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YAHT Question about Exercise 4.8
by Futari 25 Jul '09

25 Jul '09

Hi, I was trying to use the solution given, but I don't know how to use it... How do I create something that is of type List? data List a = Nil | Cons a (List a) >From the previous examples, I was thinking something like Cons 'a' 'b' 'c' would create a list ['a','b','c'] but it gave me errors... help please, thanks. -- View this message in context: http://www.nabble.com/YAHT-Question-about-Exercise-4.8-tp24655087p24655087.… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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ANNOUNCE: graphviz-2999.1.0.2
by Ivan Lazar Miljenovic 25 Jul '09

25 Jul '09

This is a bug release that fixes a bug spotted by Srihari Ramanathan where the Dot representation of Color values were double-quoted when they shouldn't have been. -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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System.Mem.performGC leaks?
by Neal Alexander 25 Jul '09

25 Jul '09

main = forever performGC The OS reported memory usage skyrockets. If i enable +RTS -S the GC statistics show the heap "live bytes" being constant. Is it accumulating statistics even when profiling is disabled (and can you turn that off), or is there something going on with the FFI call to performGC. Compiled with "ghc -O2 -fvia-C -optc-O2 -funbox-strict-fields -threaded" btw.

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Haskell on a VPS
by John Van Enk 25 Jul '09

25 Jul '09

Has any one used a service similar to (or equivelant to) Slicehost or Linode to run Haskell network applications?

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Re:Haskell-Cafe Digest, Vol 71, Issue 30
by silent_stream 24 Jul '09

