(module stream-type mzscheme

  ;; This hides the implementation of the stream type. The library is
  ;; in stream.ss

  (require (lib "lazy.ss" "srfi" "45"))  ;; avoid conflicts
  (provide (all-defined)
           s:force
           s:delay
           lazy)

  ;; Constructors
  
  (define @null (s:delay '()))

  (define-syntax @cons
    (syntax-rules ()
      ((_ a b) (s:delay (cons a b)))))

  ;; Primitive accessors
  (define (@car x) (car (s:force x)))
  (define (@cdr x) (cdr (s:force x)))


  ;; Primitive predicates.
  (define (@pair? x)
    (and (srfi-45-promise? x)
         (pair? x)))

  (define (@null? x) 
    (and (srfi-45-promise? x)
         (null? (s:force x))))

  (define (@list? x)
    (and (srfi-45-promise? x)
         (or (pair? x)
             (null? x))))

  



  )