Playing with Scalaz effects

ExperimentingWithIo.scala

import scalaz._
import Scalaz._
import effects._

object ExperimentingWithIo {

  def main(args: Array[String]): Unit = {

    val i1: IO[Unit] = for {
      _ <- putStrLn("What's your name?")
      inputStr <- readLn
      outputStr = "Hello " |+| inputStr |+| "!"
      _ <- putStrLn(outputStr)
    } yield ()

    i1.unsafePerformIO

    val i2: IO[Unit] = putStrLn("What's your name?") >|> readLn >>= { inputStr =>
      val outputStr = "Hello " |+| inputStr |+| "!"
      putStrLn(outputStr)
    }

    i2.unsafePerformIO

    val i3: IO[Unit] = for {
      v <- newIORef(5)
      _ <- v.write(9)
      _ <- v.mod(_ + 3)
      s <- v.read
      _ <- putStrLn(s.shows)
    } yield ()

    i3.unsafePerformIO

    val f = new Forall[({type l[X] = ST[X, String]})#l] {
     def apply[A] = for {
       v <- newVar[A, String]("Scala")
       _ <- v.mod(_ |+| "ble")
       s <- v.read
     } yield s
    }

    runST(f)
  }
}