title: How to convert Maybe (List) to Just List in Elm?
body: <p>I have a list which is comprised of a list of strings, declared as:</p>
  <pre><code>type alias Model =
      { board : List (List String)
      }
  
  init : Model
  init =
      { board = 
          [ [&quot;&quot;, &quot;&quot;, &quot;&quot;]
          , [&quot;&quot;, &quot;&quot;, &quot;&quot;]
          , [&quot;&quot;, &quot;&quot;, &quot;&quot;]
          ]
      }
  </code></pre>
  <p>In my update function, I am attempting to access an inner element of the lists via</p>
  <pre><code>(getAt col (getAt row model.board))
  </code></pre>
  <p>I get the following error when I try to compile it though. How do I convert from Maybe List to Just List or simply List?</p>
  <pre><code>The 2nd argument to `getAt` is not what I expect:
  
  65|                         (getAt col (getAt row model.board))
                                          ^^^^^^^^^^^^^^^^^^^^^
  This `getAt` call produces:
  
      Maybe (List String.String)
  
  But `getAt` needs the 2nd argument to be:
  
      List a
  </code></pre>