title: sort list of floating-point numbers in groups
body: <p>I have an array of floating-point numbers, which is unordered. I know that the values always fall around a few points, which are not known. For illustration, this list</p>
  
  <pre><code>[10.01,5.001,4.89,5.1,9.9,10.1,5.05,4.99]
  </code></pre>
  
  <p>has values clustered around 5 and 10, so I would like [5,10] as answer.</p>
  
  <p>I would like to find those clusters for lists with 1000+ values, where the nunber of clusters is probably around 10 (for some given tolerance). How to do that efficiently?</p>