forked from boostorg/fusion
Sync from trunk (except adapt class)
[SVN r56714]
This commit is contained in:
Joel de Guzman
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<div class="titlepage"><div><div><h5 class="title">
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<a name="fusion.algorithm.iteration.functions.fold"></a><a class="link" href="fold.html" title="fold">fold</a>
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</h5></div></div></div>
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<div class="section" lang="en">
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<div class="titlepage">
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<div><div><h5 class="title">
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<a name="fusion.algorithm.iteration.functions.fold"></a><a href="fold.html" title="fold">fold</a>
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</h5></div></div>
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</div>
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<a name="fusion.algorithm.iteration.functions.fold.description"></a><h6>
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<a name="id671348"></a>
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<a class="link" href="fold.html#fusion.algorithm.iteration.functions.fold.description">Description</a>
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<a name="id535870"></a>
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<a href="fold.html#fusion.algorithm.iteration.functions.fold.description">Description</a>
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</h6>
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<p>
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For a sequence <code class="computeroutput"><span class="identifier">Seq</span></code>, initial
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state, and binary function object or function pointer <code class="computeroutput"><span class="identifier">f</span></code>,
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fold repeatedly applies binary <code class="computeroutput"><span class="identifier">f</span></code>
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to each element of <code class="computeroutput"><span class="identifier">Seq</span></code>
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For a sequence <tt class="computeroutput"><span class="identifier">Seq</span></tt>, initial
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state, and binary function object or function pointer <tt class="computeroutput"><span class="identifier">f</span></tt>,
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fold repeatedly applies binary <tt class="computeroutput"><span class="identifier">f</span></tt>
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to each element of <tt class="computeroutput"><span class="identifier">Seq</span></tt>
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and the previous state.
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</p>
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<a name="fusion.algorithm.iteration.functions.fold.synopsis"></a><h6>
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<a name="id671393"></a>
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<a class="link" href="fold.html#fusion.algorithm.iteration.functions.fold.synopsis">Synopsis</a>
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<a name="id535948"></a>
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<a href="fold.html#fusion.algorithm.iteration.functions.fold.synopsis">Synopsis</a>
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</h6>
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<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span>
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<span class="keyword">typename</span> <span class="identifier">Sequence</span><span class="special">,</span>
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<span class="keyword">typename</span> <span class="identifier">State</span><span class="special">,</span>
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<span class="keyword">typename</span> <span class="identifier">F</span>
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<span class="special">></span>
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<span class="keyword">typename</span> <a class="link" href="../metafunctions/fold.html" title="fold"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">fold</span></code></a><span class="special"><</span><span class="identifier">Sequence</span><span class="special">,</span> <span class="identifier">State</span><span class="special">,</span> <span class="identifier">F</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">fold</span><span class="special">(</span>
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<span class="keyword">typename</span> <a href="../metafunctions/fold.html" title="fold"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">fold</span></tt></a><span class="special"><</span><span class="identifier">Sequence</span><span class="special">,</span> <span class="identifier">State</span><span class="special">,</span> <span class="identifier">F</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">fold</span><span class="special">(</span>
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<span class="identifier">Sequence</span><span class="special">&</span> <span class="identifier">seq</span><span class="special">,</span> <span class="identifier">State</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">initial_state</span><span class="special">,</span> <span class="identifier">F</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span><span class="special">);</span>
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</pre>
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<div class="table">
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<a name="id671577"></a><p class="title"><b>Table<EFBFBD>1.33.<2E>Parameters</b></p>
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<div class="table-contents"><table class="table" summary="Parameters">
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<a name="id536204"></a><p class="title"><b>Table<EFBFBD>1.33.<2E>Parameters</b></p>
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<table class="table" summary="Parameters">
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<colgroup>
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<col>
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<col>
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<col>
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</colgroup>
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<thead><tr>
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<th>
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<p>
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<th><p>
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Parameter
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</p>
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</th>
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<th>
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<p>
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</p></th>
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<th><p>
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Requirement
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</p>
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</th>
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<th>
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<p>
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</p></th>
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<th><p>
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Description
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</p>
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</th>
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</p></th>
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</tr></thead>
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<tbody>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">seq</span></code>
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</p>
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</td>
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<td>
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<p>
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A model of <a class="link" href="../../../sequence/concepts/forward_sequence.html" title="Forward Sequence">Forward
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Sequence</a>,<code class="computeroutput"><span class="identifier">f</span><span class="special">(</span><span class="identifier">e</span><span class="special">,</span><span class="identifier">s</span><span class="special">)</span></code> must be a valid expression for
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each element <code class="computeroutput"><span class="identifier">e</span></code>
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in <code class="computeroutput"><span class="identifier">seq</span></code>, and current
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state <code class="computeroutput"><span class="identifier">s</span></code>
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</p>
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</td>
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<td>
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<p>
