% -------------------------------------------------------
% Naive Bayes Belief Network plugin for Eye -- Jos De Roo
% -------------------------------------------------------

% unplug the Full Bayes Belief Network builtin
:- abolish('<http://eulersharp.sourceforge.net/2003/03swap/log-rules#biconditional>'/2).

% plugin the Naive Bayes Belief Network builtin
'<http://eulersharp.sourceforge.net/2003/03swap/log-rules#biconditional>'(['<http://eulersharp.sourceforge.net/2003/03swap/log-rules#boolean>'(A,B)|C],D) :-
	within_span(1), (bb_get(bnet,done) -> true; bnet, bb_put(bnet,done)), bvar(A), bval(B),
	nb('<http://eulersharp.sourceforge.net/2003/03swap/log-rules#boolean>'(A,B),C,D).

nb(A,B,1.0) :-
	memberchk(A,B), !.
nb('<http://eulersharp.sourceforge.net/2003/03swap/log-rules#boolean>'(A,'<http://eulersharp.sourceforge.net/2003/03swap/log-rules#T>'),B,0.0) :-
	memberchk('<http://eulersharp.sourceforge.net/2003/03swap/log-rules#boolean>'(A,'<http://eulersharp.sourceforge.net/2003/03swap/log-rules#F>'),B), !.
nb('<http://eulersharp.sourceforge.net/2003/03swap/log-rules#boolean>'(A,'<http://eulersharp.sourceforge.net/2003/03swap/log-rules#F>'),B,C) :-
	memberchk('<http://eulersharp.sourceforge.net/2003/03swap/log-rules#boolean>'(A,'<http://eulersharp.sourceforge.net/2003/03swap/log-rules#T>'),B), !, C is 0.0
	; !, nb('<http://eulersharp.sourceforge.net/2003/03swap/log-rules#boolean>'(A,'<http://eulersharp.sourceforge.net/2003/03swap/log-rules#T>'),B,D), C is 1-D.
nb(A,B,C) :-
	bcnd([A,D],E), !, nb(D,B,F), inverse(D,G), bcnd([A,G],H), C is F*E+(1-F)*H
	; nc(A,B,D), !, inverse(A,E), nc(E,B,F), C is 1/(1+2**(F-D)).

nc(_,[],0.0) :- !.
nc(A,[B|C],D) :-
	(bcnd([B,A],E); inverse(B,F), bcnd([F,A],G), E is 1-G; E is 1.0), !, (E =:= 0 -> I = 1e-16; I = E), nc(A,C,H), D is log(I)/log(2)+H.