// (c) Copyright Fernando Luis Cacciola Carballal 2000-2004 | |
// Use, modification, and distribution is subject to 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 library home page at http://www.boost.org/libs/numeric/conversion | |
// | |
// Contact the author at: fernando_cacciola@hotmail.com | |
// | |
#ifndef BOOST_NUMERIC_CONVERSION_DETAIL_IS_SUBRANGED_FLC_12NOV2002_HPP | |
#define BOOST_NUMERIC_CONVERSION_DETAIL_IS_SUBRANGED_FLC_12NOV2002_HPP | |
#include "boost/config.hpp" | |
#include "boost/limits.hpp" | |
#include "boost/mpl/int.hpp" | |
#include "boost/mpl/multiplies.hpp" | |
#include "boost/mpl/less.hpp" | |
#include "boost/mpl/equal_to.hpp" | |
#include "boost/type_traits/is_same.hpp" | |
#include "boost/numeric/conversion/detail/meta.hpp" | |
#include "boost/numeric/conversion/detail/int_float_mixture.hpp" | |
#include "boost/numeric/conversion/detail/sign_mixture.hpp" | |
#include "boost/numeric/conversion/detail/udt_builtin_mixture.hpp" | |
namespace boost { namespace numeric { namespace convdetail | |
{ | |
//--------------------------------------------------------------- | |
// Implementations of the compile time predicate "T is subranged" | |
//--------------------------------------------------------------- | |
// for integral to integral conversions | |
template<class T,class S> | |
struct subranged_Sig2Unsig | |
{ | |
// Signed to unsigned conversions are 'subranged' because of possible loose | |
// of negative values. | |
typedef mpl::true_ type ; | |
} ; | |
// for unsigned integral to signed integral conversions | |
template<class T,class S> | |
struct subranged_Unsig2Sig | |
{ | |
// IMPORTANT NOTE: | |
// | |
// This code assumes that signed/unsigned integral values are represented | |
// such that: | |
// | |
// numeric_limits<signed T>::digits + 1 == numeric_limits<unsigned T>::digits | |
// | |
// The '+1' is required since numeric_limits<>::digits gives 1 bit less for signed integral types. | |
// | |
// This fact is used by the following logic: | |
// | |
// if ( (numeric_limits<T>::digits+1) < (2*numeric_limits<S>::digits) ) | |
// then the conversion is subranged. | |
// | |
typedef mpl::int_< ::std::numeric_limits<S>::digits > S_digits ; | |
typedef mpl::int_< ::std::numeric_limits<T>::digits > T_digits ; | |
// T is signed, so take digits+1 | |
typedef typename T_digits::next u_T_digits ; | |
typedef mpl::int_<2> Two ; | |
typedef typename mpl::multiplies<S_digits,Two>::type S_digits_times_2 ; | |
typedef typename mpl::less<u_T_digits,S_digits_times_2>::type type ; | |
} ; | |
// for integral to integral conversions of the same sign. | |
template<class T,class S> | |
struct subranged_SameSign | |
{ | |
// An integral conversion of the same sign is subranged if digits(T) < digits(S). | |
typedef mpl::int_< ::std::numeric_limits<S>::digits > S_digits ; | |
typedef mpl::int_< ::std::numeric_limits<T>::digits > T_digits ; | |
typedef typename mpl::less<T_digits,S_digits>::type type ; | |
} ; | |
// for integral to float conversions | |
template<class T,class S> | |
struct subranged_Int2Float | |
{ | |
typedef mpl::false_ type ; | |
} ; | |
// for float to integral conversions | |
template<class T,class S> | |
struct subranged_Float2Int | |
{ | |
typedef mpl::true_ type ; | |
} ; | |
// for float to float conversions | |
template<class T,class S> | |
struct subranged_Float2Float | |
{ | |
// If both T and S are floats, | |
// compare exponent bits and if they match, mantisa bits. | |
typedef mpl::int_< ::std::numeric_limits<S>::digits > S_mantisa ; | |
typedef mpl::int_< ::std::numeric_limits<T>::digits > T_mantisa ; | |
typedef mpl::int_< ::std::numeric_limits<S>::max_exponent > S_exponent ; | |