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<td><p>
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<tt class="computeroutput"><span class="identifier">seq</span></tt>
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</p></td>
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<td><p>
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A model of <a href="../../../sequence/concepts/forward_sequence.html" title="Forward
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Sequence">Forward
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Sequence</a>,<tt class="computeroutput"><span class="identifier">f</span><span class="special">(</span><span class="identifier">e</span><span class="special">,</span><span class="identifier">s</span><span class="special">)</span></tt> must be a valid expression for
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each element <tt class="computeroutput"><span class="identifier">e</span></tt>
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in <tt class="computeroutput"><span class="identifier">seq</span></tt>, and current
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state <tt class="computeroutput"><span class="identifier">s</span></tt>
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</p></td>
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<td><p>
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Operation's argument
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</p>
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</td>
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</p></td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">initial_state</span></code>
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</p>
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</td>
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<td>
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<p>
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<td><p>
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<tt class="computeroutput"><span class="identifier">initial_state</span></tt>
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</p></td>
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<td><p>
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Any type
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</p>
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</td>
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<td>
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<p>
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</p></td>
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<td><p>
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Initial state
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</p>
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</td>
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</p></td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="computeroutput"><span class="identifier">f</span></code>
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</p>
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</td>
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<td>
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<p>
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<code class="computeroutput"><a href="http://www.boost.org/libs/utility/utility.htm#result_of" target="_top"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">result_of</span></code></a><span class="special"><</span><span class="identifier">F</span><span class="special">(</span><span class="identifier">E</span><span class="special">,</span><span class="identifier">S</span><span class="special">)>::</span><span class="identifier">type</span></code> is the return type of <code class="computeroutput"><span class="identifier">f</span><span class="special">(</span><span class="identifier">e</span><span class="special">,</span><span class="identifier">s</span><span class="special">)</span></code>
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for each element <code class="computeroutput"><span class="identifier">e</span></code>
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of type <code class="computeroutput"><span class="identifier">E</span></code> in <code class="computeroutput"><span class="identifier">seq</span></code>, and current state <code class="computeroutput"><span class="identifier">s</span></code> of type <code class="computeroutput"><span class="identifier">S</span></code>
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</p>
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</td>
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<td>
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<p>
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<td><p>
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<tt class="computeroutput"><span class="identifier">f</span></tt>
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</p></td>
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<td><p>
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<tt class="computeroutput"><a href="http://www.boost.org/libs/utility/utility.htm#result_of" target="_top"><tt class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">result_of</span></tt></a><span class="special"><</span><span class="identifier">F</span><span class="special">(</span><span class="identifier">E</span><span class="special">,</span><span class="identifier">S</span><span class="special">)>::</span><span class="identifier">type</span></tt> is the return type of <tt class="computeroutput"><span class="identifier">f</span><span class="special">(</span><span class="identifier">e</span><span class="special">,</span><span class="identifier">s</span><span class="special">)</span></tt>
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for each element <tt class="computeroutput"><span class="identifier">e</span></tt>
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of type <tt class="computeroutput"><span class="identifier">E</span></tt> in <tt class="computeroutput"><span class="identifier">seq</span></tt>, and current state <tt class="computeroutput"><span class="identifier">s</span></tt> of type <tt class="computeroutput"><span class="identifier">S</span></tt>
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</p></td>
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<td><p>
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Operation's argument
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</p>
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</td>
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</p></td>
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</tr>
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</tbody>
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</table></div>
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</table>
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</div>
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<br class="table-break"><a name="fusion.algorithm.iteration.functions.fold.expression_semantics"></a><h6>
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<a name="id671880"></a>
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<a class="link" href="fold.html#fusion.algorithm.iteration.functions.fold.expression_semantics">Expression
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<a name="fusion.algorithm.iteration.functions.fold.expression_semantics"></a><h6>
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<a name="id536612"></a>
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<a href="fold.html#fusion.algorithm.iteration.functions.fold.expression_semantics">Expression
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Semantics</a>
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</h6>
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<pre class="programlisting"><span class="identifier">fold</span><span class="special">(</span><span class="identifier">seq</span><span class="special">,</span> <span class="identifier">initial_state</span><span class="special">,</span> <span class="identifier">f</span><span class="special">);</span>
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</pre>
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<p>
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<span class="bold"><strong>Return type</strong></span>: Any type
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<span class="bold"><b>Return type</b></span>: Any type
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</p>
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<p>
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<span class="bold"><strong>Semantics</strong></span>: Equivalent to <code class="computeroutput"><span class="identifier">f</span><span class="special">(</span><span class="identifier">eN</span> <span class="special">....</span><span class="identifier">f</span><span class="special">(</span><span class="identifier">e2</span><span class="special">,</span><span class="identifier">f</span><span class="special">(</span><span class="identifier">e1</span><span class="special">,</span><span class="identifier">initial_state</span><span class="special">)))</span></code>
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where <code class="computeroutput"><span class="identifier">e1</span> <span class="special">...</span><span class="identifier">eN</span></code> are the elements of <code class="computeroutput"><span class="identifier">seq</span></code>.
