
% file: parallel
% query: should_marry(john, susan)?
% query: should_marry(isaac, rebeccah)?

father(tom, john).	male(john).
father(bill,susan).	female(susan).
brother(tom, bill).

son(X,Y) :-
	father(Y,X),
	male(X).
brother(X,Y) :-
	father(Fa,X),
	father(Fa,Y),
	male(Y),
	X /= Y.

should_marry(X,Y) :-
	father(Br1,X), male(X),
	father(Br2,Y),	female(Y),
	brother(Br1,Br2).

brother(abraham, nahor).
father(nahor, bethuel).
father(bethuel, rebeccah).	female(rebeccah).
father(abraham, isaac).		male(isaac).

should_marry(X,Y) :-
	father(Br1,X),	male(X),
	father(Br2,Z),	father(Z,Y), female(Y),
	brother(Br1,Br2).

