74 lines
2.4 KiB
Scheme
74 lines
2.4 KiB
Scheme
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; Copyright (c) 1993-1999 by Richard Kelsey and Jonathan Rees. See file COPYING.
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; Deal with shadowed variables.
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; When a variable is shadowed by a variable, split the existing shared
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; location into two replacement locations.
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; name (structure-ref p name) (define name ...) within a single template
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; will lose big.
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;(define *replaced-locations* '()) ;alist of (old rep ((uid ...) . new))
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(define (shadow-location! old p-uids new replacement)
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(if (location-defined? old)
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(set-contents! replacement (contents old)))
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(set-location-id! old
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(vector replacement p-uids new))
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(set-location-defined?! old #f)) ;so that exceptions will be raised
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(define maybe-replace-location
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(let ((memv memv))
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(lambda (loc p-uid) ;Package's unique id
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(let ((foo (location-id loc)))
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(if (vector? foo)
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(maybe-replace-location
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(if (memv p-uid (vector-ref foo 1))
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(vector-ref foo 2)
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(vector-ref foo 0))
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p-uid)
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loc)))))
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; Exception handler:
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(define (deal-with-replaced-variables succeed)
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(lambda (opcode reason loc . rest)
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(if (= reason (enum exception undefined-global))
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(deal-with-replaced-variable opcode reason loc rest succeed)
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(apply signal-exception opcode reason loc rest))))
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(define (deal-with-replaced-variable opcode reason loc rest succeed)
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(primitive-catch
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(lambda (cont)
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(let* ((tem (continuation-template cont))
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(index (+ (code-vector-ref (template-code tem)
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(+ (continuation-pc cont) 2))
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(* (code-vector-ref (template-code tem)
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(+ (continuation-pc cont) 1))
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byte-limit))))
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(if (eq? (template-ref tem index) loc)
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(let* ((p-uid (do ((env (continuation-env cont)
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(vector-ref env 0)))
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((not (vector? env)) env)))
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(new (maybe-replace-location loc p-uid)))
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(if (eq? new loc)
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(apply signal-exception opcode reason loc rest)
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(begin (template-set! tem index new)
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;(signal 'note "Replaced location" loc new p-uid)
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(if (location-defined? new)
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(succeed new rest)
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(apply signal-exception opcode reason new rest)))))
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(error "lossage in deal-with-replaced-variables"
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loc index))))))
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(define-exception-handler (enum op global)
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(deal-with-replaced-variables
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(lambda (loc more-args)
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(contents loc))))
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(define-exception-handler (enum op set-global!)
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(deal-with-replaced-variables
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(lambda (loc more-args)
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(set-contents! loc (car more-args)))))
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