- Haskell-Cafe - Haskell.org

Installing hledger-web
by Arnaud Bailly 04 Oct '11

04 Oct '11

Hello, I installed hledger and tried installing hledger-web but got the following error: [2 of 8] Compiling Hledger.Web.Settings.StaticFiles ( Hledger/Web/Settings/StaticFiles.hs, dist/build/hledger-web/hledger-web-tmp/Hledger/Web/Settings/StaticFiles.o ) Hledger/Web/Settings/StaticFiles.hs:1:1: Exception when trying to run compile-time code: ./static: getDirectoryContents: does not exist (No such file or directory) Code: staticFiles staticDir cabal: Error: some packages failed to install: hledger-web-0.16 failed during the building phase. The exception was: ExitFailure 1 I install on xubuntu 11.04 with ghc 7.0.3 and latest haskell platform. The installation is quite new without much other libs. Thanks for helping, Arnaud

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Trying to experiment with tangible values using GuiTV
by Martin Baldan 04 Oct '11

04 Oct '11

Hello all, I'm very new to Haskell, but still I'd like to play with "tangible values", which I find really intriguing. After getting some kind help in haskell-beginners, I managed to compile and run a small example. Which is as follows: ------------------ {-# LANGUAGE OverlappingInstances, UndecidableInstances , IncoherentInstances, FlexibleContexts , TypeSynonymInstances, FlexibleInstances , MultiParamTypeClasses #-} -- For ghc 6.6 compatibility {-# OPTIONS -fglasgow-exts -fallow-overlapping-instances -fallow-incoherent-instances #-} ---- Some GuiTV examples. See also the examples in TV. import Data.List (sort) -- my addition import Data.Monoid -- end my addition import Interface.TV.UI import Control.Arrow.DeepArrow import Data.FunArr -- TypeCompose import Data.Title -- To pick up the FunArr instance for OFun. import Interface.TV.OFun() reverseT :: CTV (String -> String) reverseT = tv (oTitle "reverse" defaultOut) reverse main = runUI reverseT ----------------------- There were some warnings during compilation: ----- [1 of 1] Compiling Main ( myexample.hs, myexample.o ) myexample.hs:7:11: Warning: -fallow-overlapping-instances is deprecated: use -XOverlappingInstances or pragma {-# LANGUAGE OverlappingInstances #-} instead myexample.hs:7:11: Warning: -fallow-incoherent-instances is deprecated: use -XIncoherentInstances or pragma {-# LANGUAGE IncoherentInstances #-} instead Linking myexample ... martin@martin-desktop:/media/ ext4logicaUnTera/cosas_linux/programs/haskell/TV/examples/src/miejemplo$ ghc --make myexample.hs myexample.hs:7:11: Warning: -fallow-overlapping-instances is deprecated: use -XOverlappingInstances or pragma {-# LANGUAGE OverlappingInstances #-} instead myexample.hs:7:11: Warning: -fallow-incoherent-instances is deprecated: use -XIncoherentInstances or pragma {-# LANGUAGE IncoherentInstances #-} instead ----- When I run it, I get a little window with the "reverse" title and two textboxes. However, when I write something in the upper box, nothing happens. I must say that when I use runIO instead of runUI in this little program, the interactive program does work. Only the GUI version doesn't. So, the person who helped me (Brandon Allbery) said it's probably because of a GuiTV being a bit too old. He recommended me to ask about the issue here, at haskell-cafe. Any suggestions? Maybe I should use GtkTV istead of GuiTV? Thanks in advance! Martin O.B.

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ghc with -fPIC support
by Phyx 03 Oct '11

03 Oct '11

Hi All, I'm trying to install GHC with -fPIC support in Fedora. I've grabbed a source tarball since it seems no binary one has this. In Build.mk i've changed the quick build type to ifeq "$(BuildFlavour)" "quick" SRC_HC_OPTS = -H64m -O0 -fasm -fPIC GhcStage1HcOpts = -O -fasm -fPIC GhcStage2HcOpts = -O0 -fasm -fPIC GhcLibHcOpts = -O -fasm -fPIC SplitObjs = NO HADDOCK_DOCS = NO BUILD_DOCBOOK_HTML = NO BUILD_DOCBOOK_PS = NO BUILD_DOCBOOK_PDF = NO endif unfortunately, when compiling i still get the ld error *** *** ghc -fglasgow-exts --make -shared -oHs2lib.a /tmp/Hs2lib924498/Hs2lib.hs dllmain.o -static -fno-warn-deprecated-flags -O2 -package ghc -package Hs2lib -i/home/phyx/Documents/Haskell/Hs2lib -optl-Wl,-s -funfolding-use-threshold=16 -optc-O3 -optc-ffast-math Linking a.out ... *** /usr/bin/ld: /tmp/Hs2lib924498/Hs2lib.o: relocation R_X86_64_32 against `ghczmprim_GHCziUnit_Z0T_closure' can not be used when making a shared object; recompile with -fPIC *** /tmp/Hs2lib924498/Hs2lib.o: could not read symbols: Bad value I've also told cabal to build any packages with -fPIC and shared. Anyone have any ideas? Regards, Phyx

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How to compile this example code?
by Magicloud Magiclouds 03 Oct '11

03 Oct '11

Hi, I am learning to use data-flags, and got this example code: import Data.Flags newtype MyFlags = MyFlags CInt deriving (Eq, Flags) #{enum MyFlags, MyFlags , myFlag1 = C_FLAG1 , myFlag2 = C_FLAG2 , myFlag3 = C_FLAG3 } I modified it trying to compile it. Well, I got illegal syntax at "#{e". In fact, I am not quite know the syntax here. Any clue? -- 竹密岂妨流水过山高哪阻野云飞

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HEADS-UP: security fix, please upgrade clientsession to >= 0.7.3.1
by Felipe Almeida Lessa 03 Oct '11

03 Oct '11

Hello! Please be advised that clientsession < 0.7.3.1 is vulnerable to timing attacks [1]. We have just released a fix and it's already on Hackage [2]. We advise all users of clientsession (and, consequently, Yesod) to upgrade as soon as possible to a version >= 0.7.3.1. With a timing attack a malicious user may be able to construct a valid MAC for his message. However, the attacker is not able to recover the MAC key or the encryption key. So you don't need to change your keys, just upgrade ASAP. Cheers, =) [1] https://github.com/snoyberg/clientsession/pull/4 [2] http://hackage.haskell.org/package/clientsession-0.7.3.1 -- Felipe.

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ghc 7.2.1 and super simple DPH
by Peter Braam 03 Oct '11

03 Oct '11

Hi - I'm trying to compile DotP.hs from http://www.haskell.org/haskellwiki/GHC/Data_Parallel_Haskell#A_simple_examp… (see below) The compiler complains and says (twice in fact): DotP.hs:17:33: Not in scope: `fromPArrayP' Could someone help me out please? Thanks a lot! Peter {-# LANGUAGE ParallelArrays #-}{-# OPTIONS_GHC -fvectorise #-} module DotP (dotp_wrapper)where import qualified Preludeimport Data.Array.Parallel.Preludeimport Data.Array.Parallel.Prelude.Double dotp_double :: [:Double:] -> [:Double:] -> Double dotp_double xs ys = sumP [:x * y | x <- xs | y <- ys:] dotp_wrapper :: PArray Double -> PArray Double -> Double{-# NOINLINE dotp_wrapper #-} dotp_wrapper v w = dotp_double (fromPArrayP v) (fromPArrayP w)

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Problem on using template haskell.
by Magicloud Magiclouds 03 Oct '11

03 Oct '11

Hi, I am trying to use data-flags library. And failed on compiling the test code. The code is like following, and the compiling error is "test.hs:4:24: parse error on input `{'" {-# LANGUAGE TemplateHaskell #-} import Data.Flags.TH $(bitmaskWrapper "Severity" ''Int [] False [ ("NotClassified", #{const (2 ^ 0)}) , ("Information", #{const (2 ^ 1)}) , ("Warning", #{const (2 ^ 2)}) , ("Average", #{const (2 ^ 3)}) , ("High", #{const (2 ^ 4)}) , ("Disaster", #{const (2 ^ 5)}) What should I do? -- 竹密岂妨流水过山高哪阻野云飞

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Parameters and patterns
by José Romildo Malaquias 03 Oct '11

03 Oct '11

Hello. When studing programming languages I have learned that parameter is a variable (name) that appears in a function definition and denotes the value to which the function is applied when the function is called. Argument is the value to which the function is applied. The parameter allows the manipulation of the argument in the body of the funtion definition in order to produce the result. Now I am not sure how to apply these concepts to Haskell, as Haskell uses pattern matching to deal with argument passing to functions. For instance, in the definition f x = 2 * x + 1 x is a parameter, and in the application f 34 34 is an argument. But in the definition g (_:xs) = xs what is the parameter of the function g? Is it the pattern (_:xs)? If so then a parameter is not necessarily a variable anymore, and that seems very strange. And what is xs? Is it a parameter, although it does not denote the value to which the function is aplied, but just part of it? I am writing some slides to use in my functional programming classes, but I am not sure how to deal with these terms. Any comments? Romildo -- DECOM - ICEB - UFOP

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Re: [Haskell-cafe] Is it possible to represent such polymorphism?
by Tom Murphy 02 Oct '11

