boost/bimap/tags/support/default_tagged.hpp
// Boost.Bimap
//
// Copyright (c) 2006-2007 Matias Capeletto
//
// Distributed under 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)
/// \file tags/support/default_tagged.hpp
/// \brief Weak tagging
#ifndef BOOST_BIMAP_TAGS_SUPPORT_DEFAULT_TAGGED_HPP
#define BOOST_BIMAP_TAGS_SUPPORT_DEFAULT_TAGGED_HPP
#if defined(_MSC_VER)
#pragma once
#endif
#include <boost/config.hpp>
#include <boost/bimap/tags/tagged.hpp>
/** \struct boost::bimaps::tags::support::default_tagged
\brief Weak tagging metafunction
\code
template< class Type, class Tag >
struct default_tagged
{
typedef {TaggedType} type;
};
\endcode
If the type is not tagged, this metafunction returns a tagged type with the
default tag. If it is tagged, the returns the type unchanged.
See also tagged, overwrite_tagged.
**/
#ifndef BOOST_BIMAP_DOXYGEN_WILL_NOT_PROCESS_THE_FOLLOWING_LINES
namespace boost {
namespace bimaps {
namespace tags {
namespace support {
// Default Tagging
// A metafunction that create a tagged type with a default tag value.
template< class Type, class DefaultTag >
struct default_tagged
{
typedef tagged<Type,DefaultTag> type;
};
template< class Type, class OldTag, class NewTag >
struct default_tagged< tagged< Type, OldTag >, NewTag >
{
typedef tagged<Type,OldTag> type;
};
} // namespace support
} // namespace tags
} // namespace bimaps
} // namespace boost
#endif // BOOST_BIMAP_DOXYGEN_WILL_NOT_PROCESS_THE_FOLLOWING_LINES
#endif // BOOST_BIMAP_TAGS_SUPPORT_DEFAULT_TAGGED_HPP