[rjprins]

This is a rather useless data structure:

You can only store integers and they must be in the range of [0, n>. The simple operations are O(1), because you can just map the positions of all integers based on their value in a second array of size n.

[tptacek]

You're not using it to replace a container ADT. You're using it for a low-overhead fast membership test. When things only store integer keys, usually that implies that you have a fast integer-keyed store for the rest of the information. Most trie implementations work the same way.

[babo]

The cheap iteration is a big plus of this data structure over a simple set.