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[SVN r24315]
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Thorsten Jørgen Ottosen
2004-08-05 19:37:40 +00:00
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Boost.Range Introduction </title>
<link rel="stylesheet" href="style.css" type="text/css">
</head>
<body>
<table border="0" >
<tr>
<td ><img src="cboost.gif" border="0" ></td>
<td ><h1 align="center">Boost.Range</h1></td>
</tr>
</table>
<h2>Introduction</h2>
<p>
This library makes it possible to treat different types as if they have
implemented a subset of the container requirements (see &sect;23.1of the C++
standard). Formally, that subset is defined by the <a href="Range.htm"
target="_self" >Range</a> concept. The subset deals mostly with iterator
returning functions and nested <code >typedef</code>s. The main goal is to treat
built-in arrays, standard containers, pairs of iterators and some iterators
uniformly.
</p>
<p >
The main advantages are
<ul >
<li >
safe use of built-in arrays
</li>
<li >
simpler implementation of generic container algorithms
</li>
<li >
more flexible client code
</li>
<li >
correct handling of null-terminated strings
</li>
</ul>
</p>
<p >
Below are given a small example (the complete example can be found <a href="../test/algorithm_example.cpp" target="_self" >here</a>
):
<pre >
//
// Example: extracting bounds in generic algorithms
//
template&lt; typename XRange, typename T &gt;
inline typename boost::iterator_of&lt;XRange&gt;::type
find( XRange& c, const T& value )
{
return std::find( boost::begin( c ), boost::end( c ), value );
}
template&lt; typename XRange, typename T &gt;
inline typename boost::const_iterator_of&lt;XRange&gt;::type
find( const XRange& c, const T& value )
{
return std::find( boost::begin( c ), boost::end( c ), value );
}
//
// replace first value and return its index
//
template&lt; typename EC, typename T &gt;
inline typename boost::size_type_of&lt; EC &gt;::type
my_generic_replace( EC& c, const T& value, const T& replacement )
{
typename boost::const_iterator_of&lt;EC&gt;::type found = find( c, value );
*found = replacement;
return std::distance( boost::begin( c ), found );
}
//
// usage
//
std::vector&lt;int&gt; my_vector;
typedef vector&lt;int&gt;::iterator iterator;
std::pair&lt;iterator,iterator&gt; my_view( my_vector.begin(), my_vector.begin(
) + N );
char str[] = "a string";
// ...
std::cout &lt;&lt; my_generic_replace( my_vector, 4, 2 )
&lt;&lt; my_generic_replace( my_view, 4, 2 )
&lt;&lt; my_generic_replace( str, 'a', 'b' );
</pre>
By using the free-standing functions and type-generators, the code automatically
works for all the types supported by this library. Notice that we have to
provide two version of <code >find()</code> since we cannot forward a non-const
rvalue with reference arguments (see this article about <a href="http://std.dkuug.dk/jtc1/sc22/wg21/docs/papers/2002/n1385.htm" target="_self" >The
Forwarding Problem</a> ).
</p>
<hr>
<p>
(C) Copyright Thorsten Ottosen 2003-2004
</p>
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