59 lines
2.1 KiB
Racket
59 lines
2.1 KiB
Racket
#lang syndicate/actor
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;; A toy spreadsheet model.
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(require racket/set)
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(define-namespace-anchor ns)
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(struct cell (name value) #:transparent) ;; assertion
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(struct set-cell (name expr) #:transparent) ;; message
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(define (binding-symbol? s)
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(and (symbol? s)
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(let ((chars (string->list (symbol->string s))))
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(and (andmap char-alphabetic? chars)
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(pair? chars)
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(char-upper-case? (car chars))))))
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(define (extract-bindings expr)
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(let walk ((expr expr))
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(match expr
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[(? binding-symbol? b) (set b)]
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[(cons a d) (set-union (walk a) (walk d))]
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[_ (set)])))
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(define (non-void-field? f) (not (void? (f))))
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(define (cell-expr->spawn-expr name expr)
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(define bindings (set->list (extract-bindings expr)))
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`(spawn (stop-when (message (set-cell ',name _)))
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(field ,@(for/list [(b bindings)] `[,b (void)]))
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(assert #:when (andmap non-void-field? (list ,@bindings))
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(cell ',name
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(let (,@(for/list [(b bindings)] `(,b (,b))))
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,expr)))
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,@(for/list [(b bindings)]
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`(on (asserted (cell ',b $value))
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(,b value)))))
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(spawn (on (message (set-cell $name $expr))
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(define spawn-expr (cell-expr->spawn-expr name expr))
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;; (local-require racket/pretty) (pretty-print spawn-expr)
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(eval spawn-expr (namespace-anchor->namespace ns))))
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(spawn (on (asserted (cell $name $value))
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(printf ">>> ~a ~v\n" name value)
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(flush-output)))
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(spawn (stop-when (message (inbound 'quit)))
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(on (message (inbound (set-cell $name $expr)))
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(send! (set-cell name expr)))
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(void (thread (lambda ()
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(let loop ()
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(define cell-name (read))
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(if (eof-object? cell-name)
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(send-ground-message 'quit)
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(let ((new-expr (read)))
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(send-ground-message (set-cell cell-name new-expr))
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(loop))))))))
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