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You can reach the person managing the list at beginners-ow...@haskell.org When replying, please edit your Subject line so it is more specific than "Re: Contents of Beginners digest..." Today's Topics: 1. Re: type ambiguity confusion (Daniel Fischer) ---------------------------------------------------------------------- Message: 1 Date: Tue, 15 Jun 2010 16:12:22 +0200 From: Daniel Fischer <daniel.is.fisc...@web.de> Subject: Re: [Haskell-beginners] type ambiguity confusion To: beginners@haskell.org Message-ID: <201006151612.22947.daniel.is.fisc...@web.de> Content-Type: text/plain; charset="iso-8859-1" On Tuesday 15 June 2010 16:07:38, Stephen Tetley wrote: > On 15 June 2010 14:57, Thomas <hask...@phirho.com> wrote: > > However: Why does the ambiguity matter in the first place? > > The corresponding value is never used (\_ -> return Nothing). > > Hi Thomas > > GHC has to resolve all types, even if they are for values that are not > used at runtime. > > > And there's another doubt: I got this example from a book (Real World > > Haskell, chapter 9) where actually the first version is used, without > > resolving the ambiguity in any way. And it does not show up in the > > errata list. > > So there's likely something I'm still missing about this issue?!?! > > The type of handle in Control.Exception has (probably) changed since > RWH was written. Right. > > latest (from ghc-6.10.1 onwards): > handle :: Exception e => (e -> IO a) -> IO a -> IO a > > old (upto ghc-6.8.3, I think, the so called Old.Exception): Small typo, no dot there, the former Control.Exception still available as Control.OldException > handle :: (Exception -> IO a) -> IO a -> IO a > > Best wishes > > Stephen ------------------------------ _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 24, Issue 15 *****************************************