ranger.scala

final class MyRange(start: Int, limit: Int, step: Int) extends IndexedSeq[Int] {
  val length: Int = {
    def plen(start: Int, limit: Int, step: Int) =
      if (limit <= start) 0 else (limit - start - 1) / step + 1
    if (step > 0) plen(start, limit, step) 
    else plen(limit, start, -step)
  }
  override def apply(idx: Int) = {
    if (idx < 0 || idx >= length) throw new IndexOutOfBoundsException(idx.toString)
    start + idx * step
  }

  override def foreach[U](f: Int => U) {
    var i = start
    while (if (step > 0) i < limit else i > limit) {
      f(i)
      i += step
    }
  }
}

object Test {
  trait RangeBuilder {
    def to2(limit: Int): MyRange
  }
  implicit def Int2Range(from: Int) = new RangeBuilder { def to2(limit:Int) = new MyRange(from, limit, 1) }

  def testRange(b: Boolean) {
    if (b) {
      for (i <- 1 to2 5)
        println(i)
    }
  }
}