Hi, I proposed in early february an enhancement to avoid having redefine hash and = together and I would like to see it integrated in 1.3. My idea is that the implicit link between these two methods should be supported by the system. A first solution is proposed on the issue tracker http://code.google.com/p/pharo/issues/detail?id=3657 To make instances of some class comparable, simply make the class use the TEquality trait. TEquality relies on message valuesToCompareForEquality sent to objects for both = and hash. The default implmentation of this message is provided by Object. Override ONLY valuesToCompareForEquality method for custom equality check. Noury http://car.mines-douai.fr/noury -- -6th National Conference on âControl Architecture of Robotsâ 24-25 may 2011, Grenoble area, France http://car2011.inrialpes.fr/ -19th ESUG International Smalltalk Conference 22-26 August 2011, Edinburgh, UK http://www.esug.org/Conferences/2011 -19èmes Journées Francophones sur les Systèmes Multi-Agents (JFSMAâ11) http://www.univ-valenciennes.fr/congres/jfsma2011/ 17-19 Octobre 2011, Valenciennes, France