title: Haskell prime test
body: <p>I'm new to Haskell, and I'm trying a bit:</p>
  
  <pre><code>isPrime :: Integer-&gt;Bool
  isPrime x = ([] == [y | y&lt;-[2..floor (sqrt x)], mod x y == 0])
  </code></pre>
  
  <p>I have a few questions.</p>
  
  <ol>
  <li>Why when I try to load the .hs, WinHugs say: Instances of <code>(Floating Integer, RealFrac Integer)</code> required for definition of <code>isPrime</code>?</li>
  <li>When the interpreter finds one element in the right set, it immediately stops or it computes all the set? I think you know what I mean.</li>
  </ol>
  
  <p>Sorry about my english.</p>