

package info (click to toggle)
boost1.55 1.55.0%2Bdfsg-3
  • links: PTS, VCS
  • area: main
  • in suites: jessie, jessie-kfreebsd
  • size: 487,824 kB
  • ctags: 673,349
  • sloc: cpp: 2,098,430; xml: 106,036; ansic: 46,744; python: 32,427; sh: 11,864; cs: 2,121; asm: 1,640; makefile: 984; perl: 714; yacc: 456; php: 132; fortran: 43; sql: 13; csh: 6
file content (222 lines) | stat: -rw-r--r-- 21,417 bytes parent folder | download 
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
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
 
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Tutorial</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="../typeof.html" title="Chapter&#160;35.&#160;Boost.Typeof">
<link rel="prev" href="../typeof.html" title="Chapter&#160;35.&#160;Boost.Typeof">
<link rel="next" href="refe.html" title="Reference">
</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="../typeof.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../typeof.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="refe.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="typeof.tuto"></a>Tutorial</h2></div></div></div>
<p>
      To start using typeof include the typeof header:
    </p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">typeof</span><span class="special">/</span><span class="identifier">typeof</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
</pre>
<p>
      To deduce the type of an expression at compile time use the <code class="computeroutput"><span class="identifier">BOOST_TYPEOF</span></code>
      macro:
    </p>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">ex1</span>
<span class="special">{</span>
    <span class="keyword">typedef</span> <span class="identifier">BOOST_TYPEOF</span><span class="special">(</span><span class="number">1</span> <span class="special">+</span> <span class="number">0.5</span><span class="special">)</span> <span class="identifier">type</span><span class="special">;</span>

    <span class="identifier">BOOST_STATIC_ASSERT</span><span class="special">((</span><span class="identifier">is_same</span><span class="special">&lt;</span><span class="identifier">type</span><span class="special">,</span> <span class="keyword">double</span><span class="special">&gt;::</span><span class="identifier">value</span><span class="special">));</span>
<span class="special">}</span>
</pre>
<p>
      In the dependent context use <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_TPL</span></code>
      instead of <code class="computeroutput"><span class="identifier">BOOST_TYPEOF</span></code>:
    </p>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">ex2</span>
<span class="special">{</span>
    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span>
    <span class="identifier">BOOST_TYPEOF_TPL</span><span class="special">(</span><span class="identifier">T</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">U</span><span class="special">())</span> <span class="identifier">add</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">&amp;</span> <span class="identifier">t</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">U</span><span class="special">&amp;</span> <span class="identifier">u</span><span class="special">)</span>
    <span class="special">{</span>
        <span class="keyword">return</span> <span class="identifier">t</span> <span class="special">+</span> <span class="identifier">u</span><span class="special">;</span>
    <span class="special">};</span>

    <span class="keyword">typedef</span> <span class="identifier">BOOST_TYPEOF</span><span class="special">(</span><span class="identifier">add</span><span class="special">(</span><span class="char">'a'</span><span class="special">,</span> <span class="number">1.5</span><span class="special">))</span> <span class="identifier">type</span><span class="special">;</span>

    <span class="identifier">BOOST_STATIC_ASSERT</span><span class="special">((</span><span class="identifier">is_same</span><span class="special">&lt;</span><span class="identifier">type</span><span class="special">,</span> <span class="keyword">double</span><span class="special">&gt;::</span><span class="identifier">value</span><span class="special">));</span>
<span class="special">}</span>
</pre>
<p>
      The above examples are possible because the Typeof Library knows about primitive
      types, such as <code class="computeroutput"><span class="keyword">int</span></code>, <code class="computeroutput"><span class="keyword">double</span></code>, <code class="computeroutput"><span class="keyword">char</span></code>,
      etc. The Typeof Library also knows about most types and templates defined by
      the Standard C++ Library, but the appropriate headers need to be included to
      take advantage of this:
    </p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">typeof</span><span class="special">/</span><span class="identifier">std</span><span class="special">/</span><span class="identifier">utility</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>

<span class="keyword">namespace</span> <span class="identifier">ex3</span>
<span class="special">{</span>
    <span class="identifier">BOOST_AUTO</span><span class="special">(</span><span class="identifier">p</span><span class="special">,</span> <span class="identifier">make_pair</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="number">2</span><span class="special">));</span>

