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// (C) Copyright Edward Diener 2011,2012,2013
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// Use, modification and distribution are subject to the Boost Software License,
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// 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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#if !defined(BOOST_TTI_MEMBER_TYPE_HPP)
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#define BOOST_TTI_MEMBER_TYPE_HPP
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#include <boost/mpl/eval_if.hpp>
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#include <boost/mpl/identity.hpp>
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#include <boost/mpl/not.hpp>
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#include <boost/type_traits/is_same.hpp>
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#include <boost/preprocessor/cat.hpp>
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#include <boost/tti/gen/member_type_gen.hpp>
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#include <boost/tti/gen/namespace_gen.hpp>
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#include <boost/tti/detail/dmem_type.hpp>
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#include <boost/tti/detail/dnotype.hpp>
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/*
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The succeeding comments in this file are in doxygen format.
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*/
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/** \file
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*/
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/// A macro expands to a metafunction whose typedef 'type' is either the named type or a marker type.
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/**
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BOOST_TTI_TRAIT_MEMBER_TYPE is a macro which expands to a metafunction.
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The metafunction tests whether an inner type with a particular name exists
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by returning the inner type or a marker type.
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The macro takes the form of BOOST_TTI_TRAIT_MEMBER_TYPE(trait,name) where
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trait = the name of the metafunction <br/>
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name = the name of the inner type.
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BOOST_TTI_TRAIT_MEMBER_TYPE generates a metafunction called "trait" where 'trait' is the macro parameter.
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@code
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template<class BOOST_TTI_TP_T,class BOOST_TTI_TP_MARKER_TYPE = boost::tti::detail::notype>
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struct trait
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{
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typedef unspecified type;
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typedef BOOST_TTI_TP_MARKER_TYPE boost_tti_marker_type;
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};
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The metafunction types and return:
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BOOST_TTI_TP_T = the enclosing type.
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The enclosing type can be a class, struct, or union.
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BOOST_TTI_TP_MARKER_TYPE = (optional) a type to use as the marker type.
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defaults to the internal boost::tti::detail::notype.
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returns = 'type' is the inner type of 'name' if the inner type exists
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within the enclosing type, else 'type' is a marker type.
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if the end-user does not specify a marker type then
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an internal boost::tti::detail::notype marker type,
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which is empty, is used.
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The metafunction also encapsulates the type of the marker type as
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a nested 'boost_tti_marker_type'.
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@endcode
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The purpose of this macro is to encapsulate the 'name' type as the typedef 'type'
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of a metafunction, but only if it exists within the enclosing type. This allows for
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an evaluation of inner type existence, without generating a compiler error,
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which can be used by other metafunctions in this library.
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*/
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#define BOOST_TTI_TRAIT_MEMBER_TYPE(trait,name) \
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BOOST_TTI_DETAIL_TRAIT_HAS_TYPE_MEMBER_TYPE(trait,name) \
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BOOST_TTI_DETAIL_TRAIT_MEMBER_TYPE(trait,name) \
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template<class BOOST_TTI_TP_T,class BOOST_TTI_TP_MARKER_TYPE = BOOST_TTI_NAMESPACE::detail::notype> \
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struct trait : \
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boost::mpl::eval_if \
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< \
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BOOST_PP_CAT(trait,_detail_has_type_member_type)<BOOST_TTI_TP_T>, \
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BOOST_PP_CAT(trait,_detail_member_type)<BOOST_TTI_TP_T>, \
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boost::mpl::identity<BOOST_TTI_TP_MARKER_TYPE> \
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> \
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{ \
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typedef BOOST_TTI_TP_MARKER_TYPE boost_tti_marker_type; \
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}; \
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/**/
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/// A macro which expands to a metafunction whose typedef 'type' is either the named type or a marker type.
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/**
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BOOST_TTI_MEMBER_TYPE is a macro which expands to a metafunction.
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The metafunction tests whether an inner type with a particular name exists
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by returning the inner type or a marker type.
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The macro takes the form of BOOST_TTI_MEMBER_TYPE(name) where
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name = the name of the inner type.
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BOOST_TTI_MEMBER_TYPE generates a metafunction called "member_type_name" where 'name' is the macro parameter.
