December 2014 - Glasgow-haskell-users

Re: ANNOUNCE: GHC 7.10.1 Release Candidate 1
by Edward Z. Yang 27 Dec '14

27 Dec '14

Hello lonetiger, I don't think any relevant logic changed in 7.10; however, this commit may be relevant: commit 8fb03bfd768ea0d5c666bbe07a50cb05214bbe92 Author: Ian Lynagh <igloo(a)earth.li> Sun Mar 18 11:42:31 2012 Committer: Ian Lynagh <igloo(a)earth.li> Sun Mar 18 11:42:31 2012 Original File: compiler/typecheck/TcForeign.lhs If we say we're treating StdCall as CCall, then actually do so But this warning should have applied even on older versions of GHC. Are you running x86_64 Windows? stdcall is specific to x86_32. Edward Excerpts from lonetiger's message of 2014-12-24 08:24:52 -0500: > Hi, > > > I’ve had some issues building this (and the git HEAD), it seems that the config.guess and config.sub in the libffi tarball is old, it doesn’t detect the platform when building with msys2. I had to unpack the tarfile and update the files, after this it correctly built. > > > Then I proceeded to try to make a shared library and got the following warning: > > > ManualCheck.hs:18:1: Warning: > the 'stdcall' calling convention is unsupported on this platform, > treating as ccall > When checking declaration: > foreign export stdcall "testFoo" testFooA :: CInt -> IO (FooPtr) > > > > Does this mean that GHC no longer supports stdcall on windows? or could this be related to issue I had building? > > > Regards, > > Tamar > > > > > > From: Austin Seipp > Sent: ‎Tuesday‎, ‎December‎ ‎23‎, ‎2014 ‎15‎:‎36 > To: ghc-devs(a)haskell.org, glasgow-haskell-users(a)haskell.org > > > > > > We are pleased to announce the first release candidate for GHC 7.10.1: > > https://downloads.haskell.org/~ghc/7.10.1-rc1/ > > This includes the source tarball and bindists for 64bit/32bit Linux > and Windows. Binary builds for other platforms will be available > shortly. (CentOS 6.5 binaries are not available at this time like they > were for 7.8.x). These binaries and tarballs have an accompanying > SHA256SUMS file signed by my GPG key id (0x3B58D86F). > > We plan to make the 7.10.1 release sometime in February of 2015. We > expect another RC to occur during January of 2015. > > Please test as much as possible; bugs are much cheaper if we find them > before the release! >

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CPP Help (was Re: Latest Template Haskell Breaks Package)
by Dominic Steinitz 25 Dec '14

