That seems better. However, the return values were almost too dark to read while there's daylight, and I got only eight commands into it before I found an error. (mod -3 5) returns -3. I don't know if that error is just in this implementation, or in many versions of Common Lisp, but a quick search shows there are versions of Common Lisp where mod is implemented correctly. (In mathematics, -3 = 2 modulo 5, or equivalently (-3 mod 5) = 2. Even Python knows that -3 % 5 == 2, where '%' is Python's modulus operator.)