Prolog Remove Duplicates

[Krytikal]

I am very new to prolog and I was wondering if am on the right approach to my programs specifications. I need to remove the duplicates from a list.

remove_duplicates([],_).
remove_duplicates([X|XS], Y) :-
member(X,Y),
remove_duplicates(XS,Y), !.
remove_duplicates([X|XS], Y) :-
\+member(X,Y),
remove_duplicates(XS,[Y|X]), !.

I have this so far and it works but I was wondering how I can use my program to confirm stuff like:

remove_duplicates([5,4,4,2,2], [5,4,2]).
and it will return true.

Thank you

 

[joel76]

You have two problems :
remove_duplicates([],_). You attach a free variable with an empty list this is why remove_duplicates([5,4,4,2,2], L). gives you [5, 4, 2 | GXXX].
You have also an error here remove_duplicates(XS,[Y|X]), !.
It should be remove_duplicates(XS,[X|Y]),but tou get [2, 4, 5] or append(Y, [X], Y1) and remove_duplicates(XS,[Y1),

The error is not seen because of your first mistake remove_duplicates([],_).