--- a/src/serialize.cc	Thu May 08 09:21:25 2008 +0200
+++ b/src/serialize.cc	Sat May 10 14:29:37 2008 +0200
@@ -39,9 +39,9 @@
 	vertices.clear();
 }
 
-bool Indexer::get(void *o, int &retidx)
+bool Indexer::get(const void *o, int &retidx)
 {
-	map <void *, int>::iterator i;
+	map <const void *, int>::iterator i;
 	i = indexmap.find(o);
 	if (i == indexmap.end())
 	{
@@ -130,17 +130,17 @@
 	}
 }
 
-ostream & operator<<(ostream &st, Shape &o)
+ostream & operator<<(ostream &st, const Shape &o)
 {
 	return o.dump(st);
 }
 
-ostream & operator<<(ostream &st, Vertex &o)
+ostream & operator<<(ostream &st, const Vertex &o)
 {
 	return o.dump(st);
 }
 
-ostream & operator<<(ostream &st, Container &o)
+ostream & operator<<(ostream &st, const Container &o)
 {
 	return o.dump(st);
 }