%#############################################

% Ex: 1.2

%#############################################

/*

male(albert).

male(edward).

female(alice).

female(alice).

parents(edward,victoria,albert).

parents(alice,victoria,albert).

sister_of(X,Y):-

female(X),

parents(X,M,F),

parents(Y,M,F).

*/

%---------------------------------------------

% use “;” to give the next answer

/* ANSWER:

?- sister_of(X,Y).

X = alice

Y = edward ;

X = alice

Y = alice ;

X = alice

Y = edward ;

X = alice

Y = alice ;

*/

%#############################################

% Ex: 1.3

%#############################################

/*********************************************

male(X).

female(X).

father(X,Y).

mother(X,Y).

parent(X,Y):-father(X,Y).

parent(X,Y):-mother(X,Y).

diff(X,Y):-not(X==Y)

*********************************************/

% test database

% jeo is the father of adam and eve,grandfather of felix,kate

% adam, eve are married

% felix,kate are childrens

male(jeo).

male(adam).

male(felix).

female(eve).

female(kate).

father(jeo,adam).

father(jeo,eve).

father(adam,felix).

father(adam,kate).

mother(eve,felix).

mother(eve,kate).

parent(X,Y):-father(X,Y).

parent(X,Y):-mother(X,Y).

diff(X,Y):-not(X==Y).

%###########################################

% ANSWERS:

%###########################################

is_mother(X):-female(X),parent(X,_).

is_father(X):-male(X),parent(X,_).

is_son(X):-male(X),parent(_,X).

sister_of(X,Y):-female(Y),parent(_,Y),diff(X,Y).

grandpa_of(X,Y):-male(X),father(X,Z),parent(Z,Y).

sibling(X,Y):-parent(Z,X),parent(Z,Y),diff(X,Y).