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Question

In the exercise the first thing I need is to get some facts, stating the existence of one place each, into a list. Someone help me please.

example.
exists(place).
exists(place2).

Code so far:

listarB([]).
listarB([B|T]):- exists(B),listarB(T).

Now I tried to get a list of lists. Each list I need is held as an argument of each of the places i was trying to get.
Now that I have the list of places I tried to get the lists each of them has as an argument and store them in another list([HL|TL])

Code so far:

listListBus([],[]).
listListBus([HB|TB],[HL|TL]) :-
   HB = base(_,[_|_],HL),
   listListBus(TB,TL).      

Answer 1

You should use findall/3 to collect all the places that "exist":

listarB(L):-
  findall(B, exists(B), L).