title: How do I multiply all elements in one collection with all the elements in another collection?
body: <p>Say I have:</p>
  
  <pre><code>(def s1 [1 2 3 4 5])
  (def s2 [1 2 3 4 5])
  </code></pre>
  
  <p>For every <code>x</code> in <code>s1</code>, I want to multiply it with every <code>y</code> in <code>s2</code>.</p>
  
  <hr>
  
  <p>To clarify, I basically want the Cartesian product, so I don't think <code>map</code> works here.</p>