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