25 Dec '14

Ok I have a cut down version of the problem and am cross posting to glasgow-haskell-users. To restate the problem: this is from code that has not been changed for 2 years. I get > Examples.hs:42:42: Parse error in pattern: con > Failed, modules loaded: none. Any help would be very gratefully received. > {-# LANGUAGE TypeFamilies, MultiParamTypeClasses, FunctionalDependencies #-} > {-# LANGUAGE FlexibleContexts #-} > {-# LANGUAGE EmptyDataDecls #-} > {-# LANGUAGE FlexibleInstances, TypeSynonymInstances #-} > {-# LANGUAGE UndecidableInstances, OverlappingInstances #-} > {-# LANGUAGE GeneralizedNewtypeDeriving, StandaloneDeriving #-} > {-# LANGUAGE RankNTypes, ScopedTypeVariables #-} > {-# LANGUAGE MagicHash, BangPatterns, UnboxedTuples #-} > {-# LANGUAGE TemplateHaskell, CPP #-} > > module Examples where > > import GHC.Prim > import GHC.Exts > import GHC.Types > import GHC.Word > import GHC.Int > > class Touchable a where > touch :: a -> IO () > > instance Touchable Bool where > touch b = IO (\s -> case touch# b s of s' -> (# s', () #)) > {-# INLINE touch #-} > > #define TOUCHABLE_INST(ty,con) \ > instance Touchable ty where { \ > touch (con x#) = IO (\s -> case touch# x# s of s' -> (# s', () #)); \ > {-# INLINE touch #-}; \ > } > > TOUCHABLE_INST(Int, I#) > > #define PRIM_COMP_INST(ty,con,le,ge) \ > instance PrimitiveOrd ty where { \ > minM' (con a#) (con b#) = \ > IO (\s -> \ > let r# = if le a# b# then a# else b# \ > in case touch# r# s of s' -> (# s', (con r#) #)); \ > } > > PRIM_COMP_INST(Int, I#, (<=#), (>=#)) Dominic Steinitz dominic(a)steinitz.org http://idontgetoutmuch.wordpress.com On 23 Dec 2014, at 15:06, Dominic Steinitz <dominic(a)steinitz.org> wrote: > Hi Erik, > > Thank you very much. With that clue the compilation now doesn’t fail at that particular point. > > The bad news is it now fails to compile this module > > https://hackage.haskell.org/package/yarr-1.3.2/docs/src/Data-Yarr-Utils-Pri… > > with a parse error(!). Not only do I not have much experience with TH but this has now exposed my ignorance of CPP. > >> Data/Yarr/Utils/Primitive.hs:119:126: Parse error in pattern: con > > If I comment out the last four lines > >> PRIM_COMP_INST(Int, I#, (<=#), (>=#)) >> PRIM_COMP_INST(Char, C#, leChar#, geChar#) >> PRIM_COMP_INST(Word, W#, leWord#, geWord#) >> PRIM_COMP_INST(Double, D#, (<=##), (>=##)) >> PRIM_COMP_INST(Float, F#, leFloat#, geFloat#) > > then the module compiles but of course then the whole package does *not* compile. > > Did something change in 7.8.3 with regard to CPP (this code has not been modified for at least two years)? > > Thanks once again. > > Dominic Steinitz > dominic(a)steinitz.org > http://idontgetoutmuch.wordpress.com > > On 23 Dec 2014, at 13:42, Erik Hesselink <hesselink(a)gmail.com> wrote: > >> Hi Dominic, >> >> It looks like just a representation change: a TySynEqn is a data type >> containing a [Type] and a Type, and those were the original two >> arguments. So it looks like with a little bit of CPP, you could >> support both versions. Something like >> >> #if MIN_VERSION_template_haskell(2,9,0) >> ... >> #else >> ... >> #endif >> >> In general, I think each major release of template haskell has quite >> some breaking changes, but I don't know of any place where they're >> enumerated. The GHC changelog only has a couple of high level bullet >> points. >> >> Regards, >> >> Erik >> >> On Tue, Dec 23, 2014 at 2:20 PM, Dominic Steinitz <dominic(a)steinitz.org> wrote: >>> I realise I should have sent this to the libraries list. >>> >>> Dominic Steinitz >>> dominic(a)steinitz.org >>> http://idontgetoutmuch.wordpress.com >>> >>> Begin forwarded message: >>> >>> From: Dominic Steinitz <dominic(a)steinitz.org> >>> Subject: Latest Template Haskell Breaks Package >>> Date: 23 December 2014 13:14:26 GMT >>> To: Haskell-Cafe <haskell-cafe(a)haskell.org> >>> >>> Hello Fellow Haskellers, >>> >>> I have become a maintainer for yarr >>> (https://hackage.haskell.org/package/yarr) This no longer compiles with >>> ghc-7.8.3 because it specifies base == 4.6. Relaxing this to base >=4.6 && >>> <4.8 tells me I need a newer version of Template Haskell >>> >>> rejecting: template-haskell-2.7.0.0, 2.6.0.0, 2.5.0.0, 2.4.0.1, 2.4.0.0, >>> 2.3.0.1, 2.3.0.0, 2.2.0.0 (conflict: yarr => template-haskell>=2.8 && <2.9) >>> >>> >>> If I now relax the constraint for Template Haskell I get a compiler error as >>> there has been a breaking change from Template Haskell 2.9 to 2.10. >>> >>> Data/Yarr/Utils/FixedVector/VecTuple.hs:45:16: >>> Couldn't match expected type ‘TypeQ -> Q Dec’ >>> with actual type ‘Q Dec’ >>> The function ‘tySynInstD’ is applied to three arguments, >>> but its type ‘Name -> TySynEqnQ -> DecQ’ has only two >>> >>> >>> And indeed looking at the changes in >>> http://git.haskell.org/packages/template-haskell.git/commitdiff/ccd7891c536… >>> I can see that the function in question has changed. >>> >>> -tySynInstD :: Name -> [TypeQ] -> TypeQ -> DecQ >>> -tySynInstD tc tys rhs = >>> +tySynInstD :: Name -> [TySynEqnQ] -> DecQ >>> +tySynInstD tc eqns = >>> >>> >>> Did I miss some announcement of this breaking change and the advice on what >>> to do about it? >>> >>> If I did can someone please point me at the relevant document. If not then I >>> feel sad and would be very grateful if someone could help me as I know very >>> little about Template Haskell. >>> >>> Many thanks >>> >>> Dominic Steinitz >>> dominic(a)steinitz.org >>> http://idontgetoutmuch.wordpress.com >>> >>> >>> >>> _______________________________________________ >>> Libraries mailing list >>> Libraries(a)haskell.org >>> http://www.haskell.org/mailman/listinfo/libraries >>> >

