Send Beginners mailing list submissions to beginners@haskell.org To subscribe or unsubscribe via the World Wide Web, visit http://www.haskell.org/mailman/listinfo/beginners or, via email, send a message with subject or body 'help' to beginners-requ...@haskell.org
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: How to solve this using State Monad? (Miguel Negrao) 2. Re: How to solve this using State Monad? (Ertugrul S?ylemez) 3. Re: How to solve this using State Monad? (Henry Lockyer) 4. GHCi won't allow type declaration as shown in LYAHFGG (Stan Kulp) 5. Re: GHCi won't allow type declaration as shown in LYAHFGG (Homero Cardoso de Almeida) 6. Re: GHCi won't allow type declaration as shown in LYAHFGG (Brandon Allbery) ---------------------------------------------------------------------- Message: 1 Date: Thu, 31 May 2012 16:46:26 +0100 From: Miguel Negrao <miguel.negrao-li...@friendlyvirus.org> Subject: Re: [Haskell-beginners] How to solve this using State Monad? To: beginners@haskell.org Message-ID: <9c2c6f14-1233-49cc-a346-b48140a6d...@friendlyvirus.org> Content-Type: text/plain; charset=windows-1252 A 31/05/2012, ?s 16:25, Michael Alan Dorman escreveu: > Ertugrul S?ylemez <e...@ertes.de> writes: >> I almost feel stupid writing these long explanations, just to see them >> getting ignored ultimately. The automaton arrow is one of the most >> useful and most underappreciated concepts for state in Haskell. > > While I'm not sure I have a need for it right now, I definitely haven't > ignored this exchange---I've read the individual emails, and a link to > the archive is filed away for future use. > > So it's been very helpful, even if those being helped aren't > participating per se. +1 Because of those posts I spent my morning reading about arrows which seems a quite interesting concept, although couldn?t yet see what is best for ( I would be curious to learn it in order to try out Yampa). I have to say that the resources I found to learn about arrows on the net were a bit disorganized. This page is really well done http://en.wikibooks.org/wiki/Haskell/Understanding_arrows but then because I don?t know much about parsers I couldn?t really progress through the second half. best, Miguel Negr?o ------------------------------ Message: 2 Date: Thu, 31 May 2012 18:18:07 +0200 From: Ertugrul S?ylemez <e...@ertes.de> Subject: Re: [Haskell-beginners] How to solve this using State Monad? To: beginners@haskell.org Message-ID: <20120531181807.37bed...@tritium.streitmacht.eu> Content-Type: text/plain; charset="utf-8" Miguel Negrao <miguel.negrao-li...@friendlyvirus.org> wrote: > Because of those posts I spent my morning reading about arrows which > seems a quite interesting concept, although couldn?t yet see what is > best for ( I would be curious to learn it in order to try out Yampa). > I have to say that the resources I found to learn about arrows on the > net were a bit disorganized. This page is really well done > http://en.wikibooks.org/wiki/Haskell/Understanding_arrows but then > because I don?t know much about parsers I couldn?t really progress > through the second half. I have started an arrow tutorial which many people found easy to follow. It's not finished yet, but since so many people found it useful I'm sharing that unfinished tutorial: <http://ertes.de/new/tutorials/arrows.html> It answers the most important questions: What? Why? How? To some extent it also answers: When? But I have to work on that question. The basics of the automaton arrow are covered, but when I find time I will extend the tutorial to cover Auto in full. Finally I also intend to cover a powerful generalization of Auto: the wire arrow, which is the basis of the Netwire AFRP library. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/ -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 836 bytes Desc: not available URL: <http://www.haskell.org/pipermail/beginners/attachments/20120531/709e5178/attachment-0001.pgp> ------------------------------ Message: 3 Date: Thu, 31 May 2012 17:23:08 +0100 From: Henry Lockyer <henry.lock...@ntlworld.com> Subject: Re: [Haskell-beginners] How to solve this using State Monad? To: beginners@haskell.org Message-ID: <41b1172f-bfa0-450e-adf9-b74fe4adf...@ntlworld.com> Content-Type: text/plain; charset=windows-1252 + I think I already said it, but, in case it was not clear: Me too. Even as a participating person I feel helped! ;-) I just haven't taken it onboard yet and need that quiet free morning to read more about it... + I think this is clearly identifying the point where the State monad(s) can become confusing at first, in my (limited) experience: "The problem of the state monad is a very fundamental one. As soon as your automaton is parametric it becomes a function: dfaWith :: DfaInput -> State DfaState DfaOutput" But I need more time to assimilate the following "Functions in Haskell are opaque. For every composition of automata you would have to write an individual loop, because you would have to force the two individual states to be combined somehow. This gets more inconvenient as your automaton library grows." best/Henry On 31 May 2012, at 16:46, Miguel Negrao wrote: > > A 31/05/2012, ?s 16:25, Michael Alan Dorman escreveu: > >> Ertugrul S?ylemez <e...