title: clojure: permutations of subsets?
body: <p>I'm new to clojure, looking for a function to generate permutations of subsets:</p>
  
  <pre><code>=&gt; (find-subsets 1 #{1 2 3 4})
  (#{1} #{2} #{3} #{4})
  
  =&gt; (find-subsets 2 #{1 2 3 4})
  (#{1 2} #{1 3} #{1 4} #{2 3} #{2 4} #{3 4})
  
  =&gt; (find-subsets 3 #{1 2 3 4})
  (#{1 2 3} #{1 3 4} #{2 3 4})
  </code></pre>
  
  <p>Does such a thing exist?  If not, is there a nice, clean, idiomatic way to code the function?</p>