% Manual Prolog
% http://www.swi-prolog.org/pldoc/doc_for?object=manual
% http://www.swi-prolog.org/pldoc/man?section=builtin



% programul: descrie ce este adevărat, eventual în funcție de condiții.
p(1).
p(2).
p(a).
p([1,2,3]).


q(X, Y) :- p(X), p(Y).

% predicatul r este adevărat dacă ambele argumente ale lui sunt același lucru și dacă p(argument al lui q) este adevărat
r(X, X) :- p(X).


%t(X) :- \+ p(X). % nu va găsi soluții singur.
% putem pune predicatul să găsească soluții dacă avem un domeniu.
t(X) :- member(X, [1,2,3,4,5,a,b,c,d]), \+ p(X).



% 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
	\+ member(Today, DaysLies), % azi minte
	member(Yesterday, DaysLies).

saysItLiedYesterday(Animal, Today) :-
	yesterday(Today, Yesterday),
	lies(Animal, DaysLies),
	member(Today, DaysLies),
	\+ member(Yesterday, DaysLies).

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


% mem/2
% mem(+E, +L)
mem(_, []) :- false. % lista vida nu poate contine elementul. Aceasta linie poate sa lipseasca.
mem(E, [H | _]) :- E = H. % elementul este primul element din lista
mem(E, [H | T]) :- E \= H, mem(E, T). % elementul nu este primul din lista.

mem2(E, [E | _]).
mem2(E, [_ | T]) :- mem2(E, T).

mem3(E, [H|T]) :- E = H; mem3(E, T).




% sumList/2
% sumList(+L, -Sum)

sumList([], 0).
sumList([H|T], Sum) :- sumList(T, SumTail), Sum is H + SumTail.


% map (+1)
incList(L, LInc) :- L = [], LInc = [].
incList(L, LInc) :-
	L = [H | T],
	LInc = [HInc | TInc],
	HInc is H + 1,
	incList(T, TInc).

incList2([], []).
incList2([H | T], [HInc | TInc]) :- HInc is H + 1, incList2(T, TInc).