Count occurrences of each element in a List[List[T]] in Scala

Question

Suppose you have

val docs = List(List(\"one\", \"two\"), List(\"two\", \"three\"))

where e.g. List(\"one\", \"two\") represents a document

Answer 1

docs.flatten.foldLeft(new Map.WithDefault(Map[String,Int](),Function.const(0))){
  (m,x) => m + (x -> (1 + m(x)))}

What a train wreck!

[Edit]

Ah, that's better!

docs.flatten.foldLeft(Map[String,Int]() withDefaultValue 0){
  (m,x) => m + (x -> (1 + m(x)))}