title: Error haskell: not in scope. What does that mean?
body: <p>I started with Haskell today and all the functions I perform on ghci display this message. I just want to know why this is happening. 
  I know there are a lot of questions about this, but this is a simple case and I need to understand this error in the beginning</p>
  
  <pre><code>function3 :: Int -&gt; [Int]
  function3 x = [a | a &lt;- [1..x] mod a x == 0]
  </code></pre>