24 Jul '09

When I compile curl-1.3.5 on Windows xp. I run the prompt "runghc Setup.hs configure " I got the following error Setup.hs: Missing dependency on a foreign library: * Missing C library: curl This problem can usually be solved by installing the system package that provides this library (you may need the "-dev" version). If the library is already installed but in a non-standard location then you can use the flags --extra-include-dirs= and --extra-lib-dirs= to specify where it is. I don't know how to fix this problem. Who knows? Please come to help me . 在2009-07-21 09:43:45，haskell-cafe-request@haskell.org 写道： >Send Haskell-Cafe mailing list submissions to > haskell-cafe(a)haskell.org > >To subscribe or unsubscribe via the World Wide Web, visit > http://www.haskell.org/mailman/listinfo/haskell-cafe >or, via email, send a message with subject or body 'help' to > haskell-cafe-request(a)haskell.org > >You can reach the person managing the list at > haskell-cafe-owner(a)haskell.org > >When replying, please edit your Subject line so it is more specific >than "Re: Contents of Haskell-Cafe digest..." > > >Today's Topics: > > 1. Hackage and version control (Vasili I. Galchin) > 2. FFI problem - possibility of CStringLen overflow? (Robin Green) > 3. Re: FFI problem - possibility of CStringLen overflow? > (Bulat Ziganshin) > 4. Re: Hackage and version control (Magnus Therning) > 5. Re: was: Debugging methods for haskell structured data types > the right way in haskell (Jon Fairbairn) > 6. Re: Hackage and version control (Bulat Ziganshin) > 7. Re: Hackage and version control (Robin Green) > 8. Re: Hackage and version control (Miguel Mitrofanov) > 9. Re: Hackage and version control (Joe Fredette) > 10. Re: Hackage and version control (Wolfgang Jeltsch) > 11. Re[2]: [Haskell-cafe] Hackage and version control > (Bulat Ziganshin) > 12. Re: ANN: cautious-file 0.1.1: Ways to write a file > cautiously, to avoid data loss (Robin Green) > 13. Re: Implicit concatenation in list comprehensions (Roel van Dijk) > 14. Re: ANN: cautious-file 0.1.1: Ways to write a file > cautiously, to avoid data loss (Felipe Lessa) > 15. Typeclass default implementation in subclasses (Andy Gimblett) > 16. ICFP contest write-up (Rafael Gustavo da Cunha Pereira Pinto) > 17. SpecConstr difficulties (Reiner Pope) > 18. Re: Typeclass default implementation in subclasses (Roel van Dijk) > 19. ANNOUNCE: graphviz-2999.1.0.1 (Ivan Lazar Miljenovic) > 20. Re: Implicit concatenation in list comprehensions (Roel van Dijk) > 21. RE: Implicit concatenation in list comprehensions > (Sittampalam, Ganesh) > 22. Re: Implicit concatenation in list comprehensions (Roel van Dijk) > 23. Re: FFI problem - possibility of CStringLen overflow? > (Jason Dagit) > 24. Anglohaskell - wifi signups (Philippa Cowderoy) > 25. Pruning the Front Page (Thomas DuBuisson) > 26. Re: Pruning the Front Page (Don Stewart) > 27. Re: Implicit concatenation in list comprehensions > (Max Bolingbroke) > 28. Re: Ambiguous type variable - help! (phil(a)beadling.co.uk) > 29. Re: Implicit concatenation in list comprehensions > (Nicolas Pouillard) > 30. Re: Implicit concatenation in list comprehensions (porges(a)porg.es) > 31. Re: Pruning the Front Page (Gwern Branwen) > > >---------------------------------------------------------------------- > >Message: 1 >Date: Mon, 20 Jul 2009 03:26:52 -0500 >From: "Vasili I. Galchin" <vigalchin(a)gmail.com> >Subject: [Haskell-cafe] Hackage and version control >To: haskell-cafe(a)haskell.org >Cc: Galchin Vasili <vigalchin(a)gmail.com> >Message-ID: > <5ae4f2ba0907200126j56a497earb06ae885dbb7bb81(a)mail.gmail.com> >Content-Type: text/plain; charset="iso-8859-1" > >Hello, > > It seems to me that Hackage doesn't provide version control, e.g. check >out and check in. Am I incorrect? > >Kind regards, Vasili >-------------- next part -------------- >An HTML attachment was scrubbed... >URL: http://www.haskell.org/pipermail/haskell-cafe/attachments/20090720/9a2c1cb3… > >------------------------------ > >Message: 2 >Date: Mon, 20 Jul 2009 03:24:49 +0100 >From: Robin Green <greenrd(a)greenrd.org> >Subject: [Haskell-cafe] FFI problem - possibility of CStringLen > overflow? >To: haskell-cafe(a)haskell.org >Message-ID: <20090720032449.690fdf47@fedora> >Content-Type: text/plain; charset=US-ASCII > >While rewriting cautious-file to use ByteStrings and FFI just now, I >came across this potential problem: > >Why does the FFI specification define CStringLen as (Ptr CChar, Int)? >As the FFI specification itself notes, Haskell 98 implementors are >allowed to have a quite small range for Int (only up to 2^29-1) - so you >could in principle have a very large String which cannot be represented >as a CStringLen, or a very large CString which cannot be represented as >a CStringLen. They would take up wads of memory, so this has probably >never happened yet, but it's in principle possible, no? > >If so, what are the implications of this for code correctness? >-- >Robin > > >------------------------------ > >Message: 3 >Date: Mon, 20 Jul 2009 12:49:38 +0400 >From: Bulat Ziganshin <bulat.ziganshin(a)gmail.com> >Subject: Re: [Haskell-cafe] FFI problem - possibility of CStringLen > overflow? >To: Robin Green <greenrd(a)greenrd.org> >Cc: haskell-cafe(a)haskell.org >Message-ID: <1096519401.20090720124938(a)gmail.com> >Content-Type: text/plain; charset=us-ascii > >Hello Robin, > >Monday, July 20, 2009, 6:24:49 AM, you wrote: > >> Why does the FFI specification define CStringLen as (Ptr CChar, Int)? > >1. i think it was done to simplify using the api >2. hugs usually don't used for data-massive apps, it's niche is learning and >quick development > >-- >Best regards, > Bulat mailto:Bulat.Ziganshin@gmail.com > > > >------------------------------ > >Message: 4 >Date: Mon, 20 Jul 2009 10:03:56 +0100 >From: Magnus Therning <magnus(a)therning.org> >Subject: Re: [Haskell-cafe] Hackage and version control >To: "Vasili I. Galchin" <vigalchin(a)gmail.com> >Cc: haskell-cafe(a)haskell.org >Message-ID: > <e040b520907200203w2f6392acy62e6571899866253(a)mail.gmail.com> >Content-Type: text/plain; charset=UTF-8 > >On Mon, Jul 20, 2009 at 9:26 AM, Vasili I. Galchin<vigalchin(a)gmail.com> wrote: >> Hello, >> >> Â Â Â Â It seems to me that Hackage doesn't provide version control, e.g. check >> out and check in. Am I incorrect? > >Hackage is, AFAIU, a repository where _released_ versions of >libraries/tools/etc related to Haskell can be kept. It is not fully >comparable to SourceForge, Github, or any other _source hosting_ >service. > >If you are looking for source hosting then take a look at SF, Github, >Google Code, or something like that. Then upload _released_ versions >to Hackage. IIRC there is also the possibility of having a Darcs repo >on community.haskell.org. > >/M > >-- >Magnus Therning (OpenPGP: 0xAB4DFBA4) >magnusï¼ therningï¼org Jabber: magnusï¼ therningï¼org >http://therning.org/magnus identi.ca|twitter: magthe > > >------------------------------ > >Message: 5 >Date: Mon, 20 Jul 2009 10:26:02 +0100 >From: Jon Fairbairn <jon.fairbairn(a)cl.cam.ac.uk> >Subject: [Haskell-cafe] Re: was: Debugging methods for haskell > structured data types the right way in haskell >To: haskell-cafe(a)haskell.org >Message-ID: <wfd47viu39.fsf(a)calligramme.charmers> >Content-Type: text/plain; charset=utf-8 > >Fernan Bolando <fernanbolando(a)mailc.net> writes: > >> On Sun, Jul 19, 2009 at 7:40 AM, wren ng thornton<wren(a)freegeek.org> wrote: >>> Fernan Bolando wrote: >>>> >>>> The intention is z0 is a system parameter and database, it contains a >>>> set of info needed to define a particular simulation >>> >>> A single-constructor ADT, especially with the labeled-fields syntax, is >>> pretty close to C structs; no need to reinvent them and give yourself >>> headaches. >>> >>> >>> Really, the only thing you should be using lists for is a variable-length >>> sequence of elements drawn from the same type and distinguished only by >>> their position in the sequence. >> >> This is the kind of code recommendations I was looking. > >I'd worked out a longer reply over the weekend, but wren got there first >(It hadn't occured to me that anyone would write that much code without >knowing about algebraic types, so thought something else was going on). > >I'd like to add that thinking about the C code for a programme like this >is counterproductive. If you are doing various mathematical operations, >it's better to go straight from the mathematics to Haskell, and work out >the appropriate abstractions (in Haskell) for the operations you are >using. You'll generally end up with much shorter code that is easier to >maintain. > >It might be worth pointing out that you can do things