SWI Prolog does not terminate

Question

:- use_module(library(clpfd)).

fact(treated=A) :- A in 0..1.
fact(numYears=B) :- B in 0..sup.
fact(numDrugs=C) :- C in 0..sup.
fact(treated2=D) :- D in 0..1.
fact(cParam=E) :- E in 0..4.

is_differentfact(X,X) :- false.
is_differentfact(Element=_,OtherElement=_) :-
    dif(Element,OtherElement).

is_fakt([]).
is_fakt([X|Xs]) :-
    fact(X),
    maplist(is_differentfact(X),Xs),
    is_fakt(Xs).

Why does ?- is_fakt(X) return a list of results answers but after a number of results answers it hangs. I don't know why Prolog cannot return all possible values of X.

Answer 1

Edited version based on the comments of false.

:- use_module(library(clpfd)).
:- use_module(library(lists)).

fact(treated-X) :- X in 0..1.
fact(numYears-X) :- X in 0..sup.
fact(numDrugs-X) :- X in 0..sup.
fact(treated2-X) :- X in 0..1.
fact(cParam-X) :- X in 0..4.

facts(Facts) :-
findall(X,fact(X),Facts).

is_fact2(_, []).
is_fact2(Facts, [X|Xs]) :-
    member(X,Facts),
    select(X,Facts,Remaining),
    is_fact2(Remaining,Xs).

is_fakt(X) :-
    facts(Facts),
    is_fact2(Facts,X),
    keysort(X,X).

This terminates now.