December 2010 - Libraries

DEPRECATED foldWithKey "Use foldrWithKey instead"
by Christian Maeder 12 Dec '10

12 Dec '10

Hi, I find this particular warning (in the subject) unjustified and annoying. Could someone (maybe the person who introduced it) simply delete it in the next version (or make a library proposal)? A matching "foldrWithKey" (and foldlWithKey) is missing in Data.IntMap. and folding without keys is also only given via "fold" in Data.Map. Data.Set contains toList and toAscList and the former is rightly not deprecated. (A function toDescList is missing though in Data.Set.) Furthermore, Data.Map.foldrWithKey is not part of the container package that came with ghc-6.10.4. Cheers Christian

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Trac for HP
by John Smith 12 Dec '10

12 Dec '10

Is there an issue tracker for Haskell Platform? Some issues go onto the Haskell Wiki, some go into the GHC trac as "not GHC", but the general impression is one of disorganised chaos (everything managed by mailing list discussions).

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Re: [GHC] #4517: Add Data.Functor.Backwards to transformers
by roconnor＠theorem.ca 10 Dec '10

10 Dec '10

#4517: Add Data.Functor.Backwards to transformers ---------------------------------+------------------------------------------ Reporter: r6 | Owner: Type: proposal | Status: new Priority: normal | Component: libraries (other) Version: 7.0.1 | Keywords: backwards Testcase: | Blockedby: Os: Unknown/Multiple | Blocking: Architecture: Unknown/Multiple | Failure: None/Unknown ---------------------------------+------------------------------------------ Data.Functor.Backwards is a wrapper for functors that allow Foldable, Traversable, and Applicative functors to be operated backwards. It is similar to Dual for Monoids. The Applicative instance runs effects in reversed order. The Foldable instance folds from right to left, The Traversable instance traverses from right to left. -- Russell O'Connor <http://r6.ca/> ``All talk about `theft,''' the general counsel of the American Graphophone Company wrote, ``is the merest claptrap, for there exists no property in ideas musical, literary or artistic, except as defined by statute.''

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it seems that symbols like \ and ' are gone form the generated documentation
by S. Doaitse Swierstra 09 Dec '10

09 Dec '10

Code in the source of a package like: @ *Main> throw ThisException `catch` \e -> putStrLn (\"Caught \" ++ show (e :: MyException)) Caught ThisException @ (from the module http://haskell.org/ghc/docs/7.0-latest/html/libraries/base-4.3.0.0/src/GHC-…) gets formatted like: *Main> throw ThisException catch e -> putStrLn ("Caught " ++ show (e :: MyException)) Caught ThisException where the underlying HTML is: </p><pre> *Main> throw ThisException <code>catch</code> e -> putStrLn ("Caught " ++ show (e :: MyException)) Caught ThisException </pre><p> This is a Haddock problem I assume? Doaitse

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Haskell Platform Proposal: HLint
by John Smith 07 Dec '10

07 Dec '10

As a beginner, I'm finding HLInt (http://hackage.haskell.org/package/hlint) extremely useful for improving my code. Would it be worthwhile including this in HP?

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build problem with process on windows
by Simon Michael 06 Dec '10

