603 lines
20 KiB
C++
603 lines
20 KiB
C++
// (c) Copyright Fernando Luis Cacciola Carballal 2000-2004
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// Use, modification, and distribution is subject to the Boost Software
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// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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// See library home page at http://www.boost.org/libs/numeric/conversion
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//
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// Contact the author at: fernando_cacciola@hotmail.com
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//
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#ifndef BOOST_NUMERIC_CONVERSION_DETAIL_CONVERTER_FLC_12NOV2002_HPP
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#define BOOST_NUMERIC_CONVERSION_DETAIL_CONVERTER_FLC_12NOV2002_HPP
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#include <functional>
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#include "boost/numeric/conversion/detail/meta.hpp"
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#include "boost/numeric/conversion/detail/conversion_traits.hpp"
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#include "boost/numeric/conversion/bounds.hpp"
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#include "boost/type_traits/is_same.hpp"
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#include "boost/mpl/integral_c.hpp"
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namespace boost { namespace numeric { namespace convdetail
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{
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// Integral Constants representing rounding modes
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typedef mpl::integral_c<std::float_round_style, std::round_toward_zero> round2zero_c ;
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typedef mpl::integral_c<std::float_round_style, std::round_to_nearest> round2nearest_c ;
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typedef mpl::integral_c<std::float_round_style, std::round_toward_infinity> round2inf_c ;
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typedef mpl::integral_c<std::float_round_style, std::round_toward_neg_infinity> round2neg_inf_c ;
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// Metafunction:
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//
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// for_round_style<RoundStyle,RoundToZero,RoundToNearest,RoundToInf,RoundToNegInf>::type
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//
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// {RoundStyle} Integral Constant specifying a round style as declared above.
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// {RoundToZero,RoundToNearest,RoundToInf,RoundToNegInf} arbitrary types.
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//
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// Selects one of the 4 types according to the value of RoundStyle.
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//
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template<class RoundStyle,class RoundToZero,class RoundToNearest,class RoundToInf,class RoundToNegInf>
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struct for_round_style
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{
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typedef ct_switch4<RoundStyle
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, round2zero_c, round2nearest_c, round2inf_c // round2neg_inf_c
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, RoundToZero , RoundToNearest , RoundToInf , RoundToNegInf
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> selector ;
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typedef typename selector::type type ;
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} ;
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//--------------------------------------------------------------------------
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// Range Checking Logic.
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//
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// The range checking logic is built up by combining 1 or 2 predicates.
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// Each predicate is encapsulated in a template class and exposes
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// the static member function 'apply'.
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//
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//--------------------------------------------------------------------------
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// Because a particular logic can combine either 1 or two predicates, the following
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// tags are used to allow the predicate applier to receive 2 preds, but optimize away
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// one of them if it is 'non-applicable'
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struct non_applicable { typedef mpl::false_ do_apply ; } ;
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struct applicable { typedef mpl::true_ do_apply ; } ;
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//--------------------------------------------------------------------------
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//
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// Range Checking Logic implementations.
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//
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// The following classes, collectivelly named 'Predicates', are instantiated within
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// the corresponding range checkers.
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// Their static member function 'apply' is called to perform the actual range checking logic.
