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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. Writing an instance of Read? (Mike Meyer) 2. Re: Writing an instance of Read? (Daniel Fischer) ---------------------------------------------------------------------- Message: 1 Date: Sat, 15 Oct 2011 17:15:54 -0700 From: Mike Meyer <m...@mired.org> Subject: [Haskell-beginners] Writing an instance of Read? To: beginners@haskell.org Message-ID: <20111015171554.7a9ac...@bhuda.mired.org> Content-Type: text/plain; charset=US-ASCII Is there a tutorial - or anything at all, for that matter - on writing Read instances? Particularly so that it integrates properly types that incoporate your type and derive Read? Real World Haskell gives one simple example (which doesn't use the first argument), points out one problem with the example, then says "many people find it easier to use Parsec." And that's the best such I could find. Thanks, <mike -- Mike Meyer <m...@mired.org> http://www.mired.org/ Independent Software developer/SCM consultant, email for more information. O< ascii ribbon campaign - stop html mail - www.asciiribbon.org ------------------------------ Message: 2 Date: Sun, 16 Oct 2011 02:42:30 +0200 From: Daniel Fischer <daniel.is.fisc...@googlemail.com> Subject: Re: [Haskell-beginners] Writing an instance of Read? To: beginners@haskell.org Message-ID: <201110160242.30906.daniel.is.fisc...@googlemail.com> Content-Type: Text/Plain; charset="iso-8859-1" On Sunday 16 October 2011, 02:15:54, Mike Meyer wrote: > Is there a tutorial - or anything at all, for that matter - on writing > Read instances? Particularly so that it integrates properly types that > incoporate your type and derive Read? Real World Haskell gives one > simple example (which doesn't use the first argument), points out one > problem with the example, then says "many people find it easier to use > Parsec." And that's the best such I could find. > > Thanks, > <mike If you're using GHC, you can directly use Text.ParserCombinators.ReadPrec and Text.ParserCombinators.ReadP to write your Read instances (define readPrec and optionally readListPrec instead of readsPrec and readList). If your parser is correct, it will automatically integrate properly with derived Read instances. ReadP has many combinators in common with Parsec, so going from Parsec to ReadP is fairly straightforward. ------------------------------ _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 40, Issue 22 *****************************************