help

Hi! I'm new to Haskell. Following someone's notes, I was doing this "doubleMe x = x + x". I did this two days ago and it worked. But I try to do it today, I got an error "parse error on input '=' ", This is rather inconsistent and should not happen in a computer compiler (i.e. day one works, day second not work) This comes up in both cases: loading a .hs file and interactively. Can anyone tell me what I did wrong? This happened to both my Win XP and my Ubuntu 10.10 PC. Thank you very much. Cheers. Simon.