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//--------------------------------------------------------------------------
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// s < Lowest(T) ? cNegOverflow : cInRange
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//
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template<class Traits>
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struct LT_LoT : applicable
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{
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typedef typename Traits::target_type T ;
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typedef typename Traits::source_type S ;
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typedef typename Traits::argument_type argument_type ;
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static range_check_result apply ( argument_type s )
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{
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return s < static_cast<S>(bounds<T>::lowest()) ? cNegOverflow : cInRange ;
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}
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} ;
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// s < 0 ? cNegOverflow : cInRange
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//
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template<class Traits>
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struct LT_Zero : applicable
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{
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typedef typename Traits::source_type S ;
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typedef typename Traits::argument_type argument_type ;
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static range_check_result apply ( argument_type s )
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{
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return s < static_cast<S>(0) ? cNegOverflow : cInRange ;
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}
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} ;
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// s <= Lowest(T)-1 ? cNegOverflow : cInRange
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//
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template<class Traits>
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struct LE_PrevLoT : applicable
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{
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typedef typename Traits::target_type T ;
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typedef typename Traits::source_type S ;
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typedef typename Traits::argument_type argument_type ;
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static range_check_result apply ( argument_type s )
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{
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return s <= static_cast<S>(bounds<T>::lowest()) - static_cast<S>(1.0)
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? cNegOverflow : cInRange ;
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}
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} ;
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// s < Lowest(T)-0.5 ? cNegOverflow : cInRange
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//
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template<class Traits>
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struct LT_HalfPrevLoT : applicable
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{
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typedef typename Traits::target_type T ;
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typedef typename Traits::source_type S ;
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typedef typename Traits::argument_type argument_type ;
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static range_check_result apply ( argument_type s )
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{
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return s < static_cast<S>(bounds<T>::lowest()) - static_cast<S>(0.5)
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? cNegOverflow : cInRange ;
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}
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} ;
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// s > Highest(T) ? cPosOverflow : cInRange
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//
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template<class Traits>
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struct GT_HiT : applicable
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{
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typedef typename Traits::target_type T ;
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typedef typename Traits::source_type S ;
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typedef typename Traits::argument_type argument_type ;
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static range_check_result apply ( argument_type s )
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{
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return s > static_cast<S>(bounds<T>::highest())
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? cPosOverflow : cInRange ;
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}
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} ;
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// s >= Lowest(T) + 1 ? cPosOverflow : cInRange
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//
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template<class Traits>
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struct GE_SuccHiT : applicable
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{
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typedef typename Traits::target_type T ;
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typedef typename Traits::source_type S ;
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typedef typename Traits::argument_type argument_type ;
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static range_check_result apply ( argument_type s )
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{
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return s >= static_cast<S>(bounds<T>::highest()) + static_cast<S>(1.0)
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? cPosOverflow : cInRange ;
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}
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} ;
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// s >= Lowest(T) + 0.5 ? cPosgOverflow : cInRange
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//
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template<class Traits>
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struct GT_HalfSuccHiT : applicable
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{
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typedef typename Traits::target_type T ;
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typedef typename Traits::source_type S ;
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typedef typename Traits::argument_type argument_type ;
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static range_check_result apply ( argument_type s )
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{
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return s >= static_cast<S>(bounds<T>::highest()) + static_cast<S>(0.5)
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? cPosOverflow : cInRange ;
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}
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} ;
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//--------------------------------------------------------------------------
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//
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// Predicate Combiner.
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//
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// This helper classes are used to possibly combine the range checking logic
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// individually performed by the predicates
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//
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//--------------------------------------------------------------------------
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// Applies both predicates: first 'PredA', and if it equals 'cInRange', 'PredB'
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template<class PredA, class PredB>
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struct applyBoth
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{
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typedef typename PredA::argument_type argument_type ;
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static range_check_result apply ( argument_type s )
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{
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range_check_result r = PredA::apply(s) ;
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if ( r == cInRange )
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r = PredB::apply(s);
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return r ;
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}
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} ;
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template<class PredA, class PredB>
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struct combine
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{
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typedef applyBoth<PredA,PredB> Both ;
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typedef void NNone ; // 'None' is defined as a macro in (/usr/X11R6/include/X11/X.h)
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typedef typename PredA::do_apply do_applyA ;
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typedef typename PredB::do_apply do_applyB ;
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typedef typename for_both<do_applyA, do_applyB, Both, PredA, PredB, NNone>::type type ;
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} ;
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//--------------------------------------------------------------------------
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// Range Checker classes.
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//
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// The following classes are VISIBLE base classes of the user-level converter<> class.
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// They supply the optimized 'out_of_range()' and 'validate_range()' static member functions
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// visible in the user interface.
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//
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//--------------------------------------------------------------------------
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// Dummy range checker.
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template<class Traits>
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struct dummy_range_checker
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{
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typedef typename Traits::argument_type argument_type ;
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static range_check_result out_of_range ( argument_type ) { return cInRange ; }
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static void validate_range ( argument_type ) {}
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} ;
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// Generic range checker.
