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4 | <title>Annex: No Variadic Macros</title> | |
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24 | </div> | |
25 | <div class="section"> | |
26 | <div class="titlepage"><div><div><h2 class="title" style="clear: both"> | |
27 | <a name="boost_localfunction.no_variadic_macros"></a><a class="link" href="no_variadic_macros.html" title="Annex: No Variadic Macros">Annex: No Variadic | |
28 | Macros</a> | |
29 | </h2></div></div></div> | |
30 | <p> | |
31 | This section illustrates an alternative syntax for compilers without variadic | |
32 | macro support. | |
33 | </p> | |
34 | <h4> | |
35 | <a name="boost_localfunction.no_variadic_macros.h0"></a> | |
36 | <span class="phrase"><a name="boost_localfunction.no_variadic_macros.sequence_syntax"></a></span><a class="link" href="no_variadic_macros.html#boost_localfunction.no_variadic_macros.sequence_syntax">Sequence Syntax</a> | |
37 | </h4> | |
38 | <p> | |
39 | Most modern compilers support <a href="http://en.wikipedia.org/wiki/Variadic_macro" target="_top">variaid | |
40 | macros</a> (notably, these include GCC, MSVC, and all <a href="http://www.open-std.org/JTC1/SC22/WG21/" target="_top">C++11</a> | |
41 | compilers). However, in the rare case that programmers need to use this library | |
42 | on a compiler without variadic macros, this library also allows to specify | |
43 | its macro parameters using a <a href="http://www.boost.org/libs/preprocessor" target="_top">Boost.Preprocessor</a> | |
44 | sequence where tokens are separated by round parenthesis <code class="computeroutput"><span class="special">()</span></code>: | |
45 | </p> | |
46 | <pre class="programlisting"><span class="special">(</span><span class="identifier">token1</span><span class="special">)</span> <span class="special">(</span><span class="identifier">token2</span><span class="special">)</span> <span class="special">...</span> <span class="comment">// All compilers.</span> | |
47 | </pre> | |
48 | <p> | |
49 | Instead of the comma-separated list that we have seen so far which requires | |
50 | variadic macros: | |
51 | </p> | |
52 | <pre class="programlisting"><span class="identifier">token1</span><span class="special">,</span> <span class="identifier">token2</span><span class="special">,</span> <span class="special">...</span> <span class="comment">// Only compilers with varidic macros.</span> | |
53 | </pre> | |
54 | <p> | |
55 | For example, the following syntax is accepted on all compilers with and without | |
56 | variadic macros (see also <a href="../../../test/add_seq.cpp" target="_top"><code class="literal">add_seq.cpp</code></a>): | |
57 | </p> | |
58 | <p> | |
59 | </p> | |
60 | <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span> | |
61 | <span class="keyword">int</span> <span class="identifier">sum</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">factor</span> <span class="special">=</span> <span class="number">10</span><span class="special">;</span> | |
62 | ||
63 | <span class="keyword">void</span> <span class="identifier">BOOST_LOCAL_FUNCTION</span><span class="special">(</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">bind</span> <span class="identifier">factor</span><span class="special">)</span> <span class="special">(</span><span class="identifier">bind</span><span class="special">&</span> <span class="identifier">sum</span><span class="special">)</span> <span class="special">(</span><span class="keyword">int</span> <span class="identifier">num</span><span class="special">)</span> <span class="special">)</span> <span class="special">{</span> | |
64 | <span class="identifier">sum</span> <span class="special">+=</span> <span class="identifier">factor</span> <span class="special">*</span> <span class="identifier">num</span><span class="special">;</span> | |
65 | <span class="special">}</span> <span class="identifier">BOOST_LOCAL_FUNCTION_NAME</span><span class="special">(</span><span class="identifier">add</span><span class="special">)</span> | |
66 | ||
67 | <span class="identifier">add</span><span class="special">(</span><span class="number">1</span><span class="special">);</span> | |
68 | <span class="keyword">int</span> <span class="identifier">nums</span><span class="special">[]</span> <span class="special">=</span> <span class="special">{</span><span class="number">2</span><span class="special">,</span> <span class="number">3</span><span class="special">};</span> | |
69 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">for_each</span><span class="special">(</span><span class="identifier">nums</span><span class="special">,</span> <span class="identifier">nums</span> <span class="special">+</span> <span class="number">2</span><span class="special">,</span> <span class="identifier">add</span><span class="special">);</span> | |
70 | ||
71 | <span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">sum</span> <span class="special">==</span> <span class="number">60</span><span class="special">);</span> | |
