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beautiful-racket/beautiful-racket-demo/basic-demo/lexer.rkt

23 lines
680 B
Racket

#lang br
(require brag/support)
(define-lex-abbrev digits (:+ (char-set "0123456789")))
(define basic-lexer
(lexer-srcloc
[(eof) (return-without-srcloc eof)]
["\n" (token 'NEWLINE)]
[whitespace (token lexeme #:skip? #t)]
[(from/stop-before "rem" "\n") (token 'REM lexeme)]
[(:or "print" "goto" "end" "+" ":") lexeme]
[digits (token 'INTEGER (string->number lexeme))]
[(:or (:seq (:? digits) "." digits)
(:seq digits "."))
(token 'DECIMAL (string->number lexeme))]
[(:or (from/to "\"" "\"") (from/to "'" "'"))
(token 'STRING
(substring lexeme
1 (sub1 (string-length lexeme))))]))
(provide basic-lexer)