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//
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// All the range checking logic for all possible combinations of source and target
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// can be arranged in terms of one or two predicates, which test overflow on both neg/pos 'sides'
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// of the ranges.
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//
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// These predicates are given here as IsNegOverflow and IsPosOverflow.
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//
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template<class Traits, class IsNegOverflow, class IsPosOverflow, class OverflowHandler>
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struct generic_range_checker
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{
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typedef OverflowHandler overflow_handler ;
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typedef typename Traits::argument_type argument_type ;
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static range_check_result out_of_range ( argument_type s )
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{
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typedef typename combine<IsNegOverflow,IsPosOverflow>::type Predicate ;
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return Predicate::apply(s);
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}
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static void validate_range ( argument_type s )
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{ OverflowHandler()( out_of_range(s) ) ; }
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} ;
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//--------------------------------------------------------------------------
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//
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// Selectors for the optimized Range Checker class.
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//
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//--------------------------------------------------------------------------
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template<class Traits,class OverflowHandler>
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struct GetRC_Sig2Sig_or_Unsig2Unsig
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{
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typedef dummy_range_checker<Traits> Dummy ;
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typedef LT_LoT<Traits> Pred1 ;
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typedef GT_HiT<Traits> Pred2 ;
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typedef generic_range_checker<Traits,Pred1,Pred2,OverflowHandler> Normal ;
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typedef typename Traits::subranged subranged ;
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typedef typename mpl::if_<subranged,Normal,Dummy>::type type ;
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} ;
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template<class Traits, class OverflowHandler>
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struct GetRC_Sig2Unsig
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{
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typedef LT_Zero<Traits> Pred1 ;
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typedef GT_HiT <Traits> Pred2 ;
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typedef generic_range_checker<Traits,Pred1,Pred2,OverflowHandler> ChoiceA ;
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typedef generic_range_checker<Traits,Pred1,non_applicable,OverflowHandler> ChoiceB ;
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typedef typename Traits::target_type T ;
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typedef typename Traits::source_type S ;
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typedef typename subranged_Unsig2Sig<S,T>::type oposite_subranged ;
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typedef typename mpl::not_<oposite_subranged>::type positively_subranged ;
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typedef typename mpl::if_<positively_subranged,ChoiceA,ChoiceB>::type type ;
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} ;
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template<class Traits, class OverflowHandler>
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struct GetRC_Unsig2Sig
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{
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typedef GT_HiT<Traits> Pred1 ;
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typedef generic_range_checker<Traits,non_applicable,Pred1,OverflowHandler> type ;
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} ;
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template<class Traits,class OverflowHandler>
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struct GetRC_Int2Int
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{
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typedef GetRC_Sig2Sig_or_Unsig2Unsig<Traits,OverflowHandler> Sig2SigQ ;
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typedef GetRC_Sig2Unsig <Traits,OverflowHandler> Sig2UnsigQ ;
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typedef GetRC_Unsig2Sig <Traits,OverflowHandler> Unsig2SigQ ;
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typedef Sig2SigQ Unsig2UnsigQ ;
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typedef typename Traits::sign_mixture sign_mixture ;
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typedef typename
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for_sign_mixture<sign_mixture,Sig2SigQ,Sig2UnsigQ,Unsig2SigQ,Unsig2UnsigQ>::type
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selector ;
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typedef typename selector::type type ;
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} ;
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template<class Traits>
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struct GetRC_Int2Float
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{
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typedef dummy_range_checker<Traits> type ;
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} ;
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template<class Traits, class OverflowHandler, class Float2IntRounder>
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struct GetRC_Float2Int
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{
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typedef LE_PrevLoT <Traits> Pred1 ;
