ext i b
α : Type u
inst✝¹ : DecidableEq α
β : Type v
inst✝ : DecidableEq β
n : ℕ
g : α → β
as : List α
h : n = as.length
⊢ (ofFn fun i => g (as.get (Fin.cast h i))) = map g as
case a.a
α : Type u
inst✝¹ : DecidableEq α
β : Type v
inst✝ : DecidableEq β
n : ℕ
g : α → β
as : List α
h : n = as.length
i : ℕ
b : β
⊢ b ∈ (ofFn fun i => g (as.get (Fin.cast h i))).get? i ↔ b ∈ (map g as).get? i