title: Why would anyone use set instead of unordered_set?
body: <p>C++0x is introducing <code>unordered_set</code> which is available in <code>boost</code> and many other places. What I understand is that <code>unordered_set</code> is hash table with <code>O(1)</code> lookup complexity. On the other hand, <code>set</code> is nothing but a tree with <code>log(n)</code> lookup complexity. <strong>Why on earth would anyone use <code>set</code> instead of <code>unordered_set</code>? i.e is there a need for <code>set</code> anymore?</strong></p>