- Glasgow-haskell-users

Bug? Or at least a better error message?
by Geoffrey Alan Washburn 05 Jun '06

05 Jun '06

While trying out the following example, in an attempt to learn something about the fiddly case where a type class instance tries to use an instance that is more specific than itself module Testing where class Foo a where { bar :: a -> Int } instance Foo Int where bar i = i instance Foo a => Foo [a] where bar [] = bar [1] bar ([x]) = 1 bar (x:xs) = (bar x) + (bar xs) It is kind of like polymorphic recursion, I suppose. I get the following exception [1 of 1] Compiling Testing ( strange.hs, interpreted ) *** Exception: typecheck/TcEnv.lhs:(365,0)-(392,32): Non-exhaustive patterns in function find_thing Is the example supposed to work? I'm trying to determine the source of a problem with type classes and GADTs and I figured this example using "normal" data types would be a good place to start in understanding what was going wrong. I was using ghci version 6.5.20060503.

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Data.Sequence?
by Michael Marte 02 Jun '06

02 Jun '06

Hello *, when importing Data.Queue in 6.4.2, I am told that it is deprecated and that I should use Data.Sequence instead. However, Data.Sequence is not part of the base package - it is there but it is missing from the package.conf file. Moreover, there is no documentation available apart from the source code itself. Regarding Data.Sequence itself: - I am missing a function for converting a sequence to a list directly; I have to create a view and convert it to a list. - Isn't the name too fuzzy? After all, a standard Haskell list is a sequence as well. Why not stay with Queue? Michael

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Understanding directory structure of ghc installation
by Brian Hulley 01 Jun '06

01 Jun '06

Hi - I've just downloaded and installed Edison using Cabal. However I now see that Edison seems to have been already installed with the ghc 6.4.2 installation, even though there's no mention of Edison in /doc/html/libraries/index.html, because there are old Edison .hi files in ghc-6.4.2/hslibs-imports/data whereas the Cabal install process copied newly built Edison files to C:\Program Files\Haskell\EdisonAPI-1.2\ghc-6.4.2\Data and C:\Program Files\Haskell\EdisonCore-1.2\ghc-6.4.2\Data I was about to just delete the old .hi files from the hslibs-imports/data directory, but then I noticed there are a few .hi files there for Set and FiniteMap, even though there are also .hi files (though of different sizes) for Set and FiniteMap stored in the imports/data directory as well. So my question is: how to understand all this? Why are there different copies of Set.hi which have different sizes, but in the same installation, and which one does ghc use when I use import Data.Set in a program? Also, what does .p_hi mean? (The new build of Edison only creates .hi files not .p_hi files but all the ghc-6.4.2 modules have both .hi and .p_hi files) (It would also be interesting to know where Cabal gets the information from to configure a package, and where the package database is stored...) Thanks, Brian. -- Logic empowers us and Love gives us purpose. Yet still phantoms restless for eras long past, congealed in the present in unthought forms, strive mightily unseen to destroy us. http://www.metamilk.com

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RE: GHC-6.4.1 on FreeBSD-amd64 port progress
by Simon Marlow 30 May '06

30 May '06

On 25 October 2005 10:01, Wilhelm B. Kloke wrote: > Simon Marlow <simonmar(a)microsoft.com> schrieb: >> On 24 October 2005 19:04, Wilhelm B. Kloke wrote: >> >> Is it that it does not find the libraries, or does it find the >> libraries but still gets a bunch of undefined references? If the >> latter, then there could be an issue with the mangler. Try an 'nm' >> on libHSbase.a to see if the missing symbols are actually defined. > > Nm shows that the problem may come from splitting. The missing symbols > are marked as locals (small d); being in different .o modules they > are not resolved. Try with splitting off: set SplitObjs=NO in your mk/build.mk. Cheers, Simon

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recompilation / overlapping instances
by Christian Maeder 29 May '06

29 May '06

Hallo Thomas, when compiling your sources in our context I get an "Overlapping instances" error (below). However, first compiling the offending file (base/TI/OrigTiMonad.hs) and then compiling the rest works (but I don't want adapt our Makefile for this to do). Could you adjust your sources? We're using ghc-6.4.2. Or is there a further compiler switch that would get this right? I don't know if both instances are identical. Cheers Christian ../programatica/tools/base/TI/OrigTiMonad.hs:61:36: Overlapping instances for Functor (Either (Error (HsIdentI i))) arising from use of `fmap' at ../programatica/tools/base/TI/OrigTiMonad.hs :61:36-39 Matching instances: Imported from Control.Monad.Error: instance Functor (Either e) ../programatica/tools/base/lib/Monads/ExceptM.hs:26:0: instance Functor (Either x) In a lambda abstraction: \ env ids -> fmap (fmap f) (m env ids) In the second argument of `($)', namely `\ env ids -> fmap (fmap f) (m env i ds)' In the definition of `fmap': fmap f (IM m) = IM $ (\ env ids -> ...)

