feedc0de/boost_fusion
1
0
Fork 0
forked from boostorg/fusion
Code Pull Requests Activity
Files
ca6f831b96121c84d69714afb5265a83781f661a
boost_fusion/doc/html/fusion/algorithms/iteration/functions/fold.html
Tobias Schwinger ca6f831b96 adds documentation for functional module 
[SVN r36959]
2007-02-15 23:11:24 +00:00

156 lines
12 KiB
HTML
Raw Blame History

This file contains invisible Unicode characters

This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>fold</title>
<link rel="stylesheet" href="../../../../boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.68.1">
<link rel="start" href="../../../../index.html" title="Chapter 1. Fusion 2.0">
<link rel="up" href="../functions.html" title="Functions">
<link rel="prev" href="../functions.html" title="Functions">
<link rel="next" href="accumulate.html" title="accumulate">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%">
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td>
<td align="center"><a href="../../../../../../../../index.htm">Home</a></td>
<td align="center"><a href="../../../../../../../libraries.htm">Libraries</a></td>
<td align="center"><a href="../../../../../../../../people/people.htm">People</a></td>
<td align="center"><a href="../../../../../../../../more/faq.htm">FAQ</a></td>
<td align="center"><a href="../../../../../../../../more/index.htm">More</a></td>
</table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="../functions.html"><img src="../../../../images/prev.png" alt="Prev"></a><a accesskey="u" href="../functions.html"><img src="../../../../images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../images/home.png" alt="Home"></a><a accesskey="n" href="accumulate.html"><img src="../../../../images/next.png" alt="Next"></a>
</div>
<div class="section" lang="en">
<div class="titlepage"><div><div><h5 class="title">
<a name="fusion.algorithms.iteration.functions.fold"></a><a href="fold.html" title="fold">fold</a></h5></div></div></div>
<a name="fusion.algorithms.iteration.functions.fold.description"></a><h6>
<a name="id1080746"></a>
<a href="fold.html#fusion.algorithms.iteration.functions.fold.description">Description</a>
</h6>
<p>
Repeatedly applies binary <a href="../../../functional/concepts/poly.html" title=" Polymorphic Function
Object">Polymorphic
Function Object</a> <code class="computeroutput"><span class="identifier">f</span></code>
to each element of a sequence and the previous state.
</p>
<a name="fusion.algorithms.iteration.functions.fold.synopsis"></a><h6>
<a name="id1080792"></a>
<a href="fold.html#fusion.algorithms.iteration.functions.fold.synopsis">Synopsis</a>
</h6>
<pre class="programlisting">
<span class="keyword">template</span><span class="special">&lt;</span>
<span class="keyword">typename</span> <span class="identifier">Sequence</span><span class="special">,</span>
<span class="keyword">typename</span> <span class="identifier">State</span><span class="special">,</span>
<span class="keyword">typename</span> <span class="identifier">F</span>
<span class="special">&gt;</span>
<span class="keyword">typename</span> <a 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">&lt;</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">&gt;::</span><span class="identifier">type</span> <span class="identifier">fold</span><span class="special">(</span>
<span class="identifier">Sequence</span><span class="special">&amp;</span> <span class="identifier">seq</span><span class="special">,</span> <span class="identifier">State</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">initial_state</span><span class="special">,</span> <span class="identifier">F</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">f</span><span class="special">);</span>
</pre>
<div class="table">
<a name="id1081019"></a><p class="title"><b>Table 1.32. Parameters</b></p>
<table class="table" summary="Parameters">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>Parameter</th>
<th>Requirement</th>
<th>Description</th>
</tr></thead>
<tbody>
<tr>
<td><code class="computeroutput"><span class="identifier">seq</span></code></td>
<td>A
model of <a href="../../../sequences/concepts/forward_sequence.html" title="Forward
Sequence">Forward
Sequence</a>,<code class="computeroutput"><span class="identifier">f</span><span class="special">(</span><span class="identifier">e</span><span class="special">)</span></code> must be a valid expression for each
element <code class="computeroutput"><span class="identifier">e</span></code> in <code class="computeroutput"><span class="identifier">seq</span></code>
</td>
<td>Operation's argument</td>
</tr>
<tr>
<td><code class="computeroutput"><span class="identifier">initial_state</span></code></td>
<td>Any
type</td>
<td>Initial state</td>
</tr>
<tr>
<td><code class="computeroutput"><span class="identifier">f</span></code></td>
<td>A
model of binary <a href="../../../functional/concepts/poly.html" title=" Polymorphic Function
Object">Polymorphic
Function Object</a>
</td>
<td>Operation's argument</td>
</tr>
</tbody>
</table>
</div>
<a name="fusion.algorithms.iteration.functions.fold.expression_semantics"></a><h6>
<a name="id1081167"></a>
<a href="fold.html#fusion.algorithms.iteration.functions.fold.expression_semantics">Expression
Semantics</a>
</h6>
<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>
</pre>
<p>
<span class="bold"><strong>Return type</strong></span>: Any type
</p>
<p>
<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>
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>.
</p>
<a name="fusion.algorithms.iteration.functions.fold.complexity"></a><h6>
<a name="id1081347"></a>
<a href="fold.html#fusion.algorithms.iteration.functions.fold.complexity">Complexity</a>
</h6>
<p>
Linear, exactly <code class="computeroutput"><a href="../../../sequences/intrinsics/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">&lt;</span><span class="identifier">Sequence</span><span class="special">&gt;::</span><span class="identifier">value</span></code> applications of <code class="computeroutput"><span class="identifier">f</span></code>.
</p>
<a name="fusion.algorithms.iteration.functions.fold.header"></a><h6>
<a name="id1081428"></a>
<a href="fold.html#fusion.algorithms.iteration.functions.fold.header">Header</a>
</h6>
<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">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">&gt;</span>
</pre>
<a name="fusion.algorithms.iteration.functions.fold.example"></a><h6>
<a name="id1081522"></a>
<a href="fold.html#fusion.algorithms.iteration.functions.fold.example">Example</a>
</h6>
<pre class="programlisting">
<span class="keyword">struct</span> <span class="identifier">make_string</span>
<span class="special">{</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">State</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">result</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">type</span><span class="special">;</span>
<span class="special">};</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">&gt;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="keyword">operator</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">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&amp;</span> <span class="identifier">str</span><span class="special">)</span> <span class="keyword">const</span>
<span class="special">{</span>
<span class="keyword">return</span> <span class="identifier">str</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">lexical_cast</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;(</span><span class="identifier">t</span><span class="special">);</span>
<span class="special">}</span>
<span class="special">};</span>
<span class="special">...</span>
<span class="keyword">const</span> <a href="../../../sequences/containers/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a><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="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"><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>
</pre>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><small>Copyright © 2001-2005 Joel de Guzman, Dan Marsden</small></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="../functions.html"><img src="../../../../images/prev.png" alt="Prev"></a><a accesskey="u" href="../functions.html"><img src="../../../../images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../images/home.png" alt="Home"></a><a accesskey="n" href="accumulate.html"><img src="../../../../images/next.png" alt="Next"></a>
</div>
</body>
</html>
View Git Blame Copy Permalink