What about : sffi :: (Integral a,Num a) => Integer -> Maybe a sffi n = go n (fromInteger n) where go a b | toInteger b == a = Just b | otherwise = Nothing -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/haskell-cafe/attachments/20090408/7a56d906/attachment.htm