title: From redis sorted set, retrieving the rank of the highest value that has score just less than given score
body: <p>From a redis sorted set, how do I retrieve the <strong>rank of highest value</strong> that has a score just less than a given score?</p>
  
  <p>For instance, imagine my sorted set is:</p>
  
  <pre><code>rank value score
  1)   'a'   -10
  2)   'd'   -4
  3)   'c'   0
  4)   'b'   2
  5)   'e'   10
  </code></pre>
  
  <p>Specifically, If I'm given the score 12, I want to retrieve rank 5. If I'm given the score 1, I want to retrieve rank 3. If I'm given a score -11, I want to retrieve nothing.</p>