Scala - convert List of Lists into a single List: List[List[A]] to List[A]

Question

What\'s the best way to convert a List of Lists in scala (2.9)?

I have a list:

List[List[A]]

which I want to convert into

Answer 1

Given the above example, I'm not sure you need recursion. Looks like you want List.flatten instead.

e.g.

scala> List(1,2,3)
res0: List[Int] = List(1, 2, 3)

scala> List(4,5,6)
res1: List[Int] = List(4, 5, 6)

scala> List(res0,res1)
res2: List[List[Int]] = List(List(1, 2, 3), List(4, 5, 6)) 

scala> res2.flatten
res3: List[Int] = List(1, 2, 3, 4, 5, 6)