1 files changed, 33 insertions, 0 deletions
diff --git a/boost/graph/property_maps/constant_property_map.hpp b/boost/graph/property_maps/constant_property_map.hpp
index dd2461e7ed..9d83ea18cc 100644
--- a/boost/graph/property_maps/constant_property_map.hpp
+++ b/boost/graph/property_maps/constant_property_map.hpp
@@ -54,6 +54,39 @@ inline constant_property_map<Key, Value>
 make_constant_property(const Value& value)
 { return constant_property_map<Key, Value>(value); }
 
+/**
+ * Same as above, but pretends to be writable as well.
+ */
+template <typename Key, typename Value>
+struct constant_writable_property_map {
+    typedef Key key_type;
+    typedef Value value_type;
+    typedef Value& reference;
+    typedef boost::read_write_property_map_tag category;
+
+    constant_writable_property_map()
+        : m_value()
+    { }
+
+    constant_writable_property_map(const value_type &value)
+        : m_value(value)
+    { }
+
+    constant_writable_property_map(const constant_writable_property_map& copy)
+        : m_value(copy.m_value)
+    { }
+
+    friend Value get(const constant_writable_property_map& me, Key) {return me.m_value;}
+    friend void put(const constant_writable_property_map&, Key, Value) {}
+
+    value_type m_value;
+};
+
+template <typename Key, typename Value>
+inline constant_writable_property_map<Key, Value>
+make_constant_writable_property(const Value& value)
+{ return constant_writable_property_map<Key, Value>(value); }
+
 } /* namespace boost */
 
 #endif