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;;; Chickadee Game Toolkit
;;; Copyright © 2017 David Thompson <dthompson2@worcester.edu>
;;;
;;; Chickadee is free software: you can redistribute it and/or modify
;;; it under the terms of the GNU General Public License as published
;;; by the Free Software Foundation, either version 3 of the License,
;;; or (at your option) any later version.
;;;
;;; Chickadee is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;; General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program. If not, see
;;; <http://www.gnu.org/licenses/>.
(define-module (chickadee scripting script)
#:use-module (ice-9 format)
#:use-module (srfi srfi-9)
#:use-module (srfi srfi-9 gnu)
#:export (script?
script-cancelled?
script-running?
script-complete?
spawn-script
script
cancel-script
yield
join)
#:replace (yield))
(define-record-type <script>
(make-script status children joined)
script?
(status script-status set-script-status!)
(children script-children set-script-children!)
(joined script-joined set-script-joined!))
(define current-script (make-parameter #f))
(define (display-script script port)
(format port "<script status: ~a>" (script-status script)))
(set-record-type-printer! <script> display-script)
(define (script-cancelled? script)
"Return #t if SCRIPT has been cancelled."
(eq? 'cancelled (script-status script)))
(define (script-running? script)
"Return #t if SCRIPT has not yet terminated or been cancelled."
(eq? 'running (script-status script)))
(define (script-complete? script)
"Return #t if SCRIPT has terminated."
(eq? 'complete (script-status script)))
(define (script-terminated? script)
"Return #t if SCRIPT is in either the completed or cancelled state."
(or (script-complete? script) (script-cancelled? script)))
(define (cancel-script script)
"Prevent further execution of SCRIPT."
(set-script-status! script 'cancelled)
(for-each cancel-script (script-children script))
(resume-joined-scripts script))
(define (add-join! script cont)
"Add CONT to the list of continuations waiting for SCRIPT to finish."
(set-script-joined! script (cons cont (script-joined script))))
(define (resume-joined-scripts script)
"Resume all scripts waiting on SCRIPT to terminate."
(for-each (lambda (cont) (cont))
(script-joined script)))
(define script-prompt (make-prompt-tag 'script))
(define (spawn-script thunk)
"Apply THUNK as a script."
(let ((script (make-script 'running '() '())))
(define (handler cont callback . args)
(define (resume . args)
;; Call the continuation that resumes the script, unless the
;; script has been cancelled in the meanwhile.
(unless (script-cancelled? script)
(call-with-prompt script-prompt
(lambda () (apply cont args))
handler)))
(when (procedure? callback)
(apply callback resume args)))
(define task
(let ((dynamic-state (current-dynamic-state)))
(lambda ()
(with-dynamic-state
dynamic-state
(lambda ()
(current-script script)
(thunk)
(set-script-status! script 'complete)
(resume-joined-scripts script))))))
;; Register child script with parent. Cancelling the parent will
;; cause all children to be cancelled as well.
(when (script? (current-script))
(set-script-children! (current-script)
(cons script (script-children (current-script)))))
;; Start the script.
(call-with-prompt script-prompt task handler)
script))
(define-syntax-rule (script body ...)
"Evaluate BODY in a script."
(spawn-script (lambda () body ...)))
(define (yield handler)
"Suspend the current script and pass its continuation to the
procedure HANDLER."
(abort-to-prompt script-prompt handler))
(define (join script)
"Suspend the current script until SCRIPT has terminated."
(unless (script-terminated? script)
(yield (lambda (cont)
(add-join! script cont)))))
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