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<span class="bold"><b>Semantics</b></span>: Equivalent to <tt class="computeroutput"><span class="identifier">f</span><span class="special">(</span><span class="identifier">eN</span> <span class="special">....</span><span class="identifier">f</span><span class="special">(</span><span class="identifier">e2</span><span class="special">,</span><span class="identifier">f</span><span class="special">(</span><span class="identifier">e1</span><span class="special">,</span><span class="identifier">initial_state</span><span class="special">)))</span></tt>
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where <tt class="computeroutput"><span class="identifier">e1</span> <span class="special">...</span><span class="identifier">eN</span></tt> are the elements of <tt class="computeroutput"><span class="identifier">seq</span></tt>.
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</p>
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<a name="fusion.algorithm.iteration.functions.fold.complexity"></a><h6>
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<a name="id672027"></a>
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<a class="link" href="fold.html#fusion.algorithm.iteration.functions.fold.complexity">Complexity</a>
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<a name="id536820"></a>
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<a href="fold.html#fusion.algorithm.iteration.functions.fold.complexity">Complexity</a>
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</h6>
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<p>
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Linear, exactly <code class="computeroutput"><a class="link" href="../../../sequence/intrinsic/metafunctions/size.html" title="size"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">size</span></code></a><span class="special"><</span><span class="identifier">Sequence</span><span class="special">>::</span><span class="identifier">value</span></code> applications of <code class="computeroutput"><span class="identifier">f</span></code>.
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Linear, exactly <tt class="computeroutput"><a href="../../../sequence/intrinsic/metafunctions/size.html" title="size"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">size</span></tt></a><span class="special"><</span><span class="identifier">Sequence</span><span class="special">>::</span><span class="identifier">value</span></tt> applications of <tt class="computeroutput"><span class="identifier">f</span></tt>.
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</p>
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<a name="fusion.algorithm.iteration.functions.fold.header"></a><h6>
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<a name="id672084"></a>
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<a class="link" href="fold.html#fusion.algorithm.iteration.functions.fold.header">Header</a>
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<a name="id536913"></a>
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<a href="fold.html#fusion.algorithm.iteration.functions.fold.header">Header</a>
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</h6>
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<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">algorithm</span><span class="special">/</span><span class="identifier">iteration</span><span class="special">/</span><span class="identifier">fold</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
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<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">fold</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
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</pre>
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<a name="fusion.algorithm.iteration.functions.fold.example"></a><h6>
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<a name="id672200"></a>
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<a class="link" href="fold.html#fusion.algorithm.iteration.functions.fold.example">Example</a>
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<a name="id537079"></a>
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<a href="fold.html#fusion.algorithm.iteration.functions.fold.example">Example</a>
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</h6>
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<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">make_string</span>
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<span class="special">{</span>
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@ -178,8 +158,8 @@
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<span class="special">}</span>
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<span class="special">};</span>
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<span class="special">...</span>
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<span class="keyword">const</span> <a class="link" href="../../../container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a><span class="special"><</span><span class="keyword">int</span><span class="special">,</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">vec</span><span class="special">(</span><span class="number">1</span><span class="special">,</span><span class="number">2</span><span class="special">);</span>
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<span class="identifier">assert</span><span class="special">(</span><a class="link" href="fold.html" title="fold"><code class="computeroutput"><span class="identifier">fold</span></code></a><span class="special">(</span><span class="identifier">vec</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="string">""</span><span class="special">),</span> <span class="identifier">make_string</span><span class="special">())</span> <span class="special">==</span> <span class="string">"12"</span><span class="special">);</span>
|
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<span class="keyword">const</span> <a href="../../../container/vector.html" title="vector"><tt class="computeroutput"><span class="identifier">vector</span></tt></a><span class="special"><</span><span class="keyword">int</span><span class="special">,</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">vec</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">assert</span><span class="special">(</span><a href="fold.html" title="fold"><tt class="computeroutput"><span class="identifier">fold</span></tt></a><span class="special">(</span><span class="identifier">vec</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="string">""</span><span class="special">),</span> <span class="identifier">make_string</span><span class="special">())</span> <span class="special">==</span> <span class="string">"12"</span><span class="special">);</span>
|
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</pre>
|
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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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