Folks, Let me chime in in favor of gcd(0,0) = 0 rather than undefined. On Tuesday, December 11, 2001, at 01:07 , Alan Bawden wrote: > Also, it is nice to be able to know that gcd(x, 0) = x for -all- x. Alan is in good company: 1. Steele in "Common Lisp: The Language" says the same thing. 2. Knuth in "The Art of Computer Programming" defines gcd(0,0)=0. ---Frank