Add SCons configure checks

[senf.git] / boost_ext / boost / bimap / tags / tagged.hpp

diff --git a/boost_ext/boost/bimap/tags/tagged.hpp b/boost_ext/boost/bimap/tags/tagged.hpp
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+// 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/tagged.hpp
+/// \brief Defines the tagged class
+
+#ifndef BOOST_BIMAP_TAGS_TAGGED_HPP
+#define BOOST_BIMAP_TAGS_TAGGED_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER>=1200)
+#pragma once
+#endif
+
+#include <boost/config.hpp>
+
+namespace boost {
+namespace bimaps {
+
+/// \brief A light non-invasive idiom to tag a type.
+/**
+
+There are a lot of ways of tagging a type. The standard library for example
+defines tags (empty structs) that are then inherited by the tagged class. To
+support built-in types and other types that simple cannot inherit from the
+tag, the standard builds another level of indirection. An example of this is
+the type_traits metafunction. This approach is useful if the tags are intended
+to be used in the library internals, and if the user does not have to create
+new tagged types often.
+
+Boost.MultiIndex is an example of a library that defines a tagged idiom that
+is better suited to the user. As an option, in the indexed by declaration
+of a multi-index container a user can \b attach a tag to each index, so it
+can be referred by it instead of by the index number. It is a very user
+friendly way of specifying a tag but is very invasive from the library writer's
+point of view. Each index must now support this additional parameter. Maybe
+not in the case of the multi-index container, but in simpler classes
+the information of the tags is used by the father class rather than by the
+tagged types.
+
+\b tagged is a light non-invasive idiom to tag a type. It is very intuitive
+and user-friendly. With the use of the defined metafunctions the library
+writer can enjoy the coding too.
+
+                                                                            **/
+
+namespace tags {
+
+/// \brief The tag holder
+/**
+
+The idea is to add a level of indirection to the type being tagged. With this
+class you wrapped a type and apply a tag to it. The only thing to remember is
+that if you write
+
+\code
+typedef tagged<type,tag> taggedType;
+\endcode
+
+Then instead to use directly the tagged type, in order to access it you have
+to write \c taggedType::value_type. The tag can be obtained using \c taggedType::tag.
+The idea is not to use this metadata directly but rather using the metafunctions
+that are defined in the support namespace. With this metafunctions you can work
+with tagged and untagged types in a consistent way. For example, the following
+code is valid:
+
+\code
+BOOST_STATIC_ASSERT( is_same< value_type_of<taggedType>, value_type_of<type> >::value );
+\endcode
+
+The are other useful metafunctions there too.
+See also value_type_of, tag_of, is_tagged, apply_to_value_type.
+
+\ingroup tagged_group
+                                                                                    **/
+template< class Type, class Tag >
+struct tagged
+{
+    typedef Type value_type;
+    typedef Tag tag;
+};
+
+} // namespace tags
+} // namespace bimaps
+} // namespace boost
+
+/** \namespace boost::bimaps::tags::support
+\brief Metafunctions to work with tagged types.
+
+This metafunctions aims to make easier the manage of tagged types. They are all mpl
+compatible metafunctions and can be used with lambda expresions.
+The metafunction value_type_of and tag_of get the data in a tagged type in a secure
+and consistent way.
+default_tagged and overwrite_tagged allows to work with the tag of a tagged type,
+and apply_to_value_type is a higher order metafunction that allow the user to change
+the type of a TaggedType.
+                                                                                    **/
+
+#endif // BOOST_BIMAP_TAGS_TAGGED_HPP
+
+
+
+