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Re: ANNOUNCE: GHC version 7.8.4
by Carter Schonwald 24 Dec '14

24 Dec '14

sure, please verify first. (also make sure haddock etc works for you, i had to remove a haddock binary from ~/.cabal/bin before haddocks were building correctly for me) On Wed, Dec 24, 2014 at 10:52 AM, Alfredo Di Napoli < alfredo.dinapoli(a)gmail.com> wrote: > Thanks Carter! > > I have just asked basically about it on Reddit, in the announce thread. > I'll give it a spin, and if it works I will share the link (if you are ok > with that!) on the > same Reddit post. > > Alfredo > > > On Tuesday, 23 December 2014, Carter Schonwald <carter.schonwald(a)gmail.com> > wrote: > > Heres a OS X build that should work with >= 10.7 > > > http://www.wellposed.com/opensource/ghc/releasebuild-unofficial/ghc-7.8.4-x… > > > > and the sha 512 > > shasum -a512 ghc-7.8.4-x86_64-apple-darwin.tar.bz2 > > > c6e76a2cd7ec7820d071ef1f417981845bb86c4c8337a57431136a375cbd0695fe810ec10963109ab1971d1a0ab80318c62d71b95eddb5657800cac296a260bd > ghc-7.8.4-x86_64-apple-darwin.tar.bz2 > > On Tue, Dec 23, 2014 at 8:12 AM, Austin Seipp <austin(a)well-typed.com> > wrote: > > > > ============================================================== > > The (Interactive) Glasgow Haskell Compiler -- version 7.8.4 > > ============================================================== > > > > The GHC Team is pleased to announce a new patchlevel release of GHC, > 7.8.4. > > > > This is an important bugfix release relative to 7.8.3 (with over 30 > > defects fixed), so we highly recommend upgrading from the previous 7.8 > > releases. > > > > The full release notes are here: > > > > > https://downloads.haskell.org/~ghc/7.8.4/docs/html/users_guide/release-7-8-… > > > > How to get it > > ~~~~~~~~~~~~~ > > > > The easy way is to go to the web page, which should be self-explanatory: > > > > https://www.haskell.org/ghc/ > > > > We supply binary builds in the native package format for many > > platforms, and the source distribution is available from the same > > place. > > > > Packages will appear as they are built - if the package for your > > system isn't available yet, please try again later. > > > > > > Background > > ~~~~~~~~~~ > > > > Haskell is a standard lazy functional programming language. > > > > GHC is a state-of-the-art programming suite for Haskell. Included is > > an optimising compiler generating good code for a variety of > > platforms, together with an interactive system for convenient, quick > > development. The distribution includes space and time profiling > > facilities, a large collection of libraries, and support for various > > language extensions, including concurrency, exceptions, and foreign > > language interfaces (C, whatever). GHC is distributed under a > > BSD-style open source license. > > > > A wide variety of Haskell related resources (tutorials, libraries, > > specifications, documentation, compilers, interpreters, references, > > contact information, links to research groups) are available from the > > Haskell home page (see below). > > > > > > On-line GHC-related resources > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > > Relevant URLs on the World-Wide Web: > > > > GHC home page http://www.haskell.org/ghc/ > > GHC developers' home page http://ghc.haskell.org/trac/ghc/ > > Haskell home page http://www.haskell.org/ > > > > > > Supported Platforms > > ~~~~~~~~~~~~~~~~~~~ > > > > The list of platforms we support, and the people responsible for them, > > is here: > > > > http://ghc.haskell.org/trac/ghc/wiki/Platforms > > http://ghc.haskell.org/trac/ghc/wiki/CodeOwners > > > > Ports to other platforms are possible with varying degrees of > > difficulty. The Building Guide describes how to go about porting to a > > new platform: > > > > http://ghc.haskell.org/trac/ghc/wiki/Building > > > > > > Developers > > ~~~~~~~~~~ > > > > We welcome new contributors. Instructions on accessing our source > > code repository, and getting started with hacking on GHC, are > > available from the GHC's developer's site run by Trac: > > > > http://ghc.haskell.org/trac/ghc/ > > > > > > Mailing lists > > ~~~~~~~~~~~~~ > > > > We run mailing lists for GHC users and bug reports; to subscribe, use > > the web interfaces at > > > > http://www.haskell.org/mailman/listinfo/glasgow-haskell-users > > http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs > > > > There are several other haskell and ghc-related mailing lists on > > www.haskell.org; for the full list, see > > > > http://www.haskell.org/mailman/listinfo/ > > > > Some GHC developers hang out on #haskell on IRC, too: > > > > http://www.haskell.org/haskellwiki/IRC_channel > > > > Please report bu >

