feedc0de/boost_range
1
0
Fork 0
forked from boostorg/range
Code Pull Requests Activity
Files
cab01e8ba3d34344f7a7780843ea79e2a89f99b1
boost_range/doc/html/range/reference/extending/method_2.html
Neil Groves 067b63da8e Boost.Range improved push_front algorithm unit test. Updated documentation. 
[SVN r61145]
2010-04-08 19:09:34 +00:00

268 lines
20 KiB
HTML
Raw Blame History

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Method 2: provide free-standing functions and specialize metafunctions</title>
<link rel="stylesheet" href="../../../../../../../doc/html/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.75.1">
<link rel="home" href="../../../index.html" title="Chapter&#160;1.&#160;Range 2.0">
<link rel="up" href="../extending.html" title="Extending the library">
<link rel="prev" href="method_1.html" title="Method 1: provide member functions and nested types">
<link rel="next" href="method_3.html" title="Method 3: provide range adaptor implementations">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr>
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
<td align="center"><a href="../../../../../../../index.html">Home</a></td>
<td align="center"><a href="../../../../../../libraries.htm">Libraries</a></td>
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="method_1.html"><img src="../../../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../extending.html"><img src="../../../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="method_3.html"><img src="../../../../../../../doc/html/images/next.png" alt="Next"></a>
</div>
<div class="section" title="Method 2: provide free-standing functions and specialize metafunctions">
<div class="titlepage"><div><div><h4 class="title">
<a name="range.reference.extending.method_2"></a><a class="link" href="method_2.html" title="Method 2: provide free-standing functions and specialize metafunctions"> Method 2: provide
free-standing functions and specialize metafunctions</a>
</h4></div></div></div>
<p>
This procedure assumes that you cannot (or do not wish to) change the types
that should be made conformant to a Range concept. If this is not true,
see <a class="link" href="method_1.html" title="Method 1: provide member functions and nested types">method 1</a>.
</p>
<p>
The primary templates in this library are implemented such that certain
functions are found via argument-dependent-lookup (ADL). Below is given
an overview of which free-standing functions a class must specify to be
useable as a certain Range concept. Let <code class="computeroutput"><span class="identifier">x</span></code>
be a variable (<code class="computeroutput"><span class="keyword">const</span></code> or <code class="computeroutput"><span class="keyword">mutable</span></code>) of the class in question.
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Function
</p>
</th>
<th>
<p>
Related concept
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">range_begin</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
<a class="link" href="../../concepts/single_pass_range.html" title="Single Pass Range">Single Pass
Range</a>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">range_end</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
<a class="link" href="../../concepts/single_pass_range.html" title="Single Pass Range">Single Pass
Range</a>
</p>
</td>
</tr>
</tbody>
</table></div>
<p>
<code class="computeroutput"><span class="identifier">range_begin</span><span class="special">()</span></code>
and <code class="computeroutput"><span class="identifier">range_end</span><span class="special">()</span></code>
must be overloaded for both <code class="computeroutput"><span class="keyword">const</span></code>
and <code class="computeroutput"><span class="keyword">mutable</span></code> reference arguments.
</p>
<p>
You must also specialize two metafunctions for your type <code class="computeroutput"><span class="identifier">X</span></code>:
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Metafunction
</p>
</th>
<th>
<p>
Related concept
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_mutable_iterator</span></code>
</p>
</td>
<td>
<p>
<a class="link" href="../../concepts/single_pass_range.html" title="Single Pass Range">Single Pass
Range</a>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_const_iterator</span></code>
</p>
</td>
<td>
<p>
<a class="link" href="../../concepts/single_pass_range.html" title="Single Pass Range">Single Pass
Range</a>
</p>
</td>
</tr>
</tbody>
</table></div>
<p>
A complete example is given here:
</p>
<p>
</p>
<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">range</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iterator</span><span class="special">&gt;</span> <span class="comment">// for std::iterator_traits, std::distance()
</span>
<span class="keyword">namespace</span> <span class="identifier">Foo</span>
<span class="special">{</span>
<span class="comment">//
</span> <span class="comment">// Our sample UDT. A 'Pair'
</span> <span class="comment">// will work as a range when the stored
</span> <span class="comment">// elements are iterators.
</span> <span class="comment">//
</span> <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">class</span> <span class="identifier">T</span> <span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">Pair</span>
<span class="special">{</span>
<span class="identifier">T</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">last</span><span class="special">;</span>
<span class="special">};</span>
<span class="special">}</span> <span class="comment">// namespace 'Foo'
</span>
<span class="keyword">namespace</span> <span class="identifier">boost</span>
<span class="special">{</span>
<span class="comment">//
</span> <span class="comment">// Specialize metafunctions. We must include the range.hpp header.
</span> <span class="comment">// We must open the 'boost' namespace.
</span> <span class="comment">//
</span>
<span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">class</span> <span class="identifier">T</span> <span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">range_mutable_iterator</span><span class="special">&lt;</span> <span class="identifier">Foo</span><span class="special">::</span><span class="identifier">Pair</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="special">&gt;</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="identifier">T</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">class</span> <span class="identifier">T</span> <span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">range_const_iterator</span><span class="special">&lt;</span> <span class="identifier">Foo</span><span class="special">::</span><span class="identifier">Pair</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="special">&gt;</span>
<span class="special">{</span>
<span class="comment">//
</span> <span class="comment">// Remark: this is defined similar to 'range_iterator'
</span> <span class="comment">// because the 'Pair' type does not distinguish
</span> <span class="comment">// between an iterator and a const_iterator.
