/*-----------------------------------------------------------------------------+
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Copyright (c) 2008-2009: Joachim Faulhaber
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+------------------------------------------------------------------------------+
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENCE.txt or copy at
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http://www.boost.org/LICENSE_1_0.txt)
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+-----------------------------------------------------------------------------*/
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#ifndef BOOST_ICL_TYPE_TRAITS_DIFFERENCE_TYPE_OF_HPP_JOFA_080911
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#define BOOST_ICL_TYPE_TRAITS_DIFFERENCE_TYPE_OF_HPP_JOFA_080911
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#include <boost/config.hpp> // For macro BOOST_STATIC_CONSTANT
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#include <boost/type_traits/is_pointer.hpp>
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#include <boost/mpl/has_xxx.hpp>
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#include <boost/mpl/or.hpp>
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#include <boost/mpl/and.hpp>
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#include <boost/mpl/not.hpp>
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#include <boost/icl/type_traits/no_type.hpp>
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#include <boost/icl/type_traits/is_numeric.hpp>
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#include <boost/icl/type_traits/rep_type_of.hpp>
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namespace boost{ namespace icl
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{
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namespace detail
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{
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BOOST_MPL_HAS_XXX_TRAIT_DEF(difference_type)
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}
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//--------------------------------------------------------------------------
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template <class Type>
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struct has_difference_type
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: mpl::bool_<detail::has_difference_type<Type>::value>
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{};
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//--------------------------------------------------------------------------
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template<class Type> // type_of(T-T)==T
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struct is_subtraction_closed
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{
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typedef is_subtraction_closed type;
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BOOST_STATIC_CONSTANT(bool,
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value = (mpl::or_< is_numeric<Type>
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, mpl::and_< has_rep_type<Type>
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, mpl::not_<has_difference_type<Type> >
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>
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>::value)
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);
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};
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//--------------------------------------------------------------------------
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template<class Type>
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struct has_difference
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{
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typedef has_difference type;
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BOOST_STATIC_CONSTANT(bool,
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value = (mpl::or_< is_subtraction_closed<Type>
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, is_pointer<Type>
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, has_difference_type<Type> >::value)
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);
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};
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//--------------------------------------------------------------------------
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template <class Type, bool has_difference, bool has_diff_type>
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struct get_difference_type;
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template <class Type>
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struct get_difference_type<Type, false, false>
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{
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typedef no_type type;
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};
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template <class Type>
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struct get_difference_type<Type*, true, false>
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{
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typedef std::ptrdiff_t type;
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};
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template <class Type>
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struct get_difference_type<Type, true, false>
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{
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typedef Type type;
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};
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template <class Type>
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struct get_difference_type<Type, true, true>
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{
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typedef typename Type::difference_type type;
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};
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//--------------------------------------------------------------------------
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template<class Type>
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struct difference_type_of
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{
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typedef typename
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get_difference_type< Type
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, has_difference<Type>::value
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, has_difference_type<Type>::value
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>::type type;
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};
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}} // namespace boost icl
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#endif
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