diff -r cd254eed75eb -r 91646df36ffc src/work/alpar/emptygraph.h
--- a/src/work/alpar/emptygraph.h	Fri Mar 12 16:13:44 2004 +0000
+++ b/src/work/alpar/emptygraph.h	Fri Mar 12 16:37:08 2004 +0000
@@ -171,8 +171,8 @@
 
     void clear() {}
 
-    int nodeNum() { return 0;}
-    int edgeNum() { return 0;}
+    int nodeNum() const { return 0;}
+    int edgeNum() const { return 0;}
 
     EmptyGraph() {}
     EmptyGraph(const EmptyGraph &G) {}