Definition eqST (cp1 cp2 : tST) :=
eqList (PosSort.sort (CPToList cp1)) (PosSort.sort (CPToList cp2)).

Lemma sortOK : forall m l, length l = m -> length (sort l) = m.
Definition ltST (cp1 cp2 : tST) :=
ltList (PosSort.sort (CPToList cp1)) (PosSort.sort (CPToList cp2)).