lexer state about chicken-lexgen HOT 2 CLOSED

(define (collect cs) 
  (let loop ((cs cs) (ax (list)))
    (cond ((null? cs)         `(,(list->string ax)))
	  ((atom? (car cs))   (loop (cdr cs) (cons (car cs) ax)))
	  (else               (cons (list->string ax) cs)))))

(define (make-exp x)
  (or (and (pair? x) 
	   (let ((x1 (collect x)))
	     (list `(exp . ,x1)))) x))

(define (make-significand x)
  (or (and (pair? x) 
	   (let ((x1 (collect x)))
	     (cons `(significand ,(car x1)) (cdr x1)))) x))

(define (make-sign x)
  (or (and (pair? x) 
	   (let ((x1 (collect x)))
	     (cons `(sign ,(car x1)) (cdr x1)))) x))


(define bnumpat 
  (let* ((digit        (range #\0 #\9))
	 (digits       (star digit))
	 (fraction     (seq (char #\.) digits))
	 (significand  (bar (seq digits (opt fraction)) fraction))
	 (exp          (seq (set "eE") (seq (opt (set "+-")) digits)))
	 (sign         (opt (char #\-)) )
	 (pat          (seq (bind make-sign sign) 
			    (seq (bind make-significand significand)
				 (bind make-exp (opt exp))))))
    pat))

(define (num-parser s) (car (lex bnumpat err s)))

((sign "-") (significand "123.45") (exp "e-6"))