@ertes.de> writes: >>> I almost feel stupid writing these long explanations, just to see them >>> getting ignored ultimately. The automaton arrow is one of the most >>> useful and most underappreciated concepts for state in Haskell. >> >> While I'm not sure I have a need for it right now, I definitely haven't >> ignored this exchange---I've read the individual emails, and a link to >> the archive is filed away for future use. >> >> So it's been very helpful, even if those being helped aren't >> participating per se. > > +1 > > Because of those posts I spent my morning reading about arrows which seems a > quite interesting concept, although couldn?t yet see what is best for ( I > would be curious to learn it in order to try out Yampa). I have to say that > the resources I found to learn about arrows on the net were a bit > disorganized. This page is really well done > http://en.wikibooks.org/wiki/Haskell/Understanding_arrows but then because I > don?t know much about parsers I couldn?t really progress through the second > half. > > best, > Miguel Negr?o > _______________________________________________ > Beginners mailing list > Beginners@haskell.org > http://www.haskell.org/mailman/listinfo/beginners ------------------------------ Message: 4 Date: Thu, 31 May 2012 12:48:02 -0700 (PDT) From: Stan Kulp <stan_k...@yahoo.com> Subject: [Haskell-beginners] GHCi won't allow type declaration as shown in LYAHFGG To: "beginners@haskell.org" <beginners@haskell.org> Message-ID: <1338493682.89984.yahoomail...@web111401.mail.gq1.yahoo.com> Content-Type: text/plain; charset="iso-8859-1" I have been working my way through "Learn You a Haskell for Greater Good" and am stumped when I get to the "Syntax in Functions - Pattern Matching" section. The book shows the following expression... ghci> lucky?::?(Integral?a)?=>?a?->?String?? ...but when I try to execute it in GHCi I get the following error... <interactive>:1:1: Not in scope: `lucky' What am I missing? ? Stan Kulp 4421 W North Pinebrook Lane Columbia, MO 65203 Home: 573-234-2065 Work: 573-522-5075 Cell: 573-864-6051 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20120531/20d1311e/attachment-0001.htm> ------------------------------ Message: 5 Date: Thu, 31 May 2012 16:52:22 -0300 From: Homero Cardoso de Almeida <homero...@gmail.com> Subject: Re: [Haskell-beginners] GHCi won't allow type declaration as shown in LYAHFGG To: Stan Kulp <stan_k...@yahoo.com> Cc: "beginners@haskell.org" <beginners@haskell.org> Message-ID: <capv0zwpdkp0a7kymgnkgc3fdw6u5pugkjc1lfvxst7eqjhu...@mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" I don't think GHCi allows function and type definitions in interactive mode. You have to write the functions in a source file and then load it. You can then call the functions as usual. Homero Cardoso de Almeida On Thu, May 31, 2012 at 4:48 PM, Stan Kulp <stan_k...@yahoo.com> wrote: > I have been working my way through "Learn You a Haskell for Greater Good" > and am stumped when I get to the "Syntax in Functions - Pattern Matching" > section. > > The book shows the following expression... > > ghci> lucky :: (Integral a) => a -> **String > > ...but when I try to execute it in GHCi I get the following error... > > <interactive>:1:1: Not in scope: `lucky' > > What am I missing? > > Stan Kulp > 4421 W North Pinebrook Lane > Columbia, MO 65203 > > Home: 573-234-2065 > Work: 573-522-5075 > Cell: 573-864-6051 > > _______________________________________________ > Beginners mailing list > Beginners@haskell.org > http://www.haskell.org/mailman/listinfo/beginners > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20120531/06a748c2/attachment-0001.htm> ------------------------------ Message: 6 Date: Thu, 31 May 2012 16:36:10 -0400 From: Brandon Allbery <allber...@gmail.com> Subject: Re: [Haskell-beginners] GHCi won't allow type declaration as shown in LYAHFGG To: Stan Kulp <stan_k...@yahoo.com> Cc: "beginners@haskell.org" <beginners@haskell.org> Message-ID: <CAKFCL4V+YtA7pE-85JsPWY85T5A1p8HE4qPqD=vjnmx6zjj...@mail.gmail.com> Content-Type: text/plain; charset="utf-8" On Thu, May 31, 2012 at 3:48 PM, Stan Kulp <stan_k...@yahoo.com> wrote: > I have been working my way through "Learn You a Haskell for Greater Good" > and am stumped when I get to the "Syntax in Functions - Pattern Matching" > section. > > The book shows the following expression... > > ghci> lucky :: (Integral a) => a -> **String > > ...but when I try to execute it in GHCi I get the following error... > > <interactive>:1:1: Not in scope: `lucky' > > What am I missing? > ghci is intended for interactive evaluation; it doesn't (currently; this might change in future versions) do declarations the same way you would in a source file. You can still do them with do-style let binding: Prelude> let lucky :: (Integral a_ => a -> String; lucky = ... (This all has to fit on a single line unless you use braces and have done ":set +m"; this may also require a recent GHC.) -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.haskell.org/pipermail/beginners/attachments/20120531/87f669f4/attachment.htm> ------------------------------ _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 47, Issue 34 *****************************************