with Haskell data >structures that you can't do conveniently in C. For example, if you were >doing something that involved calculating the determinants of matrices >fairly often, but you didn't know in advance which matrices, you could >define your own matrix type like this (roughly): > >data MyMatrix t = MM {theNumbers:: Matrix t, my_determinant:: t} > >make_matrix m > = MM {theNumbers = m, > my_determinant = determinant m > } > >and then use make_matrix whenever you make a new matrix and >my_determinant whenever you want a determinant. > >Now, although to a C programmer this looks like you calculate the >determinant of every matrix, laziness means that you only calculate the >ones you use, and calculate them at most once for each matrix. > > >-- >JÃ³n Fairbairn Jon.Fairbairn(a)cl.cam.ac.uk > > > > >------------------------------ > >Message: 6 >Date: Mon, 20 Jul 2009 13:27:06 +0400 >From: Bulat Ziganshin <bulat.ziganshin(a)gmail.com> >Subject: Re: [Haskell-cafe] Hackage and version control >To: "Vasili I. Galchin" <vigalchin(a)gmail.com> >Cc: haskell-cafe(a)haskell.org >Message-ID: <1393740130.20090720132706(a)gmail.com> >Content-Type: text/plain; charset=iso-8859-1 > >Hello Vasili, > >Monday, July 20, 2009, 12:26:52 PM, you wrote: > >> It seems to me that Hackage doesn't provide version control, >> e.g. check out and check in. Am I incorrect? > >i recommend you to use either codeplex or code.google > > >-- >Best regards, > Bulat mailto:Bulat.Ziganshin@gmail.com > > > >------------------------------ > >Message: 7 >Date: Mon, 20 Jul 2009 04:25:25 +0100 >From: Robin Green <greenrd(a)greenrd.org> >Subject: Re: [Haskell-cafe] Hackage and version control >To: haskell-cafe(a)haskell.org >Message-ID: <20090720042525.3e02b4ae@fedora> >Content-Type: text/plain; charset=UTF-8 > >On Mon, 20 Jul 2009 10:03:56 +0100 >Magnus Therning <magnus(a)therning.org> wrote: > >> On Mon, Jul 20, 2009 at 9:26 AM, Vasili I. >> Galchin<vigalchin(a)gmail.com> wrote: >> > Hello, >> > >> > Â Â Â Â It seems to me that Hackage doesn't provide version control, >> > e.g. check out and check in. Am I incorrect? >> >> Hackage is, AFAIU, a repository where _released_ versions of >> libraries/tools/etc related to Haskell can be kept. It is not fully >> comparable to SourceForge, Github, or any other _source hosting_ >> service. >> >> If you are looking for source hosting then take a look at SF, Github, >> Google Code, or something like that. Then upload _released_ versions >> to Hackage. IIRC there is also the possibility of having a Darcs repo >> on community.haskell.org. > >Yes, and darcs repos can also be hosted on patch-tag.com. >community.haskell.org requires you to wait for a volunteer to review >every new project request. Although, you don't need to make a >project request if you only want a 1-developer repository. And by the >way, it only hosts Haskell-related projects, not arbitrary darcs >repositories. > >patch-tag.com doesn't have those constraints. >-- >Robin > > >------------------------------ > >Message: 8 >Date: Mon, 20 Jul 2009 13:41:40 +0400 >From: Miguel Mitrofanov <miguelimo38(a)yandex.ru> >Subject: Re: [Haskell-cafe] Hackage and version control >To: Bulat Ziganshin <Bulat.Ziganshin(a)gmail.com> >Cc: "Vasili I. Galchin" <vigalchin(a)gmail.com>, > haskell-cafe(a)haskell.org >Message-ID: <A8F1BE77-CDC2-4800-9072-78B446CDF84E(a)yandex.ru> >Content-Type: text/plain; charset=US-ASCII; format=flowed > >Or patch-tag.com > >On 20 Jul 2009, at 13:27, Bulat Ziganshin wrote: > >> Hello Vasili, >> >> Monday, July 20, 2009, 12:26:52 PM, you wrote: >> >>> It seems to me that Hackage doesn't provide version control, >>> e.g. check out and check in. Am I incorrect? >> >> i recommend you to use either codeplex or code.google >> >> >> -- >> Best regards, >> Bulat mailto:Bulat.Ziganshin@gmail.com >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe > > > >------------------------------ > >Message: 9 >Date: Mon, 20 Jul 2009 06:36:28 -0400 >From: Joe Fredette <jfredett(a)gmail.com> >Subject: Re: [Haskell-cafe] Hackage and version control >To: Bulat Ziganshin <Bulat.Ziganshin(a)gmail.com> >Cc: "Vasili I. Galchin" <vigalchin(a)gmail.com>, > haskell-cafe(a)haskell.org >Message-ID: <4A6448AC.6060202(a)gmail.com> >Content-Type: text/plain; charset="iso-8859-1" > >Don't forget about Patch-tag! > >Bulat Ziganshin wrote: >> Hello Vasili, >> >> Monday, July 20, 2009, 12:26:52 PM, you wrote: >> >> >>> It seems to me that Hackage doesn't provide version control, >>> e.g. check out and check in. Am I incorrect? >>> >> >> i recommend you to use either codeplex or code.google >> >> >> >-------------- next part -------------- >A non-text attachment was scrubbed... >Name: jfredett.vcf >Type: text/x-vcard >Size: 296 bytes >Desc: not available >Url : http://www.haskell.org/pipermail/haskell-cafe/attachments/20090720/42d7f039… > >------------------------------ > >Message: 10 >Date: Mon, 20 Jul 2009 12:40:14 +0200 >From: Wolfgang Jeltsch <g9ks157k(a)acme.softbase.org> >Subject: Re: [Haskell-cafe] Hackage and version control >To: haskell-cafe(a)haskell.org >Message-ID: <200907201240.14760.g9ks157k(a)acme.softbase.org> >Content-Type: text/plain; charset="utf-8" > >Am Montag, 20. Juli 2009 05:25 schrieb Robin Green: >> community.haskell.org requires you to wait for a volunteer to review >> every new project request. > >However, response times are usually low. > >Best wishes, >Wolfgang > > >------------------------------ > >Message: 11 >Date: Mon, 20 Jul 2009 14:41:25 +0400 >From: Bulat Ziganshin <bulat.ziganshin(a)gmail.com> >Subject: Re[2]: [Haskell-cafe] Hackage and version control >To: Joe Fredette <jfredett(a)gmail.com> >Cc: "Vasili I. Galchin" <vigalchin(a)gmail.com>, Bulat Ziganshin > <Bulat.Ziganshin(a)gmail.com>, haskell-cafe(a)haskell.org >Message-ID: <121430820.20090720144125(a)gmail.com> >Content-Type: text/plain; charset=us-ascii > >Hello Joe, > >Monday, July 20, 2009, 2:36:28 PM, you wrote: > >afaik it provides minimal features, only VCS, while sitea i mentioned >provides full service for OSS developer > >> Don't forget about Patch-tag! > >> Bulat Ziganshin wrote: >>> Hello Vasili, >>> >>> Monday, July 20, 2009, 12:26:52 PM, you wrote: >>> >>> >>>> It seems to me that Hackage doesn't provide version control, >>>> e.g. check out and check in. Am I incorrect? >>>> >>> >>> i recommend you to use either codeplex or code.google >>> >>> >>> > > > >-- >Best regards, > Bulat mailto:Bulat.Ziganshin@gmail.com > > > >------------------------------ > >Message: 12 >Date: Mon, 20 Jul 2009 06:09:50 +0100 >From: Robin Green <greenrd(a)greenrd.org> >Subject: Re: [Haskell-cafe] ANN: cautious-file 0.1.1: Ways to write a > file cautiously, to avoid data loss >To: haskell-cafe(a)haskell.org >Message-ID: <20090720060950.076176fa@fedora> >Content-Type: text/plain; charset=US-ASCII > >I've since uploaded two new versions with the following changes: > >0.1.2: Fixed an issue where it would clobber symbolic links to files, >which is usually not what you want. Test case added for this. > >0.1.3: ByteString support! FFI is also now used under the hood to do >things in a slightly less hacky way. > >-- >Robin > >On Sun, 19 Jul 2009 23:35:34 +0100 >Robin Green <greenrd(a)greenrd.org> wrote: > >> I'm pleased to announce the first public release of cautious-file: >> >> http://hackage.haskell.org/package/cautious-file ><snip> > > >------------------------------ > >Message: 13 >Date: Mon, 20 Jul 2009 13:27:57 +0200 >From: Roel van Dijk <vandijk.roel(a)gmail.com> >Subject: Re: [Haskell-cafe] Implicit concatenation in list > comprehensions >To: haskell-cafe <haskell-cafe(a)haskell.org> >Message-ID: > <ab9dc6fa0907200427g27ef73a1vd5b852187e6b9745(a)mail.gmail.com> >Content-Type: text/plain; charset=ISO-8859-1 > >I think the tuple sections are a great idea! It also makes tuple types >and constructors more alike: > >x :: (,) String Double >x = (,) "Pi" 3.14159 > >I can also see some uses in writing pointfree code. I would definitely >want this in a future GHC (or any other Haskell compiler/interpreter) >release. > >I'm not so sure about the list comprehension concatenation. Like >Thomas Schilling wrote, it is only a bit shorter then writing it with >the current syntax. So I'm not sure if it is worth the cost. > > >------------------------------ > >Message: 14 >Date: Mon, 20 Jul 2009 09:02:54 -0300 >From: Felipe Lessa <felipe.lessa(a)gmail.com> >Subject: Re: [Haskell-cafe] ANN: cautious-file 0.1.1: Ways to write a > file cautiously, to avoid data loss >To: haskell-cafe(a)haskell.org >Message-ID: <20090720120254.GA6396(a)kira.casa> >Content-Type: text/plain; charset=us-ascii > >Nice library! > >On Sun, Jul 19, 2009 at 11:35:34PM +0100, Robin