연습문제 3.37

(define (c+ x y)
  (let ((z (make-connector)))
    (adder x y z)
    z))

(define (c* x y)
  (let ((z (make-connector)))
    (multiplier x y z))
  z)

(define (c/ x y)
  (let ((z (make-connector)))
    (multiplier x z y))
  z)

(define (cv n)
  (let ((a (make-connector)))
    (constant n a)
    a))