273 lines
8.2 KiB
Plaintext
273 lines
8.2 KiB
Plaintext
[/
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Boost.Optional
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Copyright (c) 2003-2007 Fernando Luis Cacciola Carballal
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Distributed under the Boost Software License, Version 1.0.
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(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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]
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[section conversion_traits<> traits class]
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[section Types]
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[section enumeration int_float_mixture_enum]
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namespace boost { namespace numeric {
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enum int_float_mixture_enum
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{
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integral_to_integral
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,integral_to_float
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,float_to_integral
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,float_to_float
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} ;
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} } // namespace boost::numeric
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[endsect]
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[section enumeration sign_mixture_enum]
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namespace boost { namespace numeric {
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enum sign_mixture_enum
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{
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unsigned_to_unsigned
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,signed_to_signed
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,signed_to_unsigned
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,unsigned_to_signed
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} ;
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} } // namespace boost::numeric
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[endsect]
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[section enumeration udt_builtin_mixture_enum]
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namespace boost { namespace numeric {
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enum udt_builtin_mixture_enum
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{
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builtin_to_builtin
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,builtin_to_udt
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,udt_to_builtin
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,udt_to_udt
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} ;
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} } // namespace boost::numeric
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[endsect]
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[section template class int_float_mixture<>]
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namespace boost { namespace numeric {
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template <class T, class S>
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struct int_float_mixture : mpl::integral_c<int_float_mixture_enum, impl-def-value> {} ;
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} } // namespace boost::numeric
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Classifying `S` and `T` as either integral or float, this __MPL_INTEGRAL_CONSTANT__
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indicates the combination of these attributes.
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Its `::value` is of enumeration type
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[link boost_numericconversion.conversion_traits___traits_class.types.enumeration_int_float_mixture_enum `boost::numeric::int_float_mixture_enum`]
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[endsect]
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[section template class sign_mixture<>]
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namespace boost { namespace numeric {
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template <class T, class S>
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struct sign_mixture : mpl::integral_c<sign_mixture_enum, impl-def-value> {} ;
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} } // namespace boost::numeric
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Classifying `S` and `T` as either signed or unsigned, this __MPL_INTEGRAL_CONSTANT__
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indicates the combination of these attributes.
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Its `::value` is of enumeration type
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[link boost_numericconversion.conversion_traits___traits_class.types.enumeration_sign_mixture_enum `boost::numeric::sign_mixture_enum`]
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[endsect]
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[section template class udt_builtin_mixture<>]
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namespace boost { namespace numeric {
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template <class T, class S>
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struct udt_builtin_mixture : mpl::integral_c<udt_builtin__mixture_enum, impl-def-value> {} ;
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} } // namespace boost::numeric
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Classifying `S` and `T` as either user-defined or builtin, this __MPL_INTEGRAL_CONSTANT__
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indicates the combination of these attributes.
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Its `::value` is of enumeration type
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[link boost_numericconversion.conversion_traits___traits_class.types.enumeration_udt_builtin_mixture_enum `boost::numeric::udt_builtin_mixture_enum`]
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[endsect]
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[section template class is_subranged<>]
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namespace boost { namespace numeric {
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template <class T, class S>
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struct is_subranged : mpl::bool_<impl-def-value> {} ;
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} } // namespace boost::numeric
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Indicates if the range of the target type `T` is a subset of the range of the source
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type `S`. That is: if there are some source values which fall out of the
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Target type's range.
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It is a boolean __MPL_INTEGRAL_CONSTANT__.
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It does not indicate if a particular conversion is effectively out of range;
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it indicates that some conversion might be out of range because not all the
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source values are representable as Target type.
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[endsect]
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[section template class conversion_traits<>]
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namespace boost { namespace numeric {
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template <class T, class S>
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struct conversion_traits
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{
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mpl::integral_c<int_float_mixture_enum , ...> int_float_mixture ;
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mpl::integral_c<sign_mixture_enum , ...> sign_mixture;
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mpl::integral_c<udt_builtin_mixture_enum, ...> udt_builtin_mixture ;
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mpl::bool_<...> subranged ;
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mpl::bool_<...> trivial ;
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typedef T target_type ;
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typedef S source_type ;
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typedef ... argument_type ;
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typedef ... result_type ;
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typedef ... supertype ;
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typedef ... subtype ;
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} ;
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} } // namespace numeric, namespace boost
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This traits class indicates some properties of a ['numeric conversion] direction:
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from a source type `S` to a target type `T`. It does not indicate the properties
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of a ['specific] conversion, but of the conversion direction. See
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[link boost_numericconversion.definitions.subranged_conversion_direction__subtype_and_supertype Definitions] for details.