02 Oct '11

Assuming that z :: Int, you can declare an algebraic datatype data TwoOrThree a b = Three (a, b, Int) | Two (a, b) deriving(Show, Eq) -- so you can experiment And then define expand as expand :: TwoOrThree a b -> (a, b, Int) expand (Three tuple) = tuple expand (Two (a, b)) = (a, b, 1) Tom (amindfv) On Oct 2, 2011 6:04 AM, "Du Xi" <sdiyazg(a)sjtu.edu.cn> wrote:

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ANN: Peggy 0.2.1
by Hideyuki Tanaka 02 Oct '11

02 Oct '11

Hello, all. I have released 'Peggy' a new parser generator . It is based on Parsing Expression Grammer (PEG) [1], and generates efficient packrat parsers. # Where to get it * Hackage page (http://hackage.haskell.org/package/peggy) * github repository (https://github.com/tanakh/peggy) * Some documents are at (http://tanakh.github.com/Peggy/) # Advantage * Simple and Powerful syntax * No shift/reduce conflict * Unlimited look-ahead * You don't need to prepare separated Scanner * Linear time complexity * Based on modern Haskell ecosystem (bytestring, text, ListLike, Monads, etc...) * Support to use and generate Quasi Quoters # Examples Here are few example of parsers: * http://tanakh.github.com/Peggy/example.html * https://github.com/tanakh/Peggy/blob/master/example/Json.hs There is a self defined parser of peggy syntax, used for bootstrapping: * https://github.com/tanakh/Peggy/blob/master/bootstrap/peggy.peggy Please try it and give me feedbacks! Thanks, [1]: http://en.wikipedia.org/wiki/Parsing_expression_grammar -- Hideyuki Tanaka

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Static linking for machines that don't have Haskell
by Roshan James 02 Oct '11

02 Oct '11

Hi All, I am trying to run a Haskell program compiled on my Ubuntu box on a server box that does not have GHC installed and where I dont have root privileges. I run into several missing libraries, in particular libgmp, libffi and libuuid (the later two are needed by my program). How I can statically link my program such that I can run it on this server? I have a tried static linking as follows: * ghc -static -optl-static -optl-pthread --make -o p main.hs* This gives me several warnings of the form: */usr/lib/haskell-packages/ghc6/lib/network-2.2.1.7/ghc-6.12.3/libHSnetwork-2.2.1.7.a(BSD.o): In function `sw4B_info':* *(.text+0x584c): warning: Using 'getservbyport' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking* And sure enough the generated executable segfaults on the server which has a different glibc version. Is there some way to static link all the other libraries needed except glibc? I have looked around for an example of this but to no avail and the output of the -v switch seemed a bit overwhelming. Or is there some other way to go about doing this? thanks in advance, Roshan ps. including these, in case they maybe of some use: My machine: *$ ldd p* * linux-vdso.so.1 => (0x00007fff3ffff000)* * libncurses.so.5 => /lib/libncurses.so.5 (0x00007fbdbbf4f000)* * libuuid.so.1 => /lib/x86_64-linux-gnu/libuuid.so.1 (0x00007fbdbbd4a000)* * librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007fbdbbb41000)* * libutil.so.1 => /lib/x86_64-linux-gnu/libutil.so.1 (0x00007fbdbb93e000)* * libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fbdbb73a000)* * libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fbdbb51b000)* * libgmp.so.3 => /usr/lib/libgmp.so.3 (0x00007fbdbb2be000)* * libffi.so.5 => /usr/lib/libffi.so.5 (0x00007fbdbb0b6000)* * libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fbdbae30000)* * libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fbdbaa9c000)* * /lib64/ld-linux-x86-64.so.2 (0x00007fbdbc1b5000)* Server: *$ ldd p* *./p: /lib64/libuuid.so.1: no version information available (required by ./p)* * linux-vdso.so.1 => (0x00007fffc51fd000)* * libncurses.so.5 => /usr/lib64/libncurses.so.5 (0x00000037bce00000)* * libuuid.so.1 => /lib64/libuuid.so.1 (0x00000037b7200000)* * librt.so.1 => /lib64/librt.so.1 (0x00000037b5a00000)* * libutil.so.1 => /lib64/libutil.so.1 (0x00000037bda00000)* * libdl.so.2 => /lib64/libdl.so.2 (0x00000037b4a00000)* * libpthread.so.0 => /lib64/libpthread.so.0 (0x00000037b5200000)* * libgmp.so.3 => not found* * libffi.so.5 => not found* * libm.so.6 => /lib64/libm.so.6 (0x00000037b4e00000)* * libc.so.6 => /lib64/libc.so.6 (0x00000037b4600000)* * /lib64/ld-linux-x86-64.so.2 (0x00000037b4200000)* * *

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ByteString install issues with GHC 7.0.3 on Windows 7
by Ralph Hodgson 02 Oct '11

02 Oct '11

This morning I was successfully running BlazeHtml on Windows 7. Then I installed some libraries from other packages and BlazeHtml broke. I then decided to go from ghc 6.12.1 to ghc 7.0.3 and reinstall everything. BlazeHtml installed OK. But my program also needed ByteString. So I did the following: First I tried the stable version: >cabal install bytestring-0.9.1.4 Resolving dependencies... Configuring bytestring-0.9.1.4... Preprocessing library bytestring-0.9.1.4... Building bytestring-0.9.1.4... Data\ByteString.hs:3:24: Cannot parse LANGUAGE pragma Expecting comma-separated list of language options, each starting with a capital letter E.g. {-# LANGUAGE RecordPuns, Generics #-} cabal: Error: some packages failed to install: bytestring-0.9.1.4 failed during the building phase. The exception was: ExitFailure 1 I am not experienced enough to fix this, so I tried a previous ByteString version: >cabal install bytestring-0.9.1.3 Resolving dependencies... Configuring bytestring-0.9.1.3... Preprocessing library bytestring-0.9.1.3... Building bytestring-0.9.1.3... [1 of 8] Compiling Data.ByteString.Fusion ( Data\ByteString\Fusion.hs, dist\buil d\Data\ByteString\Fusion.o ) [2 of 8] Compiling Data.ByteString.Internal ( Data\ByteString\Internal.hs, dist\ build\Data\ByteString\Internal.o ) Data\ByteString\Internal.hs:79:42: Module `GHC.IOBase' does not export `RawBuffer' cabal: Error: some packages failed to install: bytestring-0.9.1.3 failed during the building phase. The exception was: ExitFailure 1 No joy. Help appreciated. May try all this on my MAC tomorrow. Ralph Hodgson, <http://twitter.com/ralphtq> @ralphtq Mobile Phone: +1 781-789-1664

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ANNOUNCE: GA-1.0, a library for working with genetic algorithms
by Kenneth Hoste 01 Oct '11

01 Oct '11

Hello, I'm proud to announce the v1.0 release of GA [1], my library for working with genetic algorithms in Haskell. Source repo is available on github. [2] This is a major version bump compared to the previous v0.2 release, because the library is pretty mature now in my view. Major features: * flexible user-friendly API for working with genetic algorithms * Entity type class to let user define entity definition, scoring, etc. * abstraction over monad, resulting in a powerful yet simple interface * support for scoring entire population at once * support for checkpointing each generation, and restoring from last checkpoint * convergence detection, as defined by user * also available: random searching, user-defined progress output * illustrative toy examples included I'm happy to take any questions or suggestions that you might have. [1] http://hackage.haskell.org/package/GA [2] https://github.com/boegel/GA

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Haskell Cloud and Closures
by Fred Smith 01 Oct '11

01 Oct '11

I've built a little program to compute the plus function remotely by using Cloud Haskell: http://pastebin.com/RK4AcWFM but i faced an unfortunate complication, what i would like to do is to send a function to another host, no matter if the function is locally declared or at the top level. In seems to me that in cloud haskell library the function's closures can be computed only with top-level ones, is it possible to compute the closure at runtime of any function and to send it to another host? here's the code that i would like to compile: http://pastebin.com/7F4hs1Kk thank you all in advance! Fred

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Build local-gc branch of GHC
by Andreas Voellmy 01 Oct '11

