Require Export Coq.Logic.Classical.
Require Export Coq.Logic.Classical_Prop.
Require Export Coq.Logic.FunctionalExtensionality.
Require Export Coq.Classes.Equivalence.
Require Export Coq.Classes.Morphisms.
Definition stream (A: Type): Type := {h: nat -> option A | forall x y, x < y -> h x = None -> h y = None}.
Definition stream_get {A: Type} (h: stream A) (n: nat) := proj1_sig h n.
Coercion stream_get: stream >-> Funclass.

Lemma stream_extensionality {A: Type}: forall h1 h2: stream A, (forall n, h1 n = h2 n) -> h1 = h2.
Tactic Notation "stream_extensionality" ident(x) :=
match goal with
[ |- ?X = ?Y ] =>
apply stream_extensionality; intro x
end.