- Libraries - Haskell.org

ANN: bytestring-lexing 0.5.0
by wren romano 06 Jun '15

06 Jun '15

-------------------------------------------- -- bytestring-lexing 0.5.0 -------------------------------------------- The bytestring-lexing package offers extremely efficient bytestring parsers for some common lexemes: namely integral and fractional numbers. In addition, it provides efficient serializers for (some of) the formats it parses. As of version 0.3.0, bytestring-lexing offers the best-in-show parsers for integral values. (According to the Warp web server's benchmark of parsing the Content-Length field of HTTP headers.) And as of this version (0.5.0) it offers (to my knowledge) the best-in-show parser for fractional/floating numbers. -------------------------------------------- -- Changes since 0.4.3 (2013-03-21) -------------------------------------------- I've completely overhauled the parsers for fractional numbers. The old Data.ByteString.Lex.Double and Data.ByteString.Lex.Lazy.Double modules have been removed, as has their reliance on Alex as a build tool. I know some users were reluctant to use bytestring-lexing because of that dependency, and forked their own version of bytestring-lexing-0.3.0's integral parsers. This is no longer an issue, and those users are requested to switch over to using bytestring-lexing. The old modules are replaced by the new Data.ByteString.Lex.Fractional module. This module provides two variants of the primary parsers. The readDecimal and readExponential functions are very simple and should suffice for most users' needs. The readDecimalLimited and readExponentialLimited are variants which take an argument specifying the desired precision limit (in decimal digits). With care, the limited-precision parsers can perform far more efficiently than the unlimited-precision parsers. Performance aside, they can also be used to intentionally restrict the precision of your program's inputs. -------------------------------------------- -- Benchmarks -------------------------------------------- For the Criterion output of the benchmark discussed below, see <http://community.haskell.org/~wren/bytestring-lexing/bench/html/readExponen…>. The main competitors we compare against are the previous version of bytestring-lexing (which already surpassed text and attoparsec/scientific) and bytestring-read which was the previous best-in-show. The unlimited-precision parsers provide 3.3x to 3.9x speedup over the readDouble function from bytestring-lexing-0.4.3.3, as well as being polymorphic over all Fractional values. For Float/Double: these functions have essentially the same performance as bytestring-read on reasonable inputs (1.07x to 0.89x), but for inputs which have far more precision than Float/Double can handle these functions are much slower than bytestring-read (0.30x 'speedup'). However, for Rational: these functions provide 1.26x to 1.96x speedup compared to bytestring-read. The limited-precision parsers do even better, but require some care to use properly. For types with infinite precision (e.g., Rational) we can pass in an 'infinite' limit by passing the length of the input string plus one. For Rational: doing so provides 1.5x speedup over the unlimited-precision parsers (and 1.9x to 3x speedup over bytestring-read), because we can avoid intermediate renormalizations. Whether other unlimited precision types would see the same benefit remains an open question. For types with inherently limited precision (e.g., Float/Double), we could either pass in an 'infinite' limit or we could pass in the actual inherent limit. For types with inherently limited precision, passing in an 'infinite' limit degrades performance compared to the unlimited-precision parsers (0.51x to 0.8x 'speedup'). Whereas, passing in the actual inherent limit gives 1.3x to 4.5x speedup over the unlimited-precision parsers. They also provide 1.2x to 1.4x speedup over bytestring-read; for a total of 5.1x to 14.4x speedup over bytestring-lexing-0.4.3.3! -------------------------------------------- -- Links -------------------------------------------- Homepage: http://code.haskell.org/~wren/ Hackage: http://hackage.haskell.org/package/bytestring-lexing Darcs: http://community.haskell.org/~wren/bytestring-lexing Haddock (Darcs version): http://community.haskell.org/~wren/bytestring-lexing/dist/doc/html/bytestri… -- Live well, ~wren

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Re: Time files... and here's another alpha HP for 7.10
by Mark Lentczner 02 Jun '15

02 Jun '15

On Tue, Jun 2, 2015 at 4:40 AM, George Colpitts <george.colpitts(a)gmail.com> wrote: > I guess I should file a haddock bug as I got the same error installing > threadscope Does ghc --print-libdir display the correct path? (That is, with the full version number.) - Mark

