title: How do I take the last n elements of a list
body: <p>To obtain the last <code>n</code> elements of a list <code>xs</code>, I can use <code>reverse (take n (reverse xs))</code>, but that is not very good code (it keeps the complete list in memory before returning anything, and the result is not shared with the original list).</p>
  
  <p>How do I implement this <code>lastR</code> function in Haskell?</p>