Adventures in Prolog - computations with Lists V

Today's post presents a predicate defined for lists that is as simple as yesterdays rem_dups/2. flatten/2 is concerned with flattening an arbitrary list to a one-dimensional list/array.The idea behind flatten is pretty simple, i.e. if a list is non-flat we lower its dimensionality by taking theinner of that list and process it further until we reach a one-dimensional list.

%flatten/2
flatten([], []).
flatten([[]], []).
flatten([[HT]], X) :- flatten([HT], X).
flatten([[H]T], X) :- flatten([HT], X).
flatten([H[T]], X) :- flatten([HT], X).
flatten([HT], X) :-
flatten(T, Y),
append([H], Y, X).