(def null?
  (fn [a]
    (or
      (nil? a)
      (= () a))))
 
(def rember
  (fn [ a lat]
    (cond
      (null? lat) '()
      true (cond
        (= (first lat) a) (rest lat)
        true (cons (first lat)
        (rember
          a (rest lat)))))))
 
(println (rember 'banana '(apple banana orange)))
 
(def firsts
  (fn [l]
    (cond
      (null? l) '()
      true (cons (first (first l))
      (firsts (rest l))))))
 
(println (firsts '((large burger)(fries coke)(chocolate sundae))))

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