2.21.scm

#!/usr/bin/env chicken-scheme
(use (only sicp nil square) test)

(define (square-list items)
  (if (null? items)
      nil
      (cons (square (car items)) (square-list (cdr items)))))

(test '(1 4 9 16) (square-list (list 1 2 3 4)))

(define (square-list items)
  (map square items))

(test '(1 4 9 16) (square-list (list 1 2 3 4)))