sicp excercise 2.54

最新推荐文章于 2018-11-10 15:34:18 发布

Cheky_

最新推荐文章于 2018-11-10 15:34:18 发布

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分类专栏： sicp-code

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(define (equal? x y)
  (cond ((and (null? x) (null? y)) true)
        ((and (not (pair? x)) (not (pair? y))) (eq? x y))
        ((and (pair? x) (pair? y)
              (equal? (car x) (car y))
              (equal? (cdr x) (cdr y)))
         true)
        (else false)))

  (equal? '(this is a list) '(this is a list))
  (equal? '(this is a list) '(this (is a) list))
  (equal? '(1 2 3 (4 5) 6) '(1 2 3 (4 5) 6))
  (equal? '(1 2 3 (4 5) 6) '(1 2 3 (4 5 7) 6))