BufferedReader enumerator example for Scalaz 7 (with EitherT)

iteratee-io.scala

import java.io.{ BufferedReader, File, FileReader }
import scalaz._, Scalaz._, effect.IO, iteratee.{ Iteratee => I, _ }

object IterateeIOExample {
  type ErrorOr[A] = EitherT[IO, Throwable, A]

  def openFile(f: File) = IO(new BufferedReader(new FileReader(f)))
  def readLine(r: BufferedReader) = IO(Option(r.readLine))
  def closeReader(r: BufferedReader) = IO(r.close())

  def tryIO[A, B](action: IO[B]) = I.iterateeT[A, ErrorOr, B](
    EitherT(action.catchLeft).map(I.sdone(_, I.emptyInput))
  )

  def enumBuffered(r: => BufferedReader) = new EnumeratorT[String, ErrorOr] {
    lazy val reader = r
    def apply[A] = (s: StepT[String, ErrorOr, A]) => s.mapCont(k =>
      tryIO(readLine(reader)) flatMap {
        case None       => s.pointI
        case Some(line) => k(I.elInput(line)) >>== apply[A]
      }
    )
  }

  def enumFile(f: File) = new EnumeratorT[String, ErrorOr] {
    def apply[A] = (s: StepT[String, ErrorOr, A]) =>
      tryIO(openFile(f)).flatMap(reader => I.iterateeT[String, ErrorOr, A](
        EitherT(
          enumBuffered(reader).apply(s).value.run.ensuring(closeReader(reader))
        )
      ))
  }

  def main(args: Array[String]) {
    val action = (
      I.consume[String, ErrorOr, List] %=
      I.filter(_.count(_ == '0') >= 25) &=
      enumFile(new File(args(0)))
    ).run.run

    println(action.unsafePerformIO())
  }
}