01 Oct '11

Hi, I've been trying to get and build a branch of ghc that includes the new local GC algorithm ( http://www.haskell.org/pipermail/cvs-ghc/2011-June/062748.html) but I haven't been able to build it successfully. Here is what I've done: 1. Got the latest source tree using these commands: $ git clone http://darcs.haskell.org/ghc.git/ $ cd ghc $ ./sync-all --testsuite get 2. Use 'fingerprint' script to get the state of the repository for the branch mentioned in the web page I mentioned above. A fingerprint file based on the announcement above fails due to some problem with binary and haddock change sets not being found. So I modified the fingerprint to use the latest versions for binary and deleted the change for haddock entirely. I ran this command: ./utils/fingerprint/fingerprint.py restore -f local-gc.fp and my local-gc.fp fingerprint file contains this: .|ab5aad587de8e3d9dde539982ae728b33e5bca50 ghc-tarballs|e7b7b152083f7c3e3559e557a239757d41ac02a6 libraries/Cabal|6f01f56a2702b50e2da909566c4a01622cb2ca7f libraries/Win32|0cf603103e9ad3fccd862171ba5e689b87930622 libraries/array|e4b4e2e0a79f4138bdff4f10d263436b0155f449 libraries/base|be2750a0a11b919fb03cc070074e430f88bdfa90 libraries/binary|376797487651cf995bd52458ce1f7d7a283341b3 libraries/bytestring|cab9d8566fba8611598f14fb4f2ac7b8d4aae75b libraries/containers|592f6d9da9090e8d53432f22a01bb117fea2246c libraries/deepseq|91e8a93b15ed32af3941f81e927291a023feb369 libraries/directory|3a0f2e2cb94c3e4f346023acc7201409d2876ed8 libraries/extensible-exceptions|a667b48d0cb6469b6611cb516d16836aa002e782 libraries/filepath|92d211a2752fe8827582ae0d97efd18722ad3d87 libraries/ghc-prim|7fcfc880853fa399c9468049aeb14e6eadb9eae5 libraries/haskeline|125ee5bba59fa9ac2fd77aa3922c30dffc11b7b5 libraries/haskell2010|f90687bee55adfd693fe460f2ab4bc270a7f97e3 libraries/haskell98|eb655b0317665acb9670025480b4af4465bc8f55 libraries/hoopl|0febb7f04ff4326bd120fc75549845e5e9678d72 libraries/hpc|fce8babbc3f60fb195d84545753dc342422ab8e1 libraries/integer-gmp|2567c97aaa467cb676a6ecc2cf840c92ee1cb6ec libraries/integer-simple|c3e9c0268b4d59895829e429d1ac767e6041b06a libraries/mtl|a748dfa2770af1d348dfaa8ad6955b25b4935711 libraries/old-locale|7f09f55ea3011c17c526805f099394a05ec9c3fe libraries/old-time|6aae8dc2f13cef6ab48c5436c6c0e7c1b5ae3f51 libraries/parallel|f82611fac439236e22a057cd555bb9fe393597b0 libraries/pretty|e00aa7e0f82fc6f13ad85f1b3a27f53efe473e60 libraries/process|d1c2999473ba0d4ceafdc6da309debca83f91abe libraries/random|ba8cb1b9fdfddeb29fdfedd8612c8ce85a987af8 libraries/stm|ccc6d74872916e5de7747df4cc61f64de64be591 libraries/template-haskell|acd4c3292d0f7a222a1f4f426054e4732a809fc8 libraries/terminfo|f4476f1881085b74dbe65cf4a4561e8fb34017d4 libraries/unix|c9a0bf119ce343b291bef77828066339e94fb64d libraries/utf8-string|d28cd1fbd4ebaaa0608c070bd02ed72dc9b70399 libraries/xhtml|9a4d7d64d0491a1844d5b5759275b029ccd1e2cd nofib|6d3ea16e56bd99d060e778fab3583aa67a6b50d4 testsuite|6560613138d61afddd0d8d428254370f8dfdb4cd utils/hsc2hs|c46eed44ce96f1719334ffb190eddf63695bc553 3. I then run $perl boot $./configure This succeeds telling me that it will be building ghc version 7.1.20110606. 4. Run make and it fails with this output: + test -f mk/config.mk.old + cp -p mk/config.mk mk/config.mk.old touch -r mk/config.mk.old mk/config.mk + test -f mk/project.mk.old + cp -p mk/project.mk mk/project.mk.old touch -r mk/project.mk.old mk/project.mk + test -f compiler/ghc.cabal.old + cp -p compiler/ghc.cabal compiler/ghc.cabal.old touch -r compiler/ghc.cabal.old compiler/ghc.cabal ===--- building phase 0 make -r --no-print-directory -f ghc.mk phase=0 phase_0_builds libraries/dph/ghc.mk:116: *** dph_th_deps(v,seq): libraries/dph/dph-base_dist-install_GHCI_LIB not defined!. Stop. make: *** [all] Error 2 5. I don't know how to fix this, so I tried deleting libraries/dph. Then I run make again, and get a ways through the build, and then get this error: "inplace/bin/ghc-stage1" -M -dep-makefile libraries/vector/dist-install/build/.depend-v-p-dyn.haskell.tmp -dep-suffix p -dep-suffix dyn -include-pkg-deps -H32m -O -package-name vector-0.8 -hide-all-packages -i -ilibraries/vector/. -ilibraries/vector/dist-install/build -ilibraries/vector/dist-install/build/autogen -Ilibraries/vector/dist-install/build -Ilibraries/vector/dist-install/build/autogen -Ilibraries/vector/include -Ilibraries/vector/internal -optP-DVECTOR_BOUNDS_CHECKS -optP-include -optPlibraries/vector/dist-install/build/autogen/cabal_macros.h -package base-4.3.1.0 -package primitive-0.4.0.1 -O2 -XHaskell98 -XCPP -XDeriveDataTypeable -O2 -no-user-package-conf -rtsopts -odir libraries/vector/dist-install/build -hidir libraries/vector/dist-install/build -stubdir libraries/vector/dist-install/build -hisuf hi -osuf o -hcsuf hc libraries/vector/./Data/Vector/Internal/Check.hs libraries/vector/./Data/Vector/Fusion/Util.hs libraries/vector/./Data/Vector/Fusion/Stream/Size.hs libraries/vector/./Data/Vector/Fusion/Stream/Monadic.hs libraries/vector/./Data/Vector/Fusion/Stream/Monadic/Safe.hs libraries/vector/./Data/Vector/Fusion/Stream.hs libraries/vector/./Data/Vector/Fusion/Stream/Safe.hs libraries/vector/./Data/Vector/Generic/Mutable.hs libraries/vector/./Data/Vector/Generic/Mutable/Safe.hs libraries/vector/./Data/Vector/Generic/Base.hs libraries/vector/./Data/Vector/Generic/New.hs libraries/vector/./Data/Vector/Generic/New/Safe.hs libraries/vector/./Data/Vector/Generic.hs libraries/vector/./Data/Vector/Generic/Safe.hs libraries/vector/./Data/Vector/Primitive/Mutable.hs libraries/vector/./Data/Vector/Primitive/Mutable/Safe.hs libraries/vector/./Data/Vector/Primitive.hs libraries/vector/./Data/Vector/Primitive/Safe.hs libraries/vector/./Data/Vector/Storable/Internal.hs libraries/vector/./Data/Vector/Storable/Mutable.hs libraries/vector/./Data/Vector/Storable.hs libraries/vector/./Data/Vector/Unboxed/Base.hs libraries/vector/./Data/Vector/Unboxed/Mutable.hs libraries/vector/./Data/Vector/Unboxed/Mutable/Safe.hs libraries/vector/./Data/Vector/Unboxed.hs libraries/vector/./Data/Vector/Unboxed/Safe.hs libraries/vector/./Data/Vector/Mutable.hs libraries/vector/./Data/Vector/Mutable/Safe.hs libraries/vector/./Data/Vector.hs libraries/vector/./Data/Vector/Safe.hs libraries/vector/Data/Vector/Fusion/Util.hs:4:14: Unsupported extension: Trustworthy make[1]: *** [libraries/vector/dist-install/build/.depend-v-p-dyn.haskell] Error 1 make: *** [all] Error 2 I deleted this library too, but my build errors just continued. After resolving a bunch of build errors in Haskell libraries, I started getting errors in the C files in the rts directory. While I could go on fixing these problems, it seems likely that I went wrong somewhere early on. Does anyone see where I went wrong? Did I use the various tools (git, sync-all, fingerprint, boot, configure, make) in the right order and way? Regards, Andreas

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Re: [Haskell-cafe] [Haskell] mapM with Traversables
by Marc Ziegert 30 Sep '11

30 Sep '11

Hi Thomas, this should be on the haskell-cafe or haskell-beginners mailing list. Haskell@... is mainly for announcements. You have: > f :: Monad m => > a -> m b > Data.Traversable.mapM :: (Monad m, Traversable t) => > (a -> m b) -> t a -> m (t b) So, if you define g with > g a = do Data.Traversable.mapM f a or in short > g = Data.Traversable.mapM f , then the type will be > g :: (Monad m, Traversable t) => > t a -> m (t b) instead of > g :: [a] -> m (Seq b) . Try using ghci to find these things out. It helps to get not confused with the types. Besides the missing "Monad" context, g misses a generic way to convert between different Traversables, which does not exist. You can only convert from any Traversable (imagine a Tree) "toList"; not all Traversables have a "fromList" function. For conversion, you might want to use Foldable and Monoid, fold to untangle and mappend to recombine; but any specific "fromList" function will surely be more efficient. Regards - Marc -------- Original-Nachricht -------- > Datum: Wed, 28 Sep 2011 17:27:58 -0600 > Von: thomas burt <thedwards(a)gmail.com> > An: haskell(a)haskell.org > Betreff: [Haskell] mapM with Traversables > Hi - > > I have a function, "f :: Monad m => a -> m b", as well as a list of a's. > I'd > like to produce a sequence (Data.Sequence) of b's, given the a's: > > g :: [a] -> m (Seq b) > g a = do Data.Traversable.mapM f a -- type error! > > I see that "Data.Traversable.mapM f a" doesn't work... is this like asking > the compiler to infer the cons/append operation from the type signature of > g? > > Do I need to write my own function that explicitly calls the "append" > functions from Data.Sequence or can I do something else that would work > for > any "g :: Traversable t, Traversable u => t a -> m (u b)" given "f :: a -> > m > b"? > > Thanks for any comments! > Thomas

2 1

module -> package
by Roman Beslik 30 Sep '11

30 Sep '11

Hello. How can I find which installed package a specified module belongs to? ghci or cabal or ghc-pkg?

