title: Checking for consecutive True in list Haskell using fold
body: <p>I'm new to Haskell.</p>
  
  <p>For a Project Euler problem, I've generated a list of bools.</p>
  
  <pre><code>[True, False, False, True, False. . .True]
  </code></pre>
  
  <p>What I'd like is to write a function find the first four consecutive True's, then return their indices in the list.</p>
  
  <p>Intuitively, I know I should be doing this with a fold and somehow pattern matching. Could you help me? Something like this with a fold? (I have no idea how to retrieve the index of an element.)</p>
  
  <pre><code>consecutiveFourTrues (w:x:y:z):xs = if (w &amp;&amp; x &amp;&amp; y &amp;&amp; z) then w else consecutiveFourTrues (x:y:z):xs
  </code></pre>
  
  <p>Thank you for your help!</p>