DEFUN SIGN-OF is beyond repair

[phoe]

; returns sign x
(defun sign-of (x)
  (if (< x 0) (return-from sign-of -1))
  (if (eq x 0) (return-from sign-of 0))
  1)

1. (sign-of 0.0) ;=> 1, not 0
2. it uses eq on a number, which has undefined result
3. it uses multiple return-froms instead of a cond or a typecase
4. cl:signum exists

Will fix this in my fork and submit a PR along with all other koan fixes.