nested-quotes.rkt

#lang racket

(define (whitespace? c)
  (or (eqv? c #\space)
      (eqv? c #\newline)))

(define (open-quote? c)
  (eqv? c #\"))

(define (open-paren? c)
  (eqv? c #\())

(define (close-paren? c)
  (eqv? c #\)))

(define (backspace? c)
  (eqv? c #\backspace))

(define (skip-char)
  (read-char))

(define (open-quote)
  (let loop ([str '()])
    (define c (peek-char))
    (cond
      [(backspace? c) (skip-char)
		      (loop (cons (read-char)
				  str))]
      [(open-quote? c) (reverse str)]
      [else (loop (cons (read-char)
			str))])))

(define (parse-exp)
  (define c (peek-char))
  (cond
    [(open-quote? c) (skip-char)
		     (open-quote)]))

(define (parse input)
  (with-input-from-string input
    (λ ()
      (parse-exp)))) 

(parse (list->string '(#\" #\H #\I #\")))
(parse (list->string '(#\" #\H #\E #\SPACE
		           #\S #\A #\I #\D #\SPACE
			   #\BACKSPACE #\" #\H #\I
			   #\BACKSPACE #\"
		       #\")))