Hello all, As an exercise, I've implemented an algorithm for canonic relabeling of graphs. (Two graphs are isomorphic iff they have the same canonic labelling) The method used is stolen from Brendan McKay, "Practical graph isomorphism". http://cs.anu.edu.au/~bdm/nauty/PGI/ In the hope that it is useful to anyone, I attach the code (for GHC 6). Any remark is welcome. Cheers! --JP. __________________________________ Do you Yahoo!? Yahoo! SiteBuilder - Free, easy-to-use web site design software http://sitebuilder.yahoo.com