- Glasgow-haskell-users

Re: Loop optimisation with identical counters
by christian Hoener zu Siederdissen 06 Nov '10

06 Nov '10

Yes indeed, this is what some fusion code could look like. I deal with stuff like this: mk i j = enumFromN (i+1) (j-i-2) -- gen indices, sometimes index pairs f i j k = T!(i,k) + T!(k+1,j) -- table lookup using some 2d tables g i j k = fun i k + fun (k+1) j -- some funny calculation z i j = minimum $ zipWith (+) (map (f i j) $ mk i j) (map (g i j) $ mk i j) y i j = minimum (map (g i j) $ mk i j) So i would like to split my calculations into f and g as sometimes (in backtracking results) only g is needed. Furthermore, there are like 12 different f g z y mk each. Being able to seperate the worker into f g means cleaner code and that it is easier to change stuff. Note that mk in f is always called with the same borders, leading to things like my original problem. But Roman has already pointed out how often this duplication of counters can occur. Gruss, Christian PS: above is a bit pseudocode-like but captures the essentials and my thumbs are numb now... ;-) ----- Original message ----- > On 06/11/2010, at 02:27, Sebastian Fischer wrote: > > > Interesting. This approach requires `f` to be inlined into its call > > site in order to eliminate the redundant argument. This is different > > from the proposal to provide a specialized version of `f` (where the > > arguments are combined) which could be reused at different call sites. > > Which proposal do you mean? I'm not sure something like that is feasible > without knowing the call sites. You have to know which arguments to > combine. > > > How many call sites with identical arguments are there in the > > generated code that triggered this discussion and in the stream fusion > > code that would benefit from this optimization? > > In stream fusion code, there is normally exactly one call site. I > suspect that the Christian's example has also been derived from stream > fusion code. > > Roman > > > _______________________________________________ > Glasgow-haskell-users mailing list > Glasgow-haskell-users(a)haskell.org > http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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Rigid types fun
by Mitar 05 Nov '10

05 Nov '10

Hi! I have much fun with rigid types, type signatures and GADTs. And I would like to invite also others in and share my joy. ;-) Please see the attached file and chase a solution to how to make it compile. I would like to have a function which I would call like: createNerve (Axon undefined) (AxonAny undefined) and it would return proper Nerve. Similar to how asTypeOf works. I would like to do that to remove repeating code like: from <- newChan for <- newChan let nerve = Nerve (Axon from) (AxonAny for) which I have to write again and again just to make types work out. Why I cannot move that into the function? I am using GHC 6.12.3. Is this something which will work in 7.0? Mitar

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Unicode windows console output.
by David Sankel 04 Nov '10

04 Nov '10

Hello all, I'm attempting to output some Unicode on the windows console. I set my windows console code page to utf-8 using "chcp 65001". The program: -- Test.hs main = putStr "λ.x→x" The output of `runghc Test.hs`: λ.x→xxxx >From within ghci, typing `main`: λ*** Exception: <stdout>: hPutChar: permission denied (Permission denied) I suspect both of these outputs are evidence of bugs. Might I be doing something wrong? (aside from using windows ;)) TIA, David -- David Sankel Sankel Software www.sankelsoftware.com 585 617 4748 (Office)

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Re: link problem under macosx
by John Lato 04 Nov '10

04 Nov '10

> > From: Simon Michael <simon(a)joyful.com> > > On 11/2/10 10:20 AM, John Lato wrote: > > Since Apple seems disinclined to fix the system's libiconv, and macports > projects refuse to use it, the only real > > solution is to use either HP without macports or the macports GHC without > HP. Personally I chose to use the HP and > > Not so, as mentioned you just need to make sure /usr/lib is in the link > path before /opt/local/lib. Add -L/usr/lib to > your build flags for ghc --make, and put: > > extra-lib-dirs: /usr/lib > extra-lib-dirs: /opt/local/lib > > in that order in ~/.cabal/config for cabal build. > > This is a very FAQ and needs to be documented somewhere more obvious, I > wonder where. cabal-install and GHC release notes ? > As I mentioned in another reply, this worked for me until I tried to link to a macports lib (I think some regex lib) that actually used the macports libiconv (a lot of them don't even if they pull in the dependency). Then I was really stuck because I had dependencies on two different libiconv's, and neither one would link properly. As such, I consider this a pretty fragile "solution". John

