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

21 lines
619 B
Racket

8 years ago
#lang br
(require brag/support racket/contract)
(define basic-lexer
(lexer-srcloc
[(eof) eof]
[whitespace (token lexeme #:skip? #t)]
[(from/to "rem" "\n") (token 'REM lexeme)]
[(:or "print" "goto" "end" "+" ":") lexeme]
[(:+ numeric) (token 'INTEGER (string->number lexeme))]
[(:or (:seq (:+ numeric) ".")
(:seq (:* numeric) "." (:+ numeric)))
(token 'DECIMAL (string->number lexeme))]
[(from/to "\"" "\"")
(token 'STRING (trim-ends "\"" lexeme "\""))]))
(provide
(contract-out
[basic-lexer
(input-port? . -> .
(or/c eof-object? string? srcloc-token?))]))