January 2010 - Glasgow-haskell-users

tracing messages
by Serge D. Mechveliani 28 Jan '10

28 Jan '10

Dear GHC team, this is on tracing in ghc-6.12.1 (made from source on Debian Linux i-386-like machine). I wonder what is the reason for this tracing message (starting with `Step1 ...' ): ---------------------------- ... equations calc = [j < i -> true, m <= p -> true, p <= q -> true, q <= n -> true, (A p) <= (A q) -> false, (X <= Y) | (Y < X) -> true, | {not (Y <= n), not (m <= X), not (X < i), not (j < Y), (A X) <= (A Y)} -> true, | {not (X <= Y), not (Y <= j), not (m <= X), (A X) <= (A Y)} -> true, | {not (XStep 1. Starting mutual pre-reduction. The number of rules is 25. Pre-reduction done. Initial numbers of equations is 9, after reduction: 9, the pre-reduction cost is 484. ... ... ---------------------------- The main program does the following in succession: 1) finds eqs, 2) prints "equations calc =\n", shows eqs "\n\n", "Starting completion.\n", "remaining goals = ", 3) finds res by completion (`complete'), 4) prints shows (completionGoalRem res) "\n" The trace calls are set only in the function `complete'. The above message Step 1. Starting mutual pre-reduction. The number of rules is 25. Pre-reduction done. Initial numbers of equations is 9, occurs the first message of this tracing. But the main program must have printed the full last equation in eqs, and only after this any tracing message could appear. Instead, it breaks the last equation printing with the tracing messages. The further evaluation is long, so I interrupted it, without seeing the final result. But this printing break looks strange, because eqs does not depend on the results of `complete', the reverse holds: the latter applies to eqs. Generally, I often observe an effect of this kind; it is harmless, but I wonder, what might be the reason. Regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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FW: GHC core plugins
by Simon Peyton-Jones 28 Jan '10

28 Jan '10

-----Original Message----- From: Simon Peyton-Jones Sent: 28 January 2010 07:50 To: 'austin s' Subject: RE: GHC core plugins compiler/cmm/ZipDataFlow.hs But we have great ideas for making it much simpler and more modular. In progress.. S | -----Original Message----- | From: mad.one(a)gmail.com [mailto:mad.one@gmail.com] On Behalf Of austin s | Sent: 27 January 2010 16:24 | To: Simon Peyton-Jones | Subject: Re: GHC core plugins | | 2010/1/27 Simon Peyton-Jones <simonpj(a)microsoft.com>: | > | Also, is Hoopl expected to be used on core -> core plugins, and, if so, | is | > | the | > | infrastructure in place for this? | > | > no, Hoopl works on imperative control flow graphs, the C-- part of the back | end, not on Core. | > | > Simon | > _______________________________________________ | > Glasgow-haskell-users mailing list | > Glasgow-haskell-users(a)haskell.org | > http://www.haskell.org/mailman/listinfo/glasgow-haskell-users | > | | Quick Question, even if it is OT: Is the Hoopl code available anywhere? | | -- | - Austin

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Re: GHC core plugins
by austin s 27 Jan '10

27 Jan '10

On Wed, Jan 27, 2010 at 10:24 AM, austin s <as(a)nijoruj.org> wrote: > 2010/1/27 Simon Peyton-Jones <simonpj(a)microsoft.com>: >> | Also, is Hoopl expected to be used on core -> core plugins, and, if so, is >> | the >> | infrastructure in place for this? >> >> no, Hoopl works on imperative control flow graphs, the C-- part of the back end, not on Core. >> >> Simon >> _______________________________________________ >> Glasgow-haskell-users mailing list >> Glasgow-haskell-users(a)haskell.org >> http://www.haskell.org/mailman/listinfo/glasgow-haskell-users >> > > Quick Question, even if it is OT: Is the Hoopl code available anywhere? > > -- > - Austin > Whoops, forgot to add g-h-u to the to: field. ;) -- - Austin

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GHC core plugins
by José Pedro Magalhães 27 Jan '10

27 Jan '10

Hello all, What's the current status of GHC plugins [1] in HEAD? Can I use them? If not, what's the easiest way to add another core-to-core pass to the compiler? Thanks, Pedro [1] http://hackage.haskell.org/trac/ghc/wiki/Plugins

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GHC core plugins
by Max Bolingbroke 27 Jan '10

27 Jan '10

2010/1/27 José Pedro Magalhães <jpm(a)cs.uu.nl>: > Alright, ticket created: http://hackage.haskell.org/trac/ghc/ticket/3843 > > In any case, for now I am willing to hard-code a new core-to-core pass on > the compiler. Any pointers for where I have to look at? I recommend you look at compiler/simplCore/CSE.lhs. It is a simple example of a core-to-core pass. However, in short you'll need to: 1) Create a function which implements your core to core pass, of a type such as [CoreBind] -> [CoreBind] *) If that function lives in a new module, edit ghc.cabal.in to tell the build system about the module 2) Add a constructor to the CoreToDo data type in compiler/simplCore/CoreMonad.lhs 3) Add a case for it to the coreDumpFlag and Outputable instance 4) Add that pass to the list returned by getCoreToDo in CoreMonad. The order of the list is the order the passes will be run in. *) If you want the pass to be under the control of a new flag, you'll need to add a new dynflag - add a constructor to the DOpt data type in compiler/main/DynFlags.lhs, and add something to build that constructor to one of the lists that get fed to the command line handling code in the same module. It should be fairly obvious how to do this. 5) Add a handler for the new constructor to compiler/simplCore/SimplCore.lhs, in the doCorePass function which calls into the core pass function you wrote Hope that helps, Max

