added discussion on extension mechanism

[SVN r30854]
This commit is contained in:
Thorsten Jørgen Ottosen
2005-09-07 16:12:03 +00:00
parent 43a83f500e
commit 06e624858b
3 changed files with 747 additions and 402 deletions

File diff suppressed because it is too large Load Diff

125
doc/example.cpp Normal file
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@ -0,0 +1,125 @@
#include <boost/range.hpp>
#include <iterator> // for std::iterator_traits, std::distance()
namespace Foo
{
//
// Our sample UDT. A 'Pair'
// will work as a range when the stored
// elements are iterators.
//
template< class T >
struct Pair
{
T first, last;
};
} // namespace 'Foo'
namespace boost
{
//
// Specialize metafunctions. We must include the range.hpp header.
// We must open the 'boost' namespace.
//
template< class T >
struct range_value< Foo::Pair<T> >
{
typedef typename std::iterator_traits<T>::value_type type;
};
template< class T >
struct range_iterator< Foo::Pair<T> >
{
typedef T type;
};
template< class T >
struct range_const_iterator< Foo::Pair<T> >
{
//
// Remark: this is defined similar to 'range_iterator'
// because the 'Pair' type does not distinguish
// between an iterator and a const_iterator.
//
typedef T type;
};
template< class T >
struct range_difference< Foo::Pair<T> >
{
typedef typename std::iterator_traits<T>::difference_type type;
};
template< class T >
struct range_size< Foo::Pair<T> >
{
int static_assertion[ sizeof( std::size_t ) >=
sizeof( typename range_difference< Foo::Pair<T> >::type ) ];
typedef std::size_t type;
};
} // namespace 'boost'
namespace Foo
{
//
// The required functions. These should be defined in
// the same namespace as 'Pair', in this case
// in namespace 'Foo'.
//
template< class T >
inline T boost_range_begin( Pair<T>& x )
{
return x.first;
}
template< class T >
inline T boost_range_begin( const Pair<T>& x )
{
return x.first;
}
template< class T >
inline T boost_range_end( Pair<T>& x )
{
return x.last;
}
template< class T >
inline T boost_range_end( const Pair<T>& x )
{
return x.last;
}
template< class T >
inline typename boost::range_size< Pair<T> >::type
boost_range_size( const Pair<T>& x )
{
return std::distance(x.first,x.last);
}
} // namespace 'Foo'
#include <vector>
int main()
{
typedef std::vector<int>::iterator iter;
std::vector<int> vec;
Foo::Pair<iter> pair = { vec.begin(), vec.end() };
const Foo::Pair<iter>& cpair = pair;
//
// Notice that we call 'begin' etc with qualification.
//
iter i = boost::begin( pair );
iter e = boost::end( pair );
i = boost::begin( cpair );
e = boost::end( cpair );
boost::range_size< Foo::Pair<iter> >::type s = boost::size( pair );
s = boost::size( cpair );
boost::range_const_reverse_iterator< Foo::Pair<iter> >::type
ri = boost::rbegin( cpair ),
re = boost::rend( cpair );
}

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@ -386,7 +386,7 @@ VAlign="top"><code>boost::range_const_reverse_iterator&ltX>::type</code></TD>
</TR>
<TR>
<TD VAlign="top">Beginning of range</TD>
<TD VAlign="top"><code>rboost::begin(a)</code></TD>
<TD VAlign="top"><code>boost::rbegin(a)</code></TD>
<TD VAlign="top"><code>boost::range_reverse_iterator&lt;X>::type</code> if
<code>a</code> is mutable, <code>boost::range_const_reverse_iterator&lt;X>::type</code>
otherwise.</TD>
@ -394,7 +394,7 @@ otherwise.</TD>
<code>boost::range_reverse_iterator&lt;X>::type(boost::end(a))</code>.</TD> </TR>
<TR>
<TD VAlign="top">End of range</TD>
<TD VAlign="top"><code>rboost::end(a)</code></TD>
<TD VAlign="top"><code>boost::rend(a)</code></TD>
<TD VAlign="top"><code>boost::range_reverse_iterator&lt;X>::type</code> if
<code>a</code> is mutable, <code>boost::range_const_reverse_iterator&lt;X>::type</code>
otherwise.</TD>
@ -405,7 +405,7 @@ otherwise.</TD>
<h3>Complexity guarantees</h3>
<code>rboost::begin(a)</code> has the same complexity as <code>boost::end(a)</code> and <code>rboost::end(a)</code>
<code>boost::rbegin(a)</code> has the same complexity as <code>boost::end(a)</code> and <code>boost::rend(a)</code>
has the same complexity as <code>boost::begin(a)</code> from <a
href="#forward_range">Forward Range</a>.
@ -414,13 +414,13 @@ otherwise.</TD>
<Table border="1" cellpadding="5">
<TR>
<TD VAlign="top">Valid reverse range</TD>
<TD VAlign="top">For any Bidirectional Range <code>a</code>, <code>[rboost::begin(a),rboost::end(a))</code>
is a valid range, that is, <code>rboost::end(a)</code> is reachable from <code>rboost::begin(a)</code>
<TD VAlign="top">For any Bidirectional Range <code>a</code>, <code>[boost::rbegin(a),boost::rend(a))</code>
is a valid range, that is, <code>boost::rend(a)</code> is reachable from <code>boost::rbegin(a)</code>
in a finite number of increments.</TD>
</TR>
<TR>
<TD VAlign="top">Completeness</TD>
<TD VAlign="top">An algorithm that iterates through the range <code>[rboost::begin(a),rboost::end(a))</code>
<TD VAlign="top">An algorithm that iterates through the range <code>[boost::rbegin(a),boost::rend(a))</code>
will pass through every element of <code>a</code>.</TD>
</tr>
</table>