max_error_max_computation.scala

// This might look really simple, but people often get carried away validationNel (applicative) and disjunctions (monad) ended up having only errors (or a error) or a valid right.

// However we can go one step forward. Maximum error accumulation + Max computation (try hard, try hard)


  import scalaz._, Scalaz._

  def process1(int: Int): Int = throw new Exception("errors")
  def process2(int: Int) : Int = int + 1
  def process3(int: Int) : Int = int + 2
  def process4(int: Int): Int = throw new Exception("errors2")

  // The output should be NonEmptyList[errors, anotherError] \/ (intialValue + 1 + 2)

  def `try`(f: Int => Int): State[(List[String], Int), Unit] = {
    State.modify[(List[String], Int)](
      s => \/.fromTryCatchNonFatal(f(s._2)) match {
        case -\/(r) => (s._1 :+ r.getMessage, s._2)
        case \/-(r) => (s._1, r)
      }
    )
  }

 def ss: State[(List[String], Int), Unit] =
   for {
    _ <- `try`(process1)
    _ <- `try`(process2)
    _ <- `try`(process3)
    _ <- `try`(process4)
   } yield ()

  ss exec((Nil, 0))

// Result
// res24: (List[String], Int) = (List("errors", "errors2"), 3)