    <span class="identifier">BOOST_STATIC_ASSERT</span><span class="special">((</span><span class="identifier">is_same</span><span class="special">&lt;</span><span class="identifier">BOOST_TYPEOF</span><span class="special">(</span><span class="identifier">p</span><span class="special">),</span> <span class="identifier">pair</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="keyword">int</span><span class="special">&gt;</span> <span class="special">&gt;::</span><span class="identifier">value</span><span class="special">));</span>
<span class="special">}</span>
</pre>
<p>
      Here <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">typeof</span><span class="special">/</span><span class="identifier">std</span><span class="special">/</span><span class="identifier">utility</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
      includes <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">utility</span><span class="special">&gt;</span></code> and contains knowledge about templates
      defined there. This naming convention applies in general, for example to let
      the Typeof Library handle <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span></code>,
      include <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">typeof</span><span class="special">/</span><span class="identifier">std</span><span class="special">/</span><span class="identifier">vector</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>,
      etc.
    </p>
<p>
      To deduce the type of a variable from the expression, this variable is initialized
      with, use the <code class="computeroutput"><span class="identifier">BOOST_AUTO</span></code> macro
      (or <code class="computeroutput"><span class="identifier">BOOST_AUTO_TPL</span></code> in a dependent
      context:
    </p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">typeof</span><span class="special">/</span><span class="identifier">std</span><span class="special">/</span><span class="identifier">string</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>

<span class="keyword">namespace</span> <span class="identifier">ex4</span>
<span class="special">{</span>
    <span class="identifier">BOOST_AUTO</span><span class="special">(</span><span class="identifier">p</span><span class="special">,</span> <span class="keyword">new</span> <span class="keyword">int</span><span class="special">[</span><span class="number">20</span><span class="special">]);</span>

    <span class="identifier">BOOST_STATIC_ASSERT</span><span class="special">((</span><span class="identifier">is_same</span><span class="special">&lt;</span><span class="identifier">BOOST_TYPEOF</span><span class="special">(</span><span class="identifier">p</span><span class="special">),</span> <span class="keyword">int</span><span class="special">*&gt;::</span><span class="identifier">value</span><span class="special">));</span>
<span class="special">}</span>
</pre>
<p>
      Both <code class="computeroutput"><span class="identifier">BOOST_TYPEOF</span></code> and <code class="computeroutput"><span class="identifier">BOOST_AUTO</span></code> strip top-level qualifiers. Therefore,
      to allocate for example a reference, it has to be specified explicitly:
    </p>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">ex5</span>
<span class="special">{</span>
    <span class="identifier">string</span><span class="special">&amp;</span> <span class="identifier">hello</span><span class="special">()</span>
    <span class="special">{</span>
        <span class="keyword">static</span> <span class="identifier">string</span> <span class="identifier">s</span> <span class="special">=</span> <span class="string">"hello"</span><span class="special">;</span>
        <span class="keyword">return</span> <span class="identifier">s</span><span class="special">;</span>
    <span class="special">}</span>

    <span class="identifier">BOOST_AUTO</span><span class="special">(&amp;</span><span class="identifier">s</span><span class="special">,</span> <span class="identifier">hello</span><span class="special">());</span>
<span class="special">}</span>
</pre>
<p>
      To better understand this syntax, note that this gets expanded into:
    </p>
<pre class="programlisting"><span class="identifier">BOOST_TYPEOF</span><span class="special">(</span><span class="identifier">hello</span><span class="special">())</span> <span class="special">&amp;</span><span class="identifier">s</span> <span class="special">=</span> <span class="identifier">hello</span><span class="special">();</span>
</pre>
<p>
      If your define your own type, the Typeof Library cannot handle it unless you
      let it know about this type. You tell the Typeof Library about a type (or template)
      by the means of "registering" this type/template.
    </p>
<p>
      Any source or header file where types/templates are registered has to contain
      the following line before any registration is done:
    </p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="identifier">BOOST_TYPEOF_INCREMENT_REGISTRATION_GROUP</span><span class="special">()</span>
</pre>
<p>
      After this a type can be registered:
    </p>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">ex6</span>
<span class="special">{</span>
    <span class="keyword">struct</span> <span class="identifier">MyType</span>
    <span class="special">{};</span>
<span class="special">}</span>

<span class="identifier">BOOST_TYPEOF_REGISTER_TYPE</span><span class="special">(</span><span class="identifier">ex6</span><span class="special">::</span><span class="identifier">MyType</span><span class="special">)</span>
</pre>
<p>
      The registration must be done from the context of global namespace; fully qualified
      type name has to be used.
    </p>
<p>
      Any number of types can be registered in one file, each on a separate line.
    </p>
<p>
      Once your type is registered, the Typeof Library can handle it in any context:
    </p>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">ex6</span>
<span class="special">{</span>
    <span class="keyword">typedef</span> <span class="identifier">BOOST_TYPEOF</span><span class="special">(</span><span class="identifier">make_pair</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="identifier">MyType</span><span class="special">()))</span> <span class="identifier">type</span><span class="special">;</span>

