cases i
α : Type
x' : α
xs : List α
IH : ∀ (i : ℕ) (INBOUND : i < length xs), Mem (getF xs i INBOUND) xs
i : ℕ
INBOUND : i < length (x' :: xs)
⊢ Mem (getF (x' :: xs) i INBOUND) (x' :: xs)
case zero
α : Type
x' : α
xs : List α
IH : ∀ (i : ℕ) (INBOUND : i < length xs), Mem (getF xs i INBOUND) xs
INBOUND : Nat.zero < length (x' :: xs)
⊢ Mem (getF (x' :: xs) Nat.zero INBOUND) (x' :: xs)

case succ
α : Type
x' : α
xs : List α
IH : ∀ (i : ℕ) (INBOUND : i < length xs), Mem (getF xs i INBOUND) xs
n✝ : ℕ
INBOUND : Nat.succ n✝ < length (x' :: xs)
⊢ Mem (getF (x' :: xs) (Nat.succ n✝) INBOUND) (x' :: xs)