/* Learning rules for correct chess moves */
/* move(king,a,1,a,2) means move from pos(a,1) to pos(a,2) */
/* Negative examples are used to allow anonymous head variables */

background([fdiff/3,rdiff/3]).
propositional([knight,bishop,rook,queen,king,d(1),d(2)]).

/* Complete lambda model for move(king,a,1,a,2) */
move(king,a,1,a,2).
move(king,a,3,a,2).
/* Complete lambda model for move(king,a,1,b,1) */
move(king,a,1,b,1).
move(king,c,1,b,1).
/* Complete lambda model for move(king,a,1,b,2) */
move(king,a,1,b,2).
move(king,a,3,b,2).
move(king,c,1,b,2).
move(king,c,3,b,2).

/* Complete lambda model for move(knight,c,4,b,6) */
move(knight,c,4,b,6).
move(knight,c,4,b,2).
move(knight,c,4,d,2).
move(knight,c,4,d,6).
move(knight,a,4,b,6).
move(knight,a,8,b,6).
move(knight,c,8,b,6).

/* Complete lambda model for move(knight,f,1,h,2) */
move(knight,f,1,h,2).
move(knight,f,1,d,2).
move(knight,f,3,h,2).

/* Complete lambda model for move(bishop,c,4,f,7) */
move(bishop,c,4,f,7).
move(bishop,c,4,f,1).

move(rook,b,2,e,2).
move(rook,b,2,b,3).
/* Negative example to specify don't care arguments */
neg(move(rook,b,2,e,3)).

move(queen,f,1,c,4).
move(queen,f,7,c,4).
move(queen,b,2,e,2).
move(queen,a,4,a,5).

/* Negative examples to specify don't care arguments */
neg(move(queen,b,2,e,3)).
neg(move(queen,a,4,d,5)).

/* Background knowledge */

rdiff(Rank1,Rank2,d(Diff)) :-
    rank(Rank1), rank(Rank2),
    Diff1 is Rank1-Rank2,
    abs(Diff1,Diff),
    Diff < 4.

fdiff(File1,File2,d(Diff)) :-
   file(File1), file(File2),
   project(File1,Rank1),
   project(File2,Rank2),
   Diff1 is Rank1-Rank2,
   abs(Diff1,Diff),
   Diff < 4.

abs(X,X) :- X>=0.
abs(X,Y) :- X<0, Y is -X.

file(a).
file(b).
file(c).
file(d).
file(e).
file(f).
file(g).
file(h).

rank(1).
rank(2).
rank(3).
rank(4).
rank(5).
rank(6).
rank(7).
rank(8).

project(a,1).
project(b,2).
project(c,3).
project(d,4).
project(e,5).
project(f,6).
project(g,7).
project(h,8).