;;; -*- Mode: Lisp; Syntax: Common-Lisp; -*-
;;; Code from Paradigms of Artificial Intelligence Programming
;;; Copyright (c) 1991 Peter Norvig

> (gps '(son-at-home car-needs-battery have-money have-phone-book)
       '(son-at-school)
       *school-ops*)
(EXECUTING LOOK-UP-NUMBER) 
(EXECUTING TELEPHONE-SHOP) 
(EXECUTING TELL-SHOP-PROBLEM) 
(EXECUTING GIVE-SHOP-MONEY) 
(EXECUTING SHOP-INSTALLS-BATTERY) 
(EXECUTING DRIVE-SON-TO-SCHOOL) 
SOLVED

> (gps '(son-at-home car-needs-battery have-money)
       '(son-at-school)
       *school-ops*)
NIL 

> (gps '(son-at-home car-works)
       '(son-at-school)
       *school-ops*)
(EXECUTING DRIVE-SON-TO-SCHOOL) 
SOLVED

;;; ==============================

> (gps '(son-at-home have-money car-works)
       '(have-money son-at-school)
       *school-ops*)
(EXECUTING DRIVE-SON-TO-SCHOOL) 
SOLVED

;;; ==============================

> (gps '(son-at-home car-needs-battery have-money have-phone-book)
       '(have-money son-at-school)
       *school-ops*)
(EXECUTING LOOK-UP-NUMBER) 
(EXECUTING TELEPHONE-SHOP) 
(EXECUTING TELL-SHOP-PROBLEM) 
(EXECUTING GIVE-SHOP-MONEY) 
(EXECUTING SHOP-INSTALLS-BATTERY) 
(EXECUTING DRIVE-SON-TO-SCHOOL) 
SOLVED