;-*- Mode: Lisp; Syntax: Common-lisp -*- ;;;; N-Queens rules, JTRE version ;;; Last edited 1/29/93, by KDF. ;;; Copyright (c) 1986 --- 1992 Kenneth D. Forbus, Northwestern University, ;;; Johan de Kleer and Xerox Corporation. ;;; All rights reserved. ;;; See the file legal.txt for a paragraph stating scope of permission ;;; and disclaimer of warranty. The above copyright notice and that ;;; paragraph must be included in any separate copy of this file. (in-package :COMMON-LISP-USER) (contradiction 'Queens-capture *jtre*) (rule ((:IN (Queen ?column1 ?row1) :VAR ?Q1) (:IN (Queen ?column2 ?row2) :VAR ?Q2 :TEST (not (or (= ?column1 ?column2) (queens-okay? ?column1 ?row1 ?column2 ?row2))))) (rassert! Queens-capture (Death ?Q1 ?Q2)))