#lang racket/base

(require racket/string
         parser-tools/lex
         (prefix-in : parser-tools/lex-sre))

(define-tokens my-tokens (COMMENT))

(define-empty-tokens my-empty-tokens (EOF NEWLINE))

(define-lex-abbrevs
  [%whitespace (:or #\tab #\space #\vtab)]
  [%newline (:or #\newline (:seq #\return #\newline))]
  [%comment (:seq "//" (:* (:& (char-complement #\return)
                               (char-complement #\newline))))])

(define my-lexer
  (lexer-src-pos
   [(:+ %whitespace)
    (return-without-pos (my-lexer input-port))]
   [%newline
    (token-NEWLINE)]
   [%comment
    (token-COMMENT lexeme)]
   [(eof)
    'EOF]))

(define p (open-input-string "  // my-comment\r\n"))
(port-count-lines! p)

(let loop ([result null])
  (define tok (my-lexer p))
  (if ((position-token-token tok) . eq? . 'EOF)
      (reverse (cons tok result))
      (loop (cons tok result))))