title: Locally scoped updates in elm 0.18
body: <p>I have an elm 0.18 web app with a number of pages and routes.  In <code>main.elm</code> I define my update function.</p>
  
  <pre><code>update : Msg -&gt; Model -&gt; ( Model, Cmd Msg )
  update msg model =
      case msg of
          FirstUpdateAction -&gt;
      ...
  </code></pre>
  
  <p>Every action goes through this function and it's getting big.  Is it possible to create an update function to a smaller module that is nested within the overall structure?</p>
  
  <p>For example, I have a settings page that gives the user the ability to change password.  There are three fields/states (passwordOld, passwordNew, passwordConfirm) which have update actions associated with <code>onInput</code> and <code>onBlur</code> events.  Those states and actions are only relevent to the user settings page, and become irrelevent to the rest of the model when the user leaves the page.</p>
  
  <p>How could I go about setting up a scope for the user settings?</p>