- Glasgow-haskell-users

Newtype deriving mixing up types
by Emil Axelsson 17 Dec '10

17 Dec '10

Hello! I attach a program which I suspect demonstrates a bug in GHC. The important lines are: showType :: forall a . Expr a -> String showType (Lit _) = show (typeOf (undefined :: a)) test1 = showType (mk :: Expr BOOL) -- Prints "Bool" (wrong?) test2 = showType (Lit mk :: Expr BOOL) -- Prints "Main.BOOL" (correct) test1 and test2 give different results, even though showType shouldn't be able to tell them apart. It seems that the Typeable context packed with the Lit constructor is wrong in test2. I had to use two extra classes and newtype deriving to trigger this behavior. Note that if I change deriving instance B BOOL to instance B BOOL the result is correct. Tested with both 6.12.3 and 7.0.1. Should I report this as a bug? Thanks! / Emil

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Printing of asynchronous exceptions to stderr
by Mitar 16 Dec '10

16 Dec '10

Hi! I have been spend some time to debug this in my program. ;-) Why is ThreadKilled not displayed by RTS when send to thread (and unhandled), but any other exception is? For example, I am using custom exceptions to signal different kinds of thread killing. Based on those my threads cleanup in different ways. But after they cleanup they keep "running". Not really running as their computations were interrupted. But simply hanging there. And if then new custom exception arrives it is not handled anymore (as it is after my normal exception handlers already cleaned everything) and it is printed to stderr. Now I added "`finally` throwIO ThreadKilled" at the end of my cleanup computations to really kill the thread. So that possible later exceptions are not delivered anymore. Why it is not so that after all computations in a thread finish, thread is not killed/disposed of? Because it can be reused by some other computation? But then my exceptions could be delivered to wrong (new) thread while they were meant for old one? Mitar

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build issue: * Missing header file: HsBase.h
by Karel Gardas 16 Dec '10

16 Dec '10

Hello, I'm trying to recover my opensolaris builder machine after disk crash, but after reinstall I'm not able to build any GHC there. I'm trying head and now also 6.12.3 as a reference (as I'm able to build it on my workstation with the same OS). The problem I see here is when I invoke `gmake' then the process continues up to configuration of base library which fails with: checking value of ETIMEDOUT... 145 checking value of ETOOMANYREFS... 144 checking value of ETXTBSY... 26 checking value of EUSERS... 94 checking value of EWOULDBLOCK... 11 checking value of EXDEV... 18 checking value of ENOCIGAR... -1 checking value of SIGINT... 2 checking value of O_BINARY... 0 checking for library containing iconv... none required configure: creating ./config.status config.status: creating base.buildinfo config.status: creating include/HsBaseConfig.h configure: WARNING: unrecognized options: --with-compiler ghc-cabal: Missing dependency on a foreign library: * Missing header file: HsBase.h 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. gmake[1]: *** [libraries/base/dist-install/package-data.mk] Error 1 gmake: *** [all] Error 2 The problem is HsBase.h is where it is on my reference build tree on workstation: -bash-4.0$ find . -name 'HsBase.h' ./libraries/base/include/HsBase.h -bash-4.0$ I suppose some external library might be missing, but here the error is quite misleading and I cannot find which one might be the culprit of this error. Do you have any idea what to install in order to proceed? Thanks! Karel

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Re: [Haskell] Terms of Service for Haskell community server
by Christian Höner zu Siederdissen 15 Dec '10

15 Dec '10

Hi, you probably mean generating an ssh key-pair. This is a one-step operation. Is Yarrow a weapon or a crypto package? Otherwise I would suggest putting Yarrow onto your personal webpage / university system and asking for a link. Gruss, Christian PS: I have just skimmed the TOS, but apart from the crypto (weapon ;-) stuff, it seems to be mostly standard US legalize. Of course, I am no lawyer. * Frank Rosemeier <frank(a)rosemeier.info> [15.12.2010 23:57]: > > Dear Haskellers, > > as some of you may have noticed, the Yarrow home page has to be > moved because of the migration of the Haskell.org server. > It has been recommended to me by Ian Lynagh to transfer the files to > the new community server. > To do so I need first to request for an account there. > > This includes producing an ssh certificate. I will try to solve this > problem. (May be there will be questions in the future.) > > The more severe problem is related to the Terms of Service which I > have to accept with the account request. > It contains lots of legal stuff which I do not understand including > regulations for US export controls. > Of course I am neither able nor willing to send reports concerning > Yarrow to the US government! > > Are there some experts or tutors who want to help me to understand > the Terms of Service especially the export controls? > May be these regulations do not apply in my case, because I am > living in Germany? > (I have expected lots of work to be done with respect to the migration, > but I did not imagine to be involved in legal affairs which I do not > understand.) > > Thank you very much for your patience. > > > Kind regards > > Frank Rosemeier > > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell

