do

gistfile1.scala

import scala.language._

import scala.util.continuations._

import scalaz._, Scalaz._
import effect._, IO._

import scalaz.syntax.Ops

object Do {

  sealed trait DoBindOps[F[_], A] extends Ops[F[A]] {
    implicit val F: Bind[F]
    val self: F[A]
    def bind[B] = shift((k: A => F[B]) => self >>= k)
  }

  implicit def ToDoBindOps[F[_]: Bind, A](fa: F[A]) = new DoBindOps[F, A] {
    val F = implicitly[Bind[F]]
    val self = fa
  }

  def apply[F[_]: Bind, A](fa: => F[A] @cps[F[A]]) = reset(fa)

}

object Main extends SafeApp {

  import Do._

  override def runc = Do {
    ch07.basicio.bind[Unit]
    ch07.callingpure
  }

  object ch07 {

    def basicio = Do {
      putStrLn("Greetings! What is your name?").bind[Unit]
      val inpStr = readLn.bind[Unit]
      putStrLn(s"Welcome to Haskell, $inpStr!")
    }

    def callingpure = {
      def name2reply(name: String) = {
	val charcount = name.length
        s"""Pleased to meet you, $name.
Your name contains $charcount characters."""
      }
      Do {
        putStrLn("Greetings once again. What is your name?").bind[Unit]
        val inpStr = readLn.bind[Unit]
        val outStr = name2reply(inpStr)
        putStrLn(outStr)
      }
    }

  }

}