%query: perm(i,o). perm([],[]). perm([X|Y],[U|V]) :- delete(U,[X|Y],W),perm(W,V). delete(X,[X|Y],Y). delete(U,[X|Y],[X|Z]) :- delete(U,Y,Z). /*TWDESC Permutation of a list. uses delete/3. */ /*TWDEMO selected_norms([listlength]). */ /*. */