Cross product in Scala

Question

I want to have a binary operator cross (cross-product/cartesian product) that operates with traversables in Scala:

val x = Seq(1, 2)
val y = Lis         


        

Answer 1

Here is the implementation of recursive cross product of arbitrary number of lists:

def crossJoin[T](list: Traversable[Traversable[T]]): Traversable[Traversable[T]] =
  list match {
    case xs :: Nil => xs map (Traversable(_))
    case x :: xs => for {
      i <- x
      j <- crossJoin(xs)
    } yield Traversable(i) ++ j
  }

crossJoin(
  List(
    List(3, "b"),
    List(1, 8),
    List(0, "f", 4.3)
  )
)

res0: Traversable[Traversable[Any]] = List(List(3, 1, 0), List(3, 1, f), List(3, 1, 4.3), List(3, 8, 0), List(3, 8, f), List(3, 8, 4.3), List(b, 1, 0), List(b, 1, f), List(b, 1, 4.3), List(b, 8, 0), List(b, 8, f), List(b, 8, 4.3))