21 lines
630 B
Scheme
21 lines
630 B
Scheme
|
; Copyright (c) 1993-1999 by Richard Kelsey and Jonathan Rees. See file COPYING.
|
||
|
|
|
||
|
|
|
||
|
|
; Continuations implemented as vectors.
|
||
|
|
|
||
|
|
(define *continuation-marker* (list '*continuation-marker*))
|
||
|
|
|
||
|
|
(define (make-continuation len init)
|
||
|
|
(let ((c (make-vector (+ len 1) init)))
|
||
|
|
(vector-set! c 0 *continuation-marker*)
|
||
|
|
c))
|
||
|
|
|
||
|
|
(define (continuation? obj)
|
||
|
|
(and (vector? obj)
|
||
|
|
(> (vector-length obj) 0)
|
||
|
|
(eq? (vector-ref obj 0) *continuation-marker*)))
|
||
|
|
|
||
|
|
(define (continuation-length c) (- (vector-length c) 1))
|
||
|
|
(define (continuation-ref c i) (vector-ref c (+ i 1)))
|
||
|
|
(define (continuation-set! c i x) (vector-set! c (+ i 1) x))
|