IO implementation exercise

IO.scala

case class IO[A](unsafeRun: () => A):

  def map[B](f: A => B): IO[B] =
    IO(() => f(unsafeRun()))

  def flatMap[B](f: A => IO[B]): IO[B] =
    IO(() => f(unsafeRun()).unsafeRun())

val io: IO[Int] = IO(() => {
  println("Running side effect!!!")
  42
})

io.unsafeRun()
io.flatMap(_ => io.flatMap(_ => io)).unsafeRun()