25 lines
931 B
Racket
25 lines
931 B
Racket
; SPDX-License-Identifier: LGPL-3.0-or-later
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; Copyright (C) 2010-2021 Tony Garnock-Jones <tonygarnockjones@gmail.com>
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#lang syndicate
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;; Simple mutable box and count-to-infinity box client.
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(message-struct set-box (new-value))
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(assertion-struct box-state (value))
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(spawn (field [current-value 0])
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(assert (box-state (current-value)))
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(stop-when-true (= (current-value) 10)
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(log-info "box: terminating"))
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(on (message (set-box $new-value))
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(log-info "box: taking on new-value ~v" new-value)
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(current-value new-value)))
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(spawn (stop-when (retracted (observe (set-box _)))
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(log-info "client: box has gone"))
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(on (asserted (box-state $v))
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(log-info "client: learned that box's value is now ~v" v)
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(send! (set-box (+ v 1))))
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(on (retracted (box-state _))
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(log-info "client: box state disappeared")))
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