(require (lib "trace.ss"))


;PROBLEM 1

(define (for-each-element prod lista)
    (define (loop)
      (if (null? lista)
          (void)
          (begin
            (prod (car lista))
            (set! lista (cdr lista))
            (loop))))
  ;(trace loop)
    (loop))

;(trace for-each-element)


;PROBLEM 2

(define (rev l)
  (let ((res '())) ; introduce a local variable for the result
    (define (loop)
      (if (null? l)
          res
          (begin
            (set! res (cons (car l) res))
            (set! l (cdr l))
            (loop))))
    (loop)))

;PROBLEM 3
(define (count-call)
  (let((x 0))
    (lambda arg (begin
                 (cond((null? arg)  (set! x (+ x 1)) x)
                      ((eq? (car arg) 'reset) (set! x 0))
                      ((eq? (car arg) 'how-many-calls) x)
        )))))
  
(define count (count-call))