title: Getting values from a union case
body: <p>i have something like </p>
  
  <pre><code>type A = 
     | X of string
     | Y of int
  </code></pre>
  
  <p>i have a sequence of X types, <code>[X "foo"; X "boo"; X "moo"]</code>
  is there a shortcut for doing a map to convert it to <code>["foo"; "boo"; "moo"]</code> without doing a match?</p>
  
  <p>Thanks!</p>