A function to parse page set definitions with ranges. No negative numbers (it is for page numbers).

Page set parser

// A function to parse page set defintion, which supports [overlapping] ranges
def pageSet(definition: String) = {
  def pageDefToSet(pageDef: String): Set[Int] = {
    val rangeExtractor = """[^\d]*([\d]+).*-[^\d]*([\d])+[^\d]*""".r
    val numberExtractor = """[^\d]*([\d]+)[^\d]*""".r
    pageDef match {
      case rangeExtractor(from, to) => (from.toInt to to.toInt).toSet
      case numberExtractor(num) => Set(num.toInt)
      case _ => Set()
    }
  }
  definition.split(",").foldLeft(Set[Int]())((x, part) => x ++ pageDefToSet(part))
}

pageSet("1,2,3,6-8,sdf,12").toList.sorted       //> res0: List[Int] = List(1, 2, 3, 6, 7, 8, 12)