module aux.

type split    list A -> list A -> list A -> o.

split nil nil nil.
split (X::L) (X::K) M :- split L K M.
split (X::L) K (X::M) :- split L K M.

type membNrest     A -> list A -> list A -> o.

membNrest X (X::Rest) Rest.
membNrest X (Y::Tail) (Y::Rest) :- membNrest X Tail Rest.

type memb     A -> list A -> o.

memb X (X::Rest).
memb X (Y::Tail) :- memb X Tail.