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Time files... and here's another alpha HP for 7.10
by Mark Lentczner 02 Jun '15

02 Jun '15

So - I hear from a bird that 7.10.2 might be just around the corner. I'm getting ahead of the curve! I just did a fully hermetic and clean build of head of GHC 7.10 branch (what should become 7.10.2), and then brought HP up-to-date: - bootstrapped with 7.10.1 (so hptool needed fixes to build with that) - uses latest shake - built on a clean Debian Wheezy (7) install, (hence uses glibc 2.13 and should also run on Ubuntu 12.04 and later) The package versions are updated as follows: Cabal 1.22.2.0 --> 1.22.3.0 cabal-install 1.22.2.0 --> 1.22.4.0 attoparsec 0.12.1.4 --> 0.13.0.0 syb 0.4.4 --> 0.5.1 text 1.2.0.4 --> 1.2.1.1 cgi 3001.2.2.1 --> 3001.2.2.2 network 2.6.0.2 --> 2.6.2.0 network-uri 2.6.0.1 --> 2.6.0.3 QuickCheck 2.8 --> 2.8.1 hscolour 1.22 --> 1.23 GLUT 2.7.0.0 --> 2.7.0.1 GLURaw 1.5.0.0 --> 1.5.0.1 OpenGL 2.12.0.0 --> 2.12.0.1 OpenGLRaw 2.4.1.0 --> 2.5.0.0 Only package issue was: zlib 0.5.4.2 -- held back because cabal-install needs < 0.6 All the same caveats and notes from Alpha 2 still apply. All these changes are in the pre-release-2 branch on github -- I'll merge it all together later this week. There is a hp-bindist-tarball on my server: haskell-platform-7.10.1.20150528-x86_64-unknown-linux-deb7.tar.gz <http://www.ozonehouse.com/mark/platform/haskell-platform-7.10.1.20150528-x8…> SHA-256: b503c9e2c34c0865b5fee39444027667bb39b786fa7664029287e3bbf33379da I'll build and put up OS X version in a day or two. One last thing... I'm proposing that we name this release: Haskell Platform 7.10.2 ! - Mark

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[directory] status of HsDirectory.h
by Phil Ruffwind 01 Jun '15

01 Jun '15

I noticed that there aren't many things left in the HsDirectory.h: - macros from autoconf - __hscore_long_path_size - __hscore_S_IRUSR/IWUSR/IXUSR/IFDIR Most of these could be done easily using hsc so I was tempted to remove them. Not to mention, the implementation of __hscore_long_path_size is rather dangerous on systems where PATH_MAX is not defined.[1] However, I wonder if the __hscore prefix has any significance. Are these functions by any chance used in GHC internals or some other libraries? For now I intend to leave them as is. But if no-one else uses them, then I think the header should be deprecated and made private in the future. [1]: http://pubs.opengroup.org/onlinepubs/9699919799 -- Phil

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cabal-install: bug and quest for a workaround
by Wolfgang Jeltsch 01 Jun '15

01 Jun '15

Hi, I have just installed GHC 7.10.1 and cabal-install 1.22.4.0. The problem is that cabal-install often hangs when trying to download a package. With --verbose=3, I see that it gets a “301 Moved Permanently” from the server, tries to redirect, shows “Recovering connection to hackage.haskell.org”, and then hangs. Is there anything I can do to work around this issue? At the moment, I cannot work with my new GHC installation, since it is virtually impossible to install packages with cabal-install. All the best, Wolfgang

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Template Haskell changes to names and package keys
by Edward Z. Yang 29 May '15

