anchor.diff:    (propagate)
     (set-signal! input-2 1)
     (propagate))
  +
  +;;;电路设计只是一个例子，其中的设计思路是值得思考的。好好想一想，在大脑里模拟整个程序的运行过程。
  +
  +;;;;约束的传播
  +
  +(defvar *C* (make-connector))
  +(defvar *F* (make-connector))
  +(celsius-fahrenheit-converter *C* *F*)
  +
  +(defun celsisus-fahrenheit-converter (*C* *F*)
  +  (let ((u (make-connector))
  +	(v (make-connector))
  +	(w (make-connector))
  +	(x (make-connector))
  +	(y (make-connector)))
  +    (multiplier c w u)
  +    (multiplier v x u)
  +    (adder v y f)
  +    (constant 9 w)
  +    (constant 5 x)
  +    (constant 32 y)
  +    'ok))
  +
  
positive.code:   (cond ((or (= s1 1) (= s2 1)) 1)
  	(t 0)))
  ;;;;3.29
  (defun or-gate (a1 a2 output)
    (let ((na1 (make-wire))
  	(na2 (make-wire))
  	(na1a2 (make-wire)))
  
negative.code: (defparameter *and-gate-delay* 3)
  (defparameter *or-gate-delay* 5)
  (defvar the-agenda (make-agenda))
  (setq the-agenda (make-agenda))
  ;;;定义一个监测器
  (defun probe (name wire)
    (add-action! wire
  