Combining two lists in Scala

Question

From 2 lists of the form List[(Int, String):

l1 = List((1,\"a\"),(3,\"b\"))
l2 = List((3,\"a\"),(4,\"c\"))

how can I combine t

Answer 1

With Scalaz, this is a snap.

import scalaz._
import Scalaz._

val l3 = (l1.map(_.swap).toMap |+| l2.map(_.swap).toMap) toList

The |+| method is exposed on all types T for which there exists an implementation of Semigroup[T]. And it just so happens that the semigroup for Map[String, Int] is exactly what you want.