case H0
α : Type u_1
β : Type ?u.16380
h : [] ≠ []
⊢ join (drop (length [] - 1) []) = getLast [] h

case H1
α : Type u_1
β : Type ?u.16380
l✝ : List (List α)
a✝¹ : List α
a✝ : ∀ (h : l✝ ≠ []), join (drop (length l✝ - 1) l✝) = getLast l✝ h
h : l✝ ++ [a✝¹] ≠ []
⊢ join (drop (length (l✝ ++ [a✝¹]) - 1) (l✝ ++ [a✝¹])) = getLast (l✝ ++ [a✝¹]) h
α : Type u_1
β : Type ?u.16380
L : List (List α)
h : L ≠ []
⊢ join (drop (length L - 1) L) = getLast L h
induction L using List.reverseRecOn
no goals
case H0
α : Type u_1
β : Type ?u.16380
h : [] ≠ []
⊢ join (drop (length [] - 1) []) = getLast [] h
cases h rfl
no goals
case H1
α : Type u_1
β : Type ?u.16380
l✝ : List (List α)
a✝¹ : List α
a✝ : ∀ (h : l✝ ≠ []), join (drop (length l✝ - 1) l✝) = getLast l✝ h
h : l✝ ++ [a✝¹] ≠ []
⊢ join (drop (length (l✝ ++ [a✝¹]) - 1) (l✝ ++ [a✝¹])) = getLast (l✝ ++ [a✝¹]) h
simp