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HEADS UP: Tickets have been triaged a bit
by Austin Seipp 23 Dec '14

23 Dec '14

Hi *, As many of you will probably notice, I have bulk modified a lot of Trac tickets and moved their milestone out. You might be wondering why; the reasoning is that since 7.10.1 RC1 is out (see other email), we need to start prioritizing what gets done. So, I moved all tickets that were a) set to 7.10.1 milestone, b) not closed, and c) had below 'high priority', to the 7.12.1 milestone. There are some tickets in 'normal' that probably should be moved back. If you're CC'd on a ticket and think it should be fixed for 7.10.1, please: - Set the milestone back to 7.10.1 - And if you can, take ownership! GHC HQ will probably only have time to organize efforts to take on the most high priority tickets - so any help you can offer is always appreciated. You can see the current list of tickets here. We'll put notes on the page at the top as time goes on to keep people up to date. https://ghc.haskell.org/trac/ghc/wiki/Status/GHC-7.10.1 -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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ANN: deepseq-bounded, seqaid, leaky
by Andrew Seniuk 21 Dec '14

21 Dec '14

This trio of related packages explores strictness control in a variety of ways. deepseq-bounded provides classes and generic functions to artificially force evaluation, to extents controlled by static or dynamic configuration. seqaid puts that into practise, providing a GHC plugin to auto-instrument your package with a strictness harness, which is dynamically optimisable during runtime. This is supported directly in the GHC compilation pipeline, without requiring (or performing!) any edits to your sources. leaky is a minimal, prototypic executable that leaks space under current state-of-the-art compilation (GHC 7.8.3 -O2, at the present time). deepseq-bounded hackage: https://hackage.haskell.org/package/deepseq-bounded homepage: http://www.fremissant.net/deepseq-bounded seqaid hackage: https://hackage.haskell.org/package/seqaid homepage: http://www.fremissant.net/seqaid leaky hackage: https://hackage.haskell.org/package/leaky homepage: http://www.fremissant.net/leaky Reddit discussion for the three together: http://www.reddit.com/r/haskell/comments/2ps8f5/ann_deepseqbounded_seqaid_l… Easiest way to try them all, is to install seqaid and run the demo: cabal install seqaid seqaid demo This tests seqaid on a local copy of the leaky source package. It turned out to be routine to extend deepseq-bounded and seqaid to dynamically configurable parallelisation (paraid?). Many other wrappers could be explored, too! Maybe seqaid should be renamed to koolaid or something... It's a pretty complicated system, and just first release, so there's bound to be lots of problems. I've not set up a bug tracker, but will maintain a casual list of bugs and feature requests at http://www.fremissant.net/seqaid/trac and will set up a proper tracker if there's interest. Any isssues (or comments), I'm here, or on the reddit discussion (or email). Andrew Seniuk rasfar on #haskell

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Proving properties of type-level natural numbers obtained from user input
by Bas van Dijk 19 Dec '14

19 Dec '14

Hi, I have another type-level programming related question: > {-# LANGUAGE GADTs #-} > {-# LANGUAGE TypeOperators #-} > {-# LANGUAGE ScopedTypeVariables #-} > {-# LANGUAGE KindSignatures #-} > > import GHC.TypeLits Say I have a Proxy p of some type-level natural number: > p :: forall (n :: Nat). Proxy n > p = Proxy Imagine I get p from user input like this: > main :: IO () > main = do > [arg] <- getArgs > let n = read arg :: Integer > > case someNatVal n of > Nothing -> error "Input is not a natural number!" > Just (SomeNat (p :: Proxy n)) -> ... I also have a function f which takes a proxy of a natural number but it has the additional constraint that the number should be lesser than or equal to 255: > f :: forall (n :: Nat). (n <= 255) => proxy n -> () > f _ = () How do I apply f to p? Obviously, applying it directly gives the type error: > f p <interactive>:179:1: Couldn't match expected type ‘'True’ with actual type ‘n0 <=? 255’ The type variable ‘n0’ is ambiguous In the expression: f p In an equation for ‘it’: it = f p I imagine I somehow need to construct some Proof object using a function g like: > g :: forall (n :: Nat). proxy n -> Proof > g _ = ... Where the Proof constructor encapsulates the (n <= 255) constraint: > data Proof where > NoProof :: Proof > Proof :: forall (n :: Nat). (n <= 255) > => Proxy n -> Proof With g in hand I can construct c which patterns matches on g p and when there's a Proof the (n <= 255) constraint will be in scope which allows applying f to p: > c :: () > c = case g p of > NoProof -> error "Input is bigger than 255!" > Proof p -> f p But how do I define g? Cheers, Bas

