计算机程序的构造和解释习题3.33

计算机程序的构造和解释习题3.33

SICP Exercise 3.33

This is similar as the celsius-fahrenheit-converter procedure.

 ;;;Exercise 3.33
 ;;;average
 (define (averager a b c)
   (let ((half (make-connector))
         (sum (make-connector)))
     (constant 0.5 half)
     (adder a b sum)
     (multiplier half sum c)
     'ok))

the test code is:

 ;;;test averager
 (define a (make-connector))
 (define b (make-connector))
 (define c (make-connector))
 (set-value! a 5 'user)
 (probe "b" b)
 (probe "c" c)
 (define average (averager a b c))
 (set-value! b 6 'user)