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Thorsten Jørgen Ottosen
2004-07-30 01:30:27 +00:00
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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<title>Boost.Range Utility Classes </title>
<link rel="stylesheet" href="style.css" type="text/css">
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<body>
<table border="0" >
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<td ><img src="cboost.gif" border="0" ></td>
<td >
<h1 align="center">Boost.Range utility classes</h1>
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<h1></h1>
<p> Having an abstraction that encapsulates a pair of iterators is very
useful. The standard library uses <code>std::pair</code> in some
cercumstances, but that class is cumbersome to use because we need to
specify two template arguments, and for all range algorithm purposes,
we must enforce the two template arguments to be the same. Moreover,
<code>std::pair&lt;iterator,iterator></code> is hardly self-documenting
whereas more domain specific class names are. Therefore these two
classes are provided:
<ul>
<li> <a href=#iter_range><code>iterator_range</code></a>
<li> <a href=#sub_range><code>sub_range</code></a> </ul>
</ul>
The <code>iterator_range</code> class is templated on an iterator and should be
used whenever super general code is needed. The <code>sub_range</code> class
is templated on an <a href=range.html#external_range>ExternalRange</a>
and it is less general, but a bit easier to use since its template argument
is easier to specify.
</p>
<hr> <a name=iter_range></a> <h1><code>iterator_range</code></h1>
The intention of the
<code>iterator_range</code> class is to encapsulate
two iterators so they fulfill the <a href=range.html#range>Range</a> concept.
A few other functions are also provided for convinience.
<h3>Synopsis</h3>
<pre>
namespace boost
{
template< class Iterator >
class iterator_range
{
iterator_range(); // not implemented
public: // Range types
typedef ... value_type;
typedef ... difference_type;
typedef ... size_type;
typedef Iterator iterator;
typedef Iterator const_iterator;
public: // construction, assignment
template< class Iterator >
iterator_range( Iterator Begin, Iterator End );
template< class XRange >
iterator_range( XRange& r );
template< class XRange >
iterator_range( const XRange& r );
template< class XRange >
iterator_range& operator=( XRange& r );
template< class XRange >
iterator_range& operator=( const XRange& r );
public: // Range functions
iterator begin() const;
iterator end() const;
size_type size() const;
bool empty() const;
public: // convenience
operator unspecified_bool_type() const;
void swap( iterator_range& r );
};
// stream output
template< class Iterator, class T, class Traits >
std::basic_ostream&lt;T,Traits>& operator<<( std::basic_ostream&lt;T,Traits>& Os,
const iterator_range&lt;Iterator>& r );
// comparison
template< class Iterator >
bool operator==( const iterator_range&lt;Iterator>& l, const iterator_range&lt;Iterator>& r );
template< class Iterator >
bool operator!=( const iterator_range&lt;Iterator>& l, const iterator_range&lt;Iterator>& r );
// external construction
template< class Iterator >
iterator_range< Iterator >
make_iterator_range( Iterator Begin, Iterator End );
template< class XRange >
iterator_range< typename iterator_of&lt;XRange>::type >
make_iterator_range( XRange& r );
template< class XRange >
iterator_range< typename const_iterator_of&lt;XRange>::type >
make_iterator_range( const XRange& r );
// convenience
template< class Sequence, class XRange >
Sequence copy_range( const XRange& r )
template< class Sequence, class XRange, class Func >
Sequence transform_range( const XRange& r, Func func );
} // namespace 'boost'
</pre>
<p>
It is worth noticing that the templated constructors and assignment operators
allow conversion from <code>iterator_range<iterator></code> to
<code>iterator_range<const_iterator></code>. If an instance of
<code>iterator_range</code> is constructed by a client with two iterators, the
client must ensure that the two iterators delimit a valid closed-open range
<code>[begin,end)</code>.
</p>
<hr> <a name=sub_range></a>
<h1><code>sub_range</code></h1>
The <code>sub_range</code> class inherits all its functionality
from the <a href="#iter_range"><code>iterator_range</code></a> class.
The <code>sub_range</code> class is often easier to use because
one must specify the <a href="range.html#external_range">ExternalRange</a>
template argument instead of an iterator.
<h3>Synopsis</h3>
<pre>
namespace boost
{
template< class XRange >
class sub_range : public iterator_range< typename result_iterator_of&lt;XRange>::type >
{
public: // construction, assignment
template< class Iterator >
sub_range( Iterator Begin, Iterator End );
template< class XRange2 >
sub_range( XRange2& r );
template< class XRange2 >
sub_range( const Range2& r );
template< class XRange2 >
sub_range& operator=( XRange2& r );
template< class XRange2 >
sub_range& operator=( const XRange2& r );
public:
// rest of interface inherited from iterator_range
};
} // namespace 'boost'
</pre>
<hr>
<p>
(C) Copyright Thorsten Ottosen 2003-2004
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