Added boost header

test/external/boost/graph/property_maps/constant_property_map.hpp

@@ -0,0 +1,59 @@
+// (C) Copyright 2007-2009 Andrew Sutton
+//
+// 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_CONSTANT_PROPERTY_HPP
+#define BOOST_GRAPH_CONSTANT_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 constant property is one, that regardless of the edge or vertex given,
+ * will always return a constant value.
+ */
+template <typename Key, typename Value>
+struct constant_property_map
+    : public boost::put_get_helper<
+            const Value&,
+            constant_property_map<Key, Value>
+    >
+{
+    typedef Key key_type;
+    typedef Value value_type;
+    typedef const Value& reference;
+    typedef boost::readable_property_map_tag category;
+
+    constant_property_map()
+        : m_value()
+    { }
+
+    constant_property_map(const value_type &value)
+        : m_value(value)
+    { }
+
+    constant_property_map(const constant_property_map& copy)
+        : m_value(copy.m_value)
+    { }
+
+    inline reference operator [](const key_type&) const
+    { return m_value; }
+
+    value_type m_value;
+};
+
+template <typename Key, typename Value>
+inline constant_property_map<Key, Value>
+make_constant_property(const Value& value)
+{ return constant_property_map<Key, Value>(value); }
+
+} /* namespace boost */
+
+#endif