June 2010 - Haskell-Cafe

Re: [Gtk2hs-users] Woes on MacOS 10.6 - linking issues -now working, but Glade is missing in v0.11 and v0.10.1 still won't compile SOLVED compile of 10.1
by Brett Giles 12 Jun '10

12 Jun '10

Finally figured it out - leave the scripts for ghc and hsc2hs alone and do the configure for gtk2hs 0.10.11 like this: ./configure --with-hsc2hs='--cc-flag=-m32 --ld-flag=-m32' On Jun 12,2010, at 3:53 PM, Brett Giles wrote: > Hi everyone, > > Thanks for the variety of suggestions - I resolved this by uninstalling the Haskell-platform DMG based package and using the one from macports. I then, as mentioned elsewhere, manually modified my hsc2hs shell script to ensure the correct code was generated. > > However, I see that the cabal install for version 11 contains no Glade modules. I saw there was a patch posted by Andy Stewart for it a while back, is there any ETA for it for the public? > > I am, (so sad for me:) a bit hooped as I was going to give a demo of a program in a couple of days, but my code depends heavily on Glade and I can't seem to get the prior version of Gtk2HS (0.10.1) to compile at all. (Issues with x86_64 vs i386 - but I have tried for three hours to get the magic combination of modifications to the ghc script, the hsc2hs script and environment variable to no avail). > > If anyone has had luck on getting the 10.1 version to build (on a brand new install of OSx v10.6.3, macports Haskell Platform meaning GHC is 6.10.4, I'd love to hear how you did it. > > (I did check out the variety of tickets related to this, especially http://hackage.haskell.org/trac/ghc/ticket/3400 and the recent conversations on this list between Chris K. and Axel. > > > On Jun 11,2010, at 2:40 AM, Axel Simon wrote: > >> Hi Brett, >> >> On 11.06.2010, at 04:53, Brett Giles wrote: >> >>> Hi Folks >>> >>> I seem to have Gtk2HS 0.11 installed, but not quite working. Interestingly, I can run a demo, such as the hello/World.hs example, directly in ghci. However, when I try to do a ghc --make on any code containing gtk2hs I get a link error like this: >>> >>> Undefined symbols: >>> "_iconv_close", referenced from: >>> _hs_iconv_close in libHSbase-4.2.0.0.a(iconv.o) >>> (maybe you meant: _hs_iconv_close) >>> "_iconv", referenced from: >>> _hs_iconv in libHSbase-4.2.0.0.a(iconv.o) >>> (maybe you meant: _hs_iconv_open, _hs_iconv , _hs_iconv_close ) >>> "_iconv_open", referenced from: >>> _hs_iconv_open in libHSbase-4.2.0.0.a(iconv.o) >>> (maybe you meant: _hs_iconv_open) >>> ld: symbol(s) not found >>> >>> >>> I do have libiconv installed as a universal library via macports. gtk, glade etc., are also universal installed via macports. >>> >> >>> I downloaded the OSX Haskell Platform package and am running ghc 6.12.1 >>> >> >> >> The iconv issue is usually that you also have a libiconv that Apple ships. The platform ghc probably links against that while macports (and thus Gtk+) uses its own. I have no idea who's to blame here but I guess you should be trying to change your LD_LIBRARY_PATH or your DYLD_LIBRARY_PATH to /opt/sw since that contains the more complete version. >> >> Cheers, >> Axel > > Brett Giles > Grad Student, Formal Methods, Category Theory, > University of Calgary > brett.giles(a)ucalgary.ca > > > > > ------------------------------------------------------------------------------ > ThinkGeek and WIRED's GeekDad team up for the Ultimate > GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the > lucky parental unit. See the prize list and enter to win: > http://p.sf.net/sfu/thinkgeek-promo > _______________________________________________ > Gtk2hs-users mailing list > Gtk2hs-users(a)lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/gtk2hs-users > > Brett Giles Grad Student, Formal Methods, Category Theory, University of Calgary brett.giles(a)ucalgary.ca

1 0

Re: [Haskell] ANNOUNCE: Sifflet visual programming language, release 0.1.7
by Henning Thielemann 12 Jun '10

12 Jun '10

On Fri, 11 Jun 2010, Ben Millwood wrote: > On Fri, Jun 11, 2010 at 2:52 PM, Henning Thielemann > <lemming(a)henning-thielemann.de> wrote: >> >> I'm uncertain whether fgl conforms to the package versioning policy, but >> if it does, then changes in its Cabal file should not bother sifflet. >> Thus upper bound fgl < 5.4.3 should be restrictive enough. >> > > The PVP says that one of the first two numbers are required to change > if an API change is likely to break code using it, so < 5.5 would > probably suffice. A bump to fgl-5.4.3 might include API *extensions* that may break sifflet, if it imports entire FGL modules in an unqualified way.

