gistfile1.txt

#lang racket
(require parser-tools/lex)
(require (prefix-in : parser-tools/lex-sre))
(require racket/port)

(define a-lexer
  (lexer ("a" `(A ,lexeme))
         ((eof) eof)))

;; produce a list of pairs for all the A tokens in the string "aa"
(call-with-input-string "aa"
                        (lambda (p)
                          (sequence->list 
                           (in-producer (lambda () (a-lexer p)) 
                                        eof))))