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- // (C) Copyright Andrew Sutton 2007
- //
- // Use, modification and distribution are subject to the
- // Boost Software License, Version 1.0 (See accompanying file
- // LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
- #ifndef BOOST_GRAPH_NULL_PROPERTY_HPP
- #define BOOST_GRAPH_NULL_PROPERTY_HPP
- #include <boost/property_map/property_map.hpp>
- // TODO: This should really be part of the property maps library rather than
- // the Boost.Graph library.
- namespace boost
- {
- // A null property is somewhat like the inverse of the constant
- // property map except that instead of returning a single value,
- // this eats any writes and cannot be read from.
- template <typename Key, typename Value>
- struct null_property_map
- {
- typedef Key key_type;
- typedef Value value_type;
- typedef void reference;
- typedef boost::writable_property_map_tag category;
- };
- // The null_property_map<K,V> only has a put() function.
- template <typename K, typename V>
- void put(null_property_map<K,V>& /*pm*/, const K& /*key*/, const V& /*value*/)
- { }
- // A helper function for intantiating null property maps.
- template <typename Key, typename Value>
- inline null_property_map<Key, Value> make_null_property()
- { return null_property_map<Key, Value>(); }
- }
- #endif
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