2 1

Handy abbreviations for using SciTE with Haskell
by Amy de Buitléir 30 Sep '11

30 Sep '11

I often use SciTE for editing Haskell code. I wanted an easy way to type symbols such as "∀" (instead of "forall"), so I created a properties file that allows me to do that. I haven't seen anything similar online (I Googled first), so I made the code available online. You can find the file and instructions here: http://www.haskell.org/haskellwiki/Tips_for_using_SciTE_with_Haskell

1 0

Re: [Haskell-cafe] Programming with arrows, exercises
by Sergey Mironov 30 Sep '11

30 Sep '11

2011/9/30 John Lask <jvlask(a)hotmail.com>: > On 30/09/2011 7:15 AM, Sergey Mironov wrote: >> >> Hello. I am reading "Programming with Arrows" by John Hughes (very >> helpful and interesting!), the book has an exercises requiring a >> module called Circuits for checking the answer. There should be things >> like class ArrowCircuit and various functions related to digital logic >> circuits simulation. Does anybody know where can I find one? >> >> Thanks, >> Sergey >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >> >> > > This was in the old arrows library I have attached a copy, it will probably > need modification to compile. > > You should be able to use the examples with the current arrows library with > a few mods. > Yes, looks quite old. Unfotinately, it doesn't match the book.. I found that module I was looking for is in Appendix! Should I be more attentive.. Anyway, thank you!

1 0

Type family instances in Haddock?
by Sean Leather 30 Sep '11

30 Sep '11

Would it be useful/worthwhile to have type/data family instances show up in Haddock just as type class instances do? Regards, Sean

1 0

Indentation problem using Happy
by Amy de Buitléir 30 Sep '11

30 Sep '11

I'm trying to use Happy for the first time, and I'm having trouble with this very simple example: ===== BEGIN: PolyParser.y ===== { module Main where import Char ( isAlpha, isDigit, isSpace ) } %name calc %tokentype { Token } %error { parseError } %token id { TokenId $$ } ',' { TokenCOMMA } wombat { TokenWombat $$ } %% Poly : id ',' wombat { parseError :: [Token] -> a parseError _ = error "Parse error" data Poly = Poly Int String deriving Show data Token = TokenId Int | TokenCOMMA | TokenWombat String deriving Show lexer :: String -> [Token] lexer [] = [] lexer (c:cs) | isSpace c = lexer cs | isAlpha c = lexVar (c:cs) | isDigit c = lexNum (c:cs) lexer (',':cs) = TokenCOMMA : lexer cs lexNum cs = TokenInt (read num) : lexer rest where (num,rest) = span isDigit cs lexVar cs = case span isAlpha cs of (wombat,rest) -> TokenWombat wombat : lexer rest (id,rest) -> TokenId id : lexer rest main = getContents >>= print . calc . lexer } ===== END: PolyParser.y ===== The resulting PolyParser.hs has an indentation problem (second-to-last line, below), so it won't compile. happyReduce_1 = happySpecReduce_3 4 happyReduction_1 happyReduction_1 _ _ _ = HappyAbsSyn4 (parseError :: [Token] -> a parseError _ = error "Parse error" Thank you in advance to anyone who can tell me where I've gone wrong.

1 0

CFG specification and analysis directly in Haskell
by Anton Tayanovskyy 30 Sep '11

30 Sep '11

Hi, As a weekend hack, I just realized that Haskell has this wonderful DoRec syntax that among other things seems to be able to let the user express context-free grammars together with their processing rules in normal Haskell code, without template Haskell or anything like that, just like parser combinators. I am just wondering if this is this a known and useful result? Are there libraries doing similar stuff? I wrote up the Earley algorithm to demonstrate that one can in principle analyze the complete grammar (https://github.com/toyvo/haskell-earley) The result derivations `cheat` by using Data.Dynamic, but the result is quite pleasing, for example one can do: grammar :: G.Grammar (G.Rule Char E) grammar = do nat <- G.rule "NAT" [ fmap (\_ -> 0) (G.term '0') , fmap (\_ -> 1) (G.term '1') ] rec expr <- G.rule "EXPR" [ fmap Nat $ G.var nat , pure (\x _ y -> Add x y) <*> G.var expr <*> G.term '+' <*> G.var expr ] return expr Thanks, Anton

3 4

Turn GC off
by Andreas Voellmy 30 Sep '11

30 Sep '11

Hi everyone, Is there a way to completely turn garbage collection off in the Haskell runtime system? I'm aware of the -A runtime option, but I'd like to completely turn it off, if possible. I'm OK with running the program until it runs out of memory, and I'm willing to recompile GHC if needed. Regards, Andreas

6 7

Programming with arrows, exercises
by Sergey Mironov 29 Sep '11

29 Sep '11

Hello. I am reading "Programming with Arrows" by John Hughes (very helpful and interesting!), the book has an exercises requiring a module called Circuits for checking the answer. There should be things like class ArrowCircuit and various functions related to digital logic circuits simulation. Does anybody know where can I find one? Thanks, Sergey

1 0

Cabal rebuilding of the C++ code for wxHaskell
by Dave Tapley 29 Sep '11

29 Sep '11

Hi all, I've been trying to resolve a compile time issue[1] with wxHaskell, and I thought I'd throw it open to see if anyone on cafe can help. Here's the crux of the issue: The Setup.hs for wxcore (the major component of wxHaskell) uses "simpleUserHooks", overriding only "confHook". However there is also "cleanHook", which is defined by simpleUserHooks to be: cleanHook = \p _ _ f -> clean p f, If you consult the source for clean[2] you'll see that it tries to "remove the whole dist/ directory rather than tracking exactly what files we created in there". I presume that's why we have to do a full re-build every time? To try and circumvent this I modified the definition of "main" in Setup.hs to this: main = defaultMainWithHooks simpleUserHooks { confHook = myConfHook, cleanHook = (\_ _ _ _ -> return ())} Unfortunately it still seems to re-build all the C++ on each 'install' from cabal. Not sure why? Dave, [1] http://sourceforge.net/mailarchive/message.php?msg_id=28099997 [2] Taken from http://www.haskell.org/ghc/docs/6.10.4/html/libraries/Cabal/src/Distributio… -- Cleaning clean :: PackageDescription -> CleanFlags -> IO () clean pkg_descr flags = do let distPref = fromFlag $ cleanDistPref flags notice verbosity "cleaning..." maybeConfig <- if fromFlag (cleanSaveConf flags) then maybeGetPersistBuildConfig distPref else return Nothing -- remove the whole dist/ directory rather than tracking exactly what files -- we created in there. chattyTry "removing dist/" $ do exists <- doesDirectoryExist distPref when exists (removeDirectoryRecursive distPref) -- these live in the top level dir so must be removed separately removeRegScripts -- Any extra files the user wants to remove mapM_ removeFileOrDirectory (extraTmpFiles pkg_descr) -- If the user wanted to save the config, write it back maybe (return ()) (writePersistBuildConfig distPref) maybeConfig where removeFileOrDirectory :: FilePath -> IO () removeFileOrDirectory fname = do isDir <- doesDirectoryExist fname isFile <- doesFileExist fname if isDir then removeDirectoryRecursive fname else if isFile then removeFile fname else return () verbosity = fromFlag (cleanVerbosity flags)

1 0

HackageDB User Account
by Jonathan Frywater 29 Sep '11

29 Sep '11

How does one go about getting an account? I sent an email to the address provided at http://hackage.haskell.org/packages/accounts.html but haven't received any response yet. Since it's been over 3 weeks, I decided to try my luck here.

2 1

LLVM: function pointer in global struct
by Tom Schouten 29 Sep '11

29 Sep '11

Hi everyone, Using the LLVM bindings, I'm trying to create an initialized global struct variable containing a pointer to a function. > {-# LANGUAGE ScopedTypeVariables #-} > import LLVM.Core > import Data.Word > import LLVM.Util.File(writeCodeGenModule) > sm_module = do > tick :: Function (Word32 -> IO Word32) <- createFunction ExternalLinkage $ \x -> ret x > info <- createNamedGlobal False ExternalLinkage "sm_info" $ constStruct (tick & ()) > return info I run into a complaint that this pointer isn't constant when it's part of a global variable initializer. No instance for (llvm-0.10.0.1:LLVM.Core.CodeGen.IsConstStruct (Function (Word32 -> IO Word32) :& ()) a0) arising from a use of `constStruct' Possible fix: add an instance declaration for (llvm-0.10.0.1:LLVM.Core.CodeGen.IsConstStruct (Function (Word32 -> IO Word32) :& ()) a0) In the second argument of `($)', namely `constStruct (tick & ())' In a stmt of a 'do' expression: info <- createNamedGlobal False ExternalLinkage "sm_info" $ constStruct (tick & ()) In a stmt of a 'do' expression: tick :: Function (Word32 -> IO Word32) <- createFunction ExternalLinkage $ \ x -> ret x I suppose this is because of > -- |A function is simply a pointer to the function. > type Function a = Value (Ptr a) being a Value instead of ConstValue. Is there a way around this? Cheers Tom

1 0

PhD studentship in Nottingham
by Graham Hutton 29 Sep '11

29 Sep '11

Dear all, I am currently advertising a PhD Studentship in Functional Programming at the University of Nottingham in the UK: http://tinyurl.com/phd-nottingham Due to the nature of the funding, the position is only to UK/EU students who have resided in the UK for the last three years. If you are interested in applying yourself, please drop me a note by email. If you know of any good candidates who may be interested in applying, or there is a local mailing list for advertising such things, I'd be much obliged if you could pass on the above link. Many thanks, Graham Hutton -- Prof Graham Hutton Functional Programming Lab School of Computer Science University of Nottingham, UK http://www.cs.nott.ac.uk/~gmh This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please send it back to me, and immediately delete it. Please do not use, copy or disclose the information contained in this message or in any attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. This message has been checked for viruses but the contents of an attachment may still contain software viruses which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.

