April 2010 - Libraries

ANNOUNCE: syb-0.2
by José Pedro Magalhães 09 Apr '10

09 Apr '10

syb: Scrap Your Boilerplate! ================================================================================ Scrap Your Boilerplate (SYB) is a library for generic programming in Haskell. It is supported since the GHC >= 6.0 implementation of Haskell. Using this approach, you can write generic functions such as traversal schemes (e.g., everywhere and everything), as well as generic read, generic show and generic equality (i.e., gread, gshow, and geq). This approach is based on just a few primitives for type-safe cast and processing constructor applications. It was originally developed by Ralf Lämmel and Simon Peyton Jones. Since then, many people have contributed with research relating to SYB or its applications. More information is available on the webpage: http://www.cs.uu.nl/wiki/GenericProgramming/SYB What's new ---------- The biggest improvements from version 0.1 are: * Reintegration of the testsuite; * Introduction of the Generics.SYB.* module hierarchy (as synonyms for their Data.Generics.* counterparts); * Adding gshows :: Data a => a -> ShowS (more efficient than gshow); * Adding gmapAccumA :: forall b d a. (Data d, Applicative a) => (forall e. Data e => b -> e -> (b, a e)) -> b -> d -> (b, a d) ; * Adding ext1B :: (Data a, Typeable1 t) => a -> (forall b. Data b => (t b)) -> a ; * Introduction of two new generic producers ('empty' and 'constrs'). The former produces an empty value of a given datatype, while the latter produces a list of values of a datatype, each using a different constructor. Features -------- * Easy generic programming with combinators * GHC can derive Data and Typeable instances for your datatypes * Comes with many useful generic functions Requirements ------------ * GHC 6.10.1 or later * Cabal 1.6 or later Download -------- Get the package: http://hackage.haskell.org/package/syb Get the source: darcs get http://code.haskell.org/syb/ Bugs & Support -------------- Please report issues or request features at the bug tracker: http://code.google.com/p/scrapyourboilerplate/issues/list For discussion about the library with the authors, maintainers, and other interested persons use the mailing list: http://www.haskell.org/mailman/listinfo/generics

1 0

Re: [Haskell] trouble with the random number generator
by Ian Lynagh 08 Apr '10

08 Apr '10

On Thu, Apr 08, 2010 at 10:20:25AM -0400, Garrett Mitchener wrote: > > 1/2 - 2^31/(2^32-1) = 2^31( 1/2^32 - 1/(2^32-1) ) = -1.164e-10 < 0 > > which is outside the required range. Yup, looks like a bug to me. Even if it were fixed so that the maths seemed to show no bug, I wouldn't be surprised if you could get an out-of-range result due to Doubles not being able to represent all values exactly. I'd suggest you make a library submission to fix it, so that people can sanity check the new code: http://www.haskell.org/haskellwiki/Library_submissions Thanks Ian

1 0

Problem installing unix-2.3.2.0
by Antoine Latter 07 Apr '10

07 Apr '10

Hi Libraries, cabal-install tries to pull in unix-2.3.2.0 in it's install plan when installing cabal-install, but it doesn't successfully install for me under Ubuntu 9.10. Here's some cut'n'paste of what I've tried: $ cabal unpack unix-2.3.2.0 Downloading unix-2.3.2.0... Unpacking to unix-2.3.2.0/ $ cd unix-2.3.2.0/ $ cabal install <snip> Building unix-2.3.2.0... dist/build/System/Posix/Signals.hs:127:0: error: Signals.h: No such file or directory cabal: Error: some packages failed to install: unix-2.3.2.0 failed during the building phase. The exception was: ExitFailure 1 $ find . | grep Signals ./System/Posix/Signals.hsc ./System/Posix/Signals ./System/Posix/Signals/Exts.hsc unix-2.3.0.1 seems to have the same problem, and cabal-install can't form a valid install plan for unix-2.3.0.0. I have hsc2hs in my path at version 0.67, and I'm using GHC 6.12.1. Is there some step I'm missing? Thanks, Antoine

2 1

HDBC malfunctions with old-locale-1.0.0.2
by Simon Hengel 04 Apr '10

04 Apr '10

Hello, HDBC uses System.Locale.iso8601DateFormat to produce format strings for Data.Time.parseTime. This function has been changed with old-locale-1.0.0.2, and HDBC-postgresql now produce conversion errors when dealing with datetime values. The following patch has introduced that regression: Wed Sep 24 21:37:55 CEST 2008 magnus(a)therning.org * Adding 'T' to conform better to standard This is based on information found at http://en.wikipedia.org/wiki/ISO_8601#Combined_date_and_time_representations I wonder if other packages are similarly effect? How do we deal with that? Just fix HDBC? Regards, Simon

1 0

Hackage and popular packages: 2010 Q1 report
by Don Stewart 03 Apr '10

03 Apr '10

Hackage 2010 Q1 report http://donsbot.wordpress.com/2010/04/03/the-haskell-platform-q1-2010-report/ After the big move of Hackage from monk to the new abbot server, here's the first report on which packages are popular, and how Hackage is doing in general. -- Don

1 0

Re: Bug in Parsec.Token
by Greg Fitzgerald 03 Apr '10

03 Apr '10

> If the community wants to freeze on Parsec 2, then I have no problem > renaming the package, otherwise I think it is both unnecessary and a > waste of effort. Reasons one might prefer Parsec 2.1: * Haskell98 implementation * Daan Leijen's whitepapers: http://legacy.cs.uu.nl/daan/download/parsec/parsec.pdf http://legacy.cs.uu.nl/daan/download/papers/parsec-paper.pdf Reasons one might prefer Parsec 3.1: * Parametric in the input stream type (parses ByteStrings) * Monad transformer that can be stacked on arbitrary monads * More Haddock documentation Parsec 3 is certainly useful, but there are still good, valid reasons one might prefer Parsec 2.1. Derek, if you wouldn't mind renaming Parsec 3, I volunteer to become the maintainer of the Parsec package. Thanks, Greg

7 13

Terminfo package fails to load .so file on Fedora 13 prerelease
by Robin Green 01 Apr '10

01 Apr '10

I encountered a problem compiling yi on Fedora Linux 13 (prerelease): when the terminfo package was loaded by ghci, it attempted to load the native library /usr/lib/libncursesw.so. However, that file has recently been changed from a symbolic link to a library, into a plain text file, as explained here in the response to my Fedora bug report: https://bugzilla.redhat.com/show_bug.cgi?id=578509 The response suggests that ghci should instead try to load the versioned link libncursesw.so.5 (which happens to be in /lib in Fedora, incidentally). Is this something that could be changed by the terminfo package, or would there have to be a change made to ghci? -- Robin

2 1