title: Lookup query parameters in Yesod
body: <p>I just initialized a Yesod project (no database) using <code>yesod init</code>.</p>
  
  <p>My <code>HomeR</code> GET handler looks like this:</p>
  
  <pre><code>getHomeR :: Handler Html
  getHomeR = do
      (formWidget, formEnctype) &lt;- generateFormPost sampleForm
      let submission = Nothing :: Maybe (FileInfo, Text)
          handlerName = "getHomeR" :: Text
      defaultLayout $ do
          aDomId &lt;- newIdent
          setTitle "Welcome To Yesod!"
          $(widgetFile "homepage")
  </code></pre>
  
  <p>When using <code>yesod devel</code>, I can access the default homepage at <code>http://localhost:3000/</code>.</p>
  
  <p>How can I modify the handler listed above to retrieve (and display) a HTTP GET query parameter like <code>id=abc123</code> when accessing this URL:</p>
  
  <p><code>http://localhost:3000/?id=abc123</code></p>
  
  <p><strong>Note:</strong> This question was answered Q&amp;A-style and therefore intentionally doesn't show research effort!</p>