Exercise 186: Use contains? to define functions that search for "atom", "basic", and "zoo", respectively

Exercise 186: Use contains? to define functions that search for "atom", "basic", and "zoo", respectively.

The contains function is supplied by the text

; String Los -> Boolean

; to determine whether l contains the string s

(define (contains? s l)

(cond

[(empty? l) false]

[else (or (string=? (first l) s)

(contains? s (rest l)))]))

Answer 

; String Los -> Boolean
; to determine whether l contains the string s
(define (contains? s l)
  (cond
    [(empty? l) false]
    [else (or (string=? (first l) s)
              (contains? s (rest l)))]))

; Los -> Boolean
; to determine whether l contains the string "atom"
(define (contains-atom l)
  (contains? "atom" l))


; Los -> Boolean
; to determine whether l contains the string "basic"
(define (contains-basic l)
  (contains? "basic" l))


; Los -> Boolean
; to determine whether l contains the string "zoo"
(define (contains-zoo l)
  (contains? "zoo" l))