oops, correction... Richard Fateman wrote: > > aa(b,b) is not a sub-part of aa(b,a,b) or aa(b,b), so it will not match. I meant aa(b,b) is not a sub-part of aa(b,a,b) or aa(b,b,a), { or aa(a,b,b,a) or aa(a,b,b) } so it will not match.