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. haskell code to html (I. J. Kennedy) 2. Re: haskell code to html (Daniel Fischer) 3. Figuring out errors (Edward Z. Yang) 4. Re: Utter Newbie - simple problems, output - GHC vs GHCi (Magnus Therning) 5. Using FiniteMap in ghci (KwangYul Seo) 6. Re: Using FiniteMap in ghci (Chadda? Fouch?) 7. Re: Using FiniteMap in ghci (KwangYul Seo) 8. Re: Using FiniteMap in ghci (Daniel Fischer) 9. function - argument termination problem (??????? ????????????) 10. Re: function - argument termination problem (Rahul Kapoor) 11. Re: function - argument termination problem (Magnus Therning) ---------------------------------------------------------------------- Message: 1 Date: Mon, 31 Aug 2009 21:08:01 -0500 From: "I. J. Kennedy" <j...@realmode.com> Subject: [Haskell-beginners] haskell code to html To: beginners@haskell.org Message-ID: <1008bfc90908311908n12e1ef5ai83ad93caa5eea...@mail.gmail.com> Content-Type: text/plain; charset="utf-8" Is there a decent utility out there for syntax coloring haskell code?(haskell to html) -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20090831/9e81a648/attachment-0001.html ------------------------------ Message: 2 Date: Tue, 1 Sep 2009 04:18:44 +0200 From: Daniel Fischer <daniel.is.fisc...@web.de> Subject: Re: [Haskell-beginners] haskell code to html To: beginners@haskell.org Message-ID: <200909010418.45026.daniel.is.fisc...@web.de> Content-Type: text/plain; charset="iso-8859-15" Am Dienstag 01 September 2009 04:08:01 schrieb I. J. Kennedy: > Is there a decent utility out there for syntax coloring haskell > code?(haskell to html) HsColour: http://hackage.haskell.org/package/hscolour cabal update && cabal install hscolour if you have a working cabal binary (if you haven't, you should get yourself one) ------------------------------ Message: 3 Date: Mon, 31 Aug 2009 23:02:10 -0400 From: "Edward Z. Yang" <ezy...@mit.edu> Subject: [Haskell-beginners] Figuring out errors To: beginners <beginners@haskell.org> Message-ID: <1251773361-sup-1...@javelin> Content-Type: text/plain; charset=UTF-8 Hello all, I've been looking at [1] and trying to make tops and bottoms (pardon the pun) of error handling in Haskell. I am still uncertain of what to do. I recognize that there are different areas of code that may have different requirements for errors: * Pure code that is simple enough can probably get away with returning Maybe a * Pure code that has multiple failure modes (the canonical example is parsing) should return a Either e a. The type of e is a little difficult: many standard libraries seem to use String, but coming from Python this seems analogous to the long deprecated "string exceptions", which are quick and easy but not long-term maintainable due to lack of an easy way to match for them. This leads naturally into Either MyError, which is supported using throwError and catchError. * However, [1] specifically warns against using this technique in the IO monad, and I need a way to short circuit execution when a crucial pure operation fails (in Python, this would have just been an uncaught exception). This suggests using ErrorT on IO, however, [1] also claims that this is generally not a good idea, and suggests to use throwDyn (which actually looks like it's been renamed to throw) * Unfortunately, when I've tried to use this technique, I've run up against the fact that throw is implemented using bottom, so if I do a throw in a pure function, the exception might not actually surface up until I'm, say, attempting to print its return value to IO. Denizens on #haskell have instructed me to treat bottom as the bane of existence and opt for stacking ErrorT on IO (it would be nice to know if this was a good idea or bad idea) At which point, I am most thoroughly confused. Pointers, please! Cheers, Edward [1] http://www.randomhacks.net/articles/2007/03/10/haskell-8-ways-to-report-errors ------------------------------ Message: 4 Date: Wed, 2 Sep 2009 07:39:34 +0200 From: Magnus Therning <mag...