title: Haskell error parse error on input `='
body: <p>I'm new to Haskell and after starting <code>ghci</code> I tried:</p>
  
  <pre><code>f x = 2 * x
  </code></pre>
  
  <p>and I obtained:</p>
  
  <pre><code>&lt;interactive&gt;:1:4: parse error on input `='
  </code></pre>
  
  <p>which I don't understand.</p>
  
  <p>Strangely, it worked well before. I suppose that I have done misconfigured Haskell. Reinstalling ghc6 doesn't solve the problem.</p>
  
  <p>For information, I use Ubuntu 10.4 and the version of ghc6 is 6.12.1-12</p>