1 0

network 2.3.05 on windows 7 with ghc-7.2.1
by Sai Hemanth K 29 Sep '11

29 Sep '11

Hi, Apologies if this is an off-topic for the list, If someone here managed to build network 2.3.05 on windows 7 with ghc-7.2.1 , could you kindly pass me the trick? The config step fails with missing header. I tried running it with mingw (tried with the latest one too - just in case : http://sourceforge.net/projects/mingw/files/Automated%20MinGW%20Installer/) I did not face any issue for the same thing on linux. Many thanks, Hemanth K

4 5

Haskell Weekly News: Issue 201
by Daniel Santa Cruz 29 Sep '11

29 Sep '11

Welcome to issue 201 of the HWN, a newsletter covering developments in the Haskell community. This release covers the week of September 18 to 24, 2011. You can find the HTML version of this issue at: http://contemplatecode.blogspot.com/2011/09/haskell-weekly-news-issue-201.h… Announcements Jasper Van der Jeugt sent more details about the 9th GhentFPG meeting, which will take place on October the 4th, at 19:30 in the Technicum building of Ghent University. "You don't have to be a Functional Programming guru to attend, everyone eager to learn is welcome." [1] http://goo.gl/hAa5Zn New and Updated Projects * usb, bindings-libusb, usb-iteratee (Bas van Dijk; 1.0, 1.4.4, 0.4) Wrapers around the portable C library libusb-1.0 [2] http://goo.gl/lTMNJn * ivy-web (James Deng; 0.1) A lightweight web framework, with type-safe routes, based on invertible syntax, and i18n support, influenced by Django, Snap and Yesod. [3] http://goo.gl/dTcPEn * lushtags (Bit Connor) ctags compatible tags files for Haskell programs. [4] http://goo.gl/30TYen * lightweight monadic regions family (Bas van Dijk; multiple versions) Updates to regios, regions-mtl, regions-monadstf, regional-pointers, safer-file-handles, safer-file-handles-bytestring, safer-file-handles-text, and usb-safe. [5] http://goo.gl/g8P6Kn * skein (Felipe Almeida Lessa; 0.1) A family of fast secure cryptographic hash functions. [6] http://goo.gl/xwafmn Quotes of the Week * dafis: I thought a C++ friend class was one you allowed to touch your private parts * edwardk: any time i can help, just ask. i may not actually help, but i'll be sure to note your suffering. * edwardk: i have a lot fewer [haddock problems] now since i stopped bothering trying to document ;) * edwardk: Had i thought of it earlier i could have named trifecta kessel run. at this point it looks like it'll contain at least 12 parsecs. * ddarius: The history of iteratees is making a simple idea complex. * shachaf: You can never escape having learned monads. If you learn two monads, though, you can go back to only knowing one. Top Reddit Stories * GHCi now supports all top-level declarations Domain: github.com, Score: 104, Comments: 35 On Reddit: [7] http://goo.gl/GfTc9n Original: [8] http://goo.gl/Md5B3n * The best ghc bug ever Domain: twitter.com, Score: 93, Comments: 27 On Reddit: [9] http://goo.gl/3sCHUn Original: [10] http://goo.gl/N7IGdn * Running a startup on Haskell Domain: bos.github.com, Score: 73, Comments: 33 On Reddit: [11] http://goo.gl/HevD3n Original: [12] http://goo.gl/IsXedn * No chrome, Haskell is not Danish. Domain: i.imgur.com, Score: 73, Comments: 26 On Reddit: [13] http://goo.gl/AYyq4n Original: [14] http://goo.gl/whKijn * Did Haskell Platform miss the July release? It's already September. Domain: trac.haskell.org, Score: 46, Comments: 12 On Reddit: [15] http://goo.gl/6m8Yln Original: [16] http://goo.gl/r9k6tn * Iteratees at Tsuru Capital: various contributions to the hackage iteratee library used in a production trading system Domain: blog.kfish.org, Score: 36, Comments: 12 On Reddit: [17] http://goo.gl/rCTO6n Original: [18] http://goo.gl/PikaAn * Apprendre Haskell vous fera le plus grand bien ! -- LYAH in French Domain: lyah.haskell.fr, Score: 33, Comments: 15 On Reddit: [19] http://goo.gl/pV3jvn Original: [20] http://goo.gl/ixiXWn * Would You Bet $100,000,000 on Haskell? Domain: digitalmars.com, Score: 28, Comments: 44 On Reddit: [21] http://goo.gl/oPI5Kn Original: [22] http://goo.gl/YYeOln * Galois offers Haskell course: The Tao of Functional Programming Domain: corp.galois.com, Score: 26, Comments: 9 On Reddit: [23] http://goo.gl/6HX8Kn Original: [24] http://goo.gl/n7urdn Top StackOverflow Questions * What are Haskell's strictness points? votes: 59, answers: 7 Read on SO: [25] http://goo.gl/5PiDHn * Can someone explain the traverse function in Haskell votes: 14, answers: 3 Read on SO: [26] http://goo.gl/P5WtFn * Why do we have map, fmap and liftM? votes: 13, answers: 1 Read on SO: [27] http://goo.gl/TCRKwn * Does a function like this already exist? (Or, what's a better name for this function?) votes: 12, answers: 4 Read on SO: [28] http://goo.gl/QY6i8n * Question about the ~ and @ operators in Haskell votes: 11, answers: 2 Read on SO: [29] http://goo.gl/pXnV6n * Folding across Maybes in Haskell votes: 8, answers: 5 Read on SO: [30] http://goo.gl/y1ALtn * How is foldl lazy? votes: 7, answers: 4 Read on SO: [31] http://goo.gl/LQAxNn * avoid explicit passing of lookup table votes: 7, answers: 4 Read on SO: [32] http://goo.gl/tKh2wn * Why is [Char]-based input so much slower than the [Char]-based output in Haskell? votes: 7, answers: 1 Read on SO: [33] http://goo.gl/2nuqNn Until next time, Daniel Santa Cruz References 1. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/92680 2. http://permalink.gmane.org/gmane.comp.lang.haskell.general/18935 3. http://permalink.gmane.org/gmane.comp.lang.haskell.general/18936 4. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/92480 5. http://permalink.gmane.org/gmane.comp.lang.haskell.general/18940 6. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/92528 7. https://github.com/ghc/ghc/commit/3db757241ce7fb99c096c30481aefa86bb9855a1 8. http://www.reddit.com/r/haskell/comments/kmxf2/ghci_now_supports_all_toplev… 9. http://twitter.com/#!/bos31337/status/116372971509121025 10. http://www.reddit.com/r/haskell/comments/kmk6q/the_best_ghc_bug_ever/ 11. http://bos.github.com/strange-loop-2011/talk/talk.html#(1) 12. http://www.reddit.com/r/haskell/comments/km2b8/running_a_startup_on_haskell/ 13. http://i.imgur.com/D4QEO.png 14. http://www.reddit.com/r/haskell/comments/koom1/no_chrome_haskell_is_not_dan… 15. http://trac.haskell.org/haskell-platform/wiki/ReleaseTimetable 16. http://www.reddit.com/r/haskell/comments/kk9hl/did_haskell_platform_miss_th… 17. http://blog.kfish.org/2011/09/iteratees-at-tsuru.html 18. http://www.reddit.com/r/haskell/comments/kjem1/iteratees_at_tsuru_capital_v… 19. http://lyah.haskell.fr/ 20. http://www.reddit.com/r/haskell/comments/km1l6/apprendre_haskell_vous_fera_… 21. http://www.digitalmars.com/d/archives/digitalmars/D/Would_You_Bet_100_000_0… 22. http://www.reddit.com/r/haskell/comments/klhln/would_you_bet_100000000_on_h… 23. http://corp.galois.com/haskell-course 24. http://www.reddit.com/r/haskell/comments/kp6as/galois_offers_haskell_course… 25. http://stackoverflow.com/questions/7490768/what-are-haskells-strictness-poi… 26. http://stackoverflow.com/questions/7460809/can-someone-explain-the-traverse… 27. http://stackoverflow.com/questions/7463500/why-do-we-have-map-fmap-and-liftm 28. http://stackoverflow.com/questions/7518589/does-a-function-like-this-alread… 29. http://stackoverflow.com/questions/7506684/question-about-the-and-operators… 30. http://stackoverflow.com/questions/7464208/folding-across-maybes-in-haskell 31. http://stackoverflow.com/questions/7487455/how-is-foldl-lazy 32. http://stackoverflow.com/questions/7504012/avoid-explicit-passing-of-lookup… 33. http://stackoverflow.com/questions/7510078/why-is-char-based-input-so-much-…

