Mapping a Set

gistfile1.txt

Welcome to Scala version 2.10.2 (Java HotSpot(TM) 64-Bit Server VM, Java 1.7.0_09).
Type in expressions to have them evaluated.
Type :help for more information.

scala> case class Foo(a: Int, b: Int)
defined class Foo

scala> Set(Foo(1, 10), Foo(2, 10), Foo(3, 20))
res0: scala.collection.immutable.Set[Foo] = Set(Foo(1,10), Foo(2,10), Foo(3,20))

scala> res0.map(_.b)
res1: scala.collection.immutable.Set[Int] = Set(10, 20)

scala> res1.size
res2: Int = 2