+(defmethod delete-all-edges ((graph graph-container))
+ (iterate-vertexes
+ graph
+ (lambda (vertex)
+ (empty! (vertex-edges vertex))))
+ (empty! (vertex-pair->edge graph))
+ graph)
+
+;;; ---------------------------------------------------------------------------
+
+(defmethod empty! :after ((graph graph-container))
+ (empty! (vertex-pair->edge graph)))
+
+
+;;; ---------------------------------------------------------------------------
+;;; iteration