Chris@16: //  Boost next_prior.hpp header file  ---------------------------------------//
Chris@16: 
Chris@16: //  (C) Copyright Dave Abrahams and Daniel Walker 1999-2003. Distributed under the Boost
Chris@16: //  Software License, Version 1.0. (See accompanying file
Chris@16: //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: //  See http://www.boost.org/libs/utility for documentation.
Chris@16: 
Chris@16: //  Revision History
Chris@16: //  13 Dec 2003  Added next(x, n) and prior(x, n) (Daniel Walker)
Chris@16: 
Chris@16: #ifndef BOOST_NEXT_PRIOR_HPP_INCLUDED
Chris@16: #define BOOST_NEXT_PRIOR_HPP_INCLUDED
Chris@16: 
Chris@16: #include <iterator>
Chris@101: #if defined(_MSC_VER) && _MSC_VER <= 1310
Chris@101: #include <boost/mpl/and.hpp>
Chris@101: #include <boost/type_traits/is_integral.hpp>
Chris@101: #endif
Chris@101: #include <boost/type_traits/is_unsigned.hpp>
Chris@101: #include <boost/type_traits/integral_promotion.hpp>
Chris@101: #include <boost/type_traits/make_signed.hpp>
Chris@101: #include <boost/type_traits/has_plus.hpp>
Chris@101: #include <boost/type_traits/has_plus_assign.hpp>
Chris@101: #include <boost/type_traits/has_minus.hpp>
Chris@101: #include <boost/type_traits/has_minus_assign.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: //  Helper functions for classes like bidirectional iterators not supporting
Chris@16: //  operator+ and operator-
Chris@16: //
Chris@16: //  Usage:
Chris@16: //    const std::list<T>::iterator p = get_some_iterator();
Chris@16: //    const std::list<T>::iterator prev = boost::prior(p);
Chris@16: //    const std::list<T>::iterator next = boost::next(prev, 2);
Chris@16: 
Chris@16: //  Contributed by Dave Abrahams
Chris@16: 
Chris@101: namespace next_prior_detail {
Chris@101: 
Chris@101: template< typename T, typename Distance, bool HasPlus = has_plus< T, Distance >::value >
Chris@101: struct next_impl2
Chris@101: {
Chris@101:     static T call(T x, Distance n)
Chris@101:     {
Chris@101:         std::advance(x, n);
Chris@101:         return x;
Chris@101:     }
Chris@101: };
Chris@101: 
Chris@101: template< typename T, typename Distance >
Chris@101: struct next_impl2< T, Distance, true >
Chris@101: {
Chris@101:     static T call(T x, Distance n)
Chris@101:     {
Chris@101:         return x + n;
Chris@101:     }
Chris@101: };
Chris@101: 
Chris@101: 
Chris@101: template< typename T, typename Distance, bool HasPlusAssign = has_plus_assign< T, Distance >::value >
Chris@101: struct next_impl1 :
Chris@101:     public next_impl2< T, Distance >
Chris@101: {
Chris@101: };
Chris@101: 
Chris@101: template< typename T, typename Distance >
Chris@101: struct next_impl1< T, Distance, true >
Chris@101: {
Chris@101:     static T call(T x, Distance n)
Chris@101:     {
Chris@101:         x += n;
Chris@101:         return x;
Chris@101:     }
Chris@101: };
Chris@101: 
Chris@101: 
Chris@101: template<
Chris@101:     typename T,
Chris@101:     typename Distance,
Chris@101:     typename PromotedDistance = typename integral_promotion< Distance >::type,
Chris@101: #if !defined(_MSC_VER) || _MSC_VER > 1310
Chris@101:     bool IsUInt = is_unsigned< PromotedDistance >::value
Chris@101: #else
Chris@101:     // MSVC 7.1 has problems with applying is_unsigned to non-integral types
Chris@101:     bool IsUInt = mpl::and_< is_integral< PromotedDistance >, is_unsigned< PromotedDistance > >::value
Chris@101: #endif
Chris@101: >
Chris@101: struct prior_impl3
Chris@101: {
Chris@101:     static T call(T x, Distance n)
Chris@101:     {
Chris@101:         std::advance(x, -n);
Chris@101:         return x;
Chris@101:     }
Chris@101: };
Chris@101: 
Chris@101: template< typename T, typename Distance, typename PromotedDistance >
Chris@101: struct prior_impl3< T, Distance, PromotedDistance, true >
Chris@101: {
Chris@101:     static T call(T x, Distance n)
Chris@101:     {
Chris@101:         typedef typename make_signed< PromotedDistance >::type signed_distance;
Chris@101:         std::advance(x, -static_cast< signed_distance >(static_cast< PromotedDistance >(n)));
Chris@101:         return x;
Chris@101:     }
Chris@101: };
Chris@101: 
Chris@101: 
Chris@101: template< typename T, typename Distance, bool HasMinus = has_minus< T, Distance >::value >
Chris@101: struct prior_impl2 :
Chris@101:     public prior_impl3< T, Distance >
Chris@101: {
Chris@101: };
Chris@101: 
Chris@101: template< typename T, typename Distance >
Chris@101: struct prior_impl2< T, Distance, true >
Chris@101: {
Chris@101:     static T call(T x, Distance n)
Chris@101:     {
Chris@101:         return x - n;
Chris@101:     }
Chris@101: };
Chris@101: 
Chris@101: 
Chris@101: template< typename T, typename Distance, bool HasMinusAssign = has_minus_assign< T, Distance >::value >
Chris@101: struct prior_impl1 :
Chris@101:     public prior_impl2< T, Distance >
Chris@101: {
Chris@101: };
Chris@101: 
Chris@101: template< typename T, typename Distance >
Chris@101: struct prior_impl1< T, Distance, true >
Chris@101: {
Chris@101:     static T call(T x, Distance n)
Chris@101:     {
Chris@101:         x -= n;
Chris@101:         return x;
Chris@101:     }
Chris@101: };
Chris@101: 
Chris@101: } // namespace next_prior_detail
Chris@101: 
Chris@16: template <class T>
Chris@16: inline T next(T x) { return ++x; }
Chris@16: 
Chris@16: template <class T, class Distance>
Chris@16: inline T next(T x, Distance n)
Chris@16: {
Chris@101:     return next_prior_detail::next_impl1< T, Distance >::call(x, n);
Chris@16: }
Chris@16: 
Chris@16: template <class T>
Chris@16: inline T prior(T x) { return --x; }
Chris@16: 
Chris@16: template <class T, class Distance>
Chris@16: inline T prior(T x, Distance n)
Chris@16: {
Chris@101:     return next_prior_detail::prior_impl1< T, Distance >::call(x, n);
Chris@16: }
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif  // BOOST_NEXT_PRIOR_HPP_INCLUDED