hg.manuel:

Dear Haskellers,

why this program is not accepted by Hugs?

equal a a = True equal a b | not(a==b) = False

You can't pattern match 'a' and 'a' like that -- there's no implicit unification. Instead, I'd write: equal a b | a == b = True | otherwise = False Well actually, maybe I'd write: equal a b = a == b In reality, though: equal = (==) And then I'd just use (==) directly :) Cheers, Don