diff -r eff1caf6d32e -r a143f19f465b lemon/edge_set.h
--- a/lemon/edge_set.h	Tue Sep 29 10:39:20 2009 +0200
+++ b/lemon/edge_set.h	Tue Sep 29 13:03:34 2009 +0200
@@ -867,7 +867,7 @@
       arc.id = arcs.size() - 1;
     }
 
-    void next(Arc& arc) const {
+    static void next(Arc& arc) {
       --arc.id;
     }
 
@@ -1173,7 +1173,7 @@
       arc.id = arcs.size() - 1;
     }
 
-    void next(Arc& arc) const {
+    static void next(Arc& arc) {
       --arc.id;
     }
 
@@ -1181,7 +1181,7 @@
       arc.id = arcs.size() / 2 - 1;
     }
 
-    void next(Edge& arc) const {
+    static void next(Edge& arc) {
       --arc.id;
     }