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installing GSL packages on Windows
by Sean Matthews 28 Oct '15

28 Oct '15

I'm currently trying to install the gsl packages (in particular hmatrix-gsl) for a Windows 7/32 system. I've been using a fairly stripped down version of the GHC for a while, but now that I'm trying to install packages like this, I'm running into problems. Anyway, I have installed pkg-config, etc. and I believe I've got the various bits of gsl installed. However cabal is still failing at attaching this to the appropriate haskell modules, at what looks to be very near the end, and suggstions for what I can try to get things to finish would be welcome. Below is the output as generated by cabal (this is the result of several iterations and systematic googling, but google seems to have run out on me). All suggestions, advice, etc. very welcome, Sean Matthews > cabal install hmatrix-gsl --extra-include-dirs="C:\Users\sematthews\My Software\gsl-1.15-dev-win32\include" --extra-lib-dirs="C:\Users\sematthews\My Software\gsl-1.15-dev-win32\lib" > cabal install hmatrix-gsl --extra-include-dirs="C:\Users\sematthews\My Software\gsl-1.15-dev-win32\include" --extra-lib-dirs="C:\Users\sematthews\My Software\gsl-1.15-dev-win32\lib" > Resolving dependencies... > Configuring hmatrix-gsl-0.17.0.0... > Building hmatrix-gsl-0.17.0.0... > Failed to install hmatrix-gsl-0.17.0.0 > Build log ( C:\Users\sematthews\AppData\Roaming\cabal\logs\hmatrix-gsl-0.17.0.0.log ): > Building hmatrix-gsl-0.17.0.0... > Preprocessing library hmatrix-gsl-0.17.0.0... > [ 1 of 17] Compiling Graphics.Plot ( src\Graphics\Plot.hs, dist\build\Graphics\Plot.o ) > [ 2 of 17] Compiling Numeric.GSL.Internal ( src\Numeric\GSL\Internal.hs, dist\build\Numeric\GSL\Internal.o ) > [ 3 of 17] Compiling Numeric.GSL.Integration ( src\Numeric\GSL\Integration.hs, dist\build\Numeric\GSL\Integration.o ) > [ 4 of 17] Compiling Numeric.GSL.Fourier ( src\Numeric\GSL\Fourier.hs, dist\build\Numeric\GSL\Fourier.o ) > [ 5 of 17] Compiling Numeric.GSL.Polynomials ( src\Numeric\GSL\Polynomials.hs, dist\build\Numeric\GSL\Polynomials.o ) > [ 6 of 17] Compiling Numeric.GSL.Minimization ( src\Numeric\GSL\Minimization.hs, dist\build\Numeric\GSL\Minimization.o ) > [ 7 of 17] Compiling Numeric.GSL.Root ( src\Numeric\GSL\Root.hs, dist\build\Numeric\GSL\Root.o ) > [ 8 of 17] Compiling Numeric.GSL.Fitting ( src\Numeric\GSL\Fitting.hs, dist\build\Numeric\GSL\Fitting.o ) > [ 9 of 17] Compiling Numeric.GSL.ODE ( src\Numeric\GSL\ODE.hs, dist\build\Numeric\GSL\ODE.o ) > [10 of 17] Compiling Numeric.GSL.Interpolation ( src\Numeric\GSL\Interpolation.hs, dist\build\Numeric\GSL\Interpolation.o ) > [11 of 17] Compiling Numeric.GSL.LinearAlgebra ( src\Numeric\GSL\LinearAlgebra.hs, dist\build\Numeric\GSL\LinearAlgebra.o ) > [12 of 17] Compiling Numeric.GSL.SimulatedAnnealing ( src\Numeric\GSL\SimulatedAnnealing.hs, dist\build\Numeric\GSL\SimulatedAnnealing.o ) > [13 of 17] Compiling Numeric.GSL.Vector ( src\Numeric\GSL\Vector.hs, dist\build\Numeric\GSL\Vector.o ) > [14 of 17] Compiling Numeric.GSL.IO ( src\Numeric\GSL\IO.hs, dist\build\Numeric\GSL\IO.o ) > [15 of 17] Compiling Numeric.GSL.Random ( src\Numeric\GSL\Random.hs, dist\build\Numeric\GSL\Random.o ) > [16 of 17] Compiling Numeric.GSL.Differentiation ( src\Numeric\GSL\Differentiation.hs, dist\build\Numeric\GSL\Differentiation.o ) > [17 of 17] Compiling Numeric.GSL ( src\Numeric\GSL.hs, dist\build\Numeric\GSL.o ) > In-place registering hmatrix-gsl-0.17.0.0... > setup-Simple-Cabal-1.22.4.0-i386-windows-ghc-7.10.2.exe: > 'C:\Users\sematthews\My Software\Haskell\bin\ghc-pkg.exe' exited with an > error: > hmatrix-gsl-0.17.0.0: Warning: haddock-interfaces: > C:\Users\SEMATT~1\AppData\Local\Temp\cabal-tmp-8196\hmatrix-gsl-0.17.0.0\dist\doc\html\hmatrix-gsl\hmatrix-gsl.haddock > doesn't exist or isn't a file > hmatrix-gsl-0.17.0.0: Warning: haddock-html: > C:\Users\SEMATT~1\AppData\Local\Temp\cabal-tmp-8196\hmatrix-gsl-0.17.0.0\dist\doc\html\hmatrix-gsl > doesn't exist or isn't a directory > hmatrix-gsl-0.17.0.0: library-dirs: /usr/local/lib is a relative path which > makes no sense (as there is nothing for it to be relative to). You can make > paths relative to the package database itself by using ${pkgroot}. (use > --force to override) > hmatrix-gsl-0.17.0.0: include-dirs: /usr/local/include is a relative path > which makes no sense (as there is nothing for it to be relative to). You can > make paths relative to the package database itself by using ${pkgroot}. (use > --force to override) > cabal: Error: some packages failed to install: > hmatrix-gsl-0.17.0.0 failed during the building phase. The exception was: > ExitFailure 1 -- Sean Matthews seanmatthews1(a)gmail.com / +49 1515 800 1901

