235 lines
7.5 KiB
C++
235 lines
7.5 KiB
C++
// (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
|
|
|
|
|