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  • terminal does not find xmonad.hs

    - by arpho
    Iam using xmonad on ubuntu 13.04, in ~/.xmonad my computer has the file xmonad.hs, if I try to read it from terminal using nano it opens a new file, I can access the file opening it from geany or gedit, but if I try to recompile it, the system does not find that file, so I cannot configure xmonad, every thing I try on this file from console does not work, because terminal even if I am root cannot see it, can you help me solve this issue?

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  • Problem getting GOBI 2000 HS to work

    - by Zypher
    I've been trying to get my integrated GOBI WWAN card to work under 10.10 for a while now. I was able to get the network manager to see the card after installing the gobi-loader package. I was able to setup the connection, but i cannot establish a connection to Verizon. Below is the output from /var/log/daemon.log as i try to connect. Oct 19 14:29:42 gbeech-x201 AptDaemon: INFO: Quiting due to inactivity Oct 19 14:29:42 gbeech-x201 AptDaemon: INFO: Shutdown was requested Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> Activation (ttyUSB0) starting connection 'Verizon connection' Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> (ttyUSB0): device state change: 3 -> 4 (reason 0) Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) scheduled... Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) started... Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> (ttyUSB0): device state change: 4 -> 6 (reason 0) Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) complete. Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) scheduled... Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) started... Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> (ttyUSB0): device state change: 6 -> 4 (reason 0) Oct 19 14:33:45 gbeech-x201 NetworkManager[1105]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) complete. Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <warn> CDMA connection failed: (32) No service Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <info> (ttyUSB0): device state change: 4 -> 9 (reason 0) Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <info> Marking connection 'Verizon connection' invalid. Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <warn> Activation (ttyUSB0) failed. Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <info> (ttyUSB0): device state change: 9 -> 3 (reason 0) Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <info> (ttyUSB0): deactivating device (reason: 0). Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <info> Policy set 'Auto SO-GUEST' (wlan0) as default for IPv4 routing and DNS. Oct 19 14:34:46 gbeech-x201 NetworkManager[1105]: <info> Policy set 'Auto SO-GUEST' (wlan0) as default for IPv4 routing and DNS.

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  • Restart Fibre channel controller after blade bootup IBM HS bladecentre

    - by Spence
    I have a remote system that needs to resume on startup. If the system is simply powered on then the blades boot before the SAN is online and then the only thing you can do is restart the systems. Is it possible to restart the fibre channel controller? That way I could have a system restart the controller after boot, connect to the SAN and then restart all servers requiring SAN information? Please note that I'm not a sys admin, just shooting for ideas to get a clean startup to work, apologies if my terminology is wrong.

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  • Weirdness with cabal, HTF, and HUnit assertions

    - by rampion
    So I'm trying to use HTF to run some HUnit-style assertions % cat tests/TestDemo.hs {-# OPTIONS_GHC -Wall -F -pgmF htfpp #-} module Main where import Test.Framework import Test.HUnit.Base ((@?=)) import System.Environment (getArgs) -- just run some tests main :: IO () main = getArgs >>= flip runTestWithArgs Main.allHTFTests -- all these tests should fail test_fail_int1 :: Assertion test_fail_int1 = (0::Int) @?= (1::Int) test_fail_bool1 :: Assertion test_fail_bool1 = True @?= False test_fail_string1 :: Assertion test_fail_string1 = "0" @?= "1" test_fail_int2 :: Assertion test_fail_int2 = [0::Int] @?= [1::Int] test_fail_string2 :: Assertion test_fail_string2 = "true" @?= "false" test_fail_bool2 :: Assertion test_fail_bool2 = [True] @?= [False] And when I use ghc --make, it seems to work correctly. % ghc --make tests/TestDemo.hs [1 of 1] Compiling Main ( tests/TestDemo.hs, tests/TestDemo.o ) Linking tests/TestDemo ... % tests/TestDemoA ... * Tests: 6 * Passed: 0 * Failures: 6 * Errors: 0 Failures: * Main:fail_int1 (tests/TestDemo.hs:9) * Main:fail_bool1 (tests/TestDemo.hs:12) * Main:fail_string1 (tests/TestDemo.hs:15) * Main:fail_int2 (tests/TestDemo.hs:19) * Main:fail_string2 (tests/TestDemo.hs:22) * Main:fail_bool2 (tests/TestDemo.hs:25) But when I use cabal to build it, not all the tests that should fail, fail. % cat Demo.cabal ... executable test-demo build-depends: base >= 4, HUnit, HTF main-is: TestDemo.hs hs-source-dirs: tests % cabal configure Resolving dependencies... Configuring Demo-0.0.0... % cabal build Preprocessing executables for Demo-0.0.0... Building Demo-0.0.0... [1 of 1] Compiling Main ( tests/TestDemo.hs, dist/build/test-demo/test-demo-tmp/Main.o ) Linking dist/build/test-demo/test-demo ... % dist/build/test-demo/test-demo ... * Tests: 6 * Passed: 3 * Failures: 3 * Errors: 0 Failures: * Main:fail_int2 (tests/TestDemo.hs:23) * Main:fail_string2 (tests/TestDemo.hs:26) * Main:fail_bool2 (tests/TestDemo.hs:29) What's going wrong and how can I fix it?

