clen(X,[X|T]).
clen(X,[H|T]):-clen(X,T).

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

prunik([],_,[]).
prunik([H|A],B,[H|V]):-clen(H,B),!,prunik(A,B,V).
prunik([H|A],B,V):-prunik(A,B,V).

%?- prunik([1,2,3,4,5],[2,8,4,6],V).

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

sjednoceni([],B,B).
sjednoceni([H|A],B,[H|V]):-not(clen(H,B)),!,sjednoceni(A,B,V).
sjednoceni([H|A],B,V):-sjednoceni(A,B,V).

%kdyz je pouzit rez (!), nemusi byt v sjednoceni([H|A],B,V):-clen(H,B),sjednoceni(A,B,V).

%?- sjednoceni([1,2,3,4],[2,3,4,5],V).

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

%rozdil A-B
rozdil([],_,[]).
rozdil([H|A],B,[H|V]):-not(clen(H,B)),rozdil(A,B,B).
rozdil([H|A],B,V):-clen(H,B),rozdil(A,B,V).

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

cislo(1).
cislo(2).
cislo(3).

pis:-cislo(X),write(X),nl,fail.
%FAIL - nemuze skoncit. Od fail se odrazi a pomoci backtrackingu zkousi jine moznosti.
%?- pis.
pis.  %jinak kvuli fail vypise "pis" no, tekhle vypise yes


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

slovo:-repeat,write('Zadej slovo'),read(X),((X=konec;X=stop),!,write(X),fail).

%?- slovo.

/*
repeat nacita od uzivatele slova porad dokola
 kdyz neni fail, zepta se jedn jednou
 (X=konec,!,write(X),fail)   podminka, aby se to nezacyklilo :-)
 ukonci se to pozadi slova "konec", nebo "stop"
*/

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

nasob:-vstup(X),N is X*X,write('Druha mocnina '),write(X),write(' je '),write(N),nl.
%podprogram

%?- nasob.

vstup(X):-repeat,write('Zadej cislo v rozmezi 100-200'),nl,read(X),X>=100,X=<200,!.

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

termostat:-repeat,write('Je topeni zapnuto,vypnuto nebo ukonci program z/v/k: '),
    read(X),(X=k,!;write('Zadej teplotu: '),read(T),akce(X,T,V),write(V),fail).

%?- termostat.

akce(X,T,'Vypnete topeni'):-T>25,X=z,!.
akce(X,T,'Zapnete topeni'):-T<25,X=v,!.
akce(X,T,'Nedelej nic').

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