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typedef GE_SuccHiT <Traits> Pred2 ;
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typedef LT_HalfPrevLoT<Traits> Pred3 ;
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typedef GT_HalfSuccHiT<Traits> Pred4 ;
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typedef GT_HiT <Traits> Pred5 ;
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typedef LT_LoT <Traits> Pred6 ;
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typedef generic_range_checker<Traits,Pred1,Pred2,OverflowHandler> ToZero ;
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typedef generic_range_checker<Traits,Pred3,Pred4,OverflowHandler> ToNearest ;
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typedef generic_range_checker<Traits,Pred1,Pred5,OverflowHandler> ToInf ;
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typedef generic_range_checker<Traits,Pred6,Pred2,OverflowHandler> ToNegInf ;
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typedef typename Float2IntRounder::round_style round_style ;
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typedef typename for_round_style<round_style,ToZero,ToNearest,ToInf,ToNegInf>::type type ;
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} ;
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template<class Traits, class OverflowHandler>
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struct GetRC_Float2Float
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{
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typedef dummy_range_checker<Traits> Dummy ;
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typedef LT_LoT<Traits> Pred1 ;
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typedef GT_HiT<Traits> Pred2 ;
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typedef generic_range_checker<Traits,Pred1,Pred2,OverflowHandler> Normal ;
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typedef typename Traits::subranged subranged ;
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typedef typename mpl::if_<subranged,Normal,Dummy>::type type ;
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} ;
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template<class Traits, class OverflowHandler, class Float2IntRounder>
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struct GetRC_BuiltIn2BuiltIn
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{
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typedef GetRC_Int2Int<Traits,OverflowHandler> Int2IntQ ;
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typedef GetRC_Int2Float<Traits> Int2FloatQ ;
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typedef GetRC_Float2Int<Traits,OverflowHandler,Float2IntRounder> Float2IntQ ;
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typedef GetRC_Float2Float<Traits,OverflowHandler> Float2FloatQ ;
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typedef typename Traits::int_float_mixture int_float_mixture ;
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typedef typename for_int_float_mixture<int_float_mixture, Int2IntQ, Int2FloatQ, Float2IntQ, Float2FloatQ>::type selector ;
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typedef typename selector::type type ;
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} ;
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template<class Traits, class OverflowHandler, class Float2IntRounder>
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struct GetRC
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{
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typedef GetRC_BuiltIn2BuiltIn<Traits,OverflowHandler,Float2IntRounder> BuiltIn2BuiltInQ ;
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typedef dummy_range_checker<Traits> Dummy ;
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typedef mpl::identity<Dummy> DummyQ ;
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typedef typename Traits::udt_builtin_mixture udt_builtin_mixture ;
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typedef typename for_udt_builtin_mixture<udt_builtin_mixture,BuiltIn2BuiltInQ,DummyQ,DummyQ,DummyQ>::type selector ;
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typedef typename selector::type type ;
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} ;
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//--------------------------------------------------------------------------
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// Converter classes.
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//
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// The following classes are VISIBLE base classes of the user-level converter<> class.
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// They supply the optimized 'nearbyint()' and 'convert()' static member functions
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// visible in the user interface.
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//
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//--------------------------------------------------------------------------
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//
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// Trivial Converter : used when (cv-unqualified) T == (cv-unqualified) S
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//
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template<class Traits>
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struct trivial_converter_impl : public std::unary_function< BOOST_DEDUCED_TYPENAME Traits::argument_type
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,BOOST_DEDUCED_TYPENAME Traits::result_type
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>
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,public dummy_range_checker<Traits>
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{
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typedef Traits traits ;
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typedef typename Traits::source_type source_type ;
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typedef typename Traits::argument_type argument_type ;
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typedef typename Traits::result_type result_type ;
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static result_type low_level_convert ( argument_type s ) { return s ; }
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static source_type nearbyint ( argument_type s ) { return s ; }
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static result_type convert ( argument_type s ) { return s ; }
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} ;
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//
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// Rounding Converter : used for float to integral conversions.
