Mimicking grep command in Scala

gistfile1.scala

package implicits

import java.io.File
import scala.io.Source

object RichFileDemo {

  class RichFile(file: String) {
    def matchLines(source: Source, pattern: String): Iterator[(String, Int)] = {
       source.getLines.zipWithIndex.filter(l => pattern.r.findFirstIn(l._1) != None)
    }
    
    def grep(pattern: String): Unit = {
      val source = Source.fromFile(file)
      matchLines(source,pattern).foreach(x => println("line " + x._2 + ": " + x._1))
      source.close
    }
  }
  
  def main(args: Array[String]): Unit = {
    val file = new RichFile("c:/scalademo/news.txt")
    file.grep("com")
  }
  
}


//news.txt
/**
Working together with leaders of the Play Framework, Akka, and Scala open source communities, 
Typesafe seeks to give developers the modern tools they need to build the next generation of 
software applications for the era of multicore hardware and cloud computing workloads.
**/

//output program
/** 
line 0: Working together with leaders of the Play Framework, Akka, and Scala open source communities, 
line 2: software applications for the era of multicore hardware and cloud computing workloads.
**/