Kleisli compositions

gistfile1.txt

  val foo = (n: Int) => n.toString

  val bar = (s: String) => s.toInt

  // composing

  val f0 = bar compose foo
  println(f0(3))

  //what if the functions could fail..
  val oFoo: (Int) => Option[String] = foo map {Some(_)}

  val oBar: (String) => Option[Int] = bar map {Some(_)}

  //val ddd = oFoo andThen oBar //no longer works..

  // raw map style
  val f1 = oFoo(_: Int) flatMap { s => oBar(s)}

  // symbolic bind style
  val f2 = oFoo(_: Int) >>= oBar

  // kleisli magic in a point-free style
  val f3 = kleisli(oFoo) >==> oBar

  println(f1(3))
  println(f2(3))
  println(f3(3))