06 Dec '10

Trying to build process with cygwin 1.7.7 on windows XP, I get the following error. Any ideas ? $ (date && ghc --version && cabal update && cabal configure && cabal build) >log 2>&1 Mon Dec 6 14:23:11 PST 2010 The Glorious Glasgow Haskell Compilation System, version 6.12.3 Downloading the latest package list from hackage.haskell.org Resolving dependencies... Configuring process-1.0.1.4... configure: WARNING: unrecognized options: --with-compiler checking for gcc... gcc checking whether the C compiler works... yes checking for C compiler default output file name... a.exe checking for suffix of executables... .exe checking whether we are cross compiling... no checking for suffix of object files... o checking whether we are using the GNU C compiler... yes checking whether gcc accepts -g... yes checking for gcc option to accept ISO C89... none needed checking how to run the C preprocessor... gcc -E checking for grep that handles long lines and -e... /usr/bin/grep checking for egrep... /usr/bin/grep -E checking for ANSI C header files... yes checking for sys/types.h... yes checking for sys/stat.h... yes checking for stdlib.h... yes checking for string.h... yes checking for memory.h... yes checking for strings.h... yes checking for inttypes.h... yes checking for stdint.h... yes checking for unistd.h... yes checking for pid_t... yes checking vfork.h usability... no checking vfork.h presence... no checking for vfork.h... no checking for fork... yes checking for vfork... yes checking for working fork... yes checking for working vfork... (cached) yes checking signal.h usability... yes checking signal.h presence... yes checking for signal.h... yes checking sys/wait.h usability... yes checking sys/wait.h presence... yes checking for sys/wait.h... yes checking fcntl.h usability... yes checking fcntl.h presence... yes checking for fcntl.h... yes checking for setitimer,... no checking for sysconf... yes checking value of SIG_DFL... 0 checking value of SIG_IGN... 1 configure: creating ./config.status config.status: creating include/HsProcessConfig.h config.status: include/HsProcessConfig.h is unchanged configure: WARNING: unrecognized options: --with-compiler Preprocessing library process-1.0.1.4... Building process-1.0.1.4... In file included from C:/HP/lib/base-4.2.0.2/include/HsBase.h:33, from cbits\runProcess.c:12:0: C:/cygwin/usr/include/stdlib.h:110: warning: `__warning__' attribute directive ignored C:/cygwin/usr/include/stdlib.h:117: warning: `__warning__' attribute directive ignored In file included from C:/HP/mingw/bin/../lib/gcc/ mingw32/3.4.5/../../../../include/windows.h:98, from C:/HP/lib/base-4.2.0.2/include/HsBase.h:88, from cbits\runProcess.c:12:0: C:/HP/mingw/bin/../lib/gcc/mingw32/3.4.5/../../../../include/ winsock2.h:103:2: warning: #warning "fd_set and associated macros have been defined in sys/types. This may cause runtime problems with W32 sockets" In file included from cbits\runProcess.c:12:0: C:/HP/lib/base-4.2.0.2/include/HsBase.h: In function `__hscore_ftruncate': C:/HP/lib/base-4.2.0.2/include/HsBase.h:347: warning: implicit declaration of function `ftruncate' C:/HP/lib/base-4.2.0.2/include/HsBase.h: At top level: C:/HP/lib/base-4.2.0.2/include/HsBase.h:378: error: syntax error before "stsize_t" C:/HP/lib/base-4.2.0.2/include/HsBase.h:378: warning: type defaults to `int' in declaration of `stsize_t' C:/HP/lib/base-4.2.0.2/include/HsBase.h:378: warning: data definition has no type or storage class C:/HP/lib/base-4.2.0.2/include/HsBase.h: In function `__hscore_sizeof_stat': C:/HP/lib/base-4.2.0.2/include/HsBase.h:387: error: invalid application of `sizeof' to incomplete type `C:/HP/lib/base-4.2.0.2/ include/HsBase.h' C:/HP/lib/base-4.2.0.2/include/HsBase.h: In function `__hscore_st_mtime': C:/HP/lib/base-4.2.0.2/include/HsBase.h:390: error: dereferencing pointer to incomplete type C:/HP/lib/base-4.2.0.2/include/HsBase.h: At top level: C:/HP/lib/base-4.2.0.2/include/HsBase.h:391: error: syntax error before "__hscore_st_size" C:/HP/lib/base-4.2.0.2/include/HsBase.h:391: warning: return type defaults to `int' C:/HP/lib/base-4.2.0.2/include/HsBase.h: In function `__hscore_st_size': C:/HP/lib/base-4.2.0.2/include/HsBase.h:391: error: dereferencing pointer to incomplete type C:/HP/lib/base-4.2.0.2/include/HsBase.h: In function `__hscore_st_mode': C:/HP/lib/base-4.2.0.2/include/HsBase.h:393: error: dereferencing pointer to incomplete type C:/HP/lib/base-4.2.0.2/include/HsBase.h: In function `__hscore_st_dev': C:/HP/lib/base-4.2.0.2/include/HsBase.h:394: error: dereferencing pointer to incomplete type C:/HP/lib/base-4.2.0.2/include/HsBase.h: In function `__hscore_st_ino': C:/HP/lib/base-4.2.0.2/include/HsBase.h:395: error: dereferencing pointer to incomplete type C:/HP/lib/base-4.2.0.2/include/HsBase.h: In function `__hscore_stat': C:/HP/lib/base-4.2.0.2/include/HsBase.h:400: warning: implicit declaration of function `_wstati64' C:/HP/lib/base-4.2.0.2/include/HsBase.h: In function `__hscore_fstat': C:/HP/lib/base-4.2.0.2/include/HsBase.h:404: warning: implicit declaration of function `_fstati64' C:/HP/lib/base-4.2.0.2/include/HsBase.h: In function `__hscore_open': C:/HP/lib/base-4.2.0.2/include/HsBase.h:591: warning: implicit declaration of function `_wsopen' C:/HP/lib/base-4.2.0.2/include/HsBase.h: At top level: C:/HP/lib/base-4.2.0.2/include/HsBase.h:608: error: syntax error before "__hscore_lseek" C:/HP/lib/base-4.2.0.2/include/HsBase.h:608: error: syntax error before "off64_t" C:/HP/lib/base-4.2.0.2/include/HsBase.h:608: warning: return type defaults to `int' C:/HP/lib/base-4.2.0.2/include/HsBase.h: In function `__hscore_lseek': C:/HP/lib/base-4.2.0.2/include/HsBase.h:609: warning: implicit declaration of function `_lseeki64' C:/HP/lib/base-4.2.0.2/include/HsBase.h:609: error: `fd' undeclared (first use in this function) C:/HP/lib/base-4.2.0.2/include/HsBase.h:609: error: (Each undeclared identifier is reported only once C:/HP/lib/base-4.2.0.2/include/HsBase.h:609: error: for each function it appears in.) C:/HP/lib/base-4.2.0.2/include/HsBase.h:609: error: `off' undeclared (first use in this function) C:/HP/lib/base-4.2.0.2/include/HsBase.h:609: error: `whence' undeclared (first use in this function) cbits\runProcess.c: In function `runInteractiveProcess': cbits\runProcess.c:387:0: warning: implicit declaration of function `_get_osfhandle' cbits\runProcess.c:463:0: warning: implicit declaration of function `_open_osfhandle'

