title: Can anyone suggest a good constraint library for Haskell?
body: <p>I've started learning about <a href="http://en.wikipedia.org/wiki/Constraint_programming" rel="noreferrer">Constraint programming</a> and I feel it is something that would work well with Haskell (also I enjoy using Haskell).</p>
  
  <p>Are there any mature constraint frameworks for Haskell?</p>