SICP习题解答2.22
(define (square-list3 items)
(define (append list1 list2)
(cond ((null? list1) list2)
(else (cons (car list1) (append (cdr list1) list2)))))
(define (iter thing answer)
(cond ((null? thing) answer)
(else (iter (cdr thing) (append answer (cons (square (car thing)) '()))))))
(iter items '()))
(define (append list1 list2)
(cond ((null? list1) list2)
(else (cons (car list1) (append (cdr list1) list2)))))
(define (iter thing answer)
(cond ((null? thing) answer)
(else (iter (cdr thing) (append answer (cons (square (car thing)) '()))))))
(iter items '()))
