title: Hoogle and yesod - how to easily find functions in non-default packages
body: <p>I installed hoogle, using <code>stack install hoogle</code>. Now I can search for functions using a command like this from <code>stack ghci</code>:</p>
  
  <pre><code>:!hoogle --count=15 "[a] -&gt; a"
  </code></pre>
  
  <p>I am in the root directory of my Yesod project - the main reason I installed it was to get help with Yesod functions - but when I try to find a function from Yesod like <code>addHeader</code>, it doesn't recognize a type defined on Yesod:</p>
  
  <pre><code>:t addHeader
  addHeader :: MonadHandler m =&gt; Text -&gt; Text -&gt; m ()
  :!hoogle --count=15 "MonadHandler m =&gt; Text -&gt; Text -&gt; m ()"
  Warning: Unknown class MonadHandler
  .
  .
  .
  </code></pre>
  
  <p>How can I setup hoogle to work beautifully with Yesod and also this very project I am working on, so that hoogle would bring my own functions and Yesod ones?</p>