rw [cons_append, nil_append]
α β : Type u
γ : Type w
f : α → β
a : α
as : List α
⊢ ([f a] ++ List.bind as fun a => [f a]) = f a :: map f as
α β : Type u
γ : Type w
f : α → β
a : α
as : List α
⊢ (f a :: List.bind as fun a => [f a]) = f a :: map f as