inductive Vector (α : Type u) : Nat → Type u
  | nil : Vector α 0
  | cons : α → Vector α n → Vector α (n+1)
  deriving Repr

infix:67 " :: " => Vector.cons

def tabulate (f : Fin n → α) : Vector α n :=
  match n with
  | 0   => Vector.nil
  | n+1 => f 0 :: tabulate (f ∘ Fin.succ)

#eval tabulate fun i : Fin 5 => i