What is the proper way to remove elements from a scala mutable map using a predicate

Question

How to do that without creating any new collections? Is there something better than this?

val m = scala.collection.mutable.Map[String, Long](\"1\" -> 1, \"2\"         


        

Answer 1

If you are using an immutable.Map, in 2.7 it might have to be something like:

def pred(k: Int, v: String) = k % 2 == 0

m --= (m.filter(pred(_, _)).keys

As there is no retain method available. Obviously in this case m must be declared as a var