1 1

instance Enum Double considered not entirely great?
by Evan Laforge 29 Sep '11

29 Sep '11

So I've been excising occurrences of the [n..m] syntax from my code. The reason is that I had been using [0..5] as a shorthand for [0, 1, 2, 3, 4, 5], mostly in tests. This works for integral types and it appears to work for floating point types. Then I tried switching to a fixed point format, and discovered my mistake. Enum is supposed to enumerate every value between the two points, and the result is memory exhaustion. I had already been switching from enumFrom because they accumulate floating point errors, in favor of a couple of more appropriate functions: -- | Enumerate an inclusive range. Uses multiplication instead of successive -- addition to avoid loss of precision. -- -- Also it doesn't require an Enum instance. range :: (Num a, Ord a) => a -> a -> a -> [a] range start end step = go 0 where go i | val > end = [] | otherwise = val : go (i+1) where val = start + (i*step) -- | Like 'range', but includes the end. range_end :: (Num a, Ord a) => a -> a -> a -> [a] range_end start end step = go 0 where go i | val >= end = [end] | otherwise = val : go (i+1) where val = start + (i*step) -- | Infinite range. range_ :: (Num a) => a -> a -> [a] range_ start step = go 0 where go i = start + (i*step) : go (i+1) So I think the Enum instances for Float and Double are sort of a trap. They misled me into thinking the .. syntax is the range function defaulting to a step of 1, led to precision errors I had to debug then fix (and I've noticed lead to the odd stack overflow question), then led to more disaster when I switched to an Enum instance that lived up to Enum's real purpose. The problem is that the [..] syntax is convenient and tempting, especially for tests, wanting a numeric range (rather than enumeration) is very common, and as far as I know the 'range' function isn't in the standard library. So it seems like one of these things that seem convenient in the short term but come around and bite you later. Using the right functions from the start avoids all that. Is there any support for the idea of removing Enum instances for floating point numbers?

20 80

Much faster complex monad stack based on CPS state
by Nicu Ionita 28 Sep '11

28 Sep '11

Hello list, Starting from this emails (http://web.archiveorange.com/archive/v/nDNOvSM4JT3GJRSjOm9P) I could refactor my code (a UCI chess engine, with complex functions, in which the search has a complex monad stack) to run twice as fast as with even some hand unroled state transformer! So from 23-24 kilo nodes per second it does now 45 to 50 kNps! And it looks like there is still some improvement room (I have to play a little bit with strictness annotations and so on). (Previously I tried specializations, then I removed a lot of polimorphism, but nothing helped, it was like hitting a wall.) Even more amazingly is that I could program it although I cannot really understand the Cont & ContT, but just taking the code example from Ryan Ingram (newtype ContState r s a = ...) and looking a bit at the code from ContT (from the transformers library), and after fixing some compilation errors, it worked and was so fast. I wonder why the transformers library does not use this kind of state monad definition. Or does it, and what I got is just because of the unrolling? Are there monad (transformers) libraries which are faster? I saw the library kan-extensions but I did not understand (yet) how to use it. Nicu

6 8

network package Windows co-maintainer/buildbot needed (Was: network 2.3.05 on windows 7 with ghc-7.2.1)
by Johan Tibell 28 Sep '11

28 Sep '11

Let me take this opportunity to ask for a co-maintainer that can help me keep the network package working on Windows. I don't have easy access to a Windows machine (or even VM) anymore so testing on Windows is hard. What I'd really like is a buildbot that builds the following Jenkins job as a "slave" node: http://ci.johantibell.com/job/network/ config.xml: <?xml version='1.0' encoding='UTF-8'?> <matrix-project> <actions/> <description></description> <keepDependencies>false</keepDependencies> <properties/> <scm class="hudson.plugins.git.GitSCM"> <configVersion>2</configVersion> <userRemoteConfigs> <hudson.plugins.git.UserRemoteConfig> <name>origin</name> <refspec>+refs/heads/*:refs/remotes/origin/*</refspec> <url>https://github.com/haskell/network.git</url> </hudson.plugins.git.UserRemoteConfig> </userRemoteConfigs> <branches> <hudson.plugins.git.BranchSpec> <name>stable</name> </hudson.plugins.git.BranchSpec> </branches> <recursiveSubmodules>false</recursiveSubmodules> <doGenerateSubmoduleConfigurations>false</doGenerateSubmoduleConfigurations> <authorOrCommitter>false</authorOrCommitter> <clean>false</clean> <wipeOutWorkspace>false</wipeOutWorkspace> <pruneBranches>false</pruneBranches> <remotePoll>false</remotePoll> <buildChooser class="hudson.plugins.git.util.DefaultBuildChooser"/> <gitTool>Default</gitTool> <browser class="hudson.plugins.git.browser.GithubWeb"> <url>https://github.com/haskell/network/</url> </browser> <submoduleCfg class="list"/> <relativeTargetDir></relativeTargetDir> <excludedRegions></excludedRegions> <excludedUsers></excludedUsers> <gitConfigName></gitConfigName> <gitConfigEmail></gitConfigEmail> <skipTag>false</skipTag> <scmName></scmName> </scm> <canRoam>true</canRoam> <disabled>false</disabled> <blockBuildWhenDownstreamBuilding>false</blockBuildWhenDownstreamBuilding> <blockBuildWhenUpstreamBuilding>false</blockBuildWhenUpstreamBuilding> <triggers class="vector"> <hudson.triggers.SCMTrigger> <spec>*/5 * * * *</spec> </hudson.triggers.SCMTrigger> </triggers> <concurrentBuild>false</concurrentBuild> <axes> <hudson.matrix.TextAxis> <name>compiler</name> <values> <string>ghc-6.10.4</string> <string>ghc-6.12.3</string> <string>ghc-7.0.3</string> </values> </hudson.matrix.TextAxis> </axes> <builders> <hudson.tasks.Shell> <command>cabal install -w $compiler --only-dependencies --enable-tests cabal clean autoreconf cabal configure -w $compiler --enable-tests cabal build cabal test cabal sdist</command> </hudson.tasks.Shell> </builders> <publishers> <hudson.tasks.Mailer> <recipients>johan.tibell(a)gmail.com</recipients> <dontNotifyEveryUnstableBuild>false</dontNotifyEveryUnstableBuild> <sendToIndividuals>false</sendToIndividuals> </hudson.tasks.Mailer> </publishers> <buildWrappers/> <runSequentially>false</runSequentially> </matrix-project>

1 0

Binding a socket to all interfaces
by Michael Snoyman 28 Sep '11

28 Sep '11

Hi, One of the recurring issues that comes up in Warp is binding to IPv4 versus IPv6 hosts. Our current code is available at [1]. It was updated to look like that in this commit [2] in order to support both IPv4 and IPv6 hosts by default. However, now it seems than on Debian and FreeBSD, it *only* responds to IPv6 by default[3][4]. I'm frankly stumped at this point on how to have our cake and eat it too. Does anyone have an idea of the correct incantation to get Warp to do the Right Thing(tm) here? And if not, is there any advice on sensible default behavior? I'm considering allowing a few special host values: * "*" (default, what we have now): Make this bind to IPv4 * "ipv4": Again, bind to IPv4. Guaranteed not to change in the future * "ipv6": Bind to IPv6. Michael [1] https://github.com/yesodweb/wai/blob/master/warp/Network/Wai/Handler/Warp.h… [2] https://github.com/snoyberg/warp/commit/02c1396c86e3fceb48cbe7df58cb631c804… [3] https://github.com/snoyberg/warp/issues/9 [4] http://stackoverflow.com/questions/7486257/yesod-devel-server-only-listenin…

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Parsing binary data question
by Michael Oswald 28 Sep '11

28 Sep '11

Hello all, I am currently working on parser for some packets received via the network. The data structure currently is like that: data Value = ValUInt8 Int8 | ValUInt16 Int16 | ValUInt32 Int32 -- more datatypes data Parameter = Parameter { paramName :: String, paramValue :: Value } | ParameterN { paramName :: String, paramValue :: Value }deriving (Show) data TCPacket = TCPacket { tcAPID :: Word16, tcType :: Word8, tcSubType :: Word8, tcParameters :: [Parameter] } The output should a parsed packet (I am using cereal for this). The packet structure can vary depending on the type and the configuration, so I have a function which takes a TCPacket as "input template" which has already the correct list of parameters which are then parsed: parseTCPacket :: Word16 -> Word8 -> Word8 -> ByteString -> TCPacket -> TCPacket parseTCPacket apid t st pktData tmplate = TCPacket apid t st params where tmplParams = (tcParameters tmplate) params = zipWith (\p v -> p {paramValue = v} ) tmplParams values' values = map paramValue tmplParams values' = binValues values (pktData pusPkt) getBinGet :: Value -> Get Value getBinGet (ValInt8 _) = getWord8 >>= \x -> return $ ValInt8 $ fromIntegral x getBinGet (ValInt16 _) = getWord16be >>= \x -> return $ ValInt16 $ fromIntegral x -- many more datatypes getBinValues :: [Value] -> Get [Value] getBinValues inp = mapM getBinGet inp binValues :: [Value] -> ByteString -> ([Value], B.ByteString) binValues inp bytes = case runGet (getBinValues inp) bytes of Left err -> throw $ DecodeError ("binValues: " ++ err) Right x -> x This works quite well and does what I want. Now I have the problem that there are some parameters, which could be so-called "group repeaters" (the ParameterN constructor above). This means, that if such a parameter N is encountered during parsing (it has to be an int type), all following parameters are repeated N times with possible nesting. So for example if the template (where the values are all 0) is like this: [Parameter "Param1" (ValUInt32 0), ParameterN "N1" (ValUInt8 0), Parameter "Param2" (ValUint16 0), ParameterN "N2" (ValUint8 0), Parameter "Param3" (ValUint8 0)] Which means there is a group for the last 3 parameters which is repeated N1 times which contains another group which is repeated N2 times. If binary data based on the template above would be like this (datatypes omitted): 10, 2, 439, 2, 12, 13, 65535, 2, 22, 23 then a valid packet after parsing would be: [Parameter "Param1" (ValUint32 10), ParameterN "N1" (ValUint8 2), Parameter "Param2" (ValUint16 439), ParameterN "N2" (ValUint8 2), Parameter "Param3" (ValUint8 12), Parameter "Param3" (ValUint8 13), Parameter "Param2" (ValUint16 65535), ParameterN "N2" (ValUint8 2), Parameter "Param3" (ValUint8 22), Parameter "Param3" (ValUint8 23)] Now I am a bit lost on how to implement such a parser. It would be much easier if the structure would be already encoded in the binary data, but I have to stick to this template approach. I have some C++ parser which does this but of course it's very imperative and a little bit quirky implemented, so if anybody has an idea on how to proceed (cereal, attoparsec whatever), please tell me. lg, Michael

