SWISH -- SWI-Prolog for SHaring

:- use_module(library(clpfd)).

% Works but returns all possible results, which is infinte and useless.
members([], _).
members([X|Xs], List) :-
  member(X,List),
  members(Xs, List).

% Restricts the results to only the ones with a certain length, more useful.  Terminates.  Good stuff.
membersWithLength(Members, List, Bound) :-
  L = Bound,
  length(Members, L),  members(Members, List).

% Kind of works.  Finds the right results (lists with length less than Bound).
% But it loops continuously searching for more results even after it has found the correct ones.
membersLessThan(Members, List, Bound) :-
  L in 0..Bound,  % I also tried L #=< Bound here.  Same problem.
  membersWithLength(Members, List, L).

% Works.  Finds all the lists with length less than or equal to Bound.  Terminates.  Good stuff.
% But it disapponted me that I could not figure out how to use clp to bound the search.
membersLessThan_(Members, List, Bound) :-
  numlist(0,Bound,ZeroToBound),
  member(L, ZeroToBound),
  membersWithLength(Members, List, L).