~ chicken-core (chicken-5) /continuation.scm

 1;;;; continuation.scm - A better API for continuations
 2;
 3; Copyright (c) 2008-2022, The CHICKEN Team
 4; Copyright (c) 2007, Felix L. Winkelmann
 5; All rights reserved.
 6;
 7; Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following
 8; conditions are met:
 9;
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26
27(declare
28  (unit continuation)
29  (disable-interrupts))
30
31(foreign-declare "#define C_direct_continuation(dummy) t1")
32
33(module chicken.continuation
34  (continuation?
35   continuation-capture
36   continuation-graft
37   continuation-return)
38
39(import scheme chicken.base chicken.fixnum)
40
41(include "common-declarations.scm")
42
43(define (continuation-capture proc)
44  (let ((winds ##sys#dynamic-winds)
45	(k (##core#inline "C_direct_continuation" #f)))
46    (proc (##sys#make-structure 'continuation k winds))))
47
48(define (continuation? x)
49  (##sys#structure? x 'continuation))
50
51(define (continuation-graft k thunk)
52  (##sys#check-structure k 'continuation 'continuation-graft)
53  (let ([winds (##sys#slot k 2)])
54    (unless (eq? ##sys#dynamic-winds winds)
55      (##sys#dynamic-unwind winds (fx- (length ##sys#dynamic-winds) (length winds))))
56    ((##core#primitive "C_continuation_graft") k thunk)))
57
58(define continuation-return
59  (lambda (k . vals)
60    (##sys#check-structure k 'continuation 'continuation-return)
61    ((##core#primitive "C_continuation_graft") k (lambda () (apply values vals))))))