Hi, In Dr. Geo I rely a lot on hash value for the geometric object. It largely improves speed up to compare geometric items (to avoid duplicated items). For example to detect when the user is building an already created object. Also when describing geometric sketch with Smalltalk code, hundred or thousand of geometric items are created. The hash value speeds up equality check (otherwise true comparing is iterative in the geometric sketch tree and it slow down) But sometime hash collisions occur. I guess in that case, DrGeo should do the real equality check, or may be I am overusing the hash? I am interested on advices. As for now I am doing nothing special. Here is an annoying hash collision with Pharo 3/ Pharo 5 I think should not occur: (0.5@0.25) hash 67006464 (-0.5@0.25) hash 67006464 Squeak5.0 does not have this collision. It looks related to the Float hash implementation a bit different. What do you think? Hilaire -- Dr. Geo http://drgeo.eu