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Behavior of touch#
by Brandon Simmons 16 Dec '14

16 Dec '14

The `primitive` package exports a lifted version of the undocumented `touch#` http://hackage.haskell.org/package/ghc-prim-0.3.1.0/docs/GHC-Prim.html which has type: touch :: PrimMonad m => a -> m () I'd like to know if this works correctly in general, or will it suffer from the same gotches w/r/t unboxing as with addFinalizer and Weak references? i.e. must it only be passed an unboxed type? Brandon

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Re: ANNOUNCE: GHC 7.8.4 Release Candidate 1
by Mikolaj Konarski 13 Dec '14

13 Dec '14

OK. In that case, let's remember to get *that* version of cabal into 7.8.4. /me conditions himself with chocolate to help the remembering On Sat, Dec 13, 2014 at 11:02 PM, Thomas Tuegel <ttuegel(a)gmail.com> wrote: > On Sat, Dec 13, 2014 at 3:56 PM, Mikolaj Konarski > <mikolaj(a)well-typed.com> wrote: >> On Sat, Dec 13, 2014 at 8:53 PM, Carter Schonwald >> <carter.schonwald(a)gmail.com> wrote: >>> Thomas and I have found some bugs in HPC on OSX, and we're in the midst of >>> tracking those down, >> >> You mean these are regressions? If they are introduced >> in one of the non-blocker fixes in 7.8.4, we can probably >> just revert them. Anyway, thanks a lot for testing. > > Sorry, these are not regressions. It's really a bug in Cabal which > will be fixed in 1.22. When Carter wrote this, we thought the problem > was with the GHC side of HPC because of some very vague error > messages. > > -- > Thomas Tuegel >

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ANNOUNCE: GHC 7.8.4 Release Candidate 1
by Austin Seipp 13 Dec '14

13 Dec '14

We are pleased to announce the first release candidate for GHC 7.8.4: https://downloads.haskell.org/~ghc/7.8.4-rc1/ This includes the source tarball and bindists for 64bit Linux. Binary builds for other platforms will be available shortly. These binaries and tarballs have an accompanying SHA256SUMS file signed by my GPG key id (0x3B58D86F). We plan to make the 7.8.4 release sometime in the next few weeks. Please test as much as possible; bugs are much cheaper if we find them before the release! -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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confusing type error
by Evan Laforge 10 Dec '14

10 Dec '14

I recently got a confusing error msg, and reduced it to a small case: f1 :: Monad m => m Bool f1 = f2 0 0 'a' f2 :: Monad m => Int -> Float -> m Bool f2 = undefined >From this, it's clear that f2 is being given an extra Char argument it didn't ask for. However, the error msg (ghc 7.8.3) is: Couldn't match type ‘m Bool’ with ‘Bool’ Expected type: Char -> m Bool Actual type: Char -> Bool Relevant bindings include f1 :: m Bool (bound at Bug.hs:4:1) The function ‘f2’ is applied to three arguments, but its type ‘Int -> Float -> Char -> Bool’ has only three In the expression: f2 0 0 'a' In an equation for ‘f1’: f1 = f2 0 0 'a' The confusing part is that 'f2' was applied to three arguments, but it's type has only three. It includes the Char in expected and actual types, and implies that the type of 'f2' includes the Char. So I took quite a while to realize that the type of 'f2' in fact *didn't* expect a Char (and had an 'm'), so that the "but its type" is *not* in fact its declared type. I suppose it infers a type for 'f2' based on its use, and that then becomes the "actual" type, but it seems less confusing if it picked the declared type of 'f2' as its actual type. Perhaps this is working as intended, but it it is confusing! Especially the part about "expected three but got three". Ideally I'd like to see "too many arguments" or at least "expected (Char -> m Bool) but actually 'm Bool'". Actually I'd expect the other way: "expected 'm Bool' but got (Char -> m Bool)' but I think ghc has always done it backwards from how I expect. It looks like it's substituting (->) for 'm', so maybe it's one of those things where ((->) a) is also a monad.

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