Scala method to combine each element of an iterable with each element of another?

Question

If I have this:

val a = Array("a ","b ","c ")
val b = Array("x","y")

I would like to know if such a method exists which would let me traverse the first collection, and for each of it's elements, walk the entire second collection. For example, if we take the array a, we would have a,x,a,y,b,x,b,y,c,x,c,y. I know of zip but from what I've seen it only works on collections of the same sizes, and it associates elements from same positions.

Answer 1

Here's one more that does the same thing as @ziggystar's last edit but doesn't use indexed access of lists.

def combinationIterator[A](xs: Iterable[Iterable[A]]): Iterator[List[A]] = {
  xs.foldRight(Iterator(List[A]())) { (heads, tails) =>
    tails.flatMap { tail =>
      heads.map(head => head :: tail)
    }
  }
}

And the sugary version:

def combinationIterator[A](xs: Iterable[Iterable[A]]): Iterator[List[A]] = {
  (xs :\ Iterator(List[A]())) { (heads, tails) =>
    for (tail <- tails; head <- heads) yield head :: tail
  }
}