Green wrote: >> A variant, writeFileWithBackup, also allows you to supply a custom >> backup computation to backup old copy(ies) of the destination file > >It would be nice to have the backup action receive the file name >as a parameter, so it would be possible to have a library of >possible backup strategies. :) > >-- >Felipe. > > >------------------------------ > >Message: 15 >Date: Mon, 20 Jul 2009 13:16:03 +0100 >From: Andy Gimblett <haskell(a)gimbo.org.uk> >Subject: [Haskell-cafe] Typeclass default implementation in subclasses >To: haskell-cafe(a)haskell.org >Message-ID: <5A40667D-984C-4F0A-A7E3-F21980B60CE9(a)gimbo.org.uk> >Content-Type: text/plain; charset=US-ASCII; format=flowed > >Hi all, > >This email is literate Haskell. I have a question about default >implementations of typeclasses. > > > {-# LANGUAGE TypeSynonymInstances #-} > > > module Thing where > > > import Text.PrettyPrint.HughesPJ > >Let say I want to pretty-print some values, enclosed in double quotes. >The natural thing to do (within the HughesPJ pretty-printing >framework, anyway - and that's where I am in this problem's wider >context) is: > > > ppQuote :: Show a => a -> Doc > > ppQuote = doubleQuotes . text . show > >Now, this works nicely for (say) Int: > > > x :: Int > > x = 1 > >*Thing> ppQuote x >"1" > >But less nicely for String and Char, because their Show instances >already insert double/single quotes respectively: > > > y :: String > > y = "hello" > > z :: Char > > z = 'a' > >*Thing> ppQuote y >""hello"" >*Thing> ppQuote z >"'a'" > >I don't want this. I'd like them to be "hello" and "a" respectively. > >So I thought I'd create a typeclass, whose default implementation is >as above... > > > class (Show a) => Quotable a where > > quote :: a -> Doc > > quote = ppQuote > >... but with specialised instances for String and Char (the former >seems to need the TypeSynonymInstances extension?): > > > instance Quotable String where > > quote = text . show -- don't need the doubleQuotes call for String > > instance Quotable Char where > > quote c = quote [c] -- just lift it to String > >Unfortunately, while this works great for String and Char... > >*Thing> quote y >"hello" >*Thing> quote z >"a" > >... the "default implementation" mechanism doesn't work as I'd >expect/hope: > >*Thing> quote x > ><interactive>:1:0: > No instance for (Quotable Int) > arising from a use of `quote' at <interactive>:1:0-6 > Possible fix: add an instance declaration for (Quotable Int) > In the expression: quote x > In the definition of `it': it = quote x > >What I would _like_ would be for the compiler to say "OK, the Quotable >class depends on the Show class, and Int is an instance of Show so Int >is also an instance of Quotable, having the default implementation >(since there isn't a specialised one for it)" - but clearly it >doesn't. > >Please can someone tell me why this doesn't happen, and if there is a >way of making it happen? Also, if there's a more sensible way of >attacking this whole problem, I'd be curious to hear it. > >I should perhaps add that this isn't a huge problem for me, because my >instances will in practice tend to be String and Char anyway, and one >can of course add Quotable instances for anything else easily enough - >but I'm curious now I've come this far. :-) > >Many thanks! > >-Andy > > > >------------------------------ > >Message: 16 >Date: Mon, 20 Jul 2009 09:30:24 -0300 >From: Rafael Gustavo da Cunha Pereira Pinto > <RafaelGCPP.Linux(a)gmail.com> >Subject: [Haskell-cafe] ICFP contest write-up >To: Haskell Caf? <haskell-cafe(a)haskell.org> >Message-ID: > <351ff25e0907200530s2c998777g482bd7674ad5d85a(a)mail.gmail.com> >Content-Type: text/plain; charset="iso-8859-1" > >For all Portuguese reading haskellers, I am describing my ICFP 2009 contest >write-up on my blog. Feel free to comment. > >http://rafaelgcpp.blogspot.com/search/label/ICFP2009 > > >For the non-Portuguese readers, Google translation tools do a lousy job, but >it is still readable. > >Regards > >Rafael Gustavo da Cunha Pereira Pinto >-------------- next part -------------- >An HTML attachment was scrubbed... >URL: http://www.haskell.org/pipermail/haskell-cafe/attachments/20090720/30061e23… > >------------------------------ > >Message: 17 >Date: Mon, 20 Jul 2009 22:09:09 +0930 >From: Reiner Pope <reiner.pope(a)gmail.com> >Subject: [Haskell-cafe] SpecConstr difficulties >To: Haskell Cafe mailing list <haskell-cafe(a)haskell.org> >Message-ID: > <4cf038ee0907200539w1676a6e7ub29350cf5025b91a(a)mail.gmail.com> >Content-Type: text/plain; charset=ISO-8859-1 > >Hi everyone, > >I've been having some trouble getting SpecConstr to work as I want it >to. The following example (see end of email) came up in some code I >was playing around with. The loops g1 and g2 both compute the same >thing: the maximum element of the "list" (which has been fused away) >of numbers from 1 to 10. > >Since 'maximum' is a foldl1 not a foldl, I use a strict Maybe type as >an accumulator. The Maybe gets filled after the first element is seen, >so the Maybe is a Just for almost the entire running of the loop. > >It would be good to have this recognised by SpecConstr, to create an >optimised loop for the Just case. This does indeed happen for g1, but >not for g2. > >My difficulty is that I am only able to produce code similar to g2, >i.e. where the pattern matching is in a separate function, 'expose', >because the 'expose' function is implemented in a type-class, like in >stream-fusion. Is there some way to keep the SpecConstr while leaving >the 'expose' as a separate function? > >Here is the code: > >> {-# LANGUAGE BangPatterns #-} >> >> module Test(ans1,ans2) where >> >> import Prelude hiding(Maybe(..)) >> >> data Maybe a = Just !a | Nothing >> >> Nothing `mapp` Just b = Just b >> Just a `mapp` Just b = Just (max a b) >> >> ans1 = g1 Nothing (0::Int) >> >> g1 m !n = case m of >> Nothing -> if n > 10 then m else g1 (m `mapp` Just n) (n+1) >> Just x -> if n > 10 then m else g1 (m `mapp` Just n) (n+1) >> >> ans2 = g2 Nothing (0::Int) >> >> g2 m !n = expose m (if n > 10 then m else g2 (m `mapp` Just n) (n+1)) >> expose Nothing b = b >> expose (Just a) b = a `seq` b > >On a similar note, when I was having difficulties with this problem, I >started to wonder if it would be possible to come up with a more >direct way to tell GHC, "do SpecConstr on this variable". From reading >the source code of the stream-fusion package, it seems that the >current way of doing this is with 'expose' functions like I wrote >below. Could we instead have a {-# SPECCONSTR #-} pragma, to be used >on function arguments, like: > >foo {-# SPECCONSTR #-} x y {-# SPECCONSTR #-} z = ... > >This pragma should say to the GHC something like "ignore conditions >H2, H5 and H6 of the SpecConstr paper, for this function and this >argument". > >Cheers, >Reiner > > >------------------------------ > >Message: 18 >Date: Mon, 20 Jul 2009 14:40:26 +0200 >From: Roel van Dijk <vandijk.roel(a)gmail.com> >Subject: Re: [Haskell-cafe] Typeclass default implementation in > subclasses >To: Andy Gimblett <haskell(a)gimbo.org.uk> >Cc: haskell-cafe(a)haskell.org >Message-ID: > <ab9dc6fa0907200540s211a67bby6107c556bb42f171(a)mail.gmail.com> >Content-Type: text/plain; charset=ISO-8859-1 > >This post is also literate haskell. By enabling these potentially >dangerous extensions you'll get the behaviour you want. > >> {-# LANGUAGE TypeSynonymInstances #-} >> {-# LANGUAGE UndecidableInstances #-} >> {-# LANGUAGE FlexibleInstances #-} >> {-# LANGUAGE OverlappingInstances #-} > >> module Thing where > >> import Text.PrettyPrint.HughesPJ > >> ppQuote :: Show a => a -> Doc >> ppQuote = doubleQuotes . text . show > >> x :: Int >> x = 1 > >> y :: String >> y = "hello" >> z :: Char >> z = 'a' > >> class (Show a) => Quotable a where >> quote :: a -> Doc >> quote = ppQuote > >> instance (Show a) => Quotable a > >> instance Quotable String where >> quote = text . show -- don't need the doubleQuotes call for String > >> instance Quotable Char where >> quote c = quote [c] -- just lift it to String > >Example: > >*Thing> quote "pi" >"pi" >*Thing> quote 3.14159 >"3.14159" > > >------------------------------ > >Message: 19 >Date: Mon, 20 Jul 2009 23:08:49 +1000 >From: Ivan Lazar Miljenovic <ivan.miljenovic(a)gmail.com> >Subject: [Haskell-cafe] ANNOUNCE: graphviz-2999.1.0.1 >To: haskell(a)haskell.org >Cc: haskell-cafe(a)haskell.org >Message-ID: <87vdlnwlge.fsf(a)gmail.com> >Content-Type: text/plain; charset=us-ascii > >This is a bug-fix release to fix the various Attribute-related problems >in the previous release (2999.0.0.0) spotted mainly by Zsolt >Dollenstein. Please disregard version 2999.1.0.0; it had a small bug. >Similarly, people