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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">&amp;</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">&amp;</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 &#169; 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>
 258 </div></td>
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