SICP Exercise 2.21 square-list

Exercise 2.21.  The procedure square-list takes a list of numbers as argument and returns a list of the squares of those numbers.


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

Here are two different definitions of square-list. Complete both of them by filling in the missing expressions:




(define (square-list items)
  (if (null? items)
      nil
      (cons <??> <??>)))
(define (square-list items)
  (map <??> <??>))


SOLUTION
The code and tests are here.

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