should avoid using 2999.0.0.0 unless they don't use >any Either-based Attributes. > >The problem (which took me a while to realise) was that whilst I was >using Either to denote that an attribute could take one of two different >types of values (e.g. Bool and String) and the parsing for that worked. >However, since I was using Show (I know it's bad, it was on my TODO, >remember?) to generate the Dot code, then whenever one of these values >was converted then either Left or Right would appear, and GraphViz >doesn't seem to like that for some reason... > >I also took the opportunity to define custom types for more Attributes >(as they only accept certain String values). Furthermore, GraphViz >states that attributes that can accept a boolean value are set to True >when the attribute is listed on its own; the library now does this even >for those Attributes that use a custom type that combines Bool with >something else. One other small change is that the Color Attribute now >takes in a list of Colors; if you only want one, use a singleton list >(it was either that or a custom datatype that takes either a single >Color or a list of Colors...). > >Note that 2999.1.0.0 accidentally only had singleton Color values for >the Color Attribute rather than a list, hence the quick version bump. > >Nothing else has changed in the library apart from the Attributes. > >Regarding my request in the previous email about the possible new layout >of the DotGraph datatype: > >How many people actually build DotGraphs by hand or pull them apart by >hand? If there were getNodes :: DotGraph -> [Node] and getEdges :: >DotGraph -> [Edge] functions available, would you accept an all-in-one >data type that just contains a generic list of statements and thus >follows upstream more closely? Even leaving aside parsing, this would >allow for greater flexibility for creating wild and wacky graphs or for >a monadic interface or something for building DotGraphs (which someone >has asked me for, but which at the moment I have no idea how to do...). > >-- >Ivan Lazar Miljenovic >Ivan.Miljenovic(a)gmail.com >IvanMiljenovic.wordpress.com > > >------------------------------ > >Message: 20 >Date: Mon, 20 Jul 2009 15:22:24 +0200 >From: Roel van Dijk <vandijk.roel(a)gmail.com> >Subject: Re: [Haskell-cafe] Implicit concatenation in list > comprehensions >To: haskell-cafe <haskell-cafe(a)haskell.org> >Message-ID: > <ab9dc6fa0907200622h1b76481ctd7f13d65d1282261(a)mail.gmail.com> >Content-Type: text/plain; charset=ISO-8859-1 > >On Mon, Jul 20, 2009 at 1:27 PM, Roel van Dijk<vandijk.roel(a)gmail.com> wrote: >> I think the tuple sections are a great idea! It also makes tuple types >> and constructors more alike: >> >> x :: (,) String Double >> x = (,) "Pi" 3.14159 > >I just realised this is already in GHC :-) But does you patch also add >the equivalent for tuple type annotations? > >x :: (String, ) Double >x = ("Pi", ) 3.14159 > >I am also wondering what the following would/should mean: > > (1, , ( , 2), ) 'a' 'b' 'c' > >Should this mean > (1, 'a', ('b', 2), 'c') >or > (1, 'a', ('c', 2), 'b') > >Intuitively I would expect the first option. Just reading from left to >right. But it doesn't look entirely trivial. > > >------------------------------ > >Message: 21 >Date: Mon, 20 Jul 2009 14:25:56 +0100 >From: "Sittampalam, Ganesh" <ganesh.sittampalam(a)credit-suisse.com> >Subject: RE: [Haskell-cafe] Implicit concatenation in list > comprehensions >To: "haskell-cafe" <haskell-cafe(a)haskell.org> >Message-ID: > <16442B752A06A74AB4D9F9A5FF076E4B03B9F7DC(a)ELON17P32001A.csfb.cs-group.com> > >Content-Type: text/plain; charset=us-ascii > >Roel van Dijk wrote: >> On Mon, Jul 20, 2009 at 1:27 PM, Roel van >> Dijk<vandijk.roel(a)gmail.com> wrote: >>> I think the tuple sections are a great idea! It also makes tuple >>> types and constructors more alike: >>> >>> x :: (,) String Double >>> x = (,) "Pi" 3.14159 >> >> I just realised this is already in GHC :-) But does you patch also >> add the equivalent for tuple type annotations? >> >> x :: (String, ) Double >> x = ("Pi", ) 3.14159 >> >> I am also wondering what the following would/should mean: >> >> (1, , ( , 2), ) 'a' 'b' 'c' > >I would expect it to be a type error, since I think the following is the >only sane type the tuple can have (assuming numeric literals :: Int): > >(1, , ( , 2), ) :: a -> b -> (Int, a, c -> (c, Int), b) > >Ganesh > >=============================================================================== > Please access the attached hyperlink for an important electronic communications disclaimer: > http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html > =============================================================================== > > > >------------------------------ > >Message: 22 >Date: Mon, 20 Jul 2009 15:42:08 +0200 >From: Roel van Dijk <vandijk.roel(a)gmail.com> >Subject: Re: [Haskell-cafe] Implicit concatenation in list > comprehensions >To: "Sittampalam, Ganesh" <ganesh.sittampalam(a)credit-suisse.com> >Cc: haskell-cafe <haskell-cafe(a)haskell.org> >Message-ID: > <ab9dc6fa0907200642u678cfe2ep22ffeef3308927eb(a)mail.gmail.com> >Content-Type: text/plain; charset=ISO-8859-1 > >>> I am also wondering what the following would/should mean: >>> >>> (1, , ( , 2), ) 'a' 'b' 'c' >> >> I would expect it to be a type error, since I think the following is the >> only sane type the tuple can have (assuming numeric literals :: Int): >> >> (1, , ( , 2), ) :: a -> b -> (Int, a, c -> (c, Int), b) >> >> Ganesh > >Ah you're completely right! I would be applying a tuple to a Char >which is nonsense. > > >------------------------------ > >Message: 23 >Date: Mon, 20 Jul 2009 07:02:22 -0700 >From: Jason Dagit <dagit(a)codersbase.com> >Subject: Re: [Haskell-cafe] FFI problem - possibility of CStringLen > overflow? >To: Robin Green <greenrd(a)greenrd.org> >Cc: haskell-cafe(a)haskell.org >Message-ID: > <b97f58860907200702s769b48cao85d5d5c2f15f183e(a)mail.gmail.com> >Content-Type: text/plain; charset="iso-8859-1" > >On Sun, Jul 19, 2009 at 7:24 PM, Robin Green <greenrd(a)greenrd.org> wrote: > >> While rewriting cautious-file to use ByteStrings and FFI just now, I >> came across this potential problem: >> >> Why does the FFI specification define CStringLen as (Ptr CChar, Int)? > > >Do you think it was a typo and the author(s) meant (Ptr CChar, CInt) ? > >Jason >-------------- next part -------------- >An HTML attachment was scrubbed... >URL: http://www.haskell.org/pipermail/haskell-cafe/attachments/20090720/abed0080… > >------------------------------ > >Message: 24 >Date: Mon, 20 Jul 2009 15:07:23 +0100 >From: Philippa Cowderoy <flippa(a)flippac.org> >Subject: [Haskell-cafe] Anglohaskell - wifi signups >To: haskell(a)haskell.org, Haskell cafe <haskell-cafe(a)haskell.org> >Message-ID: <4A647A1B.7010408(a)flippac.org> >Content-Type: text/plain; charset=ISO-8859-1; format=flowed > >Wifi signups are Anglohaskell are now on the wiki - please add your >details by the 31st of July if you want a wifi account at MS Research >for the Friday. Alternatively, reply to this email with your full name, >institution, country of residence and email address. > >The Anglohaskell wiki page can be found at >http://www.haskell.org/haskellwiki/AngloHaskell/2009 > >There's still room for more talks if anyone's got something they fancy >giving a go - everything from cutting edge research to "what I did with >Haskell on my holiday" is welcome, as is everyone from GHC implentors to >newbies frantically writing Hello World on their laptop in the back row. > >-- >flippa(a)flippac.org > > >------------------------------ > >Message: 25 >Date: Mon, 20 Jul 2009 11:09:40 -0700 >From: Thomas DuBuisson <thomas.dubuisson(a)gmail.com> >Subject: [Haskell-cafe] Pruning the Front Page >To: haskell mailing list <haskell-cafe(a)haskell.org> >Message-ID: > <4c44d90b0907201109v75f5427ra5aadefdf1722663(a)mail.gmail.com> >Content-Type: text/plain; charset=ISO-8859-1 > >All, >I think we should remove unmaintained or refocused implementations >from the haskell.org front page. This would mean removing: > YHC - unmaintained, hasn't built for me in a while > LHC - Not a standalone compiler these days - perhaps should be >linked as a GHC subproject? > >Other than those I'd propose NHC but I'm guessing that would get some >pushback (even though it currently doesn't build for me). Before >anyone brings up HUGS I'll just say that 1) it is used 2) it builds 3) >at least it's been updated more recently than the Haskell langauge. > >Thomas > > >------------------------------ > >Message: 26 >Date: Mon, 20 Jul 2009 11:12:16 -0700 >From: Don Stewart <dons(a)galois.com> >Subject: Re: [Haskell-cafe] Pruning the Front Page >To: Thomas DuBuisson <thomas.dubuisson(a)gmail.com> >Cc: haskell mailing list <haskell-cafe(a)haskell.org> >Message-ID: <20090720181216.GL15846(a)whirlpool.galois.com> >Content-Type: text/plain; charset=us-ascii > >thomas.dubuisson: >> All, >> I think we should remove unmaintained or refocused implementations >> from the haskell.org front page. This would mean removing: >> YHC - unmaintained, hasn't built for me in a while >> LHC - Not a standalone compiler these days - perhaps should be >> linked as a GHC subproject? >> >> Other than those I'd propose NHC but I'm guessing that would get some >> pushback (even though it currently doesn't build for me). Before >> anyone brings up HUGS I'll just say that 1) it is used 2) it builds 3) >> at least it's been updated more recently than the Haskell langauge. >> > >I guess we just acknowledge that all implementations are not equal, and >for newbies we strongly recommend GHC + Haskell Platform. For >reference, we point to a page listing all implementations. > >This follows convention (i.e. Python, Ruby only point to the canonical >impls, not the various forks). > >-- Don > > >------------------------------ > >Message: 27 >Date: Mon, 20 Jul 2009 20:14:30 +0100 >From: Max Bolingbroke <batterseapower(a)hotmail.com> >Subject: Re: [Haskell-cafe] Implicit concatenation in list > comprehensions >To: Roel van Dijk <vandijk.roel(a)gmail.com> >Cc: haskell-cafe <haskell-cafe(a)haskell.org> >Message-ID: > <9d4d38820907201214n79cc48a8jc5e5f19af511129d(a)mail.gmail.com> >Content-Type: text/plain; charset=ISO-8859-1 > >2009/7/20 Roel van Dijk <vandijk.roel(a)gmail.com>: >> I just realised this is already in GHC :-) But does you patch also add >> the equivalent for tuple type annotations? >> >> x :: (String, ) Double >> x = ("Pi", ) 3.14159 > >It doesn't, and indeed it would only work in the special case where >your only missing type arguments are on the right (since we lack >type-level lambda, we can only accept eta-reduced forms). So it >probably wouldn't be worth it - it wouldn't allow you to write >anything significantly shorter than the existing form "(,) String". > >Cheers, >Max > > >------------------------------ > >Message: 28 >Date: Mon, 20 Jul 2009 21:26:05 +0100 >From: phil(a)beadling.co.uk >Subject: Re: [Haskell-cafe] Ambiguous type variable - help! >To: gale(a)sefer.org >Cc: haskell-cafe(a)haskell.org >Message-ID: <47ED22E9-0828-4B19-A182-6F69DE919CC4(a)beadling.co.uk> >Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes > > >On 19 Jul 2009, at 21:18, Yitzchak Gale wrote: > >> Hi Phil, > >> >> >>> I've concocted a very simple example to illustrate this (below) - but >>> it doesn't compile because ghc complains that my type is ambiguous >>> arising >>> from my use of 'fromSeq'. >> >> Notice that you have given two completely separate sets >> of instructions of what to do depending on whether Int >> or Double is selected. You have not given any indication >> of how to choose between them, even at runtime. Of course, >> the compiler doesn't care that your string constants "Int" and >> "Double" happen also to be the names of types if unquoted. > >I see now. I'm passing fromSeq a SeqType, but it has no way >of knowing if I want to process it as an Int or a Double. >The only thing which is polymorphic is nextSeq as it must handle >the underlying state of Int and Double. > >Your result function handles the general case and the typeclass >instances deal with the specialization depending on the state's type. > >The printResult function takes in a SeqType and then "parses" (for >want of >a better word) out the >underlying type of Int or Double. It then calls results against the >Int or Double which >in turn will invoke the correct version of nextSeq. > > >Thank you very much for explaining this! > > >Phil. > >> >> import Control.Monad.State -- Why Strict? Haskell is lazy by default. >> > >Ahh, no reason for the Strict - in the large program I'm righting it >is required >because otherwise I end up with almighty thunks. But here it serves >no purpose. > > > >------------------------------ > >Message: 29 >Date: Mon, 20 Jul 2009 22:25:30 +0200 >From: Nicolas Pouillard <nicolas.pouillard(a)gmail.com> >Subject: Re: [Haskell-cafe] Implicit concatenation in list > comprehensions >To: Max Bolingbroke <batterseapower(a)hotmail.com> >Cc: haskell-cafe <haskell-cafe(a)haskell.org> >Message-ID: <1248121473-sup-8534(a)ausone.local> >Content-Type: text/plain; charset=UTF-8 > >Excerpts from Max Bolingbroke's message of Sun Jul 19 16:58:08 +0200 2009: >> Dear Cafe, >> >> For fun, I spent a few hours yesterday implement support for this >> syntax in GHC, originally propsed by Koen Claessen: >> > >[...] > >> P.S. I also implemented tuple sections >> (http://hackage.haskell.org/trac/ghc/ticket/3377#comment:3) which are >> a lot more useful: > >I vote for both extensions. > >-- >Nicolas Pouillard >http://nicolaspouillard.fr > > >------------------------------ > >Message: 30 >Date: Tue, 21 Jul 2009 13:36:04 +1200 (NZST) >From: porges(a)porg.es >Subject: Re: [Haskell-cafe] Implicit concatenation in list > comprehensions >To: Roel van Dijk <vandijk.roel(a)gmail.com> >Cc: haskell-cafe <haskell-cafe(a)haskell.org>, "Sittampalam, Ganesh" > <ganesh.sittampalam(a)credit-suisse.com> >Message-ID: <fxdyfegnp48plbb647UYAxe124vaj_firegpg(a)mail.gmail.com> >Content-Type: text/plain; charset="utf-8" > >2009/7/21 Roel van Dijk <vandijk.roel(a)gmail.com>: >>>> I am also wondering what the following would/should mean: >>>> >>>> Â (1, , ( , 2), ) 'a' 'b' 'c' >>> >>> I would expect it to be a type error, since I think the following is the >>> only sane type the tuple can have (assuming numeric literals :: Int): >>> >>> (1, , ( , 2), ) :: a -> b -> (Int, a, c -> (c, Int), b) >>> >>> Ganesh >> >> Ah you're completely right! I would be applying a tuple to a Char >> which is nonsense. > >You can kind of do it if you indicate which 'field' is to be applied: > > import Control.Applicative > > newtype Fst b a = Fst (a,b) deriving (Show) > newtype Snd a b = Snd (a,b) deriving (Show) > > instance Functor (Fst b) where > fmap f (Fst (a,b)) = Fst (f a,b) > > instance Functor (Snd a) where > fmap f (Snd (a,b)) = Snd (a,f b) > > f <$$> x = ($x) <$> f > >... > >> Fst ((,)1,3) <$$> 2 -- no section, don't have the patch ;) >Fst ((1,2),3) >-------------- next part -------------- >A non-text attachment was scrubbed... >Name: signature.asc >Type: application/pgp-signature >Size: 908 bytes >Desc: OpenPGP digital signature >Url : http://www.haskell.org/pipermail/haskell-cafe/attachments/20090720/914e9c57… > >------------------------------ > >Message: 31 >Date: Mon, 20 Jul 2009 22:02:00 -0400 >From: Gwern Branwen <gwern0(a)gmail.com> >Subject: Re: [Haskell-cafe] Pruning the Front Page >To: Thomas DuBuisson <thomas.dubuisson(a)gmail.com> >Cc: haskell mailing list <haskell-cafe(a)haskell.org> >Message-ID: > <cbf55b100907201902h4fda9be9jc0cc333cf4ddaa42(a)mail.gmail.com> >Content-Type: text/plain; charset=UTF-8 > >On Mon, Jul 20, 2009 at 2:09 PM, Thomas >DuBuisson<thomas.dubuisson(a)gmail.com> wrote: >> All, >> I think we should remove unmaintained or refocused implementations >> from the haskell.org front page. Â This would mean removing: >> Â Â YHC - unmaintained, hasn't built for me in a while >> Â Â LHC - Not a standalone compiler these days - perhaps should be >> linked as a GHC subproject? >> >> Other than those I'd propose NHC but I'm guessing that would get some >> pushback (even though it currently doesn't build for me). Â Before >> anyone brings up HUGS I'll just say that 1) it is used 2) it builds 3) >> at least it's been updated more recently than the Haskell langauge. >> >> Thomas > >What about UHC and JHC? They're both maintained (in their varying >degrees), but I don't think they can do anything but pure Haskell >'98*, and I dunno whether they could even compile the Cabal packages >which are/depend only on Haskell '98. > >What should our criterion be? Just maintained? Maintained and at least >able to compile Haskell '98 source? Maintained, able to compile >Haskell '98, and also the pure Haskell '98 subset of Hackage? > >I prefer the last triplet since it's the best for newbies and the >minimum necessary for practicality beyond rolling everything oneself, >but perhaps that's too strict for everyone else. > >* by which I mean Haskell '98, the FFI, and hierarchical modules > >-- >gwern > > >------------------------------ > >_______________________________________________ >Haskell-Cafe mailing list >Haskell-Cafe(a)haskell.org >http://www.haskell.org/mailman/listinfo/haskell-cafe > > >End of Haskell-Cafe Digest, Vol 71, Issue 30 >********************************************

