How to write Lisp like C...

reverse-string.lisp

(defun reverse-string-c (string string-length)
  (prog ((pos 0) (half (truncate (/ string-length 2))))
START   (if (= pos half)
            (return string))
        (let ((swap-pos (- string-length pos 1)))
          (rotatef (schar string pos) (schar string swap-pos)))
        (incf pos)
        (go START)))

(defun reverse-string (string)
  (reverse-string-c string (length string)))

(reverse-string "hello")

Second revision more lispy, handles 0- and 1-length strings, but still using a goto instead of a loop :)