generalize hw : w ⟨0, stringAlgebra.proof_1⟩ = w'
Γ : Type
inst✝ : Alphabet Γ
σ : Γ
w : (Γ⋆)⋆1
⊢ treeₑ (σ⬝w { val := 0, isLt := stringAlgebra.proof_1 }) = app (some σ) (treeₑ ∘ w)
Γ : Type
inst✝ : Alphabet Γ
σ : Γ
w : (Γ⋆)⋆1
w' : Γ⋆
hw : w { val := 0, isLt := stringAlgebra.proof_1 } = w'
⊢ treeₑ (σ⬝w') = app (some σ) (treeₑ ∘ w)