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MonoLocalBinds and darcs
by Sittampalam, Ganesh 04 Nov '10

04 Nov '10

Hi, I've just been updating darcs 2.5 for GHC 7.0. I had to add about 40 signatures for MonoLocalBinds in about 140 files/30K LOC. Is that about normal? darcs does make fairly heavy use of rank 2 polymorphism which leads to quite a lot of local definitions needing to be polymorphic. Also, NoMonoLocalBinds didn't help at all, which surprised me a bit - I thought it might at least make some of the signatures unnecessary. Finally, is NoMonoLocalBinds supposed to imply NPlusKPatterns? The only changes I was able to revert when I enabled it were a couple of those! Cheers, Ganesh =============================================================================== Please access the attached hyperlink for an important electronic communications disclaimer: http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html ===============================================================================

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Re: [Haskell-cafe] change in overlapping instance behavior between GHC 6.12 and GHC 7 causes compilation failure
by David Fox 04 Nov '10

04 Nov '10

I would love to know the answer to this. On Tue, Nov 2, 2010 at 3:36 PM, Jeremy Shaw <jeremy(a)n-heptane.com> wrote: > Hello, > > I have a module, XMLGenerator, which has some overlapping instances. > I have a second module, Test, which imports that module and also adds > some more overlapping instances. > > Both modules contain {-# LANGUAGE OverlappingInstances #-} at the top. > > Under some old version of 6.13 (and probably 6.12), if I put both > modules in the same directory and try to load Test.hs, it gets the > error: > > Test.hs:16:15: > Overlapping instances for EmbedAsChild (M IO) (XMLGenT m (XML m)) > arising from a use of `asChild' at Test.hs:16:15-21 > Matching instances: > instance (m1 ~ m, EmbedAsChild m c) => > EmbedAsChild m (XMLGenT m1 c) > -- Defined at XMLGenerator.hs:16:10-68 > instance (XML m ~ x, XMLGen m) => EmbedAsChild m x > -- Defined at XMLGenerator.hs:19:10-51 > In the first argument of `($)', namely `asChild' > In the expression: asChild $ (genElement "foo") > In the definition of `asChild': > asChild b = asChild $ (genElement "foo") > > If I put the XMLGenerator module in a separate package, dummy-hsx, and > the Test modules links against it, I still get the error. > > *but* if I add: > > Extensions: OverlappingInstances > > to the dummy-hsx.cabal file, then Test.hs compiles just fine! So, for > starters, I do not understand why that happens. > > Under GHC 7.0rc1, modifying the .cabal file has no effect. Instead I > always get the error: > > Test.hs:16:15: > Overlapping instances for EmbedAsChild (M IO) (XMLGenT m (XML m)) > arising from a use of `asChild' > Matching instances: > instance [overlap ok] (m1 ~ m, EmbedAsChild m c) => > EmbedAsChild m (XMLGenT m1 c) > -- Defined in XMLGenerator > (The choice depends on the instantiation of `m' > To pick the first instance above, use -XIncoherentInstances > when compiling the other instance declarations) > > Adding the IncoherentInstances flag does make it compile -- but I have > never enabled that flag and not regretted it. > > What changed between GHC 6.12 and GHC 7.0? Is there a some solution > besides using IncoherentInstances in every module that imports > XMLGenerator? > > I have attached XMLGenerator.hs, Test.hs, and dummy-hsx.cabal. > > thanks! > - jeremy > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > >

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Fixing LDAP lib compilation on OpenBSD
by Julien Dessaux 03 Nov '10