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I for one welcome our new Robotic Overlords
by Jeremy Shaw 28 Sep '11

28 Sep '11

When the robots take over, do you want them to be developed using a sane language like Haskell or Agda? Or some dangerous untyped OO language? I think the answer is obvious. The question is, "How?". The robots will not be developed by us, but by the children of today. So, we must reach their pure minds before they have been unsafely coerced by the evil unbelievers who do not worship the gods λ, Π, and ω. My long term vision is: A company which produces an extensible robotics platform for children and adults ages 8 and up. The platform would be very open, extensible, and hackable. The robotic programming languages would be based around concepts like functional reactive programming, dependent types, etc. Children would begin with a simple FRP language to control the robot. They would solve simple problems like "go forward until an object is encountered." As the young masters grow, they can tackle more difficult problems such as maze solving. Even later they can delve into more advanced subjects like computer vision, speech recognition and synthesis, or mind control rays. The short term vision can be summarized in one word "leverage". We need to find an existing robotic platform which can be easily targeted somehow using Haskell or Agda. Perhaps something that can be targeted using atom or lava? Maybe something Arduino based? I have created a wiki page here to record your suggestions and ideas: http://haskell.org/haskellwiki/RoboticOverlords The requirements now are something that is: - hackable/open - easily obtained - reasonable in price - can easily be targeted via Haskell The only candidate I know of so far is lego mindstorms via the NXT package on hackage, Though some could argue that lego mindstorms are not reasonably priced. http://hackage.haskell.org/package/NXT Let's here your ideas! - jeremy

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Fwd: [Haskell] getting started
by Ivan Lazar Miljenovic 28 Sep '11

28 Sep '11

It helps if I actually CC the right mailing list... ---------- Forwarded message ---------- From: Ivan Lazar Miljenovic <ivan.miljenovic(a)gmail.com> Date: 28 September 2011 20:02 Subject: Re: [Haskell] getting started To: haskell <shubhammaheshwariy(a)gmail.com> Cc: cafe(a)haskell.org On 28 September 2011 19:56, haskell <shubhammaheshwariy(a)gmail.com> wrote: > i am new to haskell can you tell me the softwares to install in haskell > i have install hugs emacs > but when i write any code it gives same error can you help me start i have > lekash too i have installed some more packages Sending this over to the haskell-cafe(a)haskell.org mailing list (as that is where discussions take place, haskell(a)haskell.org is for announcements). You may wish to try the beginners mailing list however: http://www.haskell.org/mailman/listinfo/beginners If you want help, try providing the errors. However, I would recommend that you install the Haskell Platform instead of Hugs: http://hackage.haskell.org/platform/ -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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[ANN] crypto-api-tests
by Thomas DuBuisson 28 Sep '11

28 Sep '11

The crypto-api test modules have been split out into their own package, crypto-api-tests. Additionally, the tests now use the test-framework package. This should make it much easier for hash/cipher maintainers to integrate into their existing testing infrastructure. For example: $ cabal update ; cabal install cryptocipher crypto-api crypto-api-tests {- BEGIN CODE -} import Test.Framework import Test.AES (makeAESTests) import Crypto.Cipher.AES (AES128) main = do ts <- makeAESTests (a :: AES128) defaultMain ts {- END CODE -} $ ghc test.hs ; ./test ... snip ... OFBVarTxt128d.txt-125: [OK] OFBVarTxt128d.txt-126: [OK] OFBVarTxt128d.txt-127: [OK] Block Cipher tests (ident): ECBEncDecID: [OK, passed 100 tests] CBCEncDecID: [OK, passed 100 tests] CFBEncDecID: [OK, passed 100 tests] OFBEncDecID: [OK, passed 100 tests] CTREncDecID: [OK, passed 100 tests] Block Cipher tests (lazy/string bytestring equality): ECBStringLazyEq: [OK, passed 100 tests] CBCStrictLazyEq: [OK, passed 100 tests] CFBStrictLazyEq: [OK, passed 100 tests] OFBStrictLazyEq: [OK, passed 100 tests] CTRStrictLazyEq: [OK, passed 100 tests] Properties Test Cases Total Passed 10 2272 2282 Failed 0 0 0 Total 10 2272 2282 Patches for more algorithms and/or property tests for classes of algorithms are certainly welcome. Cheers, Thomas

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emacs literate haskell mode
by Mathijs Kwik 28 Sep '11

28 Sep '11

Hi all, I'm using haskell-mode for emacs and I'm using it to open a literate haskell file which uses latex. This works fine, haskell code has syntax highlighting, and special symbols like lambda get used. However, the latex itself is dull and gree, no highlighting/coloring there. Does anyone know if it's possible to turn on latex highlighting in literate haskell mode? I tried switching to latex-mode, which does the trick (but it chokes on the haskell code inbetween), so I'm pretty sure emacs has everything it needs, but haskell-mode needs to enable this somehow. Any help would be great. Greetings, Mathijs

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Re: [Haskell-cafe] mapM is supralinear?
by John Lato 27 Sep '11

27 Sep '11

> From: Daniel Fischer <daniel.is.fischer(a)googlemail.com> > > On Friday 09 September 2011, 00:41:11, Roman Cheplyaka wrote: >> * Ertugrul Soeylemez <es(a)ertes.de> [2011-09-07 16:20:03+0200] >> >> > In general it's a bad idea to use mapM over IO. >> >> Could you explain why? > > Take it with a grain of salt, there's nothing necessarily wrong with using > mapM over IO on short lists. Agreed. Whenever I'd like to use mapM (or any other function for which a *M_ is available), I've found the following rules helpful: 1. If I can guarantee the list is short (~ n<=20), go ahead and use mapM 2. Otherwise use mapM_, foldM_, or foldM if a real reduction is possible (i.e. not "foldM snocM []"). Step 2 sometimes requires changing my design, but it's always been for the better. `mapM_` tends to require more pipeline composition, so it's leveraging the language's strengths. This has served me well, especially in IO, but in other monads as well. John L.

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9th Ghent Functional Programming Group meeting on Tuesday, the 4th of October, 2011
by Jasper Van der Jeugt 27 Sep '11

27 Sep '11

Hello all, We are glad to invite you to our 9th GhentFPG [1] meeting, which takes place on Thursday, the 4th of October, 2011 at 19:30 in the Technicum building of Ghent University. You do not have to be a Functional Programming guru to attend, everyone eager to learn is welcome. As before, the electronic sliding doors will be locked, but a phone number that you can call to get in will be provided at the doors on the far left of the building. The program is as follows: First, we will have a talk by Jurriën Stutterheim, from Utrecht: Snap Framework [2] is a relatively young, but very promising and already quite popular Haskell web framework. Its upcoming 0.6 release has seen a major redesign in the way you write (reusable) components for the framework using so-called snaplets. In this talk, we will look at how you can write snaplets and how you can put them together to create modular web applications. Then, we will have a number of lightning talks in which the following projects are presented: - hCole-server [3], a web interface to a framework for compiler optimizations (Andy Georges); - GA [4], a library to write genetic algorithms in Haskell (Kenneth Hoste); - websockets [5], a Haskell library for writing WebSocket-capable servers (Jasper Van der Jeugt). If you would also like to give a lightning talk (15 mins), please contact us and we will add you to this list. Afterwards, we will have some drinks at a local bar. [1]: http://www.haskell.org/haskellwiki/Ghent_Functional_Programming_Group [2]: http://snapframework.com/ [3]: http://github.com/itkovian/hcole-server [4]: http://github.com/boegel/GA [5]: http://github.com/jaspervdj/websockets Hoping to see you there, The GhentFPG organizing commitee

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A Crypto-API-Tests package
by Thomas DuBuisson 27 Sep '11

27 Sep '11

FYI, since I figure you three are the ones interested in this right now: I'll be releasing crypto-api-tests [1] to hackage someday (this weekend?). If you want to give it a spin or add KATS before the first release then feel free. OTOH, it's not like I'd stop accepting patches after release 0.1. Cheers, Thomas [1] https://github.com/TomMD/crypto-api-tests

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which tags program should I use?
by Henry Laxen 26 Sep '11

