monadTupo.scala

case class Global[A](a: A, state: Int) {
  def map[B](fun: A => B): Global[B] = Global(fun(a), state)
  def flatMap[B](fun: A => Global[B]): Global[B] = fun(a)
  override def toString = a.toString + " " + state
}

object Global {
  def point[A](a: A): Global[A] = Global(a, 0)
}

object monadTupo {

  var global = 0
  def a(x: String): Double = { global = 1; x.toDouble }
  def b(y: Double): Int = { global = 2; y.toInt }

  def fa(x: String): Global[Double] = Global(x.toDouble, 1)
  def fb(y: Double): Global[Int] = Global(y.toInt, 2)

  def main(args: Array[String]) {
    println((a _ andThen b _)("1.1"))
    println(global)

    import Global._
    println(point("1.1").flatMap(fa).flatMap(fb))
  }
}