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Oversized libraries
by Audrius Šaikūnas 14 Dec '10

14 Dec '10

Hello, I've noticed that libraries that are compiled even with -dynamic are really huge: libHScairo-0.12.0-ghc6.12.1.so - 1.4 M libHSgio-0.12.0-ghc6.12.1.so - 1.6 M libHSgtk-0.12.0-ghc6.12.1.so - 14 M (ldd confirms that these libraries are really linked dynamically with the rest of the world) just to name a few. All of them are striped with "strip -s". At this point *bindings* to C libraries are larger that the libraries themselves, which I find unacceptable. So I decided to dig a bit deeper and when examining cairo-0.12.0 I found that Types.o object file consumes 1.5 MB. So I "cleaned" up Types.hs and tried to compile it separately from the rest of the library: % ghc -c Types.hs && ls -lh | grep Types.o -rw-r--r-- 1 angel angel 69K 2010-12-14 18:24 Types.o % rm Types.o % ghc -c Types.hs -O && ls -lh | grep Types.o -rw-r--r-- 1 angel angel 1.1M 2010-12-14 18:25 Types.o So adding -O when compiling Types.hs makes the size of object file jump from 69K to 1.1M. Just think about it - the file contains *two* *enums* and nothing more. And yet it twice as large as a full-blown application like gedit. So I would like to ask you whether such behavior is known and should such this be considered as a bug? I've attached the testcase. It also can be found here: http://hpaste.org/42331/something Btw, I'm using GHC 6.12.1, x86_64. Best regards, Audrius

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HEAD doesn't build on OS X
by Johan Tibell 14 Dec '10

14 Dec '10

Starting with a clean tree I get: "/usr/bin/ghc" -H32m -O -Wall -Werror -H64m -O0 -package-conf libraries/bootstrapping.conf -package-name ghc-7.1 -hide-all-packages -i -icompiler/basicTypes -icompiler/cmm -icompiler/codeGen -icompiler/coreSyn -icompiler/deSugar -icompiler/ghci -icompiler/hsSyn -icompiler/iface -icompiler/llvmGen -icompiler/main -icompiler/nativeGen -icompiler/parser -icompiler/prelude -icompiler/profiling -icompiler/rename -icompiler/simplCore -icompiler/simplStg -icompiler/specialise -icompiler/stgSyn -icompiler/stranal -icompiler/typecheck -icompiler/types -icompiler/utils -icompiler/vectorise -icompiler/stage1/build -icompiler/stage1/build/autogen -Icompiler/stage1/build -Icompiler/stage1/build/autogen -Icompiler/stage1 -Icompiler/../libraries/base/cbits -Icompiler/../libraries/base/include -Icompiler/. -Icompiler/parser -Icompiler/utils -optP-include -optPcompiler/stage1/build/autogen/cabal_macros.h -package Cabal-1.11.0 -package array-0.3.0.2 -package base-4.3.0.0 -package bin-package-db-0.0.0.0 -package bytestring-0.9.1.8 -package containers-0.4.0.0 -package directory-1.1.0.0 -package filepath-1.2.0.0 -package hpc-0.5.0.6 -package old-time-1.0.0.6 -package process-1.0.1.4 -package unix-2.4.1.0 -Wall -fno-warn-name-shadowing -fno-warn-orphans -XCPP -XMagicHash -XUnboxedTuples -XPatternGuards -XForeignFunctionInterface -XEmptyDataDecls -XTypeSynonymInstances -XMultiParamTypeClasses -XFlexibleInstances -XRank2Types -XScopedTypeVariables -XDeriveDataTypeable -DSTAGE=1 -no-user-package-conf -rtsopts -O -odir compiler/stage1/build -hidir compiler/stage1/build -stubdir compiler/stage1/build -hisuf hi -osuf o -hcsuf hc -c compiler/nativeGen/AsmCodeGen.lhs -o compiler/stage1/build/AsmCodeGen.o compiler/nativeGen/AsmCodeGen.lhs:83:1: parse error on input `*************' make[1]: *** [compiler/stage1/build/AsmCodeGen.o] Error 1 make[1]: *** Waiting for unfinished jobs.... make: *** [all] Error 2 $ ghc -V The Glorious Glasgow Haskell Compilation System, version 7.0.1

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Re: Functor => Applicative => Monad
by Antoine Latter 12 Dec '10

