fact: Axiom replace_at_pos_list_replace_at_pos_in_subterm : forall l1 ui l2 u i p, length l1 = i -> replace_at_pos_list (l1 ++ ui :: l2) u i p = l1 ++ (replace_at_pos ui u p) :: l2.
imports: List more_list list_permut list_set Arith