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haskell package layout: a proposal
by Mark Lentczner 06 Dec '10

06 Dec '10

Over on my blog, I've put up a proposal for changing the default layout of installed package pieces: http://mtnviewmark.wordpress.com/2010/12/02/haskell-package-layout/ Thoughts? - Mark

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Can containers depend on Template Haskell?
by Johan Tibell 05 Dec '10

05 Dec '10

Hi all, I'm working on a proposal for adding a Data.HashMap and Data.HashSet type to containers. These types could share most of their implementation with Data.IntMap (and Data.IntSet) but can be (somewhat) more efficiently implemented by specializing IntMap from data IntMap a = Nil | Tip {-# UNPACK #-} !Key a | Bin {-# UNPACK #-} !Prefix {-# UNPACK #-} !Mask !(IntMap a) !(IntMap a) to data FullList k v = FL !k v (List k v) data List k v = Nil | Cons !k v (List k v) data IntMap a = Nil | Tip {-# UNPACK #-} !Hash {-# UNPACK #-} !(FullList k v) | Bin {-# UNPACK #-} !Prefix {-# UNPACK #-} !Mask !(IntMap a) !(IntMap a) Unpacking the FullList into the Tip constructor saves one indirection and two words of overhead per key/value pair. One way to achieve this specialization would be to duplicate the implementation of Data.IntMap, but it would be nice to avoid the duplication. Template Haskell would allow most of the implementation to be shared without sacrificing performance. Can containers use Template Haskell? I think the answer is no, but I thought I'd check anyway. Johan

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Re: Functor => Pointed => Applicative => Monad
by wren ng thornton 04 Dec '10

04 Dec '10

On 12/4/10 6:32 AM, Sebastian Fischer wrote: > Hi Wren, > > On Sat, 2010-12-04 at 01:25 -0500, wren ng thornton wrote: >> data SliceUnder a b = SliceUnder (b->a) >> >> instance Functor (SliceUnder a) where >> fmap f (SliceUnder g) = SliceUnder (g . f) > > Couldn't match type `a1' with `b' Ha, righto! That one's contravariant, whoops. class ContraFunctor f where contraMap :: (a -> b) -> (f b -> f a) instance ContraFunctor (SliceUnder a) where contraMap f (SliceUnder g) = SliceUnder (g . f) That'll teach me to rattle things off without typechecking them. -- Live well, ~wren

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Re: Functor => Pointed => Applicative => Monad
by John Lato 04 Dec '10

04 Dec '10

> > From: David Menendez <dave(a)zednenem.com> > Subject: Re: Functor => Pointed => Applicative => Monad > To: Isaac Dupree <ml(a)isaac.cedarswampstudios.org> > Cc: libraries(a)haskell.org > Message-ID: > <AANLkTinkqQXYTN6ATqGawbdeVvtfq_6z51sADN8i_O8P(a)mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > On Mon, Nov 29, 2010 at 11:26 AM, Isaac Dupree > <ml(a)isaac.cedarswampstudios.org> wrote: > > On 11/29/10 03:39, John Smith wrote: > >> > >> Is there any intention to reorganise the standard class hierarchy, > >> arranging them logically instead of in order of invention? I plagiarised > >> the following example from > >> http://stackoverflow.com/questions/1634911/can-liftm-differ-from-lifta > >> and Trac: > >> > >> class Functor f where > >> map :: (a -> b) -> f a -> f b > >> > >> class Functor f => Pointed f where > >> pure :: a -> f a > > > > Is it useful to have Pointed non-Functors? > > Is Pointed useful at all? The last time this discussion came up, I > asked for algorithms which were generic over pointed functors (in the > same way that traverse is generic over applicative functors) and no > one could think of any. > It's useful for 'singleton' on probabilistic data structures (e.g. a Bloom filter). John

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