Question

I’m having a bit of a problem with a Prolog exercise.

Assume i have a list of actors that have won oscars. Like this:

(steven spielberg, steven spielberg, francis ford coppola, michael curtiz)

When a name appears two times, it means that the person won 2 oscars and so on. What i need to do is to go trough this list and find every actor that won N or more Oscars, with a predicate like

wonMoreOscars(Number, Activity):-

Where the number is the N we have to compare with the list.
I already have a function that counts the person that occurs the more times in a list and the activity the function that person has in the movie, but is already covered.

Can somebody help me, i have the code to find the person who has won more Oscars:

occS([],_,_,_,_):-write(0),nl,write('+'),nl, !.
occS([H|T],_,_,_,_):-occ([H|T],0,0,H,H).
occ([],_,Top,_,Nome):-write(Nome),nl,write(Top),nl,write('+'),nl, !.
occ([H|T],Count,Top,El_corrente,_):- compare(=,H,El_corrente),C is Count +      1,C>=Top,occ(T,C,C,El_corrente,El_corrente), !.
occ([H|T],_,Top,El_corrente,Nome):- not(compare(=,H,El_corrente)),occ(T,1,Top,H,Nome),!.
occ([H|T],Count,Top,_,Nome):- C is Count + 1,occ(T,C,Top,H,Nome), !.

But now i’m having trouble with this case.

Answer 1

I assume you want to write a predicate that takes a number and a list of actors and returns a list of those that are in the list at least specified-number-times (wonMoreOscars(Number, Activity) doesn’t have enough parameters). You can do it like this:

oscars(N, T, R) :- oscars(N, T, [], R).

oscars(N, [], A, R) :- countOscars(N, A, R).
oscars(N, [H|T], A, R) :- addOscar(H, A, A1), oscars(N, T, A1, R).

addOscar(H, [], [(H, 1)]).
addOscar(H, [(H,N)|T], [(H,N1)|T]) :- N1 is N + 1, !.
addOscar(H, [HA|T], [HA|T1]) :- addOscar(H, T, T1).

countOscars(_, [], []).
countOscars(N, [(H,HN)|T], [H|TR]) :- HN >= N, countOscars(N, T, TR), !.
countOscars(N, [_|T], TR) :- countOscars(N, T, TR).