Racket- 计算周工资。 输入列表，返回列表

递归列表项， 生成新的列表

;; wages

(define (wages hours)
  (* 12  hours)
  )

;; hours->wages list-of-number -> list-of-number
;; 计算周工资表

(define( hours-wages a-list-of-week-hours )
  (cond 
    [(empty? a-list-of-week-hours) empty]
    [else (cons (wages (first  a-list-of-week-hours)) (hours-wages (rest a-list-of-week-hours)) )  ]
   )
  )

例子： (hours-wages (cons 10 (cons 12 (cons 24 empty))))