62 lines
1.9 KiB
Racket
62 lines
1.9 KiB
Racket
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#lang racket
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(require rackunit)
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(provide (all-defined-out))
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;; Our state contains two pieces.
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(define-struct state (data ptr) #:mutable)
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;; Creates a new state, with a byte array of 30000 zeros, and
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;; the pointer at index 0.
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(define (new-state)
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(make-state (make-vector 30000 0) 0))
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;; increment the data pointer
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(define (increment-ptr a-state)
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(set-state-ptr! a-state (add1 (state-ptr a-state))))
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;; decrement the data pointer
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(define (decrement-ptr a-state)
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(set-state-ptr! a-state (sub1 (state-ptr a-state))))
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;; increment the byte at the data pointer
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(define (increment-byte a-state)
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(define v (state-data a-state))
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(define i (state-ptr a-state))
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(vector-set! v i (add1 (vector-ref v i))))
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;; decrement the byte at the data pointer
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(define (decrement-byte a-state)
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(define v (state-data a-state))
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(define i (state-ptr a-state))
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(vector-set! v i (sub1 (vector-ref v i))))
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;; print the byte at the data pointer
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(define (write-byte-to-stdout a-state)
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(define v (state-data a-state))
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(define i (state-ptr a-state))
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;(write-byte (vector-ref v i) (current-output-port)))
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(cond
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[(eof-object? (vector-ref v i));if the vector is pointing at eof; then set the current position to zero
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(vector-set! v i 0)]
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[else
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(write-byte (vector-ref v i) (current-output-port))]))
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;;prints the byte as a number at the data pointer
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(define (write-number-to-stdout a-state)
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(define v (state-data a-state))
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(define i (state-ptr a-state))
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(print (vector-ref v i) (current-output-port)))
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;; read a byte from stdin into the data pointer
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(define (read-byte-from-stdin a-state)
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(define v (state-data a-state))
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(define i (state-ptr a-state))
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(vector-set! v i (read-byte (current-input-port))))
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;; loops
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(define-syntax-rule (loop a-state body ...)
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(local [(define (loop)
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(unless (= (vector-ref (state-data a-state) (state-ptr a-state))
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0)
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body ...
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(loop)))]
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(loop)))
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