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Support for user-defined iterator categories

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[SVN r8930]
This commit is contained in:
Dave Abrahams 2001-02-04 20:33:45 +00:00
parent 90299982a6
commit 05336f45c4
1 changed files with 75 additions and 26 deletions
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101
include/boost/half_open_range.hpp
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@ -5,6 +5,7 @@
// for any purpose.
//
// Revision History:
// 04 Feb 2001 Support for user-defined iterator categories (David Abrahams)
// 30 Jan 2001 Initial Checkin (David Abrahams)
#ifndef BOOST_HALF_OPEN_RANGE_HPP_
@ -16,35 +17,69 @@
# include <boost/operators.hpp>
# include <string>
# include <stdexcept>
# include <iterator>
namespace boost {
namespace detail {
// Template class choose_finish -- allows us to maintain the invariant that
// start() <= finish() on half_open_range specializations that support random
// access.
template <class Tag>
struct choose_finish
{
template <class T>
struct rebind
{
static T choose(const T&, const T& finish)
{ return finish; }
};
};
// Template class choose_finish -- allows us to maintain the invariant that
// start() <= finish() on half_open_range specializations that support random
// access.
#ifdef __MWERKS__
template <class T>
const T& choose_finish(const T&, const T& finish, std::input_iterator_tag)
{
return finish;
}
template <>
struct choose_finish<std::random_access_iterator_tag>
{
template <class T>
struct rebind
{
static T choose(const T& start, const T& finish)
{ return finish < start ? start : finish; }
};
};
template <class T>
const T& choose_finish(const T&, const T& finish, std::output_iterator_tag)
{
return finish;
}
template <class T>
const T& choose_finish(const T& start, const T& finish, std::random_access_iterator_tag)
{
return finish < start ? start : finish;
}
#else
template <bool is_random_access> struct finish_chooser;
template <>
struct finish_chooser<false>
{
template <class T>
struct rebind
{
static T choose(const T&, const T& finish)
{ return finish; }
};
};
template <>
struct finish_chooser<true>
{
template <class T>
struct rebind
{
static T choose(const T& start, const T& finish)
{ return finish < start ? start : finish; }
};
};
template <class Category, class Incrementable>
struct choose_finish
{
static const Incrementable choose(const Incrementable& start, const Incrementable& finish)
{
return finish_chooser<(
boost::is_convertible<Category,std::random_access_iterator_tag>::value
)>::template rebind<Incrementable>::choose(start, finish);
}
};
#endif
}
template <class Incrementable>
@ -75,7 +110,12 @@ struct half_open_range
half_open_range(Incrementable start, Incrementable finish)
: m_start(start),
m_finish(
detail::choose_finish<category>::template rebind<Incrementable>::choose(start, finish))
#ifndef __MWERKS__
detail::choose_finish<category,Incrementable>::choose(start, finish)
#else
detail::choose_finish(start, finish, category())
#endif
)
{}
// Implicit conversion from std::pair<Incrementable,Incrementable> allows us
@ -83,14 +123,23 @@ struct half_open_range
half_open_range(const std::pair<Incrementable,Incrementable>& x)
: m_start(x.first),
m_finish(
detail::choose_finish<category>::template rebind<Incrementable>::choose(x.first,x.second))
#ifndef __MWERKS__
detail::choose_finish<category,Incrementable>::choose(x.first, x.second)
#else
detail::choose_finish(x.first, x.second, category())
#endif
)
{}
half_open_range& operator=(const std::pair<Incrementable,Incrementable>& x)
{
m_start = x.first;
m_finish =
detail::choose_finish<category>::template rebind<Incrementable>::choose(x.first,x.second);
#ifndef __MWERKS__
detail::choose_finish<category,Incrementable>::choose(x.first, x.second);
#else
detail::choose_finish(x.first, x.second, category();
#endif
}
iterator begin() const { return iterator(m_start); }