如果用Scheme寫的話 :)
Scheme:
(length (filter (lambda (x) (> x 5)) (map sqr '(-1 -2 -3 0 1 2 3))))
>> 2
也可以讓祂更好讀一點
(define gt5?
(lambda (x)
(> x 5)))
(define xs '(-1 -2 -3 0 1 2 3))
(length (filter gt5? (map sqr xs)))