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23 lines
830 B
Racket
23 lines
830 B
Racket
9 years ago
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#lang br
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(provide #%module-begin #%top-interaction bf-program op loop)
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(define #'(bf-program <op-or-loop> ...)
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#'(begin <op-or-loop> ...))
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(define-cases #'op
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[#'(_ ">") #'(move-pointer 1)]
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[#'(_ "<") #'(move-pointer -1)]
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[#'(_ "+") #'(set-pointer-byte! (add1 (get-pointer-byte)))]
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[#'(_ "-") #'(set-pointer-byte! (sub1 (get-pointer-byte)))]
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[#'(_ ".") #'(write-byte (get-pointer-byte))]
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[#'(_ ",") #'(set-pointer-byte! (read-byte))])
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(define #'(loop "[" <op-or-loop> ... "]")
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#'(until (zero? (get-pointer-byte))
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<op-or-loop> ...))
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(define bf-vector (make-vector 1000 0))
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(define bf-pointer 0)
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(define (get-pointer-byte) (vector-ref bf-vector bf-pointer))
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(define (set-pointer-byte! val) (vector-set! bf-vector bf-pointer val))
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(define (move-pointer how-far) (set! bf-pointer (+ bf-pointer how-far)))
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