title: Haskell arrays vs lists
body: <p>I'm playing with Haskell and Project Euler's 23rd problem. After solving it with lists I went <a href="http://www.haskell.org/haskellwiki/Euler_problems/21_to_30" rel="noreferrer" title="here">here</a> where I saw some array work. This solution was much faster than mine. 
  So here's the question.  When should I use arrays in Haskell? Is their performance better than lists' and in which cases?</p>