title: Merge two lists
body: <p>I am looking to merge 2 lists in F# in a purely functional way. I am having a hard time understanding the syntax. </p>
  
  <p>Let say I have a tuple <code>([5;3;8],[2;9;4])</code></p>
  
  <p>When I call the function, it should return <code>[5;2;3;9;8;4]</code></p>
  
  <p>Here is why I have so far, which is wrong I am sure. If someone could explain it in a simple way I would be grateful.</p>
  
  <pre><code>let rec interleave (xs,ys) = function
  |([], ys) -&gt; ys
  |(x::xs, y::ys) -&gt; x :: y::  interleave (xs,ys) 
  </code></pre>