(define (is-elem-assoc-list key assoc-list)
  (cond
    [(null? assoc-list) #f]
    [(eq? key (caar assoc-list)) #t]
    [else (lookup-assoc-list key (cdr assoc-list))]))

(define (lookup-assoc-list key assoc-list)
  (cond
    [(null? assoc-list) #f]
    [(eq? key (caar assoc-list)) (cdar assoc-list)]
    [else (lookup-assoc-list key (cdr assoc-list))]))