Pattern matching in for comprehensions

Pattern matching is useful in for comprehensions for extracting items from a collection that match a specific pattern. Let's build a collection of Name instances:

scala> val names = List(Name("Martin", "Odersky"), 
  Name("Derek", "Wyatt"))
names: List[Name] = List(Name(Martin,Odersky), Name(Derek,Wyatt))

We can use pattern matching to extract the internals of the class in a for-comprehension:

scala> for { Name(first, last) <- names } yield first
List[String] = List(Martin, Derek)

So far, nothing terribly ground-breaking. But what if we wanted to extract the surname of everyone whose first name is "Martin"?

scala> for { Name("Martin", last) <- names } yield last
List[String] = List(Odersky)

Writing Name("Martin", last) <- names extracts the elements of names that match the pattern. You might think that this is a contrived example, and it is, but the examples...