This is a zepto solution to a problem described in SICP 1.2.2

knapsack-combinatorics.zp

;; Solution to:
;; How many different ways can we make change of $ 1.00, given half-dollars, quarters, dimes, nickels, and pennies? 
;; More generally, can we write a procedure to compute the number of ways to change any given amount of money?
;;
;; Example usage for $1.00: (count-change 100) => 292
;; This computation takes around 0.6 secs on my machine in zepto.

(define (count-change amount)
  (cc amount 5))

(define (cc amount kinds-of-coins)
  (cond ((= amount 0) 1)
        ((or (< amount 0) (= kinds-of-coins 0)) 0)
        (else (+ (cc amount
                     (- kinds-of-coins 1))
                 (cc (- amount
                        (first-denomination kinds-of-coins))
                     kinds-of-coins)))))

(define first-denomination (hash-map [1 1] [2 5] [3 10] [4 25] [5 50]))