% permutations.pl
% A Prolog program for finding all permutations of a list.
% S. Tanimoto, Spring 2003.

remove(H, [H|T], T).
remove(A, [H|T], [H|B]) :- remove(A, T, B).

permutation([], []).
permutation([H|T], X) :- remove(H, X, Y), permutation(T, Y).

% permutation(X, [fee,fie,foe,foo]).