[Hugs-users] formatting and guarded expressions

Hi, Are there special formatting constraints for using guards in Hugs? My students are learning Haskell in lab and the following simple function sometimes fails

fact n | n == 0 = 1 | otherwise = n * (fact(n-1))

Hugs complains about an unexpected ; Sometimes code after a guarded expression fixes the problem. We've tried putting the | up against the > or underneath the parameter. The same code seems to work for some students but not for others. Any ideas? - Lea