mirror of
https://github.com/ashinn/chibi-scheme.git
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32 lines
1.1 KiB
Scheme
32 lines
1.1 KiB
Scheme
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; The most basic set interface. We provide a data type, low-level
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;; constructor, and membership test. This allows libraries to provide
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;; an iset API without needing to include the full iset library.
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(define-record-type Integer-Set
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(%make-iset start end bits left right)
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iset?
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(start iset-start iset-start-set!)
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(end iset-end iset-end-set!)
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(bits iset-bits iset-bits-set!)
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(left iset-left iset-left-set!)
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(right iset-right iset-right-set!))
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(define (make-iset . opt)
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(if (null? opt)
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(%make-iset 0 0 0 #f #f)
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(let ((end (if (pair? (cdr opt)) (cadr opt) (car opt))))
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(%make-iset (car opt) end #f #f #f))))
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(define (iset-contains? iset n)
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(let lp ((is iset))
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(let ((start (iset-start is)))
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(if (< n start)
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(let ((left (iset-left is))) (and left (lp left)))
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(let ((end (iset-end is)))
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(if (> n end)
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(let ((right (iset-right is))) (and right (lp right)))
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(let ((bits (iset-bits is)))
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(or (not bits)
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(bit-set? (- n start) bits)))))))))
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