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82 lines
2.5 KiB
Racket
82 lines
2.5 KiB
Racket
#lang br
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(require parser-tools/lex ragg/support "parser.rkt")
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(define (tokenize src-port)
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(define (next-token)
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(define get-token
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(lexer
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[(char-set "><-.,+[]") lexeme]
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[(char-complement (char-set "><-.,+[]")) (token 'OTHER #:skip? #t)]
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[(eof) eof]))
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(get-token src-port))
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next-token)
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(define+provide (read-syntax src-path src-port)
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(define parsed-syntax (parse src-path (tokenize src-port)))
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(strip-context
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(inject-syntax ([parsed-syntax])
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#'(module bf-interpreter br/bf
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parsed-syntax))))
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#;(module reader br
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(provide read-syntax)
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(require "bf/tokenizer.rkt" "bf/parser.rkt")
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(define (read-syntax src-path src-port)
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(define parsed-syntax (parse src-path (tokenize src-port)))
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;; `strip-context` because `read-syntax` promises
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;; a "clean" syntax object without context
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;; (so later operations can add it)
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(strip-context
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(inject-syntax ([parsed-syntax])
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#'(module bf-interpreter br/bf
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parsed-syntax)))))
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;; compact version
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#;(module reader br
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(require br/reader-utils "tokenizer.rkt" "parser.rkt")
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(define-read-and-read-syntax (src-path src-port)
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#`(module bf-interpreter br/bf
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#,(parse src-path (tokenize src-port)))))
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(provide (rename-out [bf-module-begin #%module-begin])
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#%top-interaction bf-program op loop)
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;; just relying on br's #%module-begin.
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;; Could just as easily pass through that one.
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(define #'bf-module-begin #'#%module-begin)
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;; macros to expand our parse tree into local functions
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;; bf-program doesn't do anything
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(define #'(bf-program <op-or-loop> ...)
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#'(begin <op-or-loop> ...))
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;; op branches. Note that string & number literals are
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;; matched literally in syntax patterns.
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(define-cases #'op
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[#'(_ ">") #'(move-pointer 1)]
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[#'(_ "<") #'(move-pointer -1)]
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[#'(_ "+") #'(set-pointer-byte! (add1 (get-pointer-byte)))]
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[#'(_ "-") #'(set-pointer-byte! (sub1 (get-pointer-byte)))]
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[#'(_ ".") #'(write-byte (get-pointer-byte))]
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[#'(_ ",") #'(set-pointer-byte! (read-byte))])
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(define #'(loop "[" <op-or-loop> ... "]")
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#'(until (zero? (get-pointer-byte))
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<op-or-loop> ...))
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;; bf implementation
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;; state: one vector, one pointer
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(define bf-vector (make-vector 30000 0))
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(define bf-pointer 0)
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;; gets and sets
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(define (get-pointer-byte) (vector-ref bf-vector bf-pointer))
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(define (set-pointer-byte! val) (vector-set! bf-vector bf-pointer val))
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;; pointer mover
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(define (move-pointer how-far) (set! bf-pointer (+ bf-pointer how-far))) |