title: foldr & foldl Haskell explanation
body: <p>We have been asked to answer whether <code>foldr</code> or <code>foldl</code> is more efficient.</p>
  
  <p>I am not sure, but doesn't it depend on what I am doing, especially what I want to reach with my functions?</p>
  
  <p>Is there a difference from case to case or can one say that <code>foldr</code> or <code>foldl</code> is better , because...</p>
  
  <p>Is there a general answer ? </p>
  
  <p>Thanks in advance!</p>