title: What is the difference between position() and rposition() for rust iterators and is there any reason for it?
body: <p>So I was browsing through the iterator functions (because they are cool) and I noticed that there were two functions that seemed to do the exact same thing except one takes an <code>ExactSizeIterator</code>
  and other doesn't.</p>
  <p>What would be the use case of using one function over the other?</p>