In an attempt to invent documentation for the GiNaC facilities we use, we came across the following inconsistency in the behavior of the method bool numeric::is_prime(void) const and the function bool is_prime(const numeric &x), whereby exit(1) is called (via cl_abort()) if the number to be tested is a non-positive integer. I believe is_prime() should return false in this case, as it does for, e.g., -2/7, 2/7, 3*I, and 2.8943657489. All the best Roberto P.S. I am not including a patch since this issues may be dealt with either in CLN (which I believe is the better option) or in GiNaC. -- Prof. Roberto Bagnara Computer Science Group Department of Mathematics, University of Parma, Italy http://www.cs.unipr.it/~bagnara/ mailto:bagnara@cs.unipr.it