title: Haskell - Takes a list of floats and returns a list of chars
body: <p>I am wondering to create a Haskell function to take a list of floats and returns a list of chars that represent the letter grades based off the original scores.
  I can complete this requirement without list:</p>
  
  <pre><code> convertRawsToLetters :: (RealFloat score) =&gt; score -&gt; Char
   convertRawsToLetters score
      | score &gt; 90 = 'A'
      | score &lt;= 90 &amp;&amp; score &gt; 80 = 'B'
  </code></pre>
  
  <p>How can I use condition in list? </p>