( map square '(1 2 3) )
(cons (square 1) (map square '(2 3)) )
(cons 1 '( 4 9 ) )
'( 1 4 9 )
(define (map f x)
(cond ((null? x) nil)
(else (cons (f (car x)) (map f (cdr x)))) ))
( map square '(1 2 3) )の評価は '( 1 4 9 )