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<title>Annex: No Variadic Macros</title>
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<div class="section">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="boost_localfunction.no_variadic_macros"></a><a class="link" href="no_variadic_macros.html" title="Annex: No Variadic Macros">Annex: No Variadic
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Macros</a>
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</h2></div></div></div>
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<p>
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This section illustrates an alternative syntax for compilers without variadic
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macro support.
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</p>
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<h4>
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<a name="boost_localfunction.no_variadic_macros.h0"></a>
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<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>
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</h4>
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<p>
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Most modern compilers support <a href="http://en.wikipedia.org/wiki/Variadic_macro" target="_top">variaid
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macros</a> (notably, these include GCC, MSVC, and all <a href="http://www.open-std.org/JTC1/SC22/WG21/" target="_top">C++11</a>
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compilers). However, in the rare case that programmers need to use this library
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on a compiler without variadic macros, this library also allows to specify
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its macro parameters using a <a href="http://www.boost.org/libs/preprocessor" target="_top">Boost.Preprocessor</a>
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sequence where tokens are separated by round parenthesis <code class="computeroutput"><span class="special">()</span></code>:
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</p>
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<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>
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</pre>
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<p>
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Instead of the comma-separated list that we have seen so far which requires
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variadic macros:
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</p>
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<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>
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</pre>
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<p>
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For example, the following syntax is accepted on all compilers with and without
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variadic macros (see also <a href="../../../test/add_seq.cpp" target="_top"><code class="literal">add_seq.cpp</code></a>):
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</p>
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<p>
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</p>
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<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>
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<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>
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<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>
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<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>
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<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>
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<span class="identifier">add</span><span class="special">(</span><span class="number">1</span><span class="special">);</span>
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<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>
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<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>
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<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>
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<span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">report_errors</span><span class="special">();</span>
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<span class="special">}</span>
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</pre>
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<p>
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</p>
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<p>
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However, on compilers with variadic macros the comma-separated syntax we have
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seen so far is preferred because more readable (see also <a href="../../../test/add.cpp" target="_top"><code class="literal">add.cpp</code></a>):
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</p>
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<p>
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</p>
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<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>
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<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>
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<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>
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<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>
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<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>
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<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>
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<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>
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<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>
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<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>
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<span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">report_errors</span><span class="special">();</span>
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<span class="special">}</span>
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</pre>
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<p>
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</p>
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<p>
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Note that the same macros accept both syntaxes on compilers with variadic macros
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and only the sequence syntax on compilers without variadic macros. Finally,
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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
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macros:
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</p>
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<p>
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</p>
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<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>
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<span class="keyword">return</span> <span class="number">10</span><span class="special">;</span>
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<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>
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<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>
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</pre>
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<p>
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</p>
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<h4>
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<a name="boost_localfunction.no_variadic_macros.h1"></a>
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<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>
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</h4>
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<p>
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For reference, the following is a list of most of the examples presented in
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this documentation reprogrammed using the sequence syntax instead of the comma-separated
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syntax (in alphabetic order):
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</p>
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<div class="informaltable"><table class="table">
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<colgroup><col></colgroup>
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<thead><tr><th>
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<p>
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Files
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</p>
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</th></tr></thead>
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<tbody>
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<tr><td>
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<p>
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<a href="../../../test/add_classifiers_seq.cpp" target="_top"><code class="literal">add_classifiers_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/add_default_seq.cpp" target="_top"><code class="literal">add_default_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/add_except_seq.cpp" target="_top"><code class="literal">add_except_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/add_inline_seq.cpp" target="_top"><code class="literal">add_inline_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/add_params_only_seq.cpp" target="_top"><code class="literal">add_params_only_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/add_template_seq.cpp" target="_top"><code class="literal">add_template_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/add_this_seq.cpp" target="_top"><code class="literal">add_this_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/add_typed_seq.cpp" target="_top"><code class="literal">add_typed_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/add_with_default_seq.cpp" target="_top"><code class="literal">add_with_default_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/all_decl_seq.cpp" target="_top"><code class="literal">all_decl_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/factorial_seq.cpp" target="_top"><code class="literal">factorial_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
|
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<p>
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<a href="../../../test/macro_commas_seq.cpp" target="_top"><code class="literal">macro_commas_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/nesting_seq.cpp" target="_top"><code class="literal">nesting_seq.cpp</code></a>
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</p>
|
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</td></tr>
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<tr><td>
|
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<p>
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<a href="../../../test/overload_seq.cpp" target="_top"><code class="literal">overload_seq.cpp</code></a>
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</p>
|
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</td></tr>
|
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<tr><td>
|
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<p>
|
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<a href="../../../test/return_assign_seq.cpp" target="_top"><code class="literal">return_assign_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/return_derivative_seq.cpp" target="_top"><code class="literal">return_derivative_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/return_inc_seq.cpp" target="_top"><code class="literal">return_inc_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/return_setget_seq.cpp" target="_top"><code class="literal">return_setget_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/return_this_seq.cpp" target="_top"><code class="literal">return_this_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/same_line_seq.cpp" target="_top"><code class="literal">same_line_seq.cpp</code></a>
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</p>
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</td></tr>
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<tr><td>
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<p>
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<a href="../../../test/transform_seq.cpp" target="_top"><code class="literal">transform_seq.cpp</code></a>
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</p>
|
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</td></tr>
|
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<tr><td>
|
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<p>
|
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<a href="../../../test/typeof_seq.cpp" target="_top"><code class="literal">typeof_seq.cpp</code></a>
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|
</p>
|
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</td></tr>
|
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<tr><td>
|
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<p>
|
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<a href="../../../test/typeof_template_seq.cpp" target="_top"><code class="literal">typeof_template_seq.cpp</code></a>
|
|
</p>
|
|
</td></tr>
|
|
</tbody>
|
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</table></div>
|
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</div>
|
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"></td>
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<td align="right"><div class="copyright-footer">Copyright © 2009-2012 Lorenzo
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Caminiti<p>
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Distributed under the Boost Software License, Version 1.0 (see accompanying
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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>)
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</p>
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</div></td>
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</tr></table>
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<hr>
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<div class="spirit-nav">
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<a accesskey="p" href="alternatives.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="implementation.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
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