72 | <span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">report_errors</span><span class="special">();</span> | |
73 | <span class="special">}</span> | |
74 | </pre> | |
75 | <p> | |
76 | </p> | |
77 | <p> | |
78 | However, on compilers with variadic macros the comma-separated syntax we have | |
79 | seen so far is preferred because more readable (see also <a href="../../../test/add.cpp" target="_top"><code class="literal">add.cpp</code></a>): | |
80 | </p> | |
81 | <p> | |
82 | </p> | |
83 | <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span> <span class="comment">// Some local scope.</span> | |
84 | <span class="keyword">int</span> <span class="identifier">sum</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">factor</span> <span class="special">=</span> <span class="number">10</span><span class="special">;</span> <span class="comment">// Variables in scope to bind.</span> | |
85 | ||
86 | <span class="keyword">void</span> <span class="identifier">BOOST_LOCAL_FUNCTION</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">bind</span> <span class="identifier">factor</span><span class="special">,</span> <span class="identifier">bind</span><span class="special">&</span> <span class="identifier">sum</span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">num</span><span class="special">)</span> <span class="special">{</span> | |
87 | <span class="identifier">sum</span> <span class="special">+=</span> <span class="identifier">factor</span> <span class="special">*</span> <span class="identifier">num</span><span class="special">;</span> | |
88 | <span class="special">}</span> <span class="identifier">BOOST_LOCAL_FUNCTION_NAME</span><span class="special">(</span><span class="identifier">add</span><span class="special">)</span> | |
89 | ||
90 | <span class="identifier">add</span><span class="special">(</span><span class="number">1</span><span class="special">);</span> <span class="comment">// Call the local function.</span> | |
91 | <span class="keyword">int</span> <span class="identifier">nums</span><span class="special">[]</span> <span class="special">=</span> <span class="special">{</span><span class="number">2</span><span class="special">,</span> <span class="number">3</span><span class="special">};</span> | |
92 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">for_each</span><span class="special">(</span><span class="identifier">nums</span><span class="special">,</span> <span class="identifier">nums</span> <span class="special">+</span> <span class="number">2</span><span class="special">,</span> <span class="identifier">add</span><span class="special">);</span> <span class="comment">// Pass it to an algorithm.</span> | |
93 | ||
94 | <span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">sum</span> <span class="special">==</span> <span class="number">60</span><span class="special">);</span> <span class="comment">// Assert final summation value.</span> | |
95 | <span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">report_errors</span><span class="special">();</span> | |
96 | <span class="special">}</span> | |
97 | </pre> | |
98 | <p> | |
99 | </p> | |
100 | <p> | |
101 | Note that the same macros accept both syntaxes on compilers with variadic macros | |
102 | and only the sequence syntax on compilers without variadic macros. Finally, | |
103 | an empty local function parameter list is always specified using <code class="computeroutput"><span class="keyword">void</span></code> on compilers with and without variadic | |
104 | macros: | |
105 | </p> | |
106 | <p> | |
107 | </p> | |
108 | <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">BOOST_LOCAL_FUNCTION</span><span class="special">(</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span> <span class="comment">// No parameter.</span> | |
109 | <span class="keyword">return</span> <span class="number">10</span><span class="special">;</span> | |
110 | <span class="special">}</span> <span class="identifier">BOOST_LOCAL_FUNCTION_NAME</span><span class="special">(</span><span class="identifier">ten</span><span class="special">)</span> | |
111 | ||
112 | <span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">ten</span><span class="special">()</span> <span class="special">==</span> <span class="number">10</span><span class="special">);</span> | |
113 | </pre> | |
114 | <p> | |
115 | </p> | |
116 | <h4> | |
117 | <a name="boost_localfunction.no_variadic_macros.h1"></a> | |
118 | <span class="phrase"><a name="boost_localfunction.no_variadic_macros.examples"></a></span><a class="link" href="no_variadic_macros.html#boost_localfunction.no_variadic_macros.examples">Examples</a> | |
119 | </h4> | |
120 | <p> | |
121 | For reference, the following is a list of most of the examples presented in | |
122 | this documentation reprogrammed using the sequence syntax instead of the comma-separated | |
123 | syntax (in alphabetic order): | |
124 | </p> | |
125 | <div class="informaltable"><table class="table"> | |
126 | <colgroup><col></colgroup> | |