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No more ExitException?
by Volker Wysk 27 Jan '10

27 Jan '10

Hello I'm porting my HsShellScript library from GHC-6.8 to GHC-6.10. I'm catching an ExitException in the old version. The only occurence of ExitException in the GHC 6.10 libraries is in Control.OldException. So how is this done in GHC 6.10+ ? What replaces the old ExitException? Cheers, Volker -- Volker Wysk <vw(a)volker-wysk.de>

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Splicing types.. should this work?
by Robert Greayer 25 Jan '10

25 Jan '10

Now that type-splicing works in TH, and TH has type-family support, I was wondering if the following example should compile (with 6.12.1): > {-# LANGUAGE TemplateHaskell, MultiParamTypeClasses, TypeFamilies, > FlexibleInstances, OverlappingInstances #-} > module Sample where > import Control.Monad > import Language.Haskell.TH > class Foo a where > type FooType a > createInstance :: Q Type -> Q Dec > createInstance t = instanceD (return []) > (conT ''Foo `appT` t) [ > tySynInstD ''FooType [t] (conT ''String) > ] > createInstance' :: Q Type -> Q Dec > createInstance' t = liftM head [d| > instance Foo $t where > type FooType $t = String|] the function 'createInstance' compiles without a problem, but it's (near) equivalent written using TH quotations + splices fails with the error: Sample.lhs:22:10: Type indexes must match class instance head Found `t_aMn' but expected `t_aMl' In the associated type instance for `FooType' In the instance declaration for `Foo $t' In the Template Haskell quotation [d| instance Foo $t where type instance FooType $t = String |] The compiler seems to not be able to determine that the type spliced in the class instance head will match the type spliced in the type instance. The first version works fine for my purposes, but was curious whether the failure of the 2nd was a bug or a feature. Thanks, Rob

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Question regarding the GHC users manual
by Tyson Whitehead 25 Jan '10

25 Jan '10

Hi all, Just wondering if there could be a typo in section 7.7.2.1 of the GHC manual (type family declarations) http://www.haskell.org/ghc/docs/latest/html/users_guide/type-families.html Specifically, it says type family F a b :: * -> * -- F's arity is 2, -- although its overall kind is * -> * -> * -> * along with F Char [Int] -- OK! Kind: * -> * F Char [Int] Bool -- OK! Kind: * F IO Bool -- WRONG: kind mismatch in the first argument F Bool -- WRONG: unsaturated application and I'm wondering about the overall kind. Shouldn't that be * -> * -> *, or am I not understanding something? Thanks! -Tyson

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Trying to build from the darcs repository
by Florian Weimer 25 Jan '10

25 Jan '10

How much memory does GHC need to build on amd64 GNU/Linux? I'm trying to build from the darcs repository, and this command "inplace/bin/ghc-stage1" -H32m -O -package-name terminfo-0.3.1.1 -hide-all-packages -i ilibraries/terminfo/. --ilibraries/terminfo/dist-install/build -ilibraries/terminfo/dist-install/build/autogen -Ilibraries/terminfo/dist-install/build -Ilibraries/terminfo/dist-install/build/autogen --Ilibraries/terminfo/. optP-include -optPlibraries/terminfo/dist-install/build/autogen/cabal_macros.h -package base-4.2.0.0 -package extensible-exceptions-0.1.1.1 -split-objs -Wall -XForeignFunctionInterface -XDeriveDataTypeable -XEmptyDataDecls -XScopedTypeVariables -XFlexibleInstances -O2 -XGenerics -fno-warn-deprecated-flags -odir -libraries/terminfo/dist-install/build -hidir -libraries/terminfo/dist-install/build -stubdir -libraries/terminfo/dist-install/build -hisuf hi -osuf o -hcsuf hc --c libraries/terminfo/./System/Console/Terminfo/Effects.hs -o -libraries/terminfo/dist-install/build/System/Console/Terminfo/Effects.o needs more than 3.5 GB of RAM. Or is this some sort of miscompilation problem? (I'm trying to bootstrap with GHC 6.12.1, but saw this with GHC 6.8 as well.) The start of the context is this: [Remove an out-of-date comment Ian Lynagh <igloo(a)earth.li>**20100122130853] [fix build on Windows Simon Marlow <marlowsd(a)gmail.com>**20100122121016 Ignore-this: cd690a8eff71ca4f87fe67a41a20f493 ] [fix warning on Windows Simon Marlow <marlowsd(a)gmail.com>**20100122120328 Ignore-this: 507a91e356a667dcecf8bec621fd2b95 ]

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Scriptable error messages
by Daniel Gustafsson 22 Jan '10

22 Jan '10

Hello Me and a fellow student are taking a course named Frontiers of Programming Languages, and in this course we should do a project with something. A while ago we were at a presentation of Feldspar, a Embedded Domain Specific Language, and one of the negative points of using haskell was that the error messages could be cryptic due to the various ways it was implemented. So we are now looking into the possibility of adding your own error messages to GHC as our project. We have about 8 weeks to implement, either all or some proof of concept. As such we are looking for comments, ideas and suggestions. Is this doable in GHC?, or what is needed. Thanks Daniel Gustafsson Simon Edwardsson Chalmers University of Technology (Gothenburg, Sweden)

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