split a stream in many

Question

I\'d like to know if there a elegant way to achieve something like that:

val l = Stream.from(1)

val parts = l.some_function(3)  //any number

parts.foreach(         


        

Answer 1

def roundRobin[T](n: Int, xs: Stream[T]) = {
  val groups = xs.grouped(n).map(_.toIndexedSeq).toStream
  (0 until n).map(i => groups.flatMap(_.lift(i)))
}

works in the infinite case:

scala> roundRobin(3, Stream.from(0)).map(_.take(3).force.mkString).mkString(" ")
res6: String = 036 147 258

using flatMap/lift instead of plain map/apply means it works even if the input is finite and the length isn't a multiple of n:

scala> roundRobin(3, Stream.from(0).take(10)).map(_.mkString).mkString(" ")
res5: String = 0369 147 258