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The traits class provides the following __MPL_INTEGRAL_CONSTANT__\s of enumeration
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type. They express the combination of certain attributes of the Source and
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Target types (thus they are call mixture):
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[table
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[[ ][ ]]
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[[[*int_float_mixture ]][
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Same as given by the traits class
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[link boost_numericconversion.conversion_traits___traits_class.types.template_class_int_float_mixture__ int_float_mixture]
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]]
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[[[*sign_mixture ]][
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Same as given by the traits class
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[link boost_numericconversion.conversion_traits___traits_class.types.template_class_sign_mixture__ sign_mixture]
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]]
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[[[*udt_builtin_mixture ]]
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[Same as given by the traits class
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[link boost_numericconversion.conversion_traits___traits_class.types.template_class_udt_builtin_mixture__ udt_builtin_mixture]
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]]
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]
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The traits class provides the following __MPL_INTEGRAL_CONSTANT__\s of boolean type
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which indicates indirectly the relation between the Source and Target ranges
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(see [link boost_numericconversion.definitions.range_and_precision Definitions] for details).
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[table
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[[ ][ ]]
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[[subranged ][
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Same as given by [link boost_numericconversion.conversion_traits___traits_class.types.template_class_is_subranged__ is_subranged]
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]]
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[[trivial][
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Indicates if both Source and Target, [_without cv-qualifications], are the same type.
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Its `::value` is of boolean type.
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]]
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]
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The traits class provides the following types. They are the Source and Target types classified
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and qualified for different purposes.
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[table
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[[ ][ ]]
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[[[*target_type]][
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The template parameter `T` without cv-qualifications
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]]
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[[[*source_type]][
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The template parameter `S` without cv-qualifications
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]]
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[[[*argument_type]][
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This type is either source_type or `source_type const&`.
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It represents the optimal argument type for the
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[link boost_numericconversion.converter___function_object converter] member functions.
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If S is a built-in type, this is `source_type`, otherwise, this is `source_type const&`.
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]]
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[[[*result_type]][
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This type is either target_type or target_type const&
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It represents the return type of the
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[link boost_numericconversion.converter___function_object converter] member functions.
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If `T==S`, it is `target_type const&`, otherwise, it is `target_type`.
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]]
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[[[*supertype]][
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If the conversion is subranged, it is `source_type`, otherwise, it is `target_type`
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]]
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[[[*subtype]][
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If the conversion is subranged, it is `target_type`, otherwise, it is `source_type`
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]]
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]
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[endsect]
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[endsect]
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[section Examples]
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#include <cassert>
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#include <typeinfo>
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#include <boost/numeric/conversion/conversion_traits.hpp>
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int main()
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{
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// A trivial conversion.
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typedef boost::numeric::conversion_traits<short,short> Short2Short_Traits ;
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assert ( Short2Short_Traits::trivial::value ) ;
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// A subranged conversion.
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typedef boost::numeric::conversion_traits<double,unsigned int> UInt2Double_Traits ;
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assert ( UInt2Double_Traits::int_float_mixture::value == boost::numeric::integral_to_float ) ;
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assert ( UInt2Double_Traits::sign_mixture::value == boost::numeric::unsigned_to_signed ) ;
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assert ( !UInt2Double_Traits::subranged::value ) ;
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assert ( typeid(UInt2Double_Traits::supertype) == typeid(double) ) ;
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assert ( typeid(UInt2Double_Traits::subtype) == typeid(unsigned int) ) ;
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// A doubly subranged conversion.
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assert ( (boost::numeric::conversion_traits<short, unsigned short>::subranged::value) );
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assert ( (boost::numeric::conversion_traits<unsigned short, short>::subranged::value) );
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return 0;
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}
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[endsect]
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[endsect]
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