simp [pos_app (H := H) σ (Vector.ε' h)]
Δ : RankedAlphabet
H : Type
σ : Δ.alphabet
h : RankedAlphabet.rank Δ σ = 0
⊢ Hom.hom pos (app σ (Vector.ε' h)) = Set.singleton Word.ε
Δ : RankedAlphabet
H : Type
σ : Δ.alphabet
h : RankedAlphabet.rank Δ σ = 0
⊢ (fun x =>
      match x with
      | [] => True
      | i :: tl => ∃ h_1, tl ∈ Hom.hom pos (Vector.ε' h { val := i, isLt := h_1 })) =
    Set.singleton Word.ε