Further to my previous message: [[ I've taken the suggestions made by Tom and Robert and combined them into a new module with some supporting functions and test cases. A copy is attached, in case it's of use to anyone. ]] I've tightened the maxima function code in response to a comment from Tom, and added some more partial-ordering comparison primitives. Updated code is attached: -- $Id: PartOrderedCollection.hs,v 1.4 2003/11/20 18:35:59 graham Exp $ (I just had a session trying to use the sourceforge CVS, but I can't find out how to get my combination of WinCVS and SSH tunnelling working.) #g ------------ Graham Klyne For email: http://www.ninebynine.org/#Contact