count-change.lisp

#!/usr/bin/sbcl --script
(defun count-change (amount)
  (cc amount 5))
(defun cc (amount kinds-of-coins)
    (cond ((= amount 0) 1)
       ((or (< amount 0) (= kinds-of-coins 0)) 0)
        (t (+ (cc amount
          (- kinds-of-coins 1))
            (cc (- amount
              (first-denomination kinds-of-coins))
                 kinds-of-coins)))))
(defun first-denomination (kinds-of-coins)
    (cond ((= kinds-of-coins 1) 1)
          ((= kinds-of-coins 2) 5)
          ((= kinds-of-coins 3) 10)
          ((= kinds-of-coins 4) 25)
          ((= kinds-of-coins 5) 50)))
(trace cc)
(count-change 100)