Welcome to MzScheme v4.1.4 [3m], Copyright (c) 2004-2009 PLT Scheme Inc.
> > (define a (enumerate 1 10))
> a
(1 2 3 4 5 6 7 8 9 10)
> (define a (cdr a))
> a
(2 3 4 5 6 7 8 9 10)
> (define a (cdr a))
> a
(3 4 5 6 7 8 9 10)
> (define a (cdr a))
> a
(4 5 6 7 8 9 10)
> (define (ints-from-n n) (cons n (ints-from-n (+ n 1))))
> (define b (ints-from-n 1))
  C-c C-cuser break

 === context ===
stdin::176: ints-from-n
stdin::176: ints-from-n
stdin::176: ints-from-n
stdin::176: ints-from-n
stdin::176: ints-from-n
stdin::176: ints-from-n
stdin::176: ints-from-n
stdin::176: ints-from-n
stdin::176: ints-from-n
stdin::176: ints-from-n
stdin::176: ints-from-n
stdin::176: ints-from-n
stdin::176: ints-from-n
stdin::176: ints-from-n
stdin::176: ints-from-n
stdin::176: ints-from-n
...

> a
(4 5 6 7 8 9 10)
> (define (ints-from-n n) (cons n (lambda ()(ints-from-n (+ n 1)))))
> (define b (ints-from-n 1))
> (define a (cdr a))
> a
(5 6 7 8 9 10)
> (car b)
1
> b
(1 . #<procedure>)
> ((cdr b))
(2 . #<procedure>)
> ((cdr b))
(2 . #<procedure>)
> (define b ((cdr b)))
> b
(2 . #<procedure>)
> (define b ((cdr b)))
> b
(3 . #<procedure>)
> (define b ((cdr b)))
> b
(4 . #<procedure>)
> (define (ints-from-n n) (cons n (lambda ()(ints-from-n (+ n 1)))))
> (define b ((cdr b)))
> b
(5 . #<procedure>)
> (define b ((cdr b)))
> b
(6 . #<procedure>)
> (define b ((cdr b)))
> b
(7 . #<procedure>)
> delay
stdin::610: delay: bad syntax in: delay

 === context ===
/Applications/PLTScheme/collects/scheme/private/misc.ss:74:7

> if
stdin::616: if: bad syntax in: if

 === context ===
/Applications/PLTScheme/collects/scheme/private/misc.ss:74:7

> and
stdin::619: and: bad syntax in: and

 === context ===
/Applications/PLTScheme/collects/scheme/private/qq-and-or.ss:338:6
/Applications/PLTScheme/collects/scheme/private/misc.ss:74:7

> force
#<procedure:force>
> (define a (delay 2))
> a
#<promise:a>
> (force a)
2
> (define ask-nicely force)
> a
#<promise!2>
> (ask-nicely a)
2
> (define (ints-from-n n) (cons n (delay (ints-from-n (+ n 1)))))
> (define b (ints-from-n 6))
> b
(6 . #<promise>)
> (ask-nicely (cdr b))
(7 . #<promise>)
> (define (stream-car s) (car s))
> (define (stream-cdr s) (force (cdr s)))
> b
(6 . #<promise!(7 . #<promise>)>)
> (stream-car b)
6
> (stream-cdr b)
(7 . #<promise>)
> > b
(6 . #<promise!(7 . #<promise>)>)
> (stream-filter even? b)
(6 . #<promise:...s/stream-fun.scm:12:15>)
> (define a (stream-filter even? b))
> (stream-car a)
6
> (stream-car (stream-cdr a))
8
> > b
(6 . #<promise!(7 . #<promise!(8 . #<promise>)>)>)
> (define c (add-streams b b))
> c
(12 . #<promise:...s/stream-fun.scm:19:8>)
> (stream-car (stream-cdr c))
14
> (define c (add-streams b a))
> c
(12 . #<promise:...s/stream-fun.scm:19:8>)
> (stream-car (stream-cdr c))
15
> (define ones (cons 1 (delay ones)))
> > (stream-ref c 12)
48
> (stream-ref ones 12)
1
> > (define fibs (fibgen 1 1))
> fibs
(1 . #<promise:...s/stream-fun.scm:26:10>)
> (stream-ref fibs 3)
3
> (stream-ref fibs 4)
5
> (stream-ref fibs 5)
8
>