Scala Iterator loop idiom (stateful): repeatedly produce a value until a condition is met

gistfile1.txt

    Iterator continually {
      // ...
      reader.readLine()
    } takeWhile {
      Option(_).isDefined
    } foreach {
      processExpr
    }

replaces

  while ((/* ... */ ; line = reader.readLine()) != null ; line) {
    processExpr(line)
  }