マージソートに驚いた人「マージで？」

msort.cl

(defun msort (list pred)
  (cond ((not (consp (car list)))
         (msort (mapcar (lambda (x) (cons x NIL)) list) pred))
        ((equal (cdr list) NIL)
         (car list))
        (t
          (let (merged)
            (loop
              (push (merge 'list (pop list) (pop list) pred) merged)
              (if (not list) (return (msort merged pred))))))))

(princ (msort '(1 9 2 8 3 7 4 6 5) #'<))