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#lang br
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(provide #%module-begin #%top-interaction
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bf-program op loop)
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(module reader syntax/module-reader
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#:language 'br-bf
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#:read bf-read
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#:read-syntax bf-read-syntax
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;; need this because we keep state,
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;; therefore expansion is "all or nothing"
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#:whole-body-readers? #t
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(require "tokenizer.rkt" "parser.rkt")
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(define (bf-read in)
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(syntax->datum (bf-read-syntax #f in)))
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(define (bf-read-syntax src ip)
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(define result (list (parse src (tokenize ip))))
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;; prints out corresponding s-exp source
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(for-each println (map syntax->datum result))
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result))
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(define #'(bf-program <op> ...)
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#'(begin <op> ...))
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(define #'(op <arg>)
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(syntax-case #'(op <arg>) ()
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[(op ">") #'(move-pointer 1)]
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[(op "<") #'(move-pointer -1)]
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[(op "+") #'(set-pointer-byte! (add1 (pointer-byte)))]
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[(op "-") #'(set-pointer-byte! (sub1 (pointer-byte)))]
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[(op ".") #'(write-byte (pointer-byte))]
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[(op ",") #'(set-pointer-byte! (read-byte))]
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[else #'<arg>])) ; <arg> must therefore be a loop
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(define #'(loop "[" <op> ... "]")
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#'(until (zero? (pointer-byte))
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<op> ...))
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(define bf-vector (make-vector 10 0))
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(define bf-pointer 0)
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(define (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)
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(set! bf-pointer (+ bf-pointer how-far)))
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(define (dump)
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(displayln "")
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(displayln bf-pointer)
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(displayln bf-vector))
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