38 lines
1.1 KiB
Racket
38 lines
1.1 KiB
Racket
#lang racket/base
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;;; SPDX-License-Identifier: LGPL-3.0-or-later
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;;; SPDX-FileCopyrightText: Copyright © 2016-2024 Tony Garnock-Jones <tonyg@leastfixedpoint.com>
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(provide field?
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(rename-out [make-field field])
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field-name
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field-id)
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(require "dataflow.rkt")
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(require "support/counter.rkt")
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(struct field (name ;; Symbol
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id ;; Nat
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dataflow ;; Dataflow
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[value #:mutable] ;; Any
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)
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#:methods gen:custom-write
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[(define (write-proc f port mode)
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(fprintf port "#<field:~a:~a:~s>" (field-id f) (field-name f) (field-value f)))]
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#:property prop:procedure
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(case-lambda
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[(f)
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(dataflow-record-observation! (field-dataflow f) f)
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(field-value f)]
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[(f new-value)
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(when (not (equal? (field-value f) new-value))
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(dataflow-record-damage! (field-dataflow f) f)
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(set-field-value! f new-value))]))
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(define generate-field-id (make-counter))
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(define (make-field dataflow name initial-value)
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(field name
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(generate-field-id)
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dataflow
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initial-value))
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