[kagakuninja]

I'm using Scala syntax here... If I have:

  val a = IO(42)
  def f(n: Int) = IO(n)

And I use map, then I get:

  val r: IO[IO[Int]] = a.map(f)

Which we don't want... the solution is to flatten it. This can be done with flatten, or flatMap:

  a.map(f).flatten
  a.flatMap(f)

Both produce IO[Int], and this makes sense to me using any monad. By contrast, bind means nothing to me.