. intro
  | Or.inl h =>
    cases h with
    | intro n r =>
      exists n
      exact r.right
  | Or.inr e => exists 0
case h.mp
α : Type u_1
L : Language α
w : Word α
⊢ w ∈ L⁺ ∪ {ε} → w ∈ L∗

case h.mpr
α : Type u_1
L : Language α
w : Word α
⊢ w ∈ L∗ → w ∈ L⁺ ∪ {ε}
case h.mpr
α : Type u_1
L : Language α
w : Word α
⊢ w ∈ L∗ → w ∈ L⁺ ∪ {ε}