gistfile1.scala

// we desire this pattern  Better  => (Better,Int)

type BetterUpdate = Better => (Better,Int)

val firstF:BetterUpdate = Better.sum(1)
val secondF:BetterUpdate = Better.sum(2)
val thirdF:BetterUpdate = Better.sum(3)


//     the external state is threaded through a sequence of computations
  val composeSumResults:BetterUpdate =  better =>  {

    val (firstState,firstResult) = firstF(better)
    val (secondState, secondResult) = secondF(firstState)
    val (thirdStater, thirdResult) = thirdF(secondState)    // now when this blows up, we have secondState in scope for inspection

    (thirdStater, firstResult + secondResult + thirdResult)
  }