12 Dec '10

Is there a discussion deadline, if this now a libraries proposal? For something like this, you might want to advertise the discussion on Plane Haskell, and the -cafe to get adequate discussion, as it seems sure to break quite a few things. And reddit, although I consider that a less contemplative venue. Maybe other places? Do we know of any cases where this sort of conversion will be hard to do? This is also usually the part of the discussion where I would ask for an estimate as to how much this breaks what is published on Hackage, but I think the answer would be "a lot." If I depend on a prior version of the 'base' package, I'm guessing that I'm not insulated from this change, due to how de-sugaring happens. Do other haskell compilers (Hugs, NHC?) use the base library? How does this change affect them? Are there any ways to make this sort of change not break things? There has been talk about a language extensions to make this thing work out, but they have never been fleshed out, and they've always been the sort that sounded like they would have many corner cases. I don't like breaking things, even though the new hierarchy makes a lot of sense. Antoine On Sun, Dec 12, 2010 at 7:24 AM, John Smith <voldermort(a)hotmail.com> wrote: > On 12/12/2010 15:12, Bas van Dijk wrote: >> >> On Sun, Dec 12, 2010 at 12:48 PM, John Smith<voldermort(a)hotmail.com> >> wrote: >>> >>> There's a ticket at http://trac.haskell.org/haskell-platform/ticket/155, >> >> Thanks! But why create a ticket for the Haskell Platform? This is a >> change in the base library so we should follow the library submission >> process[1] and create[2] a ticket in the ghc trac. >> >> Regards, >> >> Bas >> >> [1] http://www.haskell.org/haskellwiki/Library_submissions >> [2] >> http://hackage.haskell.org/trac/ghc/newticket?type=proposal&component=libra… > > Good point; I've moved it to http://hackage.haskell.org/trac/ghc/ticket/4834 > > > _______________________________________________ > Libraries mailing list > Libraries(a)haskell.org > http://www.haskell.org/mailman/listinfo/libraries >

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Re: Functor => Applicative => Monad
by Bas van Dijk 12 Dec '10

12 Dec '10

On Sun, Dec 12, 2010 at 12:48 PM, John Smith <voldermort(a)hotmail.com> wrote: > There's a ticket at http://trac.haskell.org/haskell-platform/ticket/155, Thanks! But why create a ticket for the Haskell Platform? This is a change in the base library so we should follow the library submission process[1] and create[2] a ticket in the ghc trac. Regards, Bas [1] http://www.haskell.org/haskellwiki/Library_submissions [2] http://hackage.haskell.org/trac/ghc/newticket?type=proposal&component=libra…

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Re: Functor => Applicative => Monad
by Bas van Dijk 12 Dec '10

