simp only [Function.updateITE]
α β : Type
inst✝ : DecidableEq α
f g : α → β
x : α
h1 : f x = g x
xs_hd : α
xs_tl : List α
xs_ih : ∀ (ys : List α), updateListITE f xs_tl (List.map f ys) x = updateListITE g xs_tl (List.map f ys) x
ys_hd : α
ys_tl : List α
⊢ updateITE (updateListITE f xs_tl (List.map f ys_tl)) xs_hd (f ys_hd) x =
    updateITE (updateListITE g xs_tl (List.map f ys_tl)) xs_hd (f ys_hd) x
α β : Type
inst✝ : DecidableEq α
f g : α → β
x : α
h1 : f x = g x
xs_hd : α
xs_tl : List α
xs_ih : ∀ (ys : List α), updateListITE f xs_tl (List.map f ys) x = updateListITE g xs_tl (List.map f ys) x
ys_hd : α
ys_tl : List α
⊢ (if x = xs_hd then f ys_hd else updateListITE f xs_tl (List.map f ys_tl) x) =
    if x = xs_hd then f ys_hd else updateListITE g xs_tl (List.map f ys_tl) x