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#lang br
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(require brag/support)
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(define-lex-abbrev digits (:+ (char-set "0123456789")))
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(define basic-lexer
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(lexer-srcloc
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[(eof) (return-without-srcloc eof)]
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["\n" (token 'NEWLINE lexeme)]
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[whitespace (token lexeme #:skip? #t)]
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[(from/stop-before "rem" "\n") (token 'REM lexeme)]
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[(:or "print" "goto" "end" "+" ":" "gosub" "return" "let" "=" "-" "for" "to" "step" "next"
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"if" "then" "else" "and" "or" "<" ">" "*" "/" "(" ")" "^" "!" "%" "input" ";" "def") (token lexeme lexeme)]
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[(:seq (:+ alphabetic) (:* (:or alphabetic numeric "$"))) (token 'ID (string->symbol lexeme))]
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[digits (token 'INTEGER (string->number lexeme))]
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[(:or (:seq (:? digits) "." digits)
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(:seq digits "."))
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(token 'DECIMAL (string->number lexeme))]
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[(:or (from/to "\"" "\"") (from/to "'" "'"))
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(token 'STRING
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(substring lexeme
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1 (sub1 (string-length lexeme))))]))
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(provide basic-lexer)
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