12 Dec '10

On Wed, Dec 1, 2010 at 10:02 AM, John Smith <voldermort(a)hotmail.com> wrote: > Regarding recent concerns as to whether Pointed is actually useful (and if > it is, is that Pointed Functors or pure Pointed?), how about a slightly more > modest reform? > > class Functor f where > map :: (a -> b) -> f a -> f b > > class Functor f => Applicative f where > pure :: a -> f a > (<*>) :: f (a -> b) -> f a -> f b > (*>) :: f a -> f b -> f b > (<*) :: f a -> f b -> f a > > class Applicative m => Monad m where > (>>=) :: m a -> (a -> m b) -> m b > f >>= x = join $ map f x > > join :: m (m a) -> m a > join x = x >>= id > > (unrelated, but also valid) > > instance MonadPlus m => Monoid (m a) where > mempty = mzero > mappend = mplus > > > module Legacy where > > fmap :: Functor f => (a -> b) -> f a -> f b > fmap = map > > liftA :: Applicative f => (a -> b) -> f a -> f b > liftA = map > > liftM :: Monad m => (a -> b) -> m a -> m b > liftM = map > > ap :: Monad m => m (a -> b) -> m a -> m b > ap = (<*>) > > (>>) :: Monad m => m a -> m b -> m b > (>>) = (*>) > > concat :: [[a]] -> [a] > concat = join > > etc. > > And for those who really want a list map, > > listMap :: (a -> b) -> [a] -> [b] > listMap = map > Linked are some patch bundles that provide an initial implementation of the new hierarchy: * http://code.haskell.org/~basvandijk/ghc_new_monad_hierarchy.dpatch This patch bundle is to prepare ghc for the new hierarchy. Most importantly it adds Functor and Applicative instances for all monads in ghc. Note that these patches are useful on their own and don't depend on the new hierarchy so they can be applied even when this proposal is not accepted. * http://code.haskell.org/~basvandijk/base_new_monad_hierarchy.dpatch This patch actually implements the new hierarchy. I tried to be even more conservative than the current proposal, namely 'return' and '>>' are still methods of Monad but have now been given default implementations in terms of Applicative. Also all names have been kept intact (fmap is still named fmap): class Functor f where fmap :: (a -> b) -> f a -> f b (<$) :: a -> f b -> f a (<$) = fmap . const class Functor f => Applicative f where pure :: a -> f a (<*>) :: f (a -> b) -> f a -> f b (*>) :: f a -> f b -> f b a *> b = fmap (const id) a <*> b (<*) :: f a -> f b -> f a a <* b = fmap const a <*> b class Applicative m => Monad m where (>>=) :: m a -> (a -> m b) -> m b m >>= f = join $ fmap f m join :: m (m a) -> m a join m = m >>= id (>>) :: m a -> m b -> m b (>>) = (*>) return :: a -> m a return = pure fail :: String -> m a fail s = error s Also see the generated library documentation: http://bifunctor.homelinux.net/~bas/doc/ghc/html/libraries/base-4.4.0.0/ Note that I am in favour of removing 'return', '>>' and 'fail' from Monad and renaming 'fmap' to 'map'. But I think it's better to do this as a separate patch. Besides patching the base library and ghc, I also needed to patch lots of other libraries in my ghc root. To get these patches, simply pull from my local ghc repository. i.e.: darcs pull http://bifunctor.homelinux.net/~bas/ghc/ darcs pull http://bifunctor.homelinux.net/~bas/ghc/libraries/base Note that ghc requires the happy parser generator. When happy generates a parser it also generates a HappyIdentity type with an according Monad instance. The following patch makes happy also generate the needed Functor and Applicative instances (This patch is already send to happy's maintainer): http://bifunctor.homelinux.net/~bas/functor_and_applicative_instance_HappyI… Feel free to ask questions or post comments about these patches. Regards, Bas P.S. John, did you already make a ticket for this proposal? I would like to attach my patches to it.

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Re: [darcs-users] How to develop on a (GHC) branch with darcs
by Ganesh Sittampalam 10 Dec '10

10 Dec '10

On Wed, 8 Dec 2010, Stephen J. Turnbull wrote: > Ganesh Sittampalam writes: > > > I think there are three things that can help with this problem: > > > > 1) a darcs rebase command. This will give you a nice way to manage the > > workflow already discussed, and you won't have to squish everything > > through into a mega-patch. You'll still have to periodically abandon one > > branch for another though (but I think that's also the case with git > > rebase). > > I'm not sure what you mean by "abandon". I mean the same as in the git world. The rebased patches have new identities, and if my ideas for tracking the relationship don't work out, they will have no relationship to the old patches. [your very clear explanation of that snipped] > > I also have some hope, though this is more speculative, of offering > > a clean way of tracking the relationship between the old branch and > > the new branch so that any stray patches against the old branch can > > be cleanly rebased to the new branch later on. > > As explained above, DAG-based VCSes like git can't do this cleanly > (that is one way of expressing the reason why rebase is severely > deprecated in some circles), and I don't think git will be able to do > so in the near future. OTOH, if Darcs gets rebase but can't handle > this, I'd have to count that as a net minus. Recombinant patching is > really what Darcs is all about IMO. darcs rebase is essentially about giving up on the recombinant patching because that's not working out for whatever reason. It's primarily intended as an alternative to manually reapplying patches to new branches using diff-and-patch, which is something significant numbers of people have ended up having to do. People generally want/need to do this to avoid conflicts, because: (a) darcs conflict handling can blow up, both because of exponential merges (primarily with v1 patches) and because of bugs (b) the UI for dealing with conflicts isn't really that pleasant and in particular once you've resolved a conflict it's a little painful to see the overall effect of the conflict resolution together with the underlying patch > In practice, git rebase needs to be kept private to a single user, and > is impractical even if private, if the user has propagated the branch > to other local repositories. Because git branching is so lightweight, > nobody really sees this as a big problem; throwaway branches are used > all the time as interim steps in many operations (eg, git stash). > Darcs branches, on the other hand, are much more heavyweight (modulo > the work you propose on colocated branches, but that's farther away > than rebase is). > > IMHO YMMV. But I strongly recommend you think carefully about this. > Analogies to git rebase are a trap here. It's implemented differently > and used to solve different problems from the way rebase is proposed > for use in Darcs. My understanding is that one of the main uses for git rebase is for "cleaning up history" prior to submission. In that regard I think there's a substantial overlap with what darcs rebase is intended for. Thanks for the detailed comments. Ganesh

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