ploua.

% parinte(Copil, Parinte)
parinte(gheorghe, ion).
parinte(gheorghe, ana).
parinte(vasile, gheorghe).
parinte(vasile, florica).

% ?- parinte(gheorghe, ion).
% ?- parinte(gheorghe, X).
% ?- parinte(gheorghe, _).
% ?- parinte(X, Y).
% ?- parinte(florica, X).
% ?- parinte(florica, _).

% bunic(Nepot, Bunic)
bunic(X, Y) :- parinte(X, Z), parinte(Z, Y).

% ?- bunic(Nepot, Bunic)





% Alice came across a lion and a unicorn in a forest of forgetfulness.
% Those two are strange beings.
% The lion lies every Monday, Tuesday and Wednesday
%	and the other days he speaks the truth.
% The unicorn lies on Thursdays, Fridays and Saturdays,
%	however the other days of the week he speaks the truth.
% Lion: Yesterday I was lying.
% Unicorn: So was I.
% Which day did they say that?

yesterday(mon, sun).
yesterday(tue, mon).
yesterday(wed, tue).
yesterday(thu, wed).
yesterday(fri, thu).
yesterday(sat, fri).
yesterday(sun, sat).

lies(lion, [mon, tue, wed]).
lies(unicorn, [thu, fri, sat]).

% Animal spune azi (Today) ca ieri a mintit
saysItLiedYesterday(Animal, Today) :-
	yesterday(Today, Yesterday),
	lies(Animal, DaysLies),  % obtine DaysLies
	not(member(Today, DaysLies)), % azi minte
	member(Yesterday, DaysLies).

saysItLiedYesterday(Animal, Today) :-
	yesterday(Today, Yesterday),
	lies(Animal, DaysLies),
	member(Today, DaysLies),
	not(member(Yesterday, DaysLies)).

% solutia
sol(Today) :- saysItLiedYesterday(lion, Today), saysItLiedYesterday(unicorn, Today).



% myMember(+Elem, +Lista)
myMember(_, []) :- fail. % lista vida nu poate contine elementul. Aceasta linie poate sa lipseasca.
% myMember(E, [H|_]) :- E == H.
myMember(E, [E|_]). % elementul este primul element din lista
myMember(E, [H|T]) :- E \= H, myMember(E, T). % elementul nu este primul din lista.

% incL(+Lin, -Lout)
incL([], []).
%incL([H|T], LO) :- H1 is H + 1, incL(T, T1), LO = [H1|T1].
incL([H|T], [H1|T1]) :-
	H1 is H + 1,
	incL(T, T1).