【SICP练习】76 练习2.47



练习2.47

这道题重点就是要理清楚list和cons的关系了。我们依次来写出过程函数。

(define (make-frame origin edge1 edge2)

(list origin edge1 edge2))

(define (origin-frame f) (car f))

(define (edge1-frame f) (cadr f))

(define (edge2-frame f) (caddr f))

(define (make-frame origin edge1 edge2)

(cons origin (cons edge1 edge2)))

(define (origin-frame f) (car f))

(define (edge1-frame f) (cadr f))

(define (edge2-frame f) (cddr f))

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