title: "multiset" & "multimap" - What's the point?
body: <p>As the question states ... I don't get the point about <a href="http://en.wikipedia.org/wiki/Multiset" rel="noreferrer"><code>multiset</code>s</a> / <a href="http://en.wikipedia.org/wiki/Multimap" rel="noreferrer"><code>multimap</code>s</a>.</p>
  
  <p>So, what's the purpose?</p>