31 lines
907 B
Scheme
31 lines
907 B
Scheme
; Copyright (c) 1993, 1994 Richard Kelsey and Jonathan Rees. See file COPYING.
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; Locations
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(define location-rtd
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(make-record-type 'location '(id defined? contents)))
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(define-record-discloser location-rtd
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(lambda (l) `(location ,(location-id l))))
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(define make-undefined-location
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(let ((make (record-constructor location-rtd
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'(id defined? contents))))
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(lambda (id)
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(make id #f '*empty*))))
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(define location? (record-predicate location-rtd))
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(define location-id (record-accessor location-rtd 'id))
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(define location-defined? (record-accessor location-rtd 'defined?))
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(define contents (record-accessor location-rtd 'contents))
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(define set-defined?! (record-modifier location-rtd 'defined?))
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(define (set-location-defined?! loc ?)
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(set-defined?! loc ?)
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(if (not ?)
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(set-contents! loc '*empty*)))
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(define set-contents! (record-modifier location-rtd 'contents))
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