@therning.org> Subject: Re: [Haskell-beginners] Utter Newbie - simple problems, output - GHC vs GHCi To: Nigel Rantor <wig...@wiggly.org> Cc: beginners@haskell.org Message-ID: <e040b520909012239t7f64b69fia83e1926f8eab...@mail.gmail.com> Content-Type: text/plain; charset=UTF-8 On Mon, Aug 31, 2009 at 12:32 AM, Nigel Rantor<wig...@wiggly.org> wrote: > Magnus Therning wrote: >> On Sun, Aug 30, 2009 at 11:09 PM, Nigel Rantor<wig...@wiggly.org> wrote: >>> >>> length( filter( Char.isLower "LoweR" ) ) >> >> try this instead >> >> length (filter Char.isLower "LoweR") >> >> `filter` takes two arguments. > > Thank you, I have been flip-flopping between having no parentheses and > lots...I think I get it now. > > I owe you a beer. > > This will, however, probably not be my last post... I'm most often in Cambridge, but do find myself in London occasionally. Adding more beers to the first one is nothing I shy away from :-) /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnusï¼ therningï¼org Jabber: magnusï¼ therningï¼org http://therning.org/magnus identi.ca|twitter: magthe ------------------------------ Message: 5 Date: Wed, 2 Sep 2009 20:21:43 +0900 From: KwangYul Seo <kwangyul....@gmail.com> Subject: [Haskell-beginners] Using FiniteMap in ghci To: beginners@haskell.org Message-ID: <7beb12420909020421v191f7210k35f5eafcccef2...@mail.gmail.com> Content-Type: text/plain; charset="utf-8" Hello, I tried to load FiniteMap module in ghci and encountered an error message like the following: Prelude> import FiniteMap Could not find module `FiniteMap': it is a member of package ghc-6.8.2, which is hidden The error message says that it is hidden. How can I use the FiniteMap? Regards, Kwang Yul Seo -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.haskell.org/pipermail/beginners/attachments/20090902/1823774e/attachment-0001.html ------------------------------ Message: 6 Date: Wed, 2 Sep 2009 14:02:28 +0200 From: Chadda? Fouch? <chaddai.fou...@gmail.com> Subject: Re: [Haskell-beginners] Using FiniteMap in ghci To: KwangYul Seo <kwangyul....@gmail.com> Cc: beginners@haskell.org Message-ID: <e9350eaf0909020502k5cd0aaa7j762f107b11b94...@mail.gmail.com> Content-Type: text/plain; charset=UTF-8 On Wed, Sep 2, 2009 at 1:21 PM, KwangYul Seo<kwangyul....@gmail.com> wrote: > The error message says that it is hidden. How can I use the FiniteMap? FiniteMap has been superceded by Data.Map, this is probably what you want to use (or Data.IntMap if your keys are Int). -- Jedaï ------------------------------ Message: 7 Date: Wed, 2 Sep 2009 21:34:42 +0900 From: KwangYul Seo <kwangyul....@gmail.com> Subject: Re: [Haskell-beginners] Using FiniteMap in ghci To: Chadda? Fouch? <chaddai.fou...@gmail.com> Cc: beginners@haskell.org Message-ID: <7beb12420909020534m31981cc9wae2da87038282...@mail.gmail.com> Content-Type: text/plain; charset=UTF-8 Oh, I see. Thanks. I was playing with code from Yet Another Haskell Tutorial, and it uses FiniteMap there. I think the tutorial needs to be updated too. Regards, Kwang Yul Seo On Wed, Sep 2, 2009 at 9:02 PM, Chaddaï Fouché <chaddai.fou...@gmail.com> wrote: > > On Wed, Sep 2, 2009 at 1:21 PM, KwangYul Seo<kwangyul....@gmail.com> wrote: > > The error message says that it is hidden. How can I use the FiniteMap? > > FiniteMap has been superceded by Data.Map, this is probably what you > want to use (or Data.IntMap if your keys are Int). > > -- > Jedaï ------------------------------ Message: 8 Date: Wed, 2 Sep 2009 15:18:38 +0200 From: Daniel Fischer <daniel.is.fisc...@web.de> Subject: Re: [Haskell-beginners] Using FiniteMap in ghci To: beginners@haskell.org Message-ID: <200909021518.38642.daniel.is.fisc...