diff -r 6f10c6ec5a21 -r ceb2756dea2a lemon/edge_set.h
--- a/lemon/edge_set.h	Mon Sep 28 15:53:20 2009 +0200
+++ b/lemon/edge_set.h	Thu Nov 05 10:27:17 2009 +0100
@@ -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;
     }