old bf expander

pull/2/head
Matthew Butterick 8 years ago
parent 202f6c9c12
commit 1b1aecbb84

@ -0,0 +1,29 @@
#lang br/quicklang
(provide #%module-begin)
(define-macro (bf-program OP-OR-LOOP ...)
#'(begin OP-OR-LOOP ...))
(provide bf-program)
(define-macro-cases op
[(op ">") #'(move-pointer 1)]
[(op "<") #'(move-pointer -1)]
[(op "+") #'(set-current-byte! (add1 (get-current-byte)))]
[(op "-") #'(set-current-byte! (sub1 (get-current-byte)))]
[(op ".") #'(write-byte (get-current-byte))]
[(op ",") #'(set-current-byte! (read-byte))])
(provide op)
(define bf-vector (make-vector 30000 0))
(define bf-pointer 0)
(define (move-pointer how-far) (set! bf-pointer (+ bf-pointer how-far)))
(define (get-current-byte) (vector-ref bf-vector bf-pointer))
(define (set-current-byte! val) (vector-set! bf-vector bf-pointer val))
(define-macro (loop LOOP-ARG ...)
#'(until (zero? (get-current-byte))
LOOP-ARG ...))
(provide loop)
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