July 2007 - Glasgow-haskell-users

partially applied type synonyms
by Arie Peterson 05 Mar '12

05 Mar '12

Dear list, Is there a good reason that partially applied type synonyms cannot be made instances of classes? - A simple example would be making the identity type 'Id' ("type Id x = x") instance of 'Monad'. This would eliminate the need for some silly occurrences of 'runIdentity', and perhaps narrow the gap between monads and monad transformers. - The reason I complain about this now is a more involved example, where introducing a newtype to work around the restriction is not an option. Well, not as far as I can see now, anyway. Partially applied type synonyms are, in a sense, the anonymous functions at the type level, and one might argue that they deserve the same 'first-class member status' as the lambda at the value level. Kind regards, Arie Peterson

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ghci and ghc -threaded broken with pipes & forking
by John Goerzen 29 Dec '08

29 Dec '08

Hi, I've been hitting my head against a wall for the past couple of days trying to figure out why my shell-like pipeline code kept hanging. I found fd leakage (file descriptors not being closed), which disrupts EOF detection and can lead to deadlocks. I just couldn't find the problem. I finally tried compiling my test with ghc instead of running it in ghci. And poof, it worked fine the first time. I tried asking on #haskell, and got the suggestion that ghci uses -threaded. I tried compiling my test program with ghc -threaded, and again, same deadlock. My program never calls forkIO or forkOS or any other threading code. You can see my test case with: darcs get '--tag=glasgow ml' http://darcs.complete.org/hsh ghc -fglasgow-exts --make -o test2 test2.hs That'll run fine. If you add -threaded, it will hang. Ideas? Thanks, -- John

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Unexpected boxing in generated code
by Neil Mitchell 07 Aug '07

07 Aug '07

Hi, I've got an inner loop that I think I can see is strict in the Int argument being passed around, but that GHC 6.6.1 isn't unboxing. In the following example both functions take a GHC.Base.Int, which I think should be an Int#. Rec { f60_rS5 :: GHC.Prim.State# GHC.Prim.RealWorld -> GHC.Base.Int -> GHC.Base.Int [GlobalId] [Arity 2 NoCafRefs Str: DmdType LL] f60_rS5 = \ (v1_aWH :: GHC.Prim.State# GHC.Prim.RealWorld) (v2_aWI :: GHC.Base.Int) -> case $wccall_r2kv v1_aWH of wild_X2j { (# ds_d1V4, ds1_d1V3 #) -> case ds1_d1V3 of wild1_X2L { __DEFAULT -> f60_rS5 ds_d1V4 v2_aWI; (-1) -> v2_aWI; 10 -> f561_r2kx ds_d1V4 v2_aWI } } f561_r2kx :: GHC.Prim.State# GHC.Prim.RealWorld -> GHC.Base.Int -> GHC.Base.Int [GlobalId] [Arity 2 NoCafRefs Str: DmdType LL] f561_r2kx = \ (v1_aWm :: GHC.Prim.State# GHC.Prim.RealWorld) (v2_aWn :: GHC.Base.Int) -> case $wccall_r2kv v1_aWm of wild_X2j { (# ds_d1V4, ds1_d1V3 #) -> case ds1_d1V3 of wild1_X2P { __DEFAULT -> case v2_aWn of wild2_a2du { GHC.Base.I# x_a2dw -> case wild1_X2P of wild3_X35 { __DEFAULT -> f60_rS5 ds_d1V4 (GHC.Base.I# (GHC.Prim.+# x_a2dw 1)); 10 -> f561_r2kx ds_d1V4 (GHC.Base.I# (GHC.Prim.+# x_a2dw 1)) } }; (-1) -> v2_aWn } } end Rec } This code comes from a line counting program, I have attached the entire source. My character counting program does infer the correct strictness, although that is based on a single self-recursive function. The largest obvious difference is that the strictness depends on the two functions which call each other - does this impeed GHC's strictness analysis? Thanks Neil

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Annotation for unfolding wanted
by Georg Martius 03 Aug '07

03 Aug '07

Hi folks, sorry for multiple copies of this email, but my mailserver had a problem and thought I am sending spam which is hopefully not true. Since I got a replay allready I modified my mail a bit. I was wondering why we don't have an annotation or pragma for function to tell the compiler that we _need_ this particular recursive function to be unfolded. If the compiler cannot do this for some reason it should produce an error message to help you modifying your code. I have regularly problems that my code is either not strict enough or my functions are not unfolded. I find it annoying that this is a regular show stopper and consumes much time to fix. Here is an example: a search function for strings, which should return the index and the rest of the string after the first occurrence: search0 will not be unfolded by ghc -O even with {#- INLINE search0 -#} (I don't know why, it looks tail-recursive to me) whereas search1 is just fine. search0 :: Int -> String -> String -> (String, Int) search0 i [] _ = ([],i) search0 i haystack needle = let len = length needle in if isPrefixOf needle haystack then (drop len haystack, i+len) else search0 (seq i (i+1)) (drop 1 haystack) needle search1 :: Int -> String -> String -> (String, Int) search1 i [] _ = ([],i) search1 i haystack needle = let i = elemIndex True $ map (isPrefixOf needle) $ tails haystack len = length needle in case i of Just index -> (drop (index+len) haystack, index + len) Nothing -> ([],0) Regards! Georg -- ---- Georg Martius, Tel: +49 177 6413311 ----- ------- http://www.flexman.homeip.net ----------

