SICP 2.18 2.19 代码

2.18 要求反转参数表
2.19 要求写出兑换零钱方式计数程序，并且零钱种类可变

#lang planet neil/sicp

;;2.18
(define (reverse input-list)
  (if (null? (cdr input-list))
      input-list
      (append (reverse (cdr input-list)) (cons (car input-list) '()))))

;;2.19
(define no-more? null?)
(define first-denomination car)
(define except-first-denomination cdr)
(define (cc amount coin-values)
  (cond ((= amount 0) 1)
        ((or (< amount 0) (no-more? coin-values)) 0)
        (else
         (+ (cc amount
                (except-first-denomination coin-values))
            (cc (- amount
                   (first-denomination coin-values))
                coin-values)))))

(define us-coins (list 50 25 10 5 1))

;;test
(reverse (list 1 2 3 4 5))
(cc 100 us-coins)