Reading a collection of lists from file in scala http://stackoverflow.com/questions/18187736/reading-a-collection-of-lists-from-file-in-scala

list.txt

1 2
1 1
1 2
4 3
4 8
1 5
8 2
8 2
8 7

makelist.scala

object Makelist  {

  val nums = """(\d+) (\d+)""".r

  val tuples = io.Source.fromFile("list.txt").getLines collect {
    case nums(label, num) => (label.toInt -> num.toInt)
  }

  def toList(tuples: Iterator[(Int, Int)]): Iterator[Seq[Int]] = {
    if(!tuples.hasNext) Iterator.empty
    else {
      val (label, num) = tuples.next
      val (succ, rest) = tuples.span(_._1 == label)
      Iterator(num :: succ.map(_._2).toList) ++ toList(rest)
    }
  }

  toList(tuples)foreach(println)
}

result.txt

2,1,2
3,8
5
2,2,7