multiple columns in IterableSource

gistfile1.scala

import com.twitter.scalding._

class HistogramTest(args : Args) extends Job(args) {
  IterableSource(List((1,2),(3,4),(5,6),(7,8)), List('a,'b))
  .read
  .map(('a,'b)->('c)){
    x:(Int,Int) =>
    x._1+x._2
  }.write(Tsv("data/histo_test"))
}