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