</span> <span class="comment">//
</span> <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="identifier">type</span><span class="special">;</span>
<span class="special">};</span>
<span class="special">}</span> <span class="comment">// namespace 'boost'
</span>
<span class="keyword">namespace</span> <span class="identifier">Foo</span>
<span class="special">{</span>
<span class="comment">//
</span> <span class="comment">// The required functions. These should be defined in
</span> <span class="comment">// the same namespace as 'Pair', in this case
</span> <span class="comment">// in namespace 'Foo'.
</span> <span class="comment">//
</span>
<span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">class</span> <span class="identifier">T</span> <span class="special">&gt;</span>
<span class="keyword">inline</span> <span class="identifier">T</span> <span class="identifier">range_begin</span><span class="special">(</span> <span class="identifier">Pair</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;&amp;</span> <span class="identifier">x</span> <span class="special">)</span>
<span class="special">{</span>
<span class="keyword">return</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">first</span><span class="special">;</span>
<span class="special">}</span>
<span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">class</span> <span class="identifier">T</span> <span class="special">&gt;</span>
<span class="keyword">inline</span> <span class="identifier">T</span> <span class="identifier">range_begin</span><span class="special">(</span> <span class="keyword">const</span> <span class="identifier">Pair</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;&amp;</span> <span class="identifier">x</span> <span class="special">)</span>
<span class="special">{</span>
<span class="keyword">return</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">first</span><span class="special">;</span>
<span class="special">}</span>
<span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">class</span> <span class="identifier">T</span> <span class="special">&gt;</span>
<span class="keyword">inline</span> <span class="identifier">T</span> <span class="identifier">range_end</span><span class="special">(</span> <span class="identifier">Pair</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;&amp;</span> <span class="identifier">x</span> <span class="special">)</span>
<span class="special">{</span>
<span class="keyword">return</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">last</span><span class="special">;</span>
<span class="special">}</span>
<span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">class</span> <span class="identifier">T</span> <span class="special">&gt;</span>
<span class="keyword">inline</span> <span class="identifier">T</span> <span class="identifier">range_end</span><span class="special">(</span> <span class="keyword">const</span> <span class="identifier">Pair</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;&amp;</span> <span class="identifier">x</span> <span class="special">)</span>
<span class="special">{</span>
<span class="keyword">return</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">last</span><span class="special">;</span>
<span class="special">}</span>
<span class="special">}</span> <span class="comment">// namespace 'Foo'
</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">vector</span><span class="special">&gt;</span>
<span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">argc</span><span class="special">,</span> <span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">argv</span><span class="special">[])</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;::</span><span class="identifier">iterator</span> <span class="identifier">iter</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">vec</span><span class="special">;</span>
<span class="identifier">Foo</span><span class="special">::</span><span class="identifier">Pair</span><span class="special">&lt;</span><span class="identifier">iter</span><span class="special">&gt;</span> <span class="identifier">pair</span> <span class="special">=</span> <span class="special">{</span> <span class="identifier">vec</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">vec</span><span class="special">.</span><span class="identifier">end</span><span class="special">()</span> <span class="special">};</span>
<span class="keyword">const</span> <span class="identifier">Foo</span><span class="special">::</span><span class="identifier">Pair</span><span class="special">&lt;</span><span class="identifier">iter</span><span class="special">&gt;&amp;</span> <span class="identifier">cpair</span> <span class="special">=</span> <span class="identifier">pair</span><span class="special">;</span>
<span class="comment">//
</span> <span class="comment">// Notice that we call 'begin' etc with qualification.
</span> <span class="comment">//
</span> <span class="identifier">iter</span> <span class="identifier">i</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">begin</span><span class="special">(</span> <span class="identifier">pair</span> <span class="special">);</span>
<span class="identifier">iter</span> <span class="identifier">e</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">end</span><span class="special">(</span> <span class="identifier">pair</span> <span class="special">);</span>
<span class="identifier">i</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">begin</span><span class="special">(</span> <span class="identifier">cpair</span> <span class="special">);</span>
<span class="identifier">e</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">end</span><span class="special">(</span> <span class="identifier">cpair</span> <span class="special">);</span>
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_difference</span><span class="special">&lt;</span> <span class="identifier">Foo</span><span class="special">::</span><span class="identifier">Pair</span><span class="special">&lt;</span><span class="identifier">iter</span><span class="special">&gt;</span> <span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">s</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">size</span><span class="special">(</span> <span class="identifier">pair</span> <span class="special">);</span>
<span class="identifier">s</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">size</span><span class="special">(</span> <span class="identifier">cpair</span> <span class="special">);</span>
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_reverse_iterator</span><span class="special">&lt;</span> <span class="keyword">const</span> <span class="identifier">Foo</span><span class="special">::</span><span class="identifier">Pair</span><span class="special">&lt;</span><span class="identifier">iter</span><span class="special">&gt;</span> <span class="special">&gt;::</span><span class="identifier">type</span>
<span class="identifier">ri</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">rbegin</span><span class="special">(</span> <span class="identifier">cpair</span> <span class="special">),</span>
<span class="identifier">re</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">rend</span><span class="special">(</span> <span class="identifier">cpair</span> <span class="special">);</span>
<span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright &#169; 2003 -2010 Thorsten Ottosen, Neil Groves<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
</p>
</div></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="method_1.html"><img src="../../../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../extending.html"><img src="../../../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="method_3.html"><img src="../../../../../../../doc/html/images/next.png" alt="Next"></a>
</div>
</body>
</html>
View Git Blame Copy Permalink