Under SBCL it would run even faster. Also, not CL, but I've got bored with Scheme and computer abstractions requiring you to proof every step on recursion by i

Under SBCL it would run even faster. Also, not CL, but I've got bored with Scheme and computer abstractions requiring you to proof every step on recursion by induction. I just put a base case at f(0) with an invariant and I tested it against f(1).