4 3

Similarities between web programming and functional programming
by Nilanjan Raychaudhuri 12 Jun '10

12 Jun '10

Hi all, As a newbie into functional programming and especially Haskell I am curious to know how functional programming style fits into building web applications? And how it compares to building web apps in Ruby or Java. Any pointer to article/literature will be helpful. Thanks Nilanjan

3 2

Re: [Gtk2hs-users] Woes on MacOS 10.6 - linking issues -now working, but Glade is missing in v0.11 and v0.10.1 still won't compile
by Brett Giles 12 Jun '10

12 Jun '10

Hi everyone, Thanks for the variety of suggestions - I resolved this by uninstalling the Haskell-platform DMG based package and using the one from macports. I then, as mentioned elsewhere, manually modified my hsc2hs shell script to ensure the correct code was generated. However, I see that the cabal install for version 11 contains no Glade modules. I saw there was a patch posted by Andy Stewart for it a while back, is there any ETA for it for the public? I am, (so sad for me:) a bit hooped as I was going to give a demo of a program in a couple of days, but my code depends heavily on Glade and I can't seem to get the prior version of Gtk2HS (0.10.1) to compile at all. (Issues with x86_64 vs i386 - but I have tried for three hours to get the magic combination of modifications to the ghc script, the hsc2hs script and environment variable to no avail). If anyone has had luck on getting the 10.1 version to build (on a brand new install of OSx v10.6.3, macports Haskell Platform meaning GHC is 6.10.4, I'd love to hear how you did it. (I did check out the variety of tickets related to this, especially http://hackage.haskell.org/trac/ghc/ticket/3400 and the recent conversations on this list between Chris K. and Axel. > > > On Jun 11,2010, at 2:40 AM, Axel Simon wrote: > >> Hi Brett, >> >> On 11.06.2010, at 04:53, Brett Giles wrote: >> >>> Hi Folks >>> >>> I seem to have Gtk2HS 0.11 installed, but not quite working. Interestingly, I can run a demo, such as the hello/World.hs example, directly in ghci. However, when I try to do a ghc --make on any code containing gtk2hs I get a link error like this: >>> >>> Undefined symbols: >>> "_iconv_close", referenced from: >>> _hs_iconv_close in libHSbase-4.2.0.0.a(iconv.o) >>> (maybe you meant: _hs_iconv_close) >>> "_iconv", referenced from: >>> _hs_iconv in libHSbase-4.2.0.0.a(iconv.o) >>> (maybe you meant: _hs_iconv_open, _hs_iconv , _hs_iconv_close ) >>> "_iconv_open", referenced from: >>> _hs_iconv_open in libHSbase-4.2.0.0.a(iconv.o) >>> (maybe you meant: _hs_iconv_open) >>> ld: symbol(s) not found >>> >>> >>> I do have libiconv installed as a universal library via macports. gtk, glade etc., are also universal installed via macports. >>> >> >>> I downloaded the OSX Haskell Platform package and am running ghc 6.12.1 >>> >> >> >> The iconv issue is usually that you also have a libiconv that Apple ships. The platform ghc probably links against that while macports (and thus Gtk+) uses its own. I have no idea who's to blame here but I guess you should be trying to change your LD_LIBRARY_PATH or your DYLD_LIBRARY_PATH to /opt/sw since that contains the more complete version. >> >> Cheers, >> Axel Brett Giles Grad Student, Formal Methods, Category Theory, University of Calgary brett.giles(a)ucalgary.ca

1 0

Looking for Haskell presenter in/around Columbus area
by Nilanjan Raychaudhuri 12 Jun '10

12 Jun '10

Hi all, I run a small meet up group called "Columbus polyglot programmer meet up group" ( http://www.meetup.com/The-Columbus-Polyglot-Programmers-Meetup-Group/) where bunch of us get together once in a month and talk about various programming languages. There is quite a bit of interest in Haskell and functional programming in general among the group. I was wondering whether anyone from the list who lives around Columbus, ohio area would be interested to talk about Haskell. Thanks Nilanjan