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No warn on type in expression?
by amindfv＠gmail.com 28 Oct '15

28 Oct '15

An expression like: x = 5 :: Int Fails with -Wall -Werror, with "Top-level binding with no type signature". I propose we don't warn on bindings whose entire expressions are typed. This cuts in half the line noise for trivial variable values. Tom

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GHC can't find DLL dependencies on Windows
by Ryan Scott 28 Oct '15

28 Oct '15

I recently decided to try out a simple diagrams-cairo project on Windows 8 (x86_64) to discover that GHC (7.10.2, to be specific) acts rather bizarrely when dealing with external DLL dependencies. To start, I downloaded MSYS2 [1], installed the libraries needed for cairo and pango to work [2], installed diagrams-cairo [3], and tried running a simple diagrams program: module Main (main) where import Diagrams.Prelude import Diagrams.Backend.Cairo.CmdLine main :: IO () main = mainWith (circle 1 :: Diagram B) like so from MSYS2: runghc Cairo.hs -o circle.svg -w 400 And it worked. Hooray! Now, I normally use cmd.exe/PowerShell for most of my Windows command-line tasks, so later I tried invoking the above command on PowerShell, only to be greeted with an error message: $ runghc.exe .\Cairo.hs -o circle.svg -w 400 Cairo.hs: warning: _tzset from msvcrt is linked instead of __imp__tzset Cairo.hs: libcairo-2: The specified procedure could not be found. Cairo.hs: <command line>: can't load .so/.DLL for: libcairo-2.dll (addDLL: could not load DLL) PowerShell, alas, couldn't find libcairo-2.dll when MSYS2 had no trouble whatsoever. I realized that MSYS2 stores all of its MinGW-related DLL files in a special location (C:\msys64\mingw64\bin). This can be observed by running cygcheck on the executable: $ C:\msys64\usr\bin\cygcheck.exe .\Cairo.exe C:\Users\ryanscot\Documents\Hacking\Haskell\Cairo.exe cygcheck: track_down: could not find libcairo-2.dll cygcheck: track_down: could not find libglib-2.0-0.dll cygcheck: track_down: could not find libgobject-2.0-0.dll cygcheck: track_down: could not find libpango-1.0-0.dll cygcheck: track_down: could not find libpangocairo-1.0-0.dll ... After reading about DLL search paths in Windows [4], I got the impression that I could add C:\msys64\mingw64\bin to my PATH, and then executables would look for DLLs there. Adding C:\msys64\mingw64\bin to my PATH seemed to make cygcheck happy: $ C:\msys64\usr\bin\cygcheck.exe .\Cairo.exe C:\Users\ryanscot\Documents\Hacking\Haskell\Cairo.exe C:\msys64\mingw64\bin\libcairo-2.dll ... But invoking runghc Cairo.exe on PowerShell still fails with the same error message! For the life of me, I can't figure out what kind of sorcery MSYS2 is doing to make C:\msys64\mingw64\bin visible to the DLL search path from GHC. The only way I can trick PowerShell into seeing libcairo-2.dll is to (1) Copy libcairo-2.dll directly to C:\Windows\System32, or (2) Invoke SetDllDirectory("C:\msys64\mingw64\bin") [5] from a PowerShell startup script Neither of these options are very satisfying, since (1) has massive security implications, and (2) only works when you have one external DLL directory (if you called SetDllDirectory again with a different directory, it overrides the first one). I know there are folks out there who have managed to get diagrams working on Windows, so can someone let me know if I'm doing something wrong? Ryan S. ----- [1] http://msys2.github.io/ [2] pacman -S mingw-w64-x86_64-cairo mingw-w64-x86_64-pango 1.38.1-1 [3] cabal install diagrams-cairo [4] https://msdn.microsoft.com/en-us/library/ms682586.aspx#search_order_for_des… [5] https://msdn.microsoft.com/en-us/library/windows/desktop/ms686203%28v=vs.85…

