Question

What’s the best way to iterate through a map, and filter out certain keys? The pseudocode might be something like

    map.foreach(tuple where !list.contains(tuple._1) => { })

Thanks
Bruce

Answer 1

val m = Map(1 -> "a", 2 -> "b", 4 -> "c", 10 -> "d")
val s = Set(1,4)
m.filterKeys { s.contains(_) == false }
// Map(2 -> b, 10 -> d)

But, if this is a huge map and a huge set, then I’d suggest sorting them first and mutually iterating through them, picking off the bits that you need as you go. The repeated calls to contains may not perform as well as you’d like, especially if you use a List instead of a Set.