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GHC back-end
by Simon Marlow 29 May '06

29 May '06

For those interested in improving the performance of GHC's generated code, especially in the area of tight loops, I have collected a bunch of ideas on this wiki page: http://hackage.haskell.org/trac/ghc/wiki/BackEndNotes This is partly the outcome of a discussion between myself and Roman Leshchinskiy, who is working on nested data parallelism. Roman has already implemented some special-case optimisations to improve performance of tight loops, and he plans to do more. If you have any thoughts, ideas, or comments on the proposals, please let us know! Also, it's not clear if/when any of this will get done. Talented compiler hackers are most welcome to help out. Cheers, Simon

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RE: [Haskell] GHC on Intel Mac
by Simon Peyton-Jones 26 May '06

26 May '06

[redirecting to ghc-users] There is no reason why GHC on Intel Mac should be hard. We have GHC on both Intel hardware and Mac OS. All that is needed is someone to spearhead the porting exercise. Indeed it looks as if Wolfgang might have it in progress http://hackage.haskell.org/trac/ghc/wiki/Contributors But I'm sure he'd like help. Simon | -----Original Message----- | From: haskell-bounces(a)haskell.org [mailto:haskell-bounces@haskell.org] On Behalf Of Thomas Davie | Sent: 24 May 2006 23:22 | To: haskell(a)haskell.org | Subject: [Haskell] GHC on Intel Mac | | Hi, | I was just wondering what the status of porting GHC to intel mac | was these days? I've finally beaten Apple into submission, and got | them to replace my broken iBook with a MacBook, so a nice fast | version would be nice. | | Bob | _______________________________________________ | Haskell mailing list | Haskell(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell

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i want a MINGW32 snapshot of HEAD
by Bulat Ziganshin 25 May '06

25 May '06

Hello , as i see on the http://www.haskell.org/ghc/dist/current/dist/ mingw snapshots of HEAD are not builded since 28 Feb. is it possible to resume building them? -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

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RE: [Haskell] GHC on Intel Mac
by Simon Peyton-Jones 25 May '06

25 May '06

[redirecting to ghc-users] | I've started a Wiki page to document the little that I have found out | about the status of GHC on Intel Macs, see http://www.haskell.org/ | haskellwiki/GHC/On_Intel_Macs | | At the moment, that page points you to this binary distribution: | http://www.uni-graz.at/imawww/haskell/ghc-6.5.20060409-i386-apple- | darwin.tar.bz2 which works with only some minor problems. Excellent. (Although the page seems empty at the moment.) However a better place would be on the GHC developers Wiki. ("Better" = more people will find it there.) The page to start from is: http://hackage.haskell.org/trac/ghc/wiki/Platforms and you can start a new page for the Intel-on-Mac platform. (See, for example, the "Platforms currently being ported" table, and the link to ArmLinuxGhc.) Simon

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Constructing a binary tree from a postorder visit
by Nuno Santos 24 May '06

24 May '06

Hi, I have this datatype: data PeAux a = Folha Char | Nodo Char (PeAux a) (PeAux a) deriving Show And i need to reconstruct a tree from its post order visit.... example "12H3V" |'m trying something like this to create the nodes and leave what lefts: converteAux [] (x,y) = (x,y) converteAux (a:t) (x,y) | ((length (a:t))<3) = converteAux [] (x,y ++ (a:t)) converteAux (a:b:t) (x,y) | ((length (a:b:t))<3) = converteAux [] (x,y ++ (a:b:t)) converteAux (a:b:c:t) (x,y) | (isNumber a) && (isNumber b) && (isLetter c) = converteAux t (x ++ [(Nodo c (Folha a) (Folha b))],y) | otherwise = converteAux (b:c:t) (x,y++[a]) and i'm trying this to rebuild the tree but i dont know what to do in the case of [] since i dont have a empty constructer preenche (x:xs) = Nodo 'H' (preenche xs) x Can anyone help me? Many thx, Nuno

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