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best practice for lifting of IO and could lifting be automated?
by Oleg 28 Oct '15

28 Oct '15

Dimitri DeFigueiredo wrote: > Imagine I need to read a .CSV file which may or may not contain column > titles on its first line. I'm not interested in the column titles, I > just want the rest of the file. I am provided a library function to read > the contents of the file (using a "callback"). The library author > provided this function in the IO monad. > withCSV :: FilePath -> (Handle -> IO r) -> IO r > withCSV path action = do > putStrLn "opening file" > h <- openFile path ReadWriteMode > r <- action h > hClose h > putStrLn "file closed" > return r > The problem arises because I also want to use the ReaderT monad > transformer. My environment information will tell me > whether or not to disregard the first (i.e. column title) line. For this particular example, the answer is easy: If you have the IO monads, you have the Reader monad, and the State/Writer as well. This is just an IORef. > getFileContents :: IO String > getFileContents = do > ref <- newIORef False > withCSV "data.csv" (myReadFile ref) > where > myReadFile :: IORef Bool -> Handle -> IO String > myReadFile ref handle = do > header <- readIORef ref -- ask --- OOOPPSss!!! FAIL! Can't ask. > case header of > False -> return "" > True -> hGetLine handle -- skip first line > text <- hGetContents handle > return text Using just IO, you can get State, Reader, Writer, and Exception (and in a modular way!) As to you general question, I will and do advocating abandoning monad transformers altogether. The paper on extensible effects demonstrated a new solution to the MonadCatchIO problem that solved the long-standing issue of discarding state upon exception. See Sec 6 of http://okmij.org/ftp/Haskell/extensible/more.pdf

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haskell-ide repository name
by Alan & Kim Zimmerman 28 Oct '15

28 Oct '15

At the moment the repository/project is called haskell-ide This leads to the impression that it is an IDE. It is actually a backend/server to provide services for an IDE We are considering changing the name. The options are haskides / ghc-ide-daemon / ghc-ide-service / ghc-ide-engine Please cast your vote at http://strawpoll.me/5842105 Thanks Alan

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asked for a mentor for some math exercises
by Roelof Wobben 28 Oct '15

28 Oct '15

Hello, I try to learn Haskell by the Craft of Functional programming book. But on Chapter 4 Designing there are a lot of very math questions which I do not understand. Is there someone who wants to be a volunteerbasis a mentor for me for this sort of problems. Regards, Roelof

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Cabal depend on local package with foreign dependencies
by Richard Lewis 27 Oct '15

