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% KRK illegal problem. This involves deciding whether a chess ending
%	with White King, White Rook and Black King is illegal
%	when White is to move. Example positions are defined as
%
%	illegal(WKRank,WKFile,WRRank,WRFile,BKRank,BKFile)
%
%	Thus the following illegal position is defined as follows:
%
%	      File
%	|~~~~~~~~~~~~~~~~| 7
%	|  WK            | 6
%	|                | 5
% Rank  |                | 4    =  illegal(6,1,3,2,3,7)
%	|    WR        BK| 3
%	|                | 2
%	|                | 1
%	|________________| 0
%	  0 1 2 3 4 5 6 7

% Background knowledge - adj(R/C,R/C)
adj(0,0).
adj(1,1).
adj(2,2).
adj(3,3).
adj(4,4).
adj(5,5).
adj(6,6).
adj(7,7).
adj(0,1).
adj(1,2).
adj(2,3).
adj(3,4).
adj(4,5).
adj(5,6).
adj(6,7).
adj(7,6).
adj(6,5).
adj(5,4).
adj(4,3).
adj(3,2).
adj(2,1).
adj(1,0).

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% Positive examples

pos(illegal(7,2,5,0,6,1)).
pos(illegal(6,1,5,0,6,1)).
pos(illegal(6,0,5,0,6,1)).
pos(illegal(6,2,5,0,6,1)).
pos(illegal(5,1,5,0,6,1)).
pos(illegal(5,0,5,0,6,1)).
pos(illegal(5,2,5,0,6,1)).
pos(illegal(7,1,5,0,6,1)).
pos(illegal(7,0,5,0,6,1)).
pos(illegal(7,2,5,0,7,2)).
pos(illegal(7,2,5,0,7,3)).
pos(illegal(7,2,5,0,7,1)).
pos(illegal(7,2,5,0,6,2)).
pos(illegal(7,2,5,0,6,3)).

pos(illegal(5,2,5,2,7,3)).
pos(illegal(4,3,5,2,7,2)).
pos(illegal(0,1,5,2,5,4)).
pos(illegal(1,3,2,4,6,5)).

% Negative examples

neg(illegal(7,2,5,0,3,4)).
neg(illegal(7,2,5,0,4,1)).
neg(illegal(7,2,5,0,6,4)).
neg(illegal(4,3,5,2,7,3)).
neg(illegal(0,1,5,2,6,4)).
neg(illegal(1,3,2,4,6,5)).