// Boost.Bimap
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//
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// Copyright (c) 2006-2007 Matias Capeletto
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//
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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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/// \file relation/support/member_with_tag.hpp
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/// \brief member_with_tag<tag,relation> metafunction
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#ifndef BOOST_BIMAP_RELATION_SUPPORT_MEMBER_WITH_TAG_HPP
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#define BOOST_BIMAP_RELATION_SUPPORT_MEMBER_WITH_TAG_HPP
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#if defined(_MSC_VER)
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#pragma once
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#endif
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#include <boost/config.hpp>
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#include <boost/bimap/relation/member_at.hpp>
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#include <boost/bimap/detail/debug/static_error.hpp>
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#include <boost/utility/enable_if.hpp>
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#include <boost/type_traits/is_same.hpp>
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#include <boost/mpl/bool.hpp>
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#include <boost/mpl/not.hpp>
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#include <boost/mpl/and.hpp>
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/** \struct boost::bimaps::relation::support::member_with_tag
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\brief Metafunction to convert user tags to the member_at idiom.
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\code
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template< class Tag, class Relation >
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struct member_with_tag
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{
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typedef member_at::{side} type;
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};
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\endcode
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We have to allow that all the metafunctions that works with tags
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and retrieves data from a Relation will work with member_at idiom
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even if the type was tagged. This will be great for the user,
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because he can choose to tag a member after he is using the
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relation and the code will still work.
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If we perform this check in every metafunction it will be very
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tedious and error prone, so instead of that all metafunctions
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that works with relations first call this metafunction that
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convert the tag to a member_at tag.
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See also member_at, is_tag_of_member_at_left, is_tag_of_member_at_right.
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\ingroup relation_group
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**/
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#ifndef BOOST_BIMAP_DOXYGEN_WILL_NOT_PROCESS_THE_FOLLOWING_LINES
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namespace boost {
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namespace bimaps {
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namespace relation {
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namespace support {
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template
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<
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class Tag,
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class Relation,
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class Enable = void
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>
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struct member_with_tag
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{
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BOOST_BIMAP_STATIC_ERROR( MEMBER_WITH_TAG_FAILURE, (Relation,Tag) );
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};
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template< class Relation >
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struct member_with_tag
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<
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member_at::left, Relation, void
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>
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{
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typedef member_at::left type;
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};
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template< class Relation >
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struct member_with_tag
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<
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member_at::right, Relation, void
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>
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{
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typedef member_at::right type;
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};
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template< class Relation >
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struct member_with_tag
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<
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member_at::info, Relation, void
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>
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{
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typedef member_at::info type;
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};
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template< class Tag, class Relation >
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struct member_with_tag
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<
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Tag, Relation,
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BOOST_DEDUCED_TYPENAME enable_if
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<
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mpl::and_
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<
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mpl::not_< is_same<Tag,member_at::left> >,
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is_same
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<
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Tag,
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BOOST_DEDUCED_TYPENAME Relation::left_tag
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>
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>
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>::type
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>
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{
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typedef member_at::left type;
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};
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template< class Tag, class Relation >
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struct member_with_tag
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<
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Tag,
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Relation,
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BOOST_DEDUCED_TYPENAME enable_if
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<
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mpl::and_
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<
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mpl::not_< is_same<Tag,member_at::right> >,
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is_same
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<
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Tag,
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BOOST_DEDUCED_TYPENAME Relation::right_tag
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>
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>
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>::type
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>
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{
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typedef member_at::right type;
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};
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template< class Tag, class Relation >
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struct member_with_tag
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<
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Tag, Relation,
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BOOST_DEDUCED_TYPENAME enable_if
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<
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mpl::and_
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<
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mpl::not_< is_same<Tag,member_at::info> >,
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is_same
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<
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Tag,
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BOOST_DEDUCED_TYPENAME Relation::info_tag
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>
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>
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>::type
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>
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{
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typedef member_at::info type;
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};
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} // namespace support
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} // namespace relation
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} // namespace bimaps
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} // namespace boost
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#endif // BOOST_BIMAP_DOXYGEN_WILL_NOT_PROCESS_THE_FOLLOWING_LINES
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#endif // BOOST_BIMAP_RELATION_SUPPORT_MEMBER_WITH_TAG_HPP
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