@web.de> Content-Type: text/plain; charset="iso-8859-15" Am Mittwoch 02 September 2009 13:21:43 schrieb KwangYul Seo: > Hello, > > I tried to load FiniteMap module in ghci and encountered an error message > like the following: > > Prelude> import FiniteMap > Could not find module `FiniteMap': > it is a member of package ghc-6.8.2, which is hidden > > The error message says that it is hidden. How can I use the FiniteMap? > > Regards, > Kwang Yul Seo As Chaddai said, it's obsolete and superceded by Data.Map and Data.IntMap. But the names and types of some functions have been changed, if you don't want to change the tutorial code so that it works with the new modules, you can ghc-pkg expose ghc-6.8.2 then work with FiniteMap and afterwards ghc-pkg hide ghc-6.8.2 ------------------------------ Message: 9 Date: Wed, 2 Sep 2009 18:48:27 +0300 From: ??????? ???????????? <giannisma...@gmail.com> Subject: [Haskell-beginners] function - argument termination problem To: beginners@haskell.org Message-ID: <cd6a21080909020848x35f413b2ua3e74bc449776...@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Hello, Is it possible to implement in haskell a function f (A) such that if A does not ever terminate then f always terminates, and if A always terminates then f does not ever terminate? I've been thinking it for a while, with no results unfortunately. the actual problem is that i can think of no way to force both ifs: a function that always terminates independently from its argument could be f (a) = 1, and a function that does not terminate even if its argument terminates could be: f (a) = f (a + 1), but i can't figure out a "hybrid" version... Is there any idea on this? Thanks in advance :-), yannis ------------------------------ Message: 10 Date: Wed, 2 Sep 2009 11:54:30 -0400 From: Rahul Kapoor <r...@trie.org> Subject: Re: [Haskell-beginners] function - argument termination problem To: ??????? ???????????? <giannisma...@gmail.com> Cc: beginners@haskell.org Message-ID: <d30711370909020854t68f512acraa9e6e60bac62...@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 > Is it possible to implement in haskell a function f (A) such that if A > does not ever terminate then f always terminates, and if A always > terminates then f does not ever terminate? Is the argument A itself another function? If so, such a function does not exist. See http://en.wikipedia.org/wiki/Halting_problem for more details. Rahul ------------------------------ Message: 11 Date: Wed, 2 Sep 2009 17:56:41 +0200 From: Magnus Therning <mag...@therning.org> Subject: Re: [Haskell-beginners] function - argument termination problem To: ??????? ???????????? <giannisma...@gmail.com> Cc: beginners@haskell.org Message-ID: <e040b520909020856v61eb2069h309adf6f25f72...@mail.gmail.com> Content-Type: text/plain; charset=UTF-8 2009/9/2 ÎÎ¹Î¬Î½Î½Î·Ï ÎανÏÎ¶Î¿Ï ÏάÏÎ¿Ï <giannisma...@gmail.com>: > Hello, > > Is it possible to implement in haskell a function f (A) such that if A > does not ever terminate then f always terminates, and if A always > terminates then f does not ever terminate? I've been thinking it for a > while, with no results unfortunately. the actual problem is that i can > think of no way to force both ifs: a function that always terminates > independently from its argument could be f (a) = 1, and a function > that does not terminate even if its argument terminates could be: f > (a) = f (a + 1), but i can't figure out a "hybrid" version... Is there > any idea on this? > > Thanks in advance :-), Isn't this the halting problem? /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnusï¼ therningï¼org Jabber: magnusï¼ therningï¼org http://therning.org/magnus identi.ca|twitter: magthe ------------------------------ _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners End of Beginners Digest, Vol 15, Issue 1 ****************************************