fact: Fixpoint is_eq (n m : nat) : {n = m} + {True} := match n, m return {n = m} + {True} with | 0, 0 =>left True (eq_refl 0) | 0, S m1 => right (0 = S m1) I | S n1, 0 => right (S n1 = 0) I | S n1, S m1 => match is_eq n1 m1 with | left H => left True (f_equal S H) | right _ => right (S n1 = S m1) I end end.
imports: Eqdep_dec Streams