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47 lines
1.3 KiB
Racket
47 lines
1.3 KiB
Racket
#lang br
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(provide (all-from-out br)
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(all-defined-out))
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(define bf-vector (make-vector 1000 0))
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(define bf-pointer 0)
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(define (byte-at-pointer) (vector-ref bf-vector bf-pointer))
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(define (change-byte-at-pointer val) (vector-set! bf-vector bf-pointer val))
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(define (change-pointer how-far)
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(set! bf-pointer (+ bf-pointer how-far)))
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(define (change-pointer-val how-much)
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(change-byte-at-pointer (+ (byte-at-pointer) how-much)))
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(define #'(bf-program arg ...)
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#'(begin arg ...))
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(define #'(expr arg)
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(case (syntax->datum #'arg)
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[(">") #'(change-pointer 1)]
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[("<") #'(change-pointer -1)]
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[("+") #'(change-pointer-val 1)]
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[("-") #'(change-pointer-val -1)]
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[(".") #'(write-byte (byte-at-pointer))]
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[(",") #'(change-byte-at-pointer (read-byte (current-input-port)))]
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[else #'arg]))
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(define #'(loop lb arg ... rb)
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#'(let loop ()
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(unless (zero? (vector-ref bf-vector bf-pointer))
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arg ...
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(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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#: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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(list (parse src (tokenize ip)))))
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