Sorry, I have forgotten to copy to the List my last note on this subject. The on-line spec of Haskell-2010 shows Eq Show \ / Num | Real | Integral Hence, for x :: Integral a => a, it is correct to apply (show x). And ghc-7.4.0.20111219 does not allow this (show x). So, it breaks the standard, and people say, this is deliberate. I witness such a break for the first time, and this looks so strange! Well, I also diskile the edge Show / Num in the standard. But it is better to implement Show as dummy for appropriate types, -- so far, -- and to wait for the next standard. Am I missing something? Regards, ------ Sergei mechvel@botik.ru