1.1 --- a/lemon/concept/graph.h	Thu Aug 11 13:15:03 2005 +0000
     1.2 +++ b/lemon/concept/graph.h	Thu Aug 11 13:16:39 2005 +0000
     1.3 @@ -176,6 +176,18 @@
     1.4          ///
     1.5          bool operator!=(Node) const { return true; }
     1.6  
     1.7 +	/// Artificial ordering operator.
     1.8 +	
     1.9 +	/// To allow the use of graph descriptors as key type in std::map or
    1.10 +	/// similar associative container we require this.
    1.11 +	///
    1.12 +	/// \note This operator only have to define some strict ordering of
    1.13 +	/// the items; this order has nothing to do with the iteration
    1.14 +	/// ordering of the items.
    1.15 +	///
    1.16 +	/// \bug This is a technical requirement. Do we really need this?
    1.17 +	bool operator<(Node) const { return false; }
    1.18 +
    1.19        };
    1.20      
    1.21        /// This iterator goes through each node.
    1.22 @@ -255,6 +267,18 @@
    1.23          /// \sa operator==(Edge n)
    1.24          ///
    1.25          bool operator!=(Edge) const { return true; }
    1.26 +
    1.27 +	/// Artificial ordering operator.
    1.28 +	
    1.29 +	/// To allow the use of graph descriptors as key type in std::map or
    1.30 +	/// similar associative container we require this.
    1.31 +	///
    1.32 +	/// \note This operator only have to define some strict ordering of
    1.33 +	/// the items; this order has nothing to do with the iteration
    1.34 +	/// ordering of the items.
    1.35 +	///
    1.36 +	/// \bug This is a technical requirement. Do we really need this?
    1.37 +	bool operator<(Edge) const { return false; }
    1.38        };
    1.39      
    1.40        /// This iterator goes trough the outgoing edges of a node.