03 Nov '10

Hi GHC folks, I'm using the LDAP lib for one of my projects and I found a problem while building it on an OpenBSD system. It wouldn't compile because there is a macro named differently in the ldap.h include file. Under linux, this macro is named LDAP_X_PROXY_AUTHZ_FAILURE but on OpenBSD (and probably other BSD flavours), it's named LDAP_PROXY_AUTHZ_FAILURE. I attached the diff I wrote in order to compile the lib on OpenBSD, but it's not a patch I can submit cause it now won't compile on Linux. How can I amend this in order to have a code that would compile on both systems? How is it possible to specify such conditional system dependent stuff for a C binding? Thanks in advance for your help, -- Julien Dessaux

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generating C stubs with GHC API
by Victor Nazarov 03 Nov '10

03 Nov '10

I would like to get access to functions exported from Haskell module and to generate custom stubs for them using GHC API. As I understand, I need to obtain a list of ForeignDecl's (data structure defined in HsDecls GHC module) for given source module. How to achieve this with GHC API? -- Victor Nazarov

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link problem under macosx
by Christian Maeder 03 Nov '10

03 Nov '10

Hi, after installing http://lambda.galois.com/hp-tmp/2010.2.0.0/haskell-platform-2010.2.0.0.i386… and various more libraries using cabal, we get the following linker error below. A simple hello program compiles and links fine and uses /usr/lib/libiconv.2.dylib (compatibility version 7.0.0, current version 7.0.0) as shown by "otool -L". Does someone have an explanation or solution? Cheers Christian Linking dist/build/hets/hets ... Undefined symbols: "_iconv_close", referenced from: _hs_iconv_close in libHSbase-4.2.0.2.a(iconv.o) "_iconv_open", referenced from: _hs_iconv_open in libHSbase-4.2.0.2.a(iconv.o) "_iconv", referenced from: _hs_iconv in libHSbase-4.2.0.2.a(iconv.o) ld: symbol(s) not found collect2: ld returned 1 exit status

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making 7.01-pre
by Serge D. Mechveliani 02 Nov '10

02 Nov '10

Dear GHC developers, I am testing this fresh ghc-7.0.0.20101028 on Debian Linux, i386-family. Making it from source by ghc-6.12.3 is all right. Then, making it from source by itself reports (here I abbreviate the messages by inserting `...') --------------------------------------------------------------------- + test -f mk/config.mk.old + cp -p mk/config.mk mk/config.mk.old ... ... "inplace/bin/mkdirhier" utils/ghc-cabal/dist/build/tmp//. "inplace/bin/mkdirhier" bootstrapping/. "/home/mechvel/ghc/7.01pre/inst1/bin/ghc" -H32m -O --make utils/ghc-cabal/ghc-cabal.hs -o utils/ghc-cabal/dist/build/tmp/ghc-cabal ... ... "rm" -f compiler/stage1/ghc_boot_platform.h Creating compiler/stage1/ghc_boot_platform.h... Done. "/usr/bin/gcc" -fno-stack-protector -DTABLES_NEXT_TO_CODE -Iincludes -Irts -DGEN_HASKELL -c includes/mkDerivedConstants.c -o includes/dist-ghcconstants/build/mkDerivedConstants.o ... ... ... utils/genprimopcode/dist/build/Lexer.o: In function `s2yT_info': (.text+0x1e1d): undefined reference to `__stginit_arrayzm0zi3zi0zi2_DataziArray_' ... ... utils/genprimopcode/dist/build/Parser.o: In function `s4pK_info': (.text+0x5691): undefined reference to `__stginit_arrayzm0zi3zi0zi2_DataziArray_' collect2: ld returned 1 exit status make[1]: *** [utils/genprimopcode/dist/build/tmp/genprimopcode] Error 1 make: *** [all] Error 2 --------------------------------------------------------------------- Why cannot it make itself? Regards, ----------------- Serge Mechveliani mechvel(a)botik.ru

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