scheme example

gistfile1.txt

(define (make-account balance)
  (define (withdraw amount)
    (if (>= balance amount)
      (begin (set! balance (- balance amount))
              balance)
      "Недостаточно денег на счете"))
  (define (deposit amount)
    (set! balance (+ balance amount))
      balance)
  (define (dispatch m)
    (cond ((eq? m ’withdraw) withdraw)
          ((eq? m ’deposit) deposit)
          (else (error "Неизвестный вызов -- MAKE-ACCOUNT"
                      m))))
  dispatch)