Environments as Objects

state.scm

; 3.1

(define (make-counter value)
  (define (incr x)
    (set! value (+ value x))
    value)
  incr)

(define counter (make-counter 100))

; > (counter 100)
; 200
; > (counter -1)
; 199
; > (counter 10)
; 209
; > (counter -150)
; 59