Chris@16: // (C) Copyright 2007-2009 Andrew Sutton
Chris@16: //
Chris@16: // Use, modification and distribution are subject to the
Chris@16: // Boost Software License, Version 1.0 (See accompanying file
Chris@16: // LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_GRAPH_CONSTANT_PROPERTY_HPP
Chris@16: #define BOOST_GRAPH_CONSTANT_PROPERTY_HPP
Chris@16: 
Chris@16: #include <boost/property_map/property_map.hpp>
Chris@16: 
Chris@16: 
Chris@16: // TODO: This should really be part of the property maps library rather than
Chris@16: // the Boost.Graph library.
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: /**
Chris@16:  * A constant property is one, that regardless of the edge or vertex given,
Chris@16:  * will always return a constant value.
Chris@16:  */
Chris@16: template <typename Key, typename Value>
Chris@16: struct constant_property_map
Chris@16:     : public boost::put_get_helper<
Chris@16:             const Value&,
Chris@16:             constant_property_map<Key, Value>
Chris@16:     >
Chris@16: {
Chris@16:     typedef Key key_type;
Chris@16:     typedef Value value_type;
Chris@16:     typedef const Value& reference;
Chris@16:     typedef boost::readable_property_map_tag category;
Chris@16: 
Chris@16:     constant_property_map()
Chris@16:         : m_value()
Chris@16:     { }
Chris@16: 
Chris@16:     constant_property_map(const value_type &value)
Chris@16:         : m_value(value)
Chris@16:     { }
Chris@16: 
Chris@16:     constant_property_map(const constant_property_map& copy)
Chris@16:         : m_value(copy.m_value)
Chris@16:     { }
Chris@16: 
Chris@16:     inline reference operator [](const key_type&) const
Chris@16:     { return m_value; }
Chris@16: 
Chris@16:     value_type m_value;
Chris@16: };
Chris@16: 
Chris@16: template <typename Key, typename Value>
Chris@16: inline constant_property_map<Key, Value>
Chris@16: make_constant_property(const Value& value)
Chris@16: { return constant_property_map<Key, Value>(value); }
Chris@16: 
Chris@16: /**
Chris@16:  * Same as above, but pretends to be writable as well.
Chris@16:  */
Chris@16: template <typename Key, typename Value>
Chris@16: struct constant_writable_property_map {
Chris@16:     typedef Key key_type;
Chris@16:     typedef Value value_type;
Chris@16:     typedef Value& reference;
Chris@16:     typedef boost::read_write_property_map_tag category;
Chris@16: 
Chris@16:     constant_writable_property_map()
Chris@16:         : m_value()
Chris@16:     { }
Chris@16: 
Chris@16:     constant_writable_property_map(const value_type &value)
Chris@16:         : m_value(value)
Chris@16:     { }
Chris@16: 
Chris@16:     constant_writable_property_map(const constant_writable_property_map& copy)
Chris@16:         : m_value(copy.m_value)
Chris@16:     { }
Chris@16: 
Chris@16:     friend Value get(const constant_writable_property_map& me, Key) {return me.m_value;}
Chris@16:     friend void put(const constant_writable_property_map&, Key, Value) {}
Chris@16: 
Chris@16:     value_type m_value;
Chris@16: };
Chris@16: 
Chris@16: template <typename Key, typename Value>
Chris@16: inline constant_writable_property_map<Key, Value>
Chris@16: make_constant_writable_property(const Value& value)
Chris@16: { return constant_writable_property_map<Key, Value>(value); }
Chris@16: 
Chris@16: } /* namespace boost */
Chris@16: 
Chris@16: #endif