27 Oct '15

Hi there, I have two libraries that I'm working on, packageA and packageB. packageA was written some time ago and depends on a foreign C library, libfoo, which I also wrote and which is installed in a non-standard location. packageB depends on packageA and is new and under active development. I have the following things, then: - libfoo is installed in ~/.local/lib, with includes in ~/.local/include/foo - packageA is in ~/src/packageA - packageB is in ~/src/packageB packageA has a .cabal file which includes: library build-depends: base, ... exposed-modules: A include-dirs: /home/richard/.local/include extra-lib-dirs: /home/richard/.local/lib executable testA ... extra-lib-dirs: /home/richard/.local/lib extra-libraries: foo I've created a cabal sandbox in packageA and I can successfully build it. Now, packageB makes use of packageA. It has a .cabal file which looks like this: library build-depends: base, packageA, ... exposed-modules: B executable testB ... extra-lib-dirs: /home/richard/.local/lib extra-libraries: foo Again, I've created a cabal sandbox in packageB. In order to be able to use packageA (which is not installed anywhere) I believe I have to do: $ cabal add-source ~/src/packageA Next, when I try and configure, it says: cabal: At least the following dependencies are missing: packageA -any That's fine, I assume, because I can now just `cabal install --only-dependencies` to get packageA built into packageB's sandbox. But when I try and do this, I get: $ cabal install --only-dependencies Resolving dependencies... Configuring packageA-0.1... Building packageA-0.1... Preprocessing library packageA-0.1... In-place registering packageA-0.1... Preprocessing executable 'testA' for packageA-0.1... Foo.hsc:10:33: fatal error: foo/foo.h: No such file or directory compilation terminated. So a target of packageA which compiles fine when doing cabal build directly from packageA now fails to compile when I attempt to build it from packageB by installing packageB's dependencies. I'm not sure how to proceed. It feels like maybe I have to tell cabal--when running it from packageB--where the include files are for packageA, because packageA needs to get compiled (which involves linking against libfoo and using libfoo's includes). I know that packageA *does* compile (because I've done that already), but it won't compile inside packageB's sandbox. Any suggestions? Richard

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Let, Equations, and Monad
by PATRICK BROWNE 27 Oct '15

27 Oct '15

{- From Learn Haskell Fast and Hard : 4.3.1. Maybe is a monad http://yannesposito.com/Scratch/en/blog/Haskell-the-Hard-Way/#maybe-monad Concerning the code below I have the following questions: 1) Are eligibleLet and eligibleEquational operationally equivalent (i.e. perform the same operations) and/or semantically equivalent(i.e. Church-Rosser)? 2) Apart from the return type of Maybe instead of Bool how does eligibleMonad differ from eligibleLet? Regards, Pat -} deposit value account = account + value withdraw value account = account - value -- You are eligible for a bonus only if your sequence of transactions stays out of the red. eligibleLet :: (Num a,Ord a) => a -> Bool eligibleLet account = let account1 = deposit 100 account in if (account1 < 0) then False else let account2 = withdraw 200 account1 in if (account2 < 0) then False else let account3 = deposit 100 account2 in if (account3 < 0) then False else let account4 = withdraw 300 account3 in if (account4 < 0) then False else let account5 = deposit 1000 account4 in if (account5 < 0) then False else True eligibleEquational :: (Num a,Ord a) => a -> Bool eligibleEquational account = let account1 = deposit 100 account in if (account1 < 0) then False else let account2 = withdraw 200 account1 in if (account2 < 0) then False else let account3 = deposit 100 account2 in if (account3 < 0) then False else let account4 = withdraw 300 account3 in if (account4 < 0) then False else let account5 = deposit 1000 account4 in if (account5 < 0) then False else True -- Monadic version depositM :: (Num a) => a -> a -> Maybe a depositM value account = Just (account + value) withdrawM :: (Num a,Ord a) => a -> a -> Maybe a withdrawM value account = if (account < value) then Nothing else Just (account - value) eligibleMonad :: (Num a, Ord a) => a -> Maybe Bool eligibleMonad account = do account1 <- depositM 100 account account2 <- withdrawM 200 account1 account3 <- depositM 100 account2 account4 <- withdrawM 300 account3 account5 <- depositM 1000 account4 Just True main = do print $ eligibleLet 300 -- True print $ eligibleLet 299 -- Falsen print $ eligibleEquational 300 -- True print $ eligibleEquational 299 -- False print $ eligibleMonad 300 -- Just True print $ eligibleMonad 299 -- Nothing -- This email originated from DIT. If you received this email in error, please delete it from your system. Please note that if you are not the named addressee, disclosing, copying, distributing or taking any action based on the contents of this email or attachments is prohibited. www.dit.ie Is ó ITBÁC a tháinig an ríomhphost seo. Má fuair tú an ríomhphost seo trí earráid, scrios de do chóras é le do thoil. Tabhair ar aird, mura tú an seolaí ainmnithe, go bhfuil dianchosc ar aon nochtadh, aon chóipeáil, aon dáileadh nó ar aon ghníomh a dhéanfar bunaithe ar an ábhar atá sa ríomhphost nó sna hiatáin seo. www.dit.ie Tá ITBÁC ag aistriú go Gráinseach Ghormáin – DIT is on the move to Grangegorman <http://www.dit.ie/grangegorman>

