Dear all, while I was trying the Prolog interfaces, I wrote ppl_relation_with_generator(P, point(1), L) which was happily accepted, but then I got a wrong result. What I meant to write was ppl_relation_with_generator(P, point(X), L) or, for more verbosity, ppl_relation_with_generator(P, point(1*X), L). Thus I thought I should change the code of the Prolog interface so that an exception is thrown in case of invalid generators such as point(1). But then I realized that silly generators can also be created in C++, even though one needs to be more motivation to come up with things like Generator g(point(LinExpression(1))); Should we disallow these things also in C++? Are there other places were we are a bit sloppy? Please, let me know what you think. Ciao Roberto -- Prof. Roberto Bagnara Computer Science Group Department of Mathematics, University of Parma, Italy http://www.cs.unipr.it/~bagnara/ mailto:bagnara@cs.unipr.it