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ANN: Leksah 0.6
by Hamish Mackenzie 24 Jul '09

24 Jul '09

Hi, Just a quick note to let people know we released a new version of Leksah this week. Thanks for the help and feedback on the previous version. We have done our best to add the features we thought were most pressing. Please give it a go and let us know what features you would like to see most in the future. http://leksah.org/ __ What's New __ * Integrated GHCi based debugging * Multi-window support (View -> Detach) * Improved layout control (drag & drop and nesting) * Regular expression find and replace * Grep files in the current package * Improved Mac OS X integration __ Known Bugs and Problems __ * The package editor works only for cabal files without configurations. * MS Windows: The check for external modifications of source files does not work. * MS Windows: Interruption of a background build does not work. * Navigation in Trace history does not work. Mac OSX users can install using Mac Ports as usual or use the provided Intel binary (tested on Leopard only). http://leksah.org/Leksah-0.6.1.0.dmg Hamish

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QuickCheck behaving strange
by Tobias Olausson 24 Jul '09

24 Jul '09

Hey Guys! I was writing a small implementation of the earliest-end-first algorithm for the Interval Scheduling problem just now. When I was done, I thought it would be a nice thing to have a QuickCheck property for my code. This is what I came up with: -- Intervals are just triplets type Interval a t = (a,t,t) end :: Interval a t -> t end (_,_,t) = t begin :: Interval a t -> t begin (_,t,_) = t And so the property: prop_schedule :: Ord t => [Interval a t] -> Bool prop_schedule [] = True prop_schedule [a] = True prop_schedule (x:y:ys) = end x <= begin y && prop_schedule (y:ys) Essentially, it looks up wheather the given list is "sorted" (given the constraints of the problem). However, in this property I forgot to add that the lists should have been run through my algorithm, which I noticed only after this strange problem appeared: *Interval> quickCheck prop_schedule +++ OK, passed 100 tests. How come QuickCheck passes 100 tests of random lists? One would think that at least one of the generated lists would be unsorted. It also passes 1000 and even 10000 tests. It also seems that changing the type helps: prop_schedule :: [Interval a Int] -> Bool ... *Interval> quickCheck prop_schedule *** Failed! Falsifiable (after 5 tests and 1 shrink): [((),0,0),((),-1,0)] -- Tobias Olausson tobsan(a)gmail.com

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Re: [Haskell] ANN: yices 0.0.0.1 - Haskell programming interface to Yices SMT solver
by Aaron Tomb 24 Jul '09

24 Jul '09

You may want to take a look at this, as well: http://www.sivity.net/projects/smt-yices Aaron On Jul 23, 2009, at 5:32 PM, Ahn, Ki Yung wrote: > http://hackage.haskell.org/package/yices > > Incomplete (no bitvectors) syntax, parser, and inter > process communication to Yices from Haskell through pipe. > Purpose for building and using this library was to generate > test cases from constraints that SMT solvers can solve. I > only used it for that particular purpose, so the code in > general is not yet fully tested. Use at your own risk and > error reports are welcomed. See http://yices.csl.sri.com/ > for further information on Yices. > > Note: this package does not include Yices. You should get it from the > Yices homepage and install it before using this library. > > @ If you already have a better API for Yices or other SMT solvers, and > if you can open the source please upload it to hacakage. That would > be > great help for some people. > > -- > Ahn, Ki Yung > > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell -- Aaron Tomb Galois, Inc. (http://www.galois.com) atomb(a)galois.com Phone: (503) 626-6616 ext. 156 Fax: (503) 350-0833

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ANN: darcs 2.3.0
by Petr Rockai 24 Jul '09

