sicp-3-1-1

(define (make-accumulator initial)
  (let ((accumulate initial))
    (lambda (x)
      (set! accumulate (+ accumulate x))
      accumulate)))

(define (make-monitored proc)
  (let ((call-times 0))
    (define (dispatch m)
      (cond
        ((eq? m 'how-many-calls?) call-times)
        ((eq? m 'reset-count) (set! call-count 0))
        (else
          (set! call-times (+ 1 call-times))
          (proc m))))
    dispatch))

(define (make-account balance password)
  (define (withdraw amount)
    (if (>= balance amount) (begin (set! balance (- balance amount)) balance)
        "Insufficient funds"))
  (define (deposit amount)
    (set! balance (+ balance amount)) balance)
  (define (dispatch pass m)
    (if (not (eq? pass password))
      (error "Bad password -- " pass)
      (cond ((eq? m 'withdraw) withdraw)
            ((eq? m 'deposit) deposit)
            (else (error "Unknown request -- MAKE-ACCOUNT" m)))))
  dispatch)

(define (make-account balance password)
  (define (withdraw amount)
    (if (>= balance amount) (begin (set! balance (- balance amount)) balance)
        "Insufficient funds"))
  (define (deposit amount)
    (set! balance (+ balance amount)) balance)
  (define (error-message amount)
    (display 'incorrect-password))
  (let ((incorrect-pass-count 0))
    (define (dispatch pass m)
        (if (not (eq? pass password))
          (begin
            (set! incorrect-pass-count (+ 1 incorrect-pass-count))
            (if (> incorrect-pass-count 7)
              call-the-cops
              error-message))
          (begin
            (set! incorrect-pass-count 0)
            (cond ((eq? m 'withdraw) withdraw)
                            ((eq? m 'deposit) deposit)
                            (else (error "Unknown request -- MAKE-ACCOUNT" m)))))))
  dispatch)