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#lang planet dyoo/whalesong
;; This is a second semantics for the language that tries to go for speed,
;; at the expense of making things a little more complicated.
;;
;; It uses features in: http://docs.racket-lang.org/reference/unsafe.html
;; to reduce the number of runtime checks.
;;
;; We also manage the state as two separate values.
;;
;; Tape out-of-bounds errors at runtime should be properly reported with
;; source location.
(require (for-syntax racket/base))
(provide (all-defined-out))
(define-syntax MAX-DATA-SIZE
(lambda (stx) #'30000))
;; Creates a new state, with a byte array of 30000 zeros, and
;; the pointer at index 0.
(define-syntax-rule (new-state)
(values (make-vector MAX-DATA-SIZE 0)
0))
;; increment the data pointer
(define-syntax-rule (increment-ptr data ptr loc)
(begin
(set! ptr (+ ptr 1))))
;; decrement the data pointer
(define-syntax-rule (decrement-ptr data ptr loc)
(set! ptr (- ptr 1)))
;; increment the byte at the data pointer
(define-syntax-rule (increment-byte data ptr)
(vector-set! data ptr
(modulo
(+ (vector-ref data ptr)
1)
256)))
;; decrement the byte at the data pointer
(define-syntax-rule (decrement-byte data ptr)
(vector-set! data ptr
(modulo
(- (vector-ref data ptr)
1)
256)))
;; print the byte at the data pointer
(define-syntax-rule (write-byte-to-stdout data ptr)
(write-byte (vector-ref data ptr)))
;; ;; read a byte from stdin into the data pointer
;; (define-syntax-rule (read-byte-from-stdin data ptr)
;; (vector-set! data ptr (let ([v (read-byte (current-input-port))])
;; (if (eof-object? v)
;; 0
;; v))))
;; Loops
(define-syntax-rule (loop data ptr body ...)
(unless (= (vector-ref data ptr)
0)
(let loop ()
body ...
(unless (= (vector-ref data ptr)
0)
(loop)))))
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