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@code
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template<class BOOST_TTI_TP_T,class BOOST_TTI_TP_MARKER_TYPE = boost::tti::detail::notype>
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struct member_type_'name'
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{
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typedef unspecified type;
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typedef BOOST_TTI_TP_MARKER_TYPE boost_tti_marker_type;
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};
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The metafunction types and return:
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BOOST_TTI_TP_T = the enclosing type.
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The enclosing type can be a class, struct, or union.
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BOOST_TTI_TP_MARKER_TYPE = (optional) a type to use as the marker type.
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defaults to the internal boost::tti::detail::notype.
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returns = 'type' is the inner type of 'name' if the inner type exists
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within the enclosing type, else 'type' is a marker type.
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if the end-user does not specify a marker type then
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an internal boost::tti::detail::notype marker type is used.
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The metafunction also encapsulates the type of the marker type as
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a nested 'boost_tti_marker_type'.
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@endcode
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The purpose of this macro is to encapsulate the 'name' type as the typedef 'type'
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of a metafunction, but only if it exists within the enclosing type. This allows for
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an evaluation of inner type existence, without generating a compiler error,
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which can be used by other metafunctions in this library.
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*/
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#define BOOST_TTI_MEMBER_TYPE(name) \
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BOOST_TTI_TRAIT_MEMBER_TYPE \
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( \
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BOOST_TTI_MEMBER_TYPE_GEN(name), \
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name \
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) \
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/**/
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namespace boost
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{
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namespace tti
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{
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/// A metafunction which checks whether the member 'type' returned from invoking the macro metafunction generated by BOOST_TTI_MEMBER_TYPE ( BOOST_TTI_TRAIT_MEMBER_TYPE ) is a valid type.
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/**
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The metafunction 'valid_member_type', which is in the boost::tti namespace, takes the form of:
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@code
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template<class BOOST_TTI_TP_T,class BOOST_TTI_TP_MARKER_TYPE = boost::tti::detail::notype>
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struct valid_member_type
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{
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static const value = unspecified;
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typedef mpl::bool_<true-or-false> type;
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};
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The metafunction types and return:
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BOOST_TTI_TP_T = returned inner 'type' from invoking the macro metafunction generated by BOOST_TTI_MEMBER_TYPE ( BOOST_TTI_TRAIT_MEMBER_TYPE ).
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BOOST_TTI_TP_MARKER_TYPE = (optional) a type to use as the marker type.
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defaults to the internal boost::tti::detail::notype.
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returns = 'value' is true if the type is valid, otherwise 'value' is false.
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A valid type means that the returned inner 'type' is not the marker type.
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@endcode
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*/
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template<class BOOST_TTI_TP_T,class BOOST_TTI_TP_MARKER_TYPE = BOOST_TTI_NAMESPACE::detail::notype>
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struct valid_member_type :
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boost::mpl::not_
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<
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boost::is_same<BOOST_TTI_TP_T,BOOST_TTI_TP_MARKER_TYPE>
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>
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{
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};
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/// A metafunction which checks whether the invoked macro metafunction generated by BOOST_TTI_MEMBER_TYPE ( BOOST_TTI_TRAIT_MEMBER_TYPE ) hold a valid type.
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/**
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The metafunction 'valid_member_metafunction', which is in the boost::tti namespace, takes the form of:
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@code
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template<class BOOST_TTI_METAFUNCTION>
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struct valid_member_metafunction
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{
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static const value = unspecified;
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typedef mpl::bool_<true-or-false> type;
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};
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The metafunction types and return:
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BOOST_TTI_METAFUNCTION = The invoked macro metafunction generated by BOOST_TTI_MEMBER_TYPE ( BOOST_TTI_TRAIT_MEMBER_TYPE ).
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returns = 'value' is true if the nested type of the invoked metafunction is valid, otherwise 'value' is false.
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A valid type means that the invoked metafunction's inner 'type' is not the marker type.
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@endcode
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*/
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template<class BOOST_TTI_METAFUNCTION>
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struct valid_member_metafunction :
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boost::mpl::not_
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<
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boost::is_same<typename BOOST_TTI_METAFUNCTION::type,typename BOOST_TTI_METAFUNCTION::boost_tti_marker_type>
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>
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{
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};
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}
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}
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#endif // BOOST_TTI_MEMBER_TYPE_HPP
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