Test whyle loop with example run and output

Test run from the command line with output

> scala whyle_test.scala Testing the whyle loop
Testing
the
whyle
loop
Predicate is being evaluated
Body is being evaluated
Testing
Predicate is being evaluated
Body is being evaluated
the
Predicate is being evaluated
Body is being evaluated
whyle
Predicate is being evaluated
Body is being evaluated
loop
Predicate is being evaluated

whyle_test.scala

import scala.annotation.tailrec

object Main {
  def main (args: Array[String]) {
    var i = 0
    whyle(i < args.length) {
      println(args(i))
      i += 1
    }

    i = 0  // reset i to 0
    whyle {
      println("Predicate is being evaluated")
      i < args.length
    } {
      println("Body is being evaluated")
      println(args(i))
      i += 1
    }
  }

  def whyle(predicate: => Boolean)(block: => Unit) {
    @tailrec
    def whyle_internal {
      if (predicate) {
        block
        whyle_internal
      }
    }
    whyle_internal
  }

}