;;; This is one of the example programs from the textbook:
;;;
;;; Artificial Intelligence: 
;;; Structures and strategies for complex problem solving
;;;
;;; by George F. Luger and William A. Stubblefield
;;; 
;;; These programs are copyrighted by Benjamin/Cummings Publishers.
;;;
;;; We offer them for use, free of charge, for educational purposes only.
;;;
;;; Disclaimer: These programs are provided with no warranty whatsoever as to
;;; their correctness, reliability, or any other property.  We have written 
;;; them for specific educational purposes, and have made no effort
;;; to produce commercial quality computer programs.  Please do not expect 
;;; more of them then we have intended.
;;;

;;; Code to run a simple thermostat simulation,
;;; using the oops object oriented programming shell of chapter 15.
;;;
;;; to run the simulation, evaluate the contents of this file, 
;;; then evaluate a form such as 
;;;
;;;     (message 'room-327 'change-temp -5)
;;;
;;; or
;;;
;;;     (message 'thermostat-327 'change-setting 70)
;;;

(def-object 'thermostat 'object '((setting 65)))

(def-object 'room 'object '((temperature 65)))

(def-object 'heater 'object '((state 'off)))

(def-object 'room-327 'room '((thermostat 'thermostat-327)))

(def-object 'thermostat-327 'thermostat 
			    '((heater 'heater-327)(location 'room-327)))

(def-object 'heater-327 'heater 
			    '((location 'room-327)))

(def-method 'room 'change-temp
   #'(lambda (amount-of-change)
       (let ((new-temp (+ amount-of-change temperature)))
	   (message self 'set-value 'temperature new-temp)
	   (terpri)
	   (prin1 "temperature in ")
	   (prin1 self)
	   (prin1 " changes to ")
	   (prin1 new-temp)
	   (prin1 " degrees.")
	   (terpri)
	   (message thermostat 'check-temp))))

(def-method 'thermostat 'check-temp
   #'(lambda ()
       (cond ((< (message location 'show-value 'temperature) setting)
		 (message heater 'turn-on))
	     (t (message heater 'turn-off)))))

(def-method 'thermostat 'change-setting
   #'(lambda (temp)
       (message self 'set-value 'setting temp)
       (terpri)
       (prin1 "New setting of ")
       (prin1 self)
       (prin1 " is ")
       (prin1 temp)
       (prin1 "degrees.")
       (terpri)
       (message self 'check-temp)))

(def-method 'heater 'turn-on
   #'(lambda ()
      (cond  ((equal state 'off)
		   (terpri)
		   (prin1 "Heater turns on in ")
		   (prin1 location) (terpri)
		   (message self 'set-value 'state 'on)))
      (message location 'change-temp 1)))

(def-method 'heater 'turn-off
   #'(lambda ()
      (cond ((equal state 'on)
		   (terpri)
		   (prin1 "Heater turns off in ")
		   (prin1 location) (terpri)
		   (message self 'set-value 'state 'off)))))