cases' i using Fin.cases with i <;> simp
case e_v.h
L : Language
M : Type w
s : Structure L M
n✝ : ℕ
e : Fin n✝ → M
ξ✝ : Type u_1
ε : ξ✝ → M
o : Operator L 2
t u : Semiterm L ξ✝ n✝
i : Fin 2
⊢ val s e ε (![t, u] i) = ![val s e ε t, val s e ε u] i
no goals