;;; $Id: seq-as-ast.scm,v 1.3 2006/01/05 22:24:09 leavens Exp $

;;; INFINITE SEQUENCES AS RECORDS

(module seq-as-ast (lib "typedscm.ss" "typedscm")

(provide seq-repeat seq-generator seq-nth seq-add)

(deftype seq-repeat (-> (number) seq))
(deftype seq-generator
  (-> ((-> (number) number)) seq))
(deftype seq-nth (-> (seq number) number))
(deftype seq-add (-> (seq seq) seq))

(define-datatype seq seq?
  (seq-repeat
    (num number?))
  (seq-generator
    (f (-> (number?) number?)))
  (seq-add
    (s1 seq?) (s2 seq?)))

(define seq-nth
  (lambda (s n)
    (cases seq s
      (seq-repeat (num) num)
      (seq-generator (f) (f n))
      (seq-add (s1 s2)
         (+ (seq-nth s1 n)
            (seq-nth s2 n))))))

) ; end module