;;;
;;; srfi-190 - Coroutine generator
;;;
;;;   Copyright (c) 2020  Shiro Kawai  <shiro@acm.org>
;;;
;;;   Redistribution and use in source and binary forms, with or without
;;;   modification, are permitted provided that the following conditions
;;;   are met:
;;;
;;;   1. Redistributions of source code must retain the above copyright
;;;      notice, this list of conditions and the following disclaimer.
;;;
;;;   2. Redistributions in binary form must reproduce the above copyright
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;;;      documentation and/or other materials provided with the distribution.
;;;
;;;   3. Neither the name of the authors nor the names of its contributors
;;;      may be used to endorse or promote products derived from this
;;;      software without specific prior written permission.
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;; EXPERIMENTAL - not using identifier syntax
;; NB: This isn't correct.  See the mail archive of srfi-190.

(define-module srfi-190
  (use gauche.generator)
  (export coroutine-generator yield define-coroutine-generator))
(select-module srfi-190)

(define yield-proc
  (make-parameter (^_ (error "yield used outside coroutine generator"))))

(define (yield x) ((yield-proc) x))

(define-syntax coroutine-generator
  (syntax-rules ()
    [(_ . body)
     (make-coroutine-generator
      (^[%yield]
       (parameterize ((yield-proc %yield))
         . body)))]))

(define-syntax define-coroutine-generator
  (syntax-rules ()
    [(_ name . body) (define name (coroutine-generator . body))]))
