On Wed, Mar 07, 2007 at 10:54:55PM +0000, Dave@haskell.org wrote:

...

io f = interact (unlines . f . lines) showln = (++ "\n") . show

-- Compute a simple cksum of a file

main = interact $ showln . foldl' k 5381 where k h c = h * 33 + ord c

========

Hugs> :load chksum.hs ERROR "chksum.hs":15 - Unresolved top-level overloading *** Binding : showln *** Outstanding context : Show b

Text.Printf>

This error has been around for a while.

Yes, it's a documented divergence from Haskell 98 in the handling of the Monomorphism Restriction.

Workarounds are to give an explicit signature for showln, or to tweak the definition so it's a function:

showln x = show x ++ "\n"

(or, better)

showln x = shows x "\n"

That Works. Thanks, Dave