;;; $Id: iseq-mod.scm,v 1.2 2006/01/05 22:24:09 leavens Exp $

;;; <iseq> ::= <number> <iseq>

(module iseq-mod (lib "typedscm.ss" "typedscm")

(provide iseq? iseq iseq->head iseq->tail)

(deftype iseq? (type-predicate-for iseq))

(deftype iseq (-> (number (-> () iseq)) iseq))

(deftype iseq->head (-> (iseq) number))
(deftype iseq->tail (-> (iseq) iseq))

(defrep (iseq (pair-of number (-> () iseq))))

(define iseq?
  (lambda (d)
    (and (pair? d)
         (number? (car d))
         (procedure? (cdr d)))))

(define iseq
  (lambda (num thunk)
     (cons num (has-type-trusted (-> () iseq) thunk))))

(define iseq->head
  (lambda (iseq)
    (car iseq)))

(define iseq->tail
  (lambda (iseq)
    (has-type-trusted
      (pair-of number (-> () iseq))
      ((cdr iseq)))))

) ;; end module