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//
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template<class Traits,class RangeChecker,class RawConverter,class Float2IntRounder>
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struct rounding_converter : public std::unary_function< BOOST_DEDUCED_TYPENAME Traits::argument_type
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,BOOST_DEDUCED_TYPENAME Traits::result_type
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>
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,public RangeChecker
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,public Float2IntRounder
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,public RawConverter
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{
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typedef RangeChecker RangeCheckerBase ;
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typedef Float2IntRounder Float2IntRounderBase ;
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typedef RawConverter RawConverterBase ;
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typedef Traits traits ;
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typedef typename Traits::source_type source_type ;
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typedef typename Traits::argument_type argument_type ;
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typedef typename Traits::result_type result_type ;
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static result_type convert ( argument_type s )
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{
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RangeCheckerBase::validate_range(s);
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source_type s1 = Float2IntRounderBase::nearbyint(s);
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return RawConverterBase::low_level_convert(s1);
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}
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} ;
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//
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// Non-Rounding Converter : used for all other conversions.
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//
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template<class Traits,class RangeChecker,class RawConverter>
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struct non_rounding_converter : public std::unary_function< BOOST_DEDUCED_TYPENAME Traits::argument_type
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,BOOST_DEDUCED_TYPENAME Traits::result_type
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>
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,public RangeChecker
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,public RawConverter
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{
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typedef RangeChecker RangeCheckerBase ;
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typedef RawConverter RawConverterBase ;
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typedef Traits traits ;
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typedef typename Traits::source_type source_type ;
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typedef typename Traits::argument_type argument_type ;
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typedef typename Traits::result_type result_type ;
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static source_type nearbyint ( argument_type s ) { return s ; }
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static result_type convert ( argument_type s )
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{
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RangeCheckerBase::validate_range(s);
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return RawConverterBase::low_level_convert(s);
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}
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} ;
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//--------------------------------------------------------------------------
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//
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// Selectors for the optimized Converter class.
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//
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//--------------------------------------------------------------------------
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template<class Traits,class OverflowHandler,class Float2IntRounder,class RawConverter, class UserRangeChecker>
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struct get_non_trivial_converter
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{
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typedef GetRC<Traits,OverflowHandler,Float2IntRounder> InternalRangeCheckerQ ;
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typedef is_same<UserRangeChecker,UseInternalRangeChecker> use_internal_RC ;
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typedef mpl::identity<UserRangeChecker> UserRangeCheckerQ ;
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typedef typename
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mpl::eval_if<use_internal_RC,InternalRangeCheckerQ,UserRangeCheckerQ>::type
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RangeChecker ;
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typedef non_rounding_converter<Traits,RangeChecker,RawConverter> NonRounding ;
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typedef rounding_converter<Traits,RangeChecker,RawConverter,Float2IntRounder> Rounding ;
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typedef mpl::identity<NonRounding> NonRoundingQ ;
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typedef mpl::identity<Rounding> RoundingQ ;
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typedef typename Traits::int_float_mixture int_float_mixture ;
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typedef typename
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for_int_float_mixture<int_float_mixture, NonRoundingQ, NonRoundingQ, RoundingQ, NonRoundingQ>::type
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selector ;
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typedef typename selector::type type ;
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} ;
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template< class Traits
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,class OverflowHandler
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,class Float2IntRounder
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,class RawConverter
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,class UserRangeChecker
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>
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struct get_converter_impl
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{
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#if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT( 0x0561 ) )
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// bcc55 prefers sometimes template parameters to be explicit local types.
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// (notice that is is illegal to reuse the names like this)
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typedef Traits Traits ;
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typedef OverflowHandler OverflowHandler ;
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typedef Float2IntRounder Float2IntRounder ;
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typedef RawConverter RawConverter ;
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typedef UserRangeChecker UserRangeChecker ;
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#endif
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typedef trivial_converter_impl<Traits> Trivial ;
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typedef mpl::identity <Trivial> TrivialQ ;
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typedef get_non_trivial_converter< Traits
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,OverflowHandler
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,Float2IntRounder
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,RawConverter
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,UserRangeChecker
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> NonTrivialQ ;
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typedef typename Traits::trivial trivial ;
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typedef typename mpl::eval_if<trivial,TrivialQ,NonTrivialQ>::type type ;
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} ;
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} } } // namespace boost::numeric::convdetail
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#endif
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