Sets
Lists, as you have seen, allow duplicate elements (and are ordered, so duplicates – and other elements – can be identified by their position). But sometimes you want a collection that guarantees that its items are unique. For that, you use a Set.
Sets are like Lists in many ways. They use the same iteration functions, and Set also comes in read-only and mutable flavors.
But there are two major differences between lists and sets: The elements of a set are unique, and a set does not provide index-based mutators, because the items in a set are not guaranteed to be in any particular order. (That said, you can still read an element at a particular index, which we will discuss shortly.)
Creating a set
Just as you can ...