Sorting it out!

Scala provides sorted, sortBy and sortWith methods. We will take a quick look at them and then tackle an interesting memoization problem.

Sorted

The sorted method uses natural ordering amongst the elements of the collection. Natural ordering well, seems natural.

For example, given the following numbers:

1, 11, 22, 2

The natural ordering would be:

1, 2, 11, 22

And the alphanumeric ordering would be:

1, 11, 2, 22

Alternatively, please see http://blog.codinghorror.com/sorting-for-humans-natural-sort-order/ for more on natural ordering.

Here is sorted in action:

scala> import scala.util.Random
import scala.util.Random
scala> val list = List.fill(10)(Random.nextInt(100))
list: List[Int] = List(5, 49, 37, 56, 54, 64, 9, 85, 76, 28)
scala> list.sorted
res0: List[Int] = List(5, 9, 28, 37, 49, 54, 56, 64, 76, 85) 

This, of course, creates a new list as the original list is immutable.

SortBy

This method sorts on an attribute of the compound type. For example, given a list of tuples:

scala...