title: Extracting a list of values from a list of maybes without fromJust
body: <p>Input: <code>[Just "foo", Just "bar", Nothing, Just "quux"]</code></p>
  
  <p>Output: <code>["foo", "bar", "quux"]</code></p>
  
  <p>I'm not satisfied with the following solution using <code>fromJust</code> because it's not very portable to <em>elm</em> which doesn't like unsafe functions:</p>
  
  <p><code>extract list = map fromJust $ filter isJust list</code></p>
  
  <p>Is there another concise / idiomatic way to achieve this?</p>