127 | <thead><tr><th> | |
128 | <p> | |
129 | Files | |
130 | </p> | |
131 | </th></tr></thead> | |
132 | <tbody> | |
133 | <tr><td> | |
134 | <p> | |
135 | <a href="../../../test/add_classifiers_seq.cpp" target="_top"><code class="literal">add_classifiers_seq.cpp</code></a> | |
136 | </p> | |
137 | </td></tr> | |
138 | <tr><td> | |
139 | <p> | |
140 | <a href="../../../test/add_default_seq.cpp" target="_top"><code class="literal">add_default_seq.cpp</code></a> | |
141 | </p> | |
142 | </td></tr> | |
143 | <tr><td> | |
144 | <p> | |
145 | <a href="../../../test/add_except_seq.cpp" target="_top"><code class="literal">add_except_seq.cpp</code></a> | |
146 | </p> | |
147 | </td></tr> | |
148 | <tr><td> | |
149 | <p> | |
150 | <a href="../../../test/add_inline_seq.cpp" target="_top"><code class="literal">add_inline_seq.cpp</code></a> | |
151 | </p> | |
152 | </td></tr> | |
153 | <tr><td> | |
154 | <p> | |
155 | <a href="../../../test/add_params_only_seq.cpp" target="_top"><code class="literal">add_params_only_seq.cpp</code></a> | |
156 | </p> | |
157 | </td></tr> | |
158 | <tr><td> | |
159 | <p> | |
160 | <a href="../../../test/add_template_seq.cpp" target="_top"><code class="literal">add_template_seq.cpp</code></a> | |
161 | </p> | |
162 | </td></tr> | |
163 | <tr><td> | |
164 | <p> | |
165 | <a href="../../../test/add_this_seq.cpp" target="_top"><code class="literal">add_this_seq.cpp</code></a> | |
166 | </p> | |
167 | </td></tr> | |
168 | <tr><td> | |
169 | <p> | |
170 | <a href="../../../test/add_typed_seq.cpp" target="_top"><code class="literal">add_typed_seq.cpp</code></a> | |
171 | </p> | |
172 | </td></tr> | |
173 | <tr><td> | |
174 | <p> | |
175 | <a href="../../../test/add_with_default_seq.cpp" target="_top"><code class="literal">add_with_default_seq.cpp</code></a> | |
176 | </p> | |
177 | </td></tr> | |
178 | <tr><td> | |
179 | <p> | |
180 | <a href="../../../test/all_decl_seq.cpp" target="_top"><code class="literal">all_decl_seq.cpp</code></a> | |
181 | </p> | |
182 | </td></tr> | |
183 | <tr><td> | |
184 | <p> | |
185 | <a href="../../../test/factorial_seq.cpp" target="_top"><code class="literal">factorial_seq.cpp</code></a> | |
186 | </p> | |
187 | </td></tr> | |
188 | <tr><td> | |
189 | <p> | |
190 | <a href="../../../test/macro_commas_seq.cpp" target="_top"><code class="literal">macro_commas_seq.cpp</code></a> | |
191 | </p> | |
192 | </td></tr> | |
193 | <tr><td> | |
194 | <p> | |
195 | <a href="../../../test/nesting_seq.cpp" target="_top"><code class="literal">nesting_seq.cpp</code></a> | |
196 | </p> | |
197 | </td></tr> | |
198 | <tr><td> | |
199 | <p> | |
200 | <a href="../../../test/overload_seq.cpp" target="_top"><code class="literal">overload_seq.cpp</code></a> | |
201 | </p> | |
202 | </td></tr> | |
203 | <tr><td> | |
204 | <p> | |
205 | <a href="../../../test/return_assign_seq.cpp" target="_top"><code class="literal">return_assign_seq.cpp</code></a> | |
206 | </p> | |
207 | </td></tr> | |
208 | <tr><td> | |
209 | <p> | |
210 | <a href="../../../test/return_derivative_seq.cpp" target="_top"><code class="literal">return_derivative_seq.cpp</code></a> | |
211 | </p> | |
212 | </td></tr> | |
213 | <tr><td> | |
214 | <p> | |
215 | <a href="../../../test/return_inc_seq.cpp" target="_top"><code class="literal">return_inc_seq.cpp</code></a> | |
216 | </p> | |
217 | </td></tr> | |
218 | <tr><td> | |
219 | <p> | |
220 | <a href="../../../test/return_setget_seq.cpp" target="_top"><code class="literal">return_setget_seq.cpp</code></a> | |
221 | </p> | |
222 | </td></tr> | |
223 | <tr><td> | |
224 | <p> | |
225 | <a href="../../../test/return_this_seq.cpp" target="_top"><code class="literal">return_this_seq.cpp</code></a> | |
226 | </p> | |
227 | </td></tr> | |
228 | <tr><td> | |
229 | <p> | |
230 | <a href="../../../test/same_line_seq.cpp" target="_top"><code class="literal">same_line_seq.cpp</code></a> | |
231 | </p> | |
232 | </td></tr> | |
233 | <tr><td> | |
234 | <p> | |
235 | <a href="../../../test/transform_seq.cpp" target="_top"><code class="literal">transform_seq.cpp</code></a> | |
236 | </p> | |
237 | </td></tr> | |
238 | <tr><td> | |
239 | <p> | |
240 | <a href="../../../test/typeof_seq.cpp" target="_top"><code class="literal">typeof_seq.cpp</code></a> | |
241 | </p> | |
242 | </td></tr> | |
243 | <tr><td> | |
244 | <p> | |
245 | <a href="../../../test/typeof_template_seq.cpp" target="_top"><code class="literal">typeof_template_seq.cpp</code></a> | |
246 | </p> | |
247 | </td></tr> | |
248 | </tbody> | |
249 | </table></div> | |
250 | </div> | |
251 | <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> | |
252 | <td align="left"></td> | |
253 | <td align="right"><div class="copyright-footer">Copyright © 2009-2012 Lorenzo | |
254 | Caminiti<p> | |
255 | Distributed under the Boost Software License, Version 1.0 (see accompanying | |
256 | file LICENSE_1_0.txt or a copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) | |
257 | </p> | |
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