exact ⟨rfl, rfl⟩
case a
α : Type u_1
σ : Stream' α
x : α
f : α → ℕ
g : α → α
⊢ match (f x, corec f g (g x)) with
  | (acc₁, σ) =>
    match (f x, g x) with
    | (acc₂, x) => acc₁ = acc₂ ∧ σ = corec f g x
no goals