26 Sep '11

Dear Group, I have a simple question, that as far as I can tell, has never really been well answered. I would like to generate TAGS files for haskell source. Reading the http://www.haskell.org/haskellwiki/Tags page suggests using :etags in GHCI or hasktags, or gasbag. Of the three, hasktags comes closest to "working" but it has (for me) a major inconvenience, namely it finds both function definitions and type signatures, resulting in two TAGS entries such as: ./Main.hs,63 module Main where6,7 main ::24,25 main =25,26 Now when I do an emacs find-tag (I use icicles) I will always have to choose which tag I want to visit, and the completion buffer contains something like: main :: hs/Main.hs main = hs/Main.hs Granted, this is a minor (and very specialized) complaint, but if hasktags were to select only ONE of either the type signature (my first choice) or the function definition, (if no type signature) this annoyance would disappear. I also tried using etags, which I think would work, but it seems to have one killer bug (feature), namely that it dies if it finds an uninterpreted import: when (not is_interpreted) $ let mName = GHC.moduleNameString (GHC.moduleName m) in ghcError (CmdLineError ("module '" ++ mName ++ "' is not interpreted")) I think it would work much better if it just warned you, instead of dying. This makes it unusable any time you import something precompiled. Now some looking at the README of hasktags leads me to: "In the past this tool was distributed with ghc. I forked and added some features. hasktags itself was moved out of the ghc repository. Then I only verified that my fork finds at least as much tags as the one forked by Igloo." That makes me feel a little queasy. A google search for hasktags igloo turns up http://hackage.haskell.org/trac/ghc/ticket/1508 whose title is "hasktags program needs replacement" which makes me feel even more queasy. So I guess my question is, what are us disciples of "the one true editor" to do? Thanks in advance for you sage advice. Best wishes, Henry Laxen

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Attoparsec: Limiting Parsers to N Bytes, or Combing Parsers?
by Michael Craig 26 Sep '11

26 Sep '11

Suppose we want to parse a 24-bit hex color value: input :: ByteString input = "af093c blah blah blah" type Color = (Word8, Word8, Word8) Attoparsec.Char8 exports a nice hexadecimal parser, but it consumes all available hex-flavored input. I'd like to make it consume exactly two bytes, so I could write my color parser like this: color :: Parser Color color = do r <- hex2 g <- hex2 b <- hex2 return $ Color (r, g, b) hex2 :: Parser Word8 hex2 = ??? So my question is "how do I write hex2?" I could easily rewrite hexadecimal, but it would be nicer to reuse its hex-handling logic. Best, Mike S Craig (908) 328 8030

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Job opportunities at Citrix Systems (Cambridge, UK)
by Mike McClurg 26 Sep '11

26 Sep '11

Hi folks, I just wanted to let everyone know that Citrix is hiring developers to work on the OCaml-based XenAPI toolstack. We are looking to recruit top-class engineers to work on the toolstack; applicants must have a good knowledge of data structures and algorithms, experience of programming in the context of large systems and general aesthetic good taste when it comes to code and architecture. Our code base is significant and varied: over 130,000 lines of OCaml, solving problems ranging from the low-level (Xen hypercalls) to the high-level (resource pool management), to the compiler-driven (generating language bindings for our Xen datamodel). Our ideal candidate will have: * significant experience with applications programming in high-level functional languages (such as OCaml) * an aptitude for implementing (and reasoning about) complex concurrent and distributed systems * the skills required to contribute to both the architectural design and day-to-day development of a large code-base * strong communication skills and problem solving ability * a determination to deliver clean and reliable solutions that meet our customers' needs So if you want to tackle interesting and challenging programming problems and contribute to an innovative, fast-growing product that is already used by tens of thousands of customers across the world, please don't hesitate to send me your CV. Thanks, Mike McClurg PS: Please note that you must have UK right to work. Here are the official job postings, but if you apply please send me your CV directly. * Req #11673 - Software Development Engineer: http://careers.peopleclick.com/careerscp/client_citrix/emea_region/jobDetai… * Req #11897 - Senior Software Developer: http://careers.peopleclick.com/careerscp/client_citrix/emea_region/jobDetai… And here are some links to our company, products and open source projects and code. * The Xen Hypervisor - http://xen.org/ * Citrix XenServer - http://www.citrix.com/English/ps2/products/product.asp?contentID=683148 * Our GitHub account - https://github.com/xen-org

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SPECIALIZE in the presence of constraints
by Nicu Ionita 25 Sep '11

25 Sep '11

Hallo List, I can't understand how pragma SPECIALIZE works in the presence of constraints. I have 2 modules, one which defines a general search framework, and one which implements it in a concrete context. The general module defines functions like: {-# SPECIALIZE pvQSearch :: Node (Game m) Move Int => Int -> Int -> Int -> Search (Game m) Move Int Int #-} pvQSearch :: Node m e s => s -> s -> Int -> Search m e s s pvQSearch a b c = do ... while the implementation uses concrete data types Move and Int (for e and s respectively) and defines instances and other types (like the polimorphic type Game m, where m is a monad). Node m e s is a class and the instance Node (Game m) Move Int is defined in the implementation module. From outside this construct is used by calling a generic search function, but giving parameters which match the implementation (i.e. with Move and Int for e and s, for example). Now what I don't understand: 1. how can the compiler (here ghc) know which function to expose as the correct generic search function? There must be two search functions generated, one generic and its specialization. Does the module export both and later the linker chooses the correct one, when the client module is known? 2. how can I know that the specialization is really used? When I have constraints, will the specializations be generated in the assumption that the constraint is matched? When will be this match checked? My problem is that, with or without specializations, the performance of the code is the same - so I doubt the specializations are used. Thanks, Nicu

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Is there still at list of active Haskell projects
by Vasili I. Galchin 25 Sep '11

25 Sep '11

Hello, On http://www.haskell.org I didn't see a list of active Haskell projects. ?? Thanks, Bill

3 2

A Missing Issue on Second Generation Strategies
by Burak Ekici 24 Sep '11

24 Sep '11

Dear List, I am trying to parallelize RSA encryption and decryption by using below manner, but when I run executable output file with "+RTS -s -N2" command on Windows 7, output stats say 4 sparks are being created however none of them converted into real OS threads. -- SPARKS :4 (0 converted, 4 pruned) -- I was thinking that the problem could occur due to lack of forcing parallelization but, as far as I know 'rdeepseq' works for that aim. Briefly, I could not solve the issue why parallelization was not being implemented. I would be appreciated if any of you shed a light on the issue that I missed. Here is the mentioned part of code: split4ToEnc :: RSAPublicKey -> [Integer] -> [Integer] split4ToEnc (PUB n e) [] = [] split4ToEnc (PUB n e) (x:xs) = ((ersa (PUB n e) secondPart2) ++ (ersa (PUB n e) secondPart1) ++ (ersa (PUB n e) firstPart2) ++ (ersa (PUB n e) firstPart1)) `using` strategy where firstPart1 = fst (Main.splitAt((length (x:xs)) `div` 4) (fst(Main.splitAt ((length (x:xs)) `div` 2) (x:xs)))) firstPart2 = snd (Main.splitAt((length (x:xs)) `div` 4) (fst(Main.splitAt ((length (x:xs)) `div` 2) (x:xs)))) secondPart1 = fst (Main.splitAt((length (x:xs)) `div` 4) (snd(Main.splitAt ((length (x:xs)) `div` 2) (x:xs)))) secondPart2 = snd (Main.splitAt((length (x:xs)) `div` 4) (snd(Main.splitAt ((length (x:xs)) `div` 2) (x:xs)))) strategy res = do a <- rpar (ersa (PUB n e) (firstPart1) `using` rdeepseq) b <- rpar (ersa (PUB n e) (firstPart2) `using` rdeepseq) c <- rpar (ersa (PUB n e) (secondPart1) `using` rdeepseq) d <- rpar (ersa (PUB n e) (secondPart2) `using` rdeepseq) rdeepseq res Thanks a lot, Burak.

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Fwd: problem with cabal install MissingH-1.1.1.0
by Ozgur Akgun 24 Sep '11

24 Sep '11

Ooops, apparently I forgot to reply to the list. Sorry. ---------- Forwarded message ---------- From: Ozgur Akgun <ozgurakgun(a)gmail.com> Date: 22 September 2011 16:49 Subject: Re: [Haskell-cafe] problem with cabal install MissingH-1.1.1.0 To: Mariano Cortesi <mcortesi(a)gmail.com> Hi Mariano. On 22 September 2011 12:48, Mariano Cortesi <mcortesi(a)gmail.com> wrote: > I'm with mac OS X lion, ghc version 7.2.1 > and when a i try to install MissingH version 1.1.1.0 it fails with > > [24 of 47] Compiling Data.BinPacking ( src/Data/BinPacking.hs, > dist/build/Data/BinPacking.o ) > > src/Data/BinPacking.hs:45:6: > Illegal datatype context (use -XDatatypeContexts): (Num size, > This is weird, because on OS X Lion, and with the following versions, it doesn't fail for me: The Glorious Glasgow Haskell Compilation System, version 7.2.1 cabal-install version 0.10.2 using version 1.12.0 of the Cabal library Nevertheless, you can try the following to do what cabal asks you to do: cabal install --ghc-option=-XDatatypeContexts Which will give a warning, but should succeed anyway. Hope this helps, Ozgur -- Ozgur Akgun

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Where is SNMap for stable names?
by Sean Leather 24 Sep '11

24 Sep '11

There is an abstract type called SNMap for stable names referred to in [1]. This has apparently disappeared from GHC a long time ago. Is it still available somewhere, or is there a suitable replacement for it? Regards, Sean [1] "Stretching the storage manager: weak pointers and stable names in Haskell" - http://research.microsoft.com/apps/pubs/default.aspx?id=67497

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