The Art of Prolog - Exercise 2.1 Pag. 34

gistfile1.pl

% The Art of Prolog - 2nd Edition
% Exercise 2.1 pag. 34

father(terach, abraham).
father(terach, nachor).
father(terach, haran).
father(abraham, isaac).
father(haran, lot).
father(haran, milcah).
father(haran, yiscah).

mother(sarah, isaac).

male(terach).
male(abraham).
male(nachor).
male(haran).
male(isaac).
male(lot).

female(sarah).
female(milcah).
female(yiscah).

married_couple(sarah, abraham).

% Rules
parent(X, Y) :- father(X, Y).
parent(X, Y) :- mother(X, Y).

uncle(Uncle, Person) :- 
	brother(Uncle, Parent), 
	parent(Parent, Person).

niece(Niece, Person) :- 
	sibling(Parent, Person),
	parent(Parent, Niece),
	female(Niece).

sibling(Sib1, Sib2) :- 
	parent(Parent, Sib1), 
	parent(Parent, Sib2), 
	Sib1 =\= Sib2.

full_sibling(Sib1, Sib2) :- 
	father(Father, Sib1), 
	father(Father, Sib2), 
	mother(Mother, Sib1), 
	mother(Mother, Sib2), 
	Sib1 =\= Sib2.

brother(Brother, Sib) :- 
	parent(Parent, Brother), 
	parent(Parent, Sib), 
	male(Brother), 
	Brother =\= Sib.

sister(Sister, Sib) :- 
	parent(Parent, Sister), 
	parent(Parent, Sib), 
	female(Sister), 
	Sister =\= Sib.

% This is what in Italian we call 'Suocera', so she is the mother of the Wife or 
% the mother of the husband.
mother_in_law(MotherInLaw, Husband) :- 
	married_couple(Wife, Husband),
	mother(MotherInLaw, Wife).
mother_in_law(MotherInLaw, Wife) :-
	married_couple(Wife, Husband),
	mother(MotherInLaw, Husband).

% This is what in Italian we call 'Genero', so he is the husband of a female.
son_in_law(SonInLaw, Parent) :- 
	married_couple(Wife, SonInLaw),
	parent(Parent, Wife).

% This is wht in Italian we call 'Cognato', so he is the:
% 1- brother of the husband
brother_in_law(BrotherInLaw, Wife) :- 
	married_couple(Wife, Husband),
	brother(BrotherInLaw, Husband).
% 2- brother of the wife
brother_in_law(BrotherInLaw, Husband) :-
	married_couple(Wife, Husband),
	brother(BrotherInLaw, Wife).
% 3- the husband of the sister (it is not legally possible to have the opposite)
brother_in_law(BrotherInLaw, Sister) :-
	married_couple(Wife, BrotherInLaw),
	sister(Wife, Sister).