title: How to add a condition to a match in case ... of
body: <p>In functional languages, one can add a condition to a branch of a pattern matching: for example, in OCaml:</p>
  
  <pre class="lang-ml prettyprint-override"><code>let value = match something with
  | OneThing -&gt; "1"
  | Another when condition -&gt; "2"
  | _ -&gt; "3"
  </code></pre>
  
  <p>How to do this in elm? I tried <code>when</code> and <code>if</code>, but nothing worked.</p>