29 May '15

In GHC 7.10, we changed the internal representation of names to be based on package keys (base_XXXXXX) rather than package IDs (base-4.7.0.1), however, we forgot to update the Template Haskell API to track these changes. This lead to some bugs in TH code which was synthesizing names by using package name and version directly, e.g. https://ghc.haskell.org/trac/ghc/ticket/10279 We now propose the following changes to the TH API in order to track these changes: 1. Currently, a TH NameG contains a PkgName, defined as: newtype PkgName = PkgName String This is badly misleading, even in the old world order, since these needed version numbers as well. We propose that this be renamed to PkgKey: newtype PkgKey = PkgKey String mkPackageKey :: String -> PackageKey mkPackageKey = PkgKey 2. Package keys are somewhat hard to synthesize, so we also offer an API for querying the package database of the GHC which is compiling your code for information about packages. So, we introduce a new abstract data type: data Package packageKey :: Package -> PkgKey and some functions for getting packages: searchPackage :: String -- Package name -> String -- Version -> Q [Package] reifyPackage :: PkgKey -> Q Package We could add other functions (e.g., return all packages with a package name). 3. Commonly, a user wants to get the package key of the current package. Following Simon's suggestion, this will be done by augmenting ModuleInfo: data ModuleInfo = ModuleInfo { mi_this_mod :: Module -- new , mi_imports :: [Module] } We'll also add a function for accessing the module package key: modulePackageKey :: Module -> PkgKey And a convenience function for accessing the current module: thisPackageKey :: Q PkgKey thisPackageKey = fmap (modulePackageKey . mi_this_mod) qReifyModule thisPackage :: Q Package thisPackage = reifyPackage =<< thisPackageKey Discussion period: 1 month Thanks, Edward (apologies to cc'd folks, I sent from my wrong email address)

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mapM /= traverse?
by Simon Marlow 28 May '15

28 May '15

I was hoping that in GHC 7.10 we would make mapM = traverse for lists, but it appears this isn't the case: the Traversable instance for lists overrides mapM to be the manually-defined version in terms of foldr. Why is this? Fusion? Unfortunately since I want mapM = traverse (for Haxl) I'll need to continue to redefine it in our custom Prelude. Cheers, Simon

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aeson-utils: aeson-0.9 compatibility package
by Adam Bergmark 25 May '15

25 May '15

Hi folks, aeson-0.9 was released today. It changes the behavior of `decode` and `eitherDecode`: They now both allow atomic values on the top level. Previously the behavior was inconsistent, `encode 1 = "1"` but `decode "1" :: Maybe Int = Nothing`. aeson-utils[1] has the functions `decodeV` and `eitherDecodeV` that work like aeson-0.9's `decode` and `eitherDecode` respectively, also with older aeson versions. If you want to stay backwards compatible without having varying semantics based on dependencies, check it out! [1] http://hackage.haskell.org/package/aeson-utils Regards, Adam

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Proposal: liftData for Template Haskell
by Edward Z. Yang 14 May '15

14 May '15

I propose adding the following function to Language.Haskell.TH: -- | 'liftData' is a variant of 'lift' in the 'Lift' type class which -- works for any type with a 'Data' instance. liftData :: Data a => a -> Q Exp liftData = dataToExpQ (const Nothing) I don't really know which submodule this should come from; since it uses 'dataToExpQ', you might put it in Language.Haskell.TH.Quote but arguably 'dataToExpQ' doesn't belong in this module either, and it only lives there because it is a useful function for defining quasiquoters and it was described in the quasiquoting paper. I might propose getting rid of the 'Lift' class entirely, but you might prefer that class since it doesn't go through SYB (and have the attendant slowdown). This mode of use of 'dataToExpQ' deserves more attention. Discussion period: 1 month Cheers, Edward

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maintaining pre-AMP+FTP-Prelude in external package
by Henning Thielemann 14 May '15

14 May '15

The Prelude of GHC-7.10/base-4.8 introduces several name clashes mostly due to the AMP and FTP: (<*) clashes with Accelerate, (<*>) clashes with NumericPrelude, (and (<>) would clash with HMatrix if added to Prelude), 'join', 'pure', 'traverse', 'fold' clash with custom defined functions. "import Prelude hiding (pure)" is not yet supported by GHC-7.4 (as shipped with Ubuntu 12.04) and in newer GHC versions it generates an annoying warning. The only remaining option is to explicitly import identifiers from Prelude. What about maintaining the pre-AMP+FTP-Prelude in a package on Hackage? Then we could maintain compatibility with a range of GHC versions by disabling import of Prelude and importing preamplified (so to speak) Prelude. The base-compat package seems to support the other way round, that is, providing new 'base' functions to old compilers.

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