simp [mmap, LawfulMonad.bind_pure, LawfulMonad.pure_bind]
m : Type → Type
inst✝ : LawfulMonad m
α β : Type
f : α → m β
x✝ : List α
⊢ mmap f ([] ++ x✝) = do
    let bs ← mmap f []
    let bs' ← mmap f x✝
    pure (bs ++ bs')
no goals