typedef mpl::int_< ::std::numeric_limits<T>::max_exponent > T_exponent ; | |
typedef typename mpl::less<T_exponent,S_exponent>::type T_smaller_exponent ; | |
typedef typename mpl::equal_to<T_exponent,S_exponent>::type equal_exponents ; | |
typedef mpl::less<T_mantisa,S_mantisa> T_smaller_mantisa ; | |
typedef mpl::eval_if<equal_exponents,T_smaller_mantisa,mpl::false_> not_bigger_exponent_case ; | |
typedef typename | |
mpl::eval_if<T_smaller_exponent,mpl::true_,not_bigger_exponent_case>::type | |
type ; | |
} ; | |
// for Udt to built-in conversions | |
template<class T,class S> | |
struct subranged_Udt2BuiltIn | |
{ | |
typedef mpl::true_ type ; | |
} ; | |
// for built-in to Udt conversions | |
template<class T,class S> | |
struct subranged_BuiltIn2Udt | |
{ | |
typedef mpl::false_ type ; | |
} ; | |
// for Udt to Udt conversions | |
template<class T,class S> | |
struct subranged_Udt2Udt | |
{ | |
typedef mpl::false_ type ; | |
} ; | |
//------------------------------------------------------------------- | |
// Selectors for the implementations of the subranged predicate | |
//------------------------------------------------------------------- | |
template<class T,class S> | |
struct get_subranged_Int2Int | |
{ | |
typedef subranged_SameSign<T,S> Sig2Sig ; | |
typedef subranged_Sig2Unsig<T,S> Sig2Unsig ; | |
typedef subranged_Unsig2Sig<T,S> Unsig2Sig ; | |
typedef Sig2Sig Unsig2Unsig ; | |
typedef typename get_sign_mixture<T,S>::type sign_mixture ; | |
typedef typename | |
for_sign_mixture<sign_mixture, Sig2Sig, Sig2Unsig, Unsig2Sig, Unsig2Unsig>::type | |
type ; | |
} ; | |
template<class T,class S> | |
struct get_subranged_BuiltIn2BuiltIn | |
{ | |
typedef get_subranged_Int2Int<T,S> Int2IntQ ; | |
typedef subranged_Int2Float <T,S> Int2Float ; | |
typedef subranged_Float2Int <T,S> Float2Int ; | |
typedef subranged_Float2Float<T,S> Float2Float ; | |
typedef mpl::identity<Int2Float > Int2FloatQ ; | |
typedef mpl::identity<Float2Int > Float2IntQ ; | |
typedef mpl::identity<Float2Float> Float2FloatQ ; | |
typedef typename get_int_float_mixture<T,S>::type int_float_mixture ; | |
typedef for_int_float_mixture<int_float_mixture, Int2IntQ, Int2FloatQ, Float2IntQ, Float2FloatQ> for_ ; | |
typedef typename for_::type selected ; | |
typedef typename selected::type type ; | |
} ; | |
template<class T,class S> | |
struct get_subranged | |
{ | |
typedef get_subranged_BuiltIn2BuiltIn<T,S> BuiltIn2BuiltInQ ; | |
typedef subranged_BuiltIn2Udt<T,S> BuiltIn2Udt ; | |
typedef subranged_Udt2BuiltIn<T,S> Udt2BuiltIn ; | |
typedef subranged_Udt2Udt<T,S> Udt2Udt ; | |
typedef mpl::identity<BuiltIn2Udt> BuiltIn2UdtQ ; | |
typedef mpl::identity<Udt2BuiltIn> Udt2BuiltInQ ; | |
typedef mpl::identity<Udt2Udt > Udt2UdtQ ; | |
typedef typename get_udt_builtin_mixture<T,S>::type udt_builtin_mixture ; | |
typedef typename | |
for_udt_builtin_mixture<udt_builtin_mixture, BuiltIn2BuiltInQ, BuiltIn2UdtQ, Udt2BuiltInQ, Udt2UdtQ>::type | |
selected ; | |
typedef typename selected::type selected2 ; | |
typedef typename selected2::type type ; | |
} ; | |
//------------------------------------------------------------------- | |
// Top level implementation selector. | |
//------------------------------------------------------------------- | |
template<class T, class S> | |
struct get_is_subranged | |
{ | |
typedef get_subranged<T,S> non_trivial_case ; | |
typedef mpl::identity<mpl::false_> trivial_case ; | |
typedef is_same<T,S> is_trivial ; | |
typedef typename mpl::if_<is_trivial,trivial_case,non_trivial_case>::type selected ; | |
typedef typename selected::type type ; | |
} ; | |
} } } // namespace boost::numeric::convdetail | |
#endif | |