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// Boost next_prior.hpp header file ---------------------------------------//
// (C) Copyright Dave Abrahams and Daniel Walker 1999-2003. Distributed under the Boost
// Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
// See http://www.boost.org/libs/utility for documentation.
// Revision History
// 13 Dec 2003 Added next(x, n) and prior(x, n) (Daniel Walker)
#ifndef BOOST_NEXT_PRIOR_HPP_INCLUDED
#define BOOST_NEXT_PRIOR_HPP_INCLUDED
#include <iterator>
#if defined(_MSC_VER) && _MSC_VER <= 1310
#include <boost/mpl/and.hpp>
#include <boost/type_traits/is_integral.hpp>
#endif
#include <boost/type_traits/is_unsigned.hpp>
#include <boost/type_traits/integral_promotion.hpp>
#include <boost/type_traits/make_signed.hpp>
#include <boost/type_traits/has_plus.hpp>
#include <boost/type_traits/has_plus_assign.hpp>
#include <boost/type_traits/has_minus.hpp>
#include <boost/type_traits/has_minus_assign.hpp>
namespace boost {
// Helper functions for classes like bidirectional iterators not supporting
// operator+ and operator-
//
// Usage:
// const std::list<T>::iterator p = get_some_iterator();
// const std::list<T>::iterator prev = boost::prior(p);
// const std::list<T>::iterator next = boost::next(prev, 2);
// Contributed by Dave Abrahams
namespace next_prior_detail {
template< typename T, typename Distance, bool HasPlus = has_plus< T, Distance >::value >
struct next_impl2
{
static T call(T x, Distance n)
{
std::advance(x, n);
return x;
}
};
template< typename T, typename Distance >
struct next_impl2< T, Distance, true >
{
static T call(T x, Distance n)
{
return x + n;
}
};
template< typename T, typename Distance, bool HasPlusAssign = has_plus_assign< T, Distance >::value >
struct next_impl1 :
public next_impl2< T, Distance >
{
};
template< typename T, typename Distance >
struct next_impl1< T, Distance, true >
{
static T call(T x, Distance n)
{
x += n;
return x;
}
};
template<
typename T,
typename Distance,
typename PromotedDistance = typename integral_promotion< Distance >::type,
#if !defined(_MSC_VER) || _MSC_VER > 1310
bool IsUInt = is_unsigned< PromotedDistance >::value
#else
// MSVC 7.1 has problems with applying is_unsigned to non-integral types
bool IsUInt = mpl::and_< is_integral< PromotedDistance >, is_unsigned< PromotedDistance > >::value
#endif
>
struct prior_impl3
{
static T call(T x, Distance n)
{
std::advance(x, -n);
return x;
}
};
template< typename T, typename Distance, typename PromotedDistance >
struct prior_impl3< T, Distance, PromotedDistance, true >
{
static T call(T x, Distance n)
{
typedef typename make_signed< PromotedDistance >::type signed_distance;
std::advance(x, -static_cast< signed_distance >(static_cast< PromotedDistance >(n)));
return x;
}
};
template< typename T, typename Distance, bool HasMinus = has_minus< T, Distance >::value >
struct prior_impl2 :
public prior_impl3< T, Distance >
{
};
template< typename T, typename Distance >
struct prior_impl2< T, Distance, true >
{
static T call(T x, Distance n)
{
return x - n;
}
};
template< typename T, typename Distance, bool HasMinusAssign = has_minus_assign< T, Distance >::value >
struct prior_impl1 :
public prior_impl2< T, Distance >
{
};
template< typename T, typename Distance >
struct prior_impl1< T, Distance, true >
{
static T call(T x, Distance n)
{
x -= n;
return x;
}
};
} // namespace next_prior_detail
template <class T>
inline T next(T x) { return ++x; }
template <class T, class Distance>
inline T next(T x, Distance n)
{
return next_prior_detail::next_impl1< T, Distance >::call(x, n);
}
template <class T>
inline T prior(T x) { return --x; }
template <class T, class Distance>
inline T prior(T x, Distance n)
{
return next_prior_detail::prior_impl1< T, Distance >::call(x, n);
}
} // namespace boost
#endif // BOOST_NEXT_PRIOR_HPP_INCLUDED
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