title: How can I generate all the combinations of lists in scala?
body: <p>So, If I have a sequence 1,2,3,4,5,6,7,8,9
  I need a collection of all possible lists of the same elements
  for example</p>
  
  <pre><code>2,4,3,9,8,6,5,7,1
  2,4,3,9,6,8,5,7,1
  1,4,3,9,6,8,5,7,2
  </code></pre>
  
  <p>et cetera...</p>
  
  <p>How can I do this with for comprehension?</p>