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Ticky Ticky profiling
by Cristian Perfumo 02 Aug '07

02 Aug '07

Hi all!. I modified build.mk in order to allow Ticky-Ticky profiling (GhcLibWays=t). Now, when I try to make I get this error: ------------------------------------------------------------------------ == make way=t all; PWD = (the_whole_path)/ghc-6.6.1/rts ------------------------------------------------------------------------ ../compiler/ghc-inplace -H32m -O -fasm -W -fno-warn-unused-matches -fwarn-unused-imports -optc-O2 -static -I. -#include HCIncludes.h -fvia-C -dcmm-lint -hisuf t_hi -hcsuf t_hc -osuf t_o -ticky -#include posix/Itimer.h -c PrimOps.cmm -o PrimOps.t_o ghc-6.6.1: panic! (the 'impossible' happened) (GHC version 6.6.1 for i386-unknown-linux): ToDo: tickyAllocThunk Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug Any clue? Thanks in advance. Cristian Perfumo.

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Re: building ghc6 on ppc64 linux
by Jens Petersen 30 Jul '07

30 Jul '07

[Oops, I forgot to include g-h-u in my first reply.] On 30 Jul 2007 04:01:56 -0000, kahl(a)cas.mcmaster.ca <kahl(a)cas.mcmaster.ca> wrote: > Perhaps the following snippet from the gentoo ebuild helps: > > # GHC build system knows to build unregisterised on alpha and hppa, > # but we have to tell it to build unregisterised on some other arches > if use ppc64 || use sparc; then > echo "GhcUnregisterised=YES" >> mk/build.mk > echo "GhcWithNativeCodeGen=NO" >> mk/build.mk > echo "GhcWithInterpreter=NO" >> mk/build.mk > echo "SplitObjs=NO" >> mk/build.mk > echo "GhcRTSWays := debug" >> mk/build.mk > echo "GhcNotThreaded=YES" >> mk/build.mk > fi Thanks for that tip - I shuold have thought to check. Unfortunately I still get the same undefined __DISCARD__ with that. Also perhaps I should mention that earlier I am seeing a *lot* of warnings like these: /usr/bin/ghc -H16m -O -I. -Iinclude -Rghc-timing -ignore-package Cabal -I../libraries -fglasgow-exts -no-recomp -c Compat/Directory.hs -o Compat/Directory.o -ohi Compat/Director y.hi Warning: retaining unknown function `.L.__stginit_CompatziDirectory' in output from C compiler Warning: retaining unknown function `.L.__stginit_CompatziDirectory_' in output from C compiler Warning: retaining unknown function `.L.CompatziDirectory_createDirectoryIfMissing_entry' in output from C compiler Warning: retaining unknown function `.L.s2U5_ret' in output from C compiler Warning: retaining unknown function `.L.s2PU_1_alt' in output from C compiler Warning: retaining unknown function `.L.s2PU_0_alt' in output from C compiler Warning: retaining unknown function `.L.s2U8_1_alt' in output from C compiler Warning: retaining unknown function `.L.s2U8_0_alt' in output from C compiler Warning: retaining unknown function `.L.s2U9_1_alt' in output from C compiler Warning: retaining unknown function `.L.s2U9_0_alt' in output from C compiler Warning: retaining unknown function `.L.s2Ua_1_alt' in output from C compiler Warning: retaining unknown function `.L.s2Ua_0_alt' in output from C compiler Warning: retaining unknown function `.L.s2Q0_dflt' in output from C compiler Warning: retaining unknown function `.L.s2PH_entry' in output from C compiler Warning: retaining unknown function `.L.r2Ly_entry' in output from C compiler Warning: retaining unknown function `.L.s2U2_1_alt' in output from C compiler Warning: retaining unknown function `.L.s2U2_0_alt' in output from C compiler Warning: retaining unknown function `.L.s2U3_ret' in output from C compiler : : : But I don't know if they matter or are related to my __DISCARD__ problem. Jens

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Call for Submissions - First Workshop on Languages and Tools for Parallel and Distributed Programming (LTPD 2007)
by heron_carvalho 29 Jul '07

