(define-module set
  :imports ("cxr.slime")
  :exports (make find contains? insert!)

  (define key-not-found-index -1)

  (define (make . vals)
    (set-type!
     (if vals
         (list vals)
       '(()))
     :set))

  (define (find set val)
    (let ((values (car set)))
      (define (inner values current-index)
        (cond ((null? values) key-not-found-index)
              ((= (car values) val) current-index)
              (else (inner (cdr values) (+ 1 current-index)))))
      (inner values 0)))

  (define (contains? set val)
    (unless (= (find set val) key-not-found-index)
      t))

  (define (insert! set value)
    (unless (contains? set value)
      (set! set (cons (cons value (car set)) ()))
      (set-type! set :set))
    set)
  )