7 Mar
2007
7 Mar
'07
11:45 p.m.
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