1 0

Iteratee rest and monad instance
by Tilo Wiklund 12 Jun '10

12 Jun '10

I've mostly been studying the Iteratee IO slides (with notes), so these things may already have been noted elsewhere (though I have not been able to find them with my cursory search). Also excuse my probably somewhat confused terminology, I hope I get the point across anyway. In both the slides and the current hackage package "finished" iteratees carry with them (in the constructor) the rest of the stream. I may miss something obvious here, but this seems to lead to some fishy details in the monad instance of iteratees presented in the slides. Firstly the iteratee given by return/pure has to carry with it a rest before a stream comes into the picture, though I guess one could argue that (Chunk "") is some kind of identity but this does not seem to be enforced in any way. Furthermore in the bind operator the rest of the iteratee from the bound (RHS) function seems to be ignored at some times and not at others (depending on the rest of the bound LHS value). I am probably missing something obvious or something relating to optimisation/server software but defining iteratees as "Iteratee s a = Cont (s -> Either (s, a) (Iteratee s a))" seems to lead to a more natural monad instance, and does not suffer from (what seems to me to be an issue) having to make predictions about the stream it will be passed. My question is thus, why the "rest" stream has to be carried by an Iteratee constructor, rather then be part of the value of the continuation function.

2 1

GATD and pattern matching
by Dupont Corentin 12 Jun '10

12 Jun '10

Hello, I am making a little GATD: > {-# LANGUAGE GADTs#-} > data Obs a where > Equal :: Obs a -> Obs a -> Obs Bool > Plus :: (Num a) => Obs a -> Obs a -> Obs a (etc..) > instance Show t => Show (Obs t) where > show (Equal a b) = (show a) ++ " Equal " ++ (show b) > show (Plus a b) = (show a) ++ " Plus " ++ (show b) > instance Eq t => Eq (Obs t) where > a `Equal` b == c `Equal` d = (a == c) && (b == d) > a `Plus` b == c `Plus` d = (a == c) && (b == d) The Equal constructor causes me problems, while the Plus is fine: test3.lhs:8:26: Could not deduce (Show a) from the context (t ~ Bool) arising from a use of `show' at test3.lhs:8:26-31 Possible fix: add (Show a) to the context of the constructor `Equal' In the first argument of `(++)', namely `(show a)' In the expression: (show a) ++ " Equal " ++ (show b) In the definition of `show': show (Equal a b) = (show a) ++ " Equal " ++ (show b) I guess this is because GADT refines type with pattern matching. Since Equal return type is Obs Bool and not Obs a, it cannot bind the type variable a to belong to Show. I don't see how to precise the type in the pattern match. I have another problem: test3.lhs:12:41: Couldn't match expected type `a' against inferred type `a1' `a' is a rigid type variable bound by the constructor `Equal' at test3.lhs:12:8 `a1' is a rigid type variable bound by the constructor `Equal' at test3.lhs:12:23 Expected type: Obs a Inferred type: Obs a1 In the second argument of `(==)', namely `c' In the first argument of `(&&)', namely `(a == c)' Cheers, Corentin

8 14

Re: [Haskell-cafe] Problems with threading?
by Isaac Gouy 11 Jun '10

11 Jun '10

--- On Thu, 6/10/10, Louis Wasserman <wasserman.louis(a)gmail.com> wrote: > Date: Thursday, June 10, 2010, 1:32 AM > Yeah, Control.Parallel would be nice to have. Heck, ideally I could get > the whole Haskell Platform, which would be a reasonable comparison to > the huge Java and C++ libraries accessible to those languages. And having the whole Haskell Platform still isn't enough to compile those regex-dna programs.

1 0

Code review of text-xml-generic
by Oscar Finnsson 11 Jun '10

11 Jun '10

Hi, I've been working on a (de)serialization package from/to XML (using SYB) and wondering if anyone feels like giving me a quick code review before I upload it to hackagedb. The source code can be found at http://github.com/finnsson/Text.XML.Generic It is *heavily* inspired by Text.JSON.Generic. The three files DataEx.hs (slightly modified version of Olegs code), ExGeneric.hs and ExTestGeneric.hs are not part of the package yet since I haven't got the deserialization to work for existentials yet (but I haven't given up!). I plan to upload the package to hackagedb by the end of this weekend so any comments before (and after) are more than welcome. -- Oscar

1 0

Encoding the encoding type of a string into its type
by Christopher Done 11 Jun '10

11 Jun '10

There are a lot of issues with string encoding type mismatches. Especially "automatic" conversions. This mailing list gets enough posts about encoding confusions. Would it make sense to make the string depend on its encoding type? E.g. a String UTF16 cannot be used with putStrLn :: String UTF8, it has to be used with putStrLn :: String UTF16. Provided the fundamental functions that read and write strings are type safe, there'll be no mix-ups? I'll think about this more later. Just putting the question out there so that I remember when I get home.

2 1