    <span class="identifier">BOOST_STATIC_ASSERT</span><span class="special">((</span><span class="identifier">is_same</span><span class="special">&lt;</span><span class="identifier">type</span><span class="special">,</span> <span class="identifier">pair</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="identifier">MyType</span><span class="special">&gt;</span> <span class="special">&gt;::</span><span class="identifier">value</span><span class="special">));</span>
<span class="special">}</span>
</pre>
<p>
      A template is registered by specifying its fully qualified name, and describing
      its parameters. In the simplest case, when all parameters are type parameters,
      only their number needs to be specified:
    </p>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">ex7</span>
<span class="special">{</span>
    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span>
    <span class="keyword">struct</span> <span class="identifier">MyTemplate</span>
    <span class="special">{};</span>
<span class="special">}</span>

<span class="identifier">BOOST_TYPEOF_REGISTER_TEMPLATE</span><span class="special">(</span><span class="identifier">ex7</span><span class="special">::</span><span class="identifier">MyTemplate</span><span class="special">,</span> <span class="number">2</span><span class="special">)</span>

<span class="keyword">namespace</span> <span class="identifier">ex7</span>
<span class="special">{</span>
    <span class="keyword">typedef</span> <span class="identifier">BOOST_TYPEOF</span><span class="special">(</span><span class="identifier">make_pair</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="identifier">MyTemplate</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="identifier">ex6</span><span class="special">::</span><span class="identifier">MyType</span><span class="special">&gt;()))</span> <span class="identifier">type</span><span class="special">;</span>

    <span class="identifier">BOOST_STATIC_ASSERT</span><span class="special">((</span><span class="identifier">is_same</span><span class="special">&lt;</span><span class="identifier">type</span><span class="special">,</span>
        <span class="identifier">pair</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="identifier">MyTemplate</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="identifier">ex6</span><span class="special">::</span><span class="identifier">MyType</span><span class="special">&gt;</span> <span class="special">&gt;</span>
    <span class="special">&gt;::</span><span class="identifier">value</span><span class="special">));</span>
<span class="special">}</span>
</pre>
<p>
      When a template has integral template parameters, all parameters need to be
      described in the preprocessor sequence:
    </p>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">ex8</span>
<span class="special">{</span>
    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">n</span><span class="special">&gt;</span>
    <span class="keyword">struct</span> <span class="identifier">MyTemplate</span>
    <span class="special">{};</span>
<span class="special">}</span>

<span class="identifier">BOOST_TYPEOF_REGISTER_TEMPLATE</span><span class="special">(</span><span class="identifier">ex8</span><span class="special">::</span><span class="identifier">MyTemplate</span><span class="special">,</span> <span class="special">(</span><span class="keyword">class</span><span class="special">)(</span><span class="keyword">int</span><span class="special">))</span>

<span class="keyword">namespace</span> <span class="identifier">ex8</span>
<span class="special">{</span>
    <span class="keyword">typedef</span> <span class="identifier">BOOST_TYPEOF</span><span class="special">(</span><span class="identifier">make_pair</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="identifier">MyTemplate</span><span class="special">&lt;</span><span class="identifier">ex7</span><span class="special">::</span><span class="identifier">MyTemplate</span><span class="special">&lt;</span><span class="identifier">ex6</span><span class="special">::</span><span class="identifier">MyType</span><span class="special">,</span> <span class="keyword">int</span><span class="special">&gt;,</span> <span class="number">0</span><span class="special">&gt;()))</span> <span class="identifier">type</span><span class="special">;</span>

    <span class="identifier">BOOST_STATIC_ASSERT</span><span class="special">((</span><span class="identifier">is_same</span><span class="special">&lt;</span><span class="identifier">type</span><span class="special">,</span>
        <span class="identifier">pair</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="identifier">MyTemplate</span><span class="special">&lt;</span><span class="identifier">ex7</span><span class="special">::</span><span class="identifier">MyTemplate</span><span class="special">&lt;</span><span class="identifier">ex6</span><span class="special">::</span><span class="identifier">MyType</span><span class="special">,</span> <span class="keyword">int</span><span class="special">&gt;,</span> <span class="number">0</span><span class="special">&gt;</span> <span class="special">&gt;</span>
    <span class="special">&gt;::</span><span class="identifier">value</span><span class="special">));</span>
<span class="special">}</span>
</pre>
<p>
      Please see the reference for more details.
    </p>
</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; 2004, 2005 Arkadiy Vertleyb, Peder Holt<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="../typeof.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../typeof.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="refe.html"><img src="../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>