; a lexical closure / functor / lambda

; variabele count is lexically scoped within the make-counter function,
; therefore it remains accessible by the counter procedure even after
; make-counter has finished.

(defun make-counter ()
  (let ((count 0))
    (lambda ()
      (setq count (+ count 1))
      count)))

(define counter_1 (make-counter))
(define counter_2 (make-counter))

(defvar i 0)
(while (< i 10)
  (print (counter_1)) ; each counter keeps its own count
  (print (counter_2))
  (setq i (+ i 1))
)