title: In C++ does std::multiset keep a stable sorting order?
body: <p>Suppose I have two items, a and b, that compare the same. So a &lt; b is false, and b &lt; a is false. If these items are inserted into a std::multiset (or std::multimap) as keys, do I have any guarantees of their final sorted order?</p>
  
  <p>I've checked a couple of references, but I couldn't find the answer. I'm tempted to think that there are no guarantees and that it's left up to each particular implementation.</p>
  
  <p>Thanks.</p>