24 Jul '09

Hello! I'd like to announce immediate availability of a new stable release of darcs, 2.3.0. There is a number of improvements and bugfixes over the previous stable release, 2.2. Moreover, work has been done to improve performance of "darcs whatsnew" for large repositories. As in the past, there are two source tarballs available. As of this release, the cabal-based build is preferred, and the autoconf build is deprecated. You can obtain the source tarballs at these addresses: * http://repos.mornfall.net/darcs/darcs-2.3.0.tar.gz * http://repos.mornfall.net/darcs/darcs-2.3.0_autoconf.tar.gz The build instructions are available in the enclosed README file in those tarballs. Moreover, if you have cabal-install available, you can install latest stable release of darcs by issuing the following commands (no tarballs needed): $ cabal update $ cabal install darcs This should give you a darcs binary in `~/.cabal/bin` -- you should probably add this to your PATH. More detailed instructions for installing on Windows are available near the end of this announcement. What's New ---------- This is a summary of important changes since the last stable release (2.2): * Lots and lots of documentation changes (Trent). * Haskeline improvements (Judah). * Cabal as default buildsystem (many contributors). * Fixes in darcs check/repair memory usage (Bertram, David). * Performance improvement in subtree record (Reinier). * New option: --summary --xml (Florian Gilcher). * New option: changes --max-count (Eric and Petr). * Fix changes --only-to-files for renames (Dmitry). * Performance fix in "darcs changes" (Benedikt). * Hardlinks on NTFS (Salvatore). * Coalesce more changes when creating rollbacks (David). * New unit test runner (Reinier). * Inclusion of darcs-shell in contrib (László, Trent). * Author name/address canonisation: .authorspellings (Simon). * Working directory index and substantial "darcs wh" optimisation (Petr). * New command: "darcs show index" (Petr). * Gzip CRC check and repair feature (Ganesh). A number of issues has been resolved since 2.2 as well. See http://bugs.darcs.net/issueN for details on bug number N. * 948 darcsman (Trent) * 1206 countable nouns (Trent) * 1285 cabal test v. cabal clean (Trent) * 1302 use resolved, not resolved-in-unstable (Trent) * 1235 obliterate --summary (Rob) * 1270 no MOTD for --xml-output (Lele) * 1311 cover more timezones (Dave) * 1292 re-encoding haskeline input (Judah) * 1313 clickable ToC and refs in PDF manual Trent) * 1310 create merged \darcsCommand{add} (Trent) * 1333 better "cannot push to current repository" warning (Petr) * 1347 (autoconf) check for unsafeMMapFile if mmap use enabled (Dave) * 1361 specify required includes for curl in cabal file (Reinier) * 1379 remove libwww support (Trent) * 1366 remove unreachable code for direct ncurses use (Trent) * 1271 do not install two copies of darcs.pdf (Trent) * 1358 encode non-ASCII characters in mail headers (Reinier) * 1393 swap "darcs mv" and "darcs move" (Trent) * 1405 improve discoverability of global author file (Trent) * 1402 don't "phone home" about bugs (Trent) * 1301 remove obsolete zsh completion scripts (Trent) * 1162 makeAbsolute is now a total function (Ben F) * 1269 setpref predist - exitcode ignored bug (Ben M) * 1415 --edit-long-comment, not --edit-description, in help (Trent) * 1413 remove duplicate documentation (Trent) * 1423 complain about empty add/remove (Trent) * 1437 Implement darcs changes --max-count (Eric) * 1430 lazy pattern matching in (-:-) from Changes command module (Dmitry) * 1434 refactor example test (Trent) * 1432 refer to %APPDATA%, not %USERPROFILE% (Trent) * 1186 give a chance to abort if user did not edit description file (Dmitry) * 1446 make amend-record -m foo replace only the patch name (Dmitry) * 1435 default to get --hashed from a darcs-1.0 source (Trent) * 1312 update and reduce build notes (Trent) * 1351 fix repository path handling on Windows (Salvatore) * 1173 support hard links on NTFS (Salvatore) * 1248 support compressed inventories for darcs-1 repos (Ganesh) * 1455 implement "darcs help environment" (Trent) The question of GHC 6.8 ----------------------- Using GHC 6.10.3 or newer is *strongly recommended*. You may compile darcs with GHC 6.8, but there are several caveats. If you are using 6.8.2 or older, please disable mmap support (pass -f-mmap to cabal install or runghc Setup configure). Note that the GHC 6.8.2 that ships with Debian Lenny is not affected and it should be safe to keep mmap enabled. It is also recommended to disable use of Hackage zlib when compiling with GHC 6.8.2 (including the Debian Lenny version): pass -f-zlib to cabal. When using zlib, we have seen occasional crashes with error messages like "openBinaryFile: file locked" -- this is a known GHC 6.8.2 bug (and is fixed in GHC 6.8.3). Last, if you are using a 64-bit system, darcs may hang when you exit a pager when compiled with GHC older than 6.10.3. Although this is harmless, it is quite inconvenient. Overall, the status of GHC 6.8 is "semi-supported": for many cases, things will work just fine, especially if you take a little extra caution with compilation flags. Installing on Windows --------------------- To install darcs on Windows systems from scratch, please download the Haskell Platform and MSYS: * http://hackage.haskell.org/platform/2009.2.0.1/HaskellPlatform-2009.2.0.1-s… * http://sourceforge.net/projects/mingw/files/MSYS+Base+System/MSYS-1.0.11-rc… After installing both, you should have an "MSYS" icon: run MSYS and in the terminal window type (the `$` character denotes the prompt, do not repeat it): $ cabal update $ cabal install darcs -f-curl This should download, compile and install all required dependencies and also darcs itself. The resulting darcs executable will be placed into the Haskell Platform executables folder, and should be accessible from the MSYS shell (just type "darcs --version" to check). Yours, Petr.

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Static linking
by Michael Oswald 24 Jul '09

24 Jul '09

Hello, I wrote a small installer program which configures and installs some software packages. In order to be able to let it run on a different machine, where I possibly don't have the needed shared libraries, I tried to link it statically, following this advice: http://www.haskell.org/haskellwiki/Practical_web_programming_in_Haskell#Dep… g_statically_linked_applications However I get some linking errors: ghc --make Installer.hs -static -optl-static /usr/lib/ghc-6.10.3/unix-2.3.2.0/libHSunix-2.3.2.0.a(User__143.o)(.text+0xf1): In function `s7Tu_info': : warning: Using 'getgrnam_r' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking /usr/lib/gcc-lib/i586-suse-linux/3.3.3/../../../libedit.a(readline.o)(.text+0x7b 2): In function `username_completion_function': /home/oswald/build/libedit-20090610-3.0/src/readline.c:1467:0: warning: Using 'getpwent' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking src/dlmalloc.c:2486:0: undefined reference to `pthread_mutex_lock' /usr/lib/ghc-6.10.3/libffi.a(closures.o)(.text+0x132):src/dlmalloc.c:2493: undefined reference to `pthread_mutex_unlock' /usr/lib/ghc-6.10.3/libffi.a(closures.o)(.text+0x184):src/dlmalloc.c:2490: undefined reference to `pthread_mutex_init' /usr/lib/ghc-6.10.3/libffi.a(closures.o)(.text+0x227): In function `ffi_closure_free': Because of the undefined references to pthread_mutex_lock I then tried various versions of ghc --make Installer.hs -static -optl-static -lpthread -lrt and reordered the -l switches, but neither combination helped. I always get the same error. Does somebody know how to correctly specify the pthread library for this? lg, Michael

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