31 lines
956 B
Scheme
31 lines
956 B
Scheme
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;;; Tail-weak tables. This is for internal use only, for real life
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;;; applications we have to provide a more general interface with the
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;;; 3 combinations of head and tail weakness.
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(define make-weak-table make-table)
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(define (weak-table-set! table number set-me)
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(table-set! table number (if set-me (make-weak-pointer set-me) #f)))
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(define (weak-table-ref table number)
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(let ((ref (table-ref table number)))
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(if (weak-pointer? ref)
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(let ((val (weak-pointer-ref ref)))
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(if val
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val
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(begin (table-set! table number #f)
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#f)))
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ref)))
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(define (weak-table-walk proc table)
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(table-walk
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(lambda (number value)
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(proc number (if (weak-pointer? value) (weak-pointer-ref value) value)))
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table))
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(define (strengthen-weak-table-ref table number)
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(table-set! table number (weak-table-ref table number)))
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(define (weaken-weak-table-ref table number)
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(weak-table-set! table number (weak-table-ref table number)))
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