slime/bin/sets.slime

(import "cxr.slime")

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

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

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

(define (set-insert! set value)
  (unless (set-contains? set value)
    (mutate set (pair (pair value (first set)) ()))
    (set-type set :set))
  set)