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simplify br-bf

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This commit is contained in:
Matthew Butterick 2016-04-08 10:47:25 -07:00
parent 43d8464743
commit 780b656543
1 changed files with 17 additions and 37 deletions
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54
br-bf/main.rkt
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@ -1,39 +1,27 @@
#lang br
(provide #%module-begin #%top-interaction
bf-program op loop)
(provide #%module-begin #%top-interaction bf-program op loop)
(module reader syntax/module-reader
#:language 'br-bf
#:read bf-read
#:read-syntax bf-read-syntax
;; need this because we keep state,
;; therefore expansion is "all or nothing"
#:whole-body-readers? #t
(require "tokenizer.rkt" "parser.rkt")
(define (bf-read in)
(syntax->datum (bf-read-syntax #f in)))
(define (bf-read-syntax src ip)
(define result (list (parse src (tokenize ip))))
;; prints out corresponding s-exp source
(for-each println (map syntax->datum result))
result))
(module reader br
(require "tokenizer.rkt" "parser.rkt" syntax/strip-context)
(provide read-syntax)
(define (read-syntax src-path src-port)
(define src-exprs (list (parse src-path (tokenize src-port))))
;; todo: why is `replace-context` necessary ; why does #'here work
(replace-context #'here
(inject-syntax ([#'(<src-expr> ...) src-exprs])
#'(module bf-interpreter br-bf
<src-expr> ...)))))
(define #'(bf-program <op-or-loop> ...)
#'(begin <op-or-loop> ...))
(define-cases #'op
[#'(_ ">") #'(move-pointer 1)]
[#'(_ "<") #'(move-pointer -1)]
[#'(_ "+") #'(set-pointer-byte! (add1 (get-pointer-byte)))]
[#'(_ "-") #'(set-pointer-byte! (sub1 (get-pointer-byte)))]
[#'(_ ".") #'(write-byte (get-pointer-byte))]
[#'(_ ",") #'(set-pointer-byte! (read-byte))])
(define-cases f
[(_ arg) (add1 arg)]
[(_ arg1 arg2) (+ arg1 arg2)])
[#'(_ ">") #'(move-pointer 1)]
[#'(_ "<") #'(move-pointer -1)]
[#'(_ "+") #'(set-pointer-byte! (add1 (get-pointer-byte)))]
[#'(_ "-") #'(set-pointer-byte! (sub1 (get-pointer-byte)))]
[#'(_ ".") #'(write-byte (get-pointer-byte))]
[#'(_ ",") #'(set-pointer-byte! (read-byte))])
(define #'(loop "[" <op-or-loop> ... "]")
#'(until (zero? (get-pointer-byte))
@ -44,11 +32,3 @@
(define (get-pointer-byte) (vector-ref bf-vector bf-pointer))
(define (set-pointer-byte! val) (vector-set! bf-vector bf-pointer val))
(define (move-pointer how-far) (set! bf-pointer (+ bf-pointer how-far)))
(define (dump)
(displayln "")
(displayln bf-pointer)
(displayln bf-vector))