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;;; Sly
;;; Copyright (C) 2013, 2014 David Thompson <dthompson2@worcester.edu>
;;;
;;; This program 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.
;;;
;;; This program 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/>.
;;; Commentary:
;;
;; Cooperative multi-tasking.
;;
;;; Code:
(define-module (sly coroutine)
#:export (call-with-coroutine
coroutine
colambda
codefine
codefine*)
#:replace (yield))
(define (call-with-coroutine thunk)
"Apply THUNK with a coroutine prompt."
(define (handler cont callback . args)
(define (resume . args)
;; Call continuation that resumes the procedure.
(call-with-prompt 'coroutine-prompt
(lambda () (apply cont args))
handler))
(when (procedure? callback)
(apply callback resume args)))
;; Call procedure.
(call-with-prompt 'coroutine-prompt thunk handler))
;; emacs: (put 'coroutine 'scheme-indent-function 0)
(define-syntax-rule (coroutine body ...)
"Evaluate BODY as a coroutine."
(call-with-coroutine (lambda () body ...)))
;; emacs: (put 'colambda 'scheme-indent-function 1)
(define-syntax-rule (colambda args body ...)
"Syntacic sugar for a lambda that is run as a coroutine."
(lambda args
(call-with-coroutine
(lambda () body ...))))
;; emacs: (put 'codefine 'scheme-indent-function 1)
(define-syntax-rule (codefine (name ...) . body)
"Syntactic sugar for defining a procedure that is run as a
coroutine."
(define (name ...)
;; Create an inner procedure with the same signature so that a
;; recursive procedure call does not create a new prompt.
(define (name ...) . body)
(call-with-coroutine
(lambda () (name ...)))))
;; emacs: (put 'codefine* 'scheme-indent-function 1)
(define-syntax-rule (codefine* (name . formals) . body)
"Syntactic sugar for defining a procedure that is run as a
coroutine."
(define (name . args)
;; Create an inner procedure with the same signature so that a
;; recursive procedure call does not create a new prompt.
(define* (name . formals) . body)
(call-with-coroutine
(lambda () (apply name args)))))
(define (yield callback)
"Yield continuation to a CALLBACK procedure."
(abort-to-prompt 'coroutine-prompt callback))
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