29 Jul '07

------------------------------------------------------------ First Workshop on Languages and Tools for Parallel and Distributed Programming (LTPD 2007) http://computacao.ucpel.tche.br/ltpd/ Gramado, RS - Brazil Co-located with SBAC-PAD 2007 (24-27 October 2007) *** Submissão de artigos: 24 de Agosto *** ------------------------------------------------------------ The objective of this workshop is to bring together researchers working on the design and implementation of programming languages, tools and techniques for distributed, parallel and mobile programming. Submitted papers should present original research that is unpublished and not submitted elsewhere. We encourage the submission of work in progress, especially by MSc and PhD students. We plan to provide a friendly environment where researchers can discuss current and future trends in programming languages for parallel and distributed programming. Papers can be written in English, Portuguese and Spanish. Papers should have 4 pages, following the IEEE Computer Society Proceedings Manuscript Formatting Guidelines. All accepted papers will be published in the On-Line conference proceedings, and as a technical report. The SBAC-PAD organization will also publish the electronic proceedings in CD. We plan to publish selected high quality papers from the proceedings in a local brazilian journal. At least one author of an accepted paper must attend the workshop and all workshop attendees must be registered to SBAC-PAD. Topics of Interest ------ -- -------- Topics of interest include, but are not limited to: * Programming Multi-Core Machines * Coordination Languages * Concurrent and Parallel Garbage Collection * Type systems and semantics for parallel, distributed and mobile languages * Declarative parallel, distributed and mobile languages * Languages for mobile and ubiquitous computing * Calculi for Mobility and Concurrency * Design Patterns * Distributed Objects * Distributed Component Models * Mobile Agents Languages * Software issues for multicore or multithreaded processors Important Dates --------- ----- * Deadline for paper submission: August 24, 2007 * Accepted Papers Notification: September 10, 2007 * Camera-Ready Submission: September 17, 2007 Organizing Committee ---------- --------- André Rauber Du Bois (Chair) - UCPel Francisco Heron de Carvalho Junior (Chair)- UFC Program Committe ------- -------- Adenauer Correa Yammin - UCPel Alcides Calsavara - PUCPR Álvaro Freitas Moreira - UFRGS André Rauber Du Bois - UCPel André Santos - UFPE Claudio Fernando Resin Geyer - UFRGS Cristiano Vasconcellos - UFPel Francisco Heron De Carvalho Jr - UFC Hans-Wolfgang Loidl - LMU, Germany Iara Augustin - UFSM Jorge Luis Victoria Barbosa - Unisinos Marco Túlio de Oliveira Valente - PUC-MG Phil Trinder - Heriot-Watt University, UK Rafael Dueire Lins - UFPE Ricardo Corrêa - UFC

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building ghc6 on ppc64 linux
by Jens Petersen 29 Jul '07

29 Jul '07

I am starting work on trying to bootstrap ghc-6.6.1 on ppc64 (yes 64bit) linux for Fedora. Has anyone successfully built it on ppc64 yet? The latest build I can find in a distro is ghc-6.4.2 in gentoo. Has anyone tried ghc6 on ppc64? Thanks in advance for idea comments or experiences you can share, Jens

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*****SPAM***** Annotation for unfolding wanted
by Georg Martius 29 Jul '07

29 Jul '07

Spam detection software, running on the system "h7568.serverkompetenz.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Hi Tim, thanks for the hint, but I tried this without success. My point is, that I don't want to try a pragma and see whether it works. I would like to specify the requirement that a function has to be in constant space and if it cannot be done, that the program should not compile. Would it be complicated to include in the compiler? [...] Content analysis details: (7.4 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.1 FORGED_RCVD_HELO Received: contains a forged HELO 3.0 BAYES_95 BODY: Bayesian spam probability is 95 to 99% [score: 0.9674] 1.9 RCVD_IN_NJABL_DUL RBL: NJABL: dialup sender did non-local SMTP [87.172.161.188 listed in combined.njabl.org] 2.0 RCVD_IN_SORBS_DUL RBL: SORBS: sent directly from dynamic IP address [87.172.161.188 listed in dnsbl.sorbs.net] 0.2 AWL AWL: From: address is in the auto white-list

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*****SPAM***** Annotation for unfolding wanted
by Georg Martius 28 Jul '07

28 Jul '07

Spam detection software, running on the system "h7568.serverkompetenz.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Hi, I was wondering why we don't have an annotation or pragma for function to tell the compiler that we need this particular recursive function to be unfolded. If the compiler cannot do this for some reason it should produce an error message to help you modifying your code. I have regularly problems that my code is either not strict enough or my functions are not unfolded. I find it annoying that this is a regular show stopper and consumes much time to fix. Here is an example: a search function for strings, which should return the index and the rest of the string after the first occurrence: search0 will not be unfolded by ghc -O. (I don't know why, it looks tail-recursive to me) whereas search1 is just fine. [...] Content analysis details: (7.6 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.1 FORGED_RCVD_HELO Received: contains a forged HELO 3.5 BAYES_99 BODY: Bayesian spam probability is 99 to 100% [score: 1.0000] 1.9 RCVD_IN_NJABL_DUL RBL: NJABL: dialup sender did non-local SMTP [87.172.170.59 listed in combined.njabl.org] 2.0 RCVD_IN_SORBS_DUL RBL: SORBS: sent directly from dynamic IP address [87.172.170.59 listed in dnsbl.sorbs.net] The original message was not completely plain text, and may be unsafe to open with some email clients; in particular, it may contain a virus, or confirm that your address can receive spam. If you wish to view it, it may be safer to save it to a file and open it with an editor.

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