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SQL select for HDBC.ODBC MSSQL driver
by Anakreontas 27 Oct '15

27 Oct '15

Hello. I obtain a connection and try to execute a query on MSSQL server with HDBC c <- connectODBC "Driver={SQL Server};Server=.;Database=Pure_Local;Trusted_Connection=yes;" stm <- quickQuery c "select count(*) as cnt from X__FD" [] HDBC obtains the connection but the SQL query raises an exception with the following message: SqlError {seState = "[\"25000\"]", seNativeError = -1, seErrorMsg = "disconnect: [\"0: [Microsoft][ODBC SQL Server Driver]Invalid transaction state\"]"} No matter which statement I tried, I always get the "Invalid transaction state" message.

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Haskell Report Infelicity?
by Dominic Steinitz 27 Oct '15

27 Oct '15

I have probably misunderstood but is the following expected? floor, round, truncate and ceiling give similar results (all methods of the RealFrac class). properFraction :: (Integral b, RealFrac a) => a -> (b, a) *Girsanov> properFraction (-1 / 0) (-17976931348623159077293051907890247336179769789423065727343008115773267 5805500963132708477322407536021120113879871393357658789768814416622492847 4306394741243777678934248654852763022196012460941194530829520850057688381 5068234246288147391311054082723716335051068458629823994724593847971630483 5356329624224137216,0.0) *Girsanov> properFraction (1 / 0) (179769313486231590772930519078902473361797697894230657273430081157732675 8055009631327084773224075360211201138798713933576587897688144166224928474 3063947412437776789342486548527630221960124609411945308295208500576883815 0682342462881473913110540827237163350510684586298239947245938479716304835 356329624224137216,0.0) *Girsanov> properFraction (0 / 0) (-26965397022934738615939577861835371004269654684134598591014512173659901 3708251444699062715983611304031680170819807090036488184653221624933739271 1459592111865666518401372982279144533294018691411791796244281275086532572 2602351369432221086966581124085574502576602687944735992086890771957445725 3034494436336205824,0.0) The Haskell Report "6.4.6 Coercions and Component Extraction" is silent on what to expect with NaN, Infinity and -Infinity so I think it should be amended. Alternatively, one could expect implementations to throw a runtime error? In ghc, the problem is here https://phabricator.haskell.org/D160a /* This is expected to replace uses of __decodeDouble_2Int() in the long run */ StgInt __decodeDouble_Int64 (StgInt64 *const mantissa, const StgDouble dbl) { if (dbl) { int exp = 0; *mantissa = (StgInt64)scalbn(frexp(dbl, &exp), DBL_MANT_DIG); return exp-DBL_MANT_DIG; } else { *mantissa = 0; return 0; } } I believe frexp [1] and scalbn [2] both pass through NaN, Infinity and -Infinity and I think type coercion in C is undefined for these values. Furthermore exp is undefined for these values [1]. 1. http://en.cppreference.com/w/cpp/numeric/math/frexp 2. http://en.cppreference.com/w/cpp/numeric/math/scalbn Dominic Steinitz dominic(a)steinitz.org http://idontgetoutmuch.wordpress.com

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