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  • Call an haskell function in .net

    - by SuperBloup
    Hi, I want to use an Haskell function with the following type :: string -> string from a C# programm. I want to use hs-dotnet to bridge both worlds, the author claim that it's possible, but provide no sample of this case. The only samples provided are the one to use .net from haskell. Does anyone got a sample of this use, or got an idea how to use it? (I used reflector on the bridging assembly but didn't understood a thing)

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  • Strange type-related error

    - by vsb
    I wrote following program: isPrime x = and [x `mod` i /= 0 | i <- [2 .. truncate (sqrt x)]] primes = filter isPrime [1 .. ] it should construct list of prime numbers. But I got this error: [1 of 1] Compiling Main ( 7/main.hs, interpreted ) 7/main.hs:3:16: Ambiguous type variable `a' in the constraints: `Floating a' arising from a use of `isPrime' at 7/main.hs:3:16-22 `RealFrac a' arising from a use of `isPrime' at 7/main.hs:3:16-22 `Integral a' arising from a use of `isPrime' at 7/main.hs:3:16-22 Possible cause: the monomorphism restriction applied to the following: primes :: [a] (bound at 7/main.hs:3:0) Probable fix: give these definition(s) an explicit type signature or use -XNoMonomorphismRestriction Failed, modules loaded: none. If I specify signature for isPrime function explicitly: isPrime :: Integer -> Bool isPrime x = and [x `mod` i /= 0 | i <- [2 .. truncate (sqrt x)]] I can't even compile isPrime function: [1 of 1] Compiling Main ( 7/main.hs, interpreted ) 7/main.hs:2:45: No instance for (RealFrac Integer) arising from a use of `truncate' at 7/main.hs:2:45-61 Possible fix: add an instance declaration for (RealFrac Integer) In the expression: truncate (sqrt x) In the expression: [2 .. truncate (sqrt x)] In a stmt of a list comprehension: i <- [2 .. truncate (sqrt x)] 7/main.hs:2:55: No instance for (Floating Integer) arising from a use of `sqrt' at 7/main.hs:2:55-60 Possible fix: add an instance declaration for (Floating Integer) In the first argument of `truncate', namely `(sqrt x)' In the expression: truncate (sqrt x) In the expression: [2 .. truncate (sqrt x)] Failed, modules loaded: none. Can you help me understand, why am I getting these errors?

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  • JVM hs_err.log not being generated on Linux

    - by halfwarp
    Hello, I'm currently having some issues with a Java application I'm developing. Namely the JVM is crashing with a segfault. I'm trying to locate the hs_err.log file which should contain some helpful info about the issue. However, I can't find this file. I've used find, locate, etc, and nothing. Any ideas on why the log file isn't being generated?

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  • Why this Either-monad code does not type check?

    - by pf_miles
    instance Monad (Either a) where return = Left fail = Right Left x >>= f = f x Right x >>= _ = Right x this code frag in 'baby.hs' caused the horrible compilation error: Prelude> :l baby [1 of 1] Compiling Main ( baby.hs, interpreted ) baby.hs:2:18: Couldn't match expected type `a1' against inferred type `a' `a1' is a rigid type variable bound by the type signature for `return' at <no location info> `a' is a rigid type variable bound by the instance declaration at baby.hs:1:23 In the expression: Left In the definition of `return': return = Left In the instance declaration for `Monad (Either a)' baby.hs:3:16: Couldn't match expected type `[Char]' against inferred type `a1' `a1' is a rigid type variable bound by the type signature for `fail' at <no location info> Expected type: String Inferred type: a1 In the expression: Right In the definition of `fail': fail = Right baby.hs:4:26: Couldn't match expected type `a1' against inferred type `a' `a1' is a rigid type variable bound by the type signature for `>>=' at <no location info> `a' is a rigid type variable bound by the instance declaration at baby.hs:1:23 In the first argument of `f', namely `x' In the expression: f x In the definition of `>>=': Left x >>= f = f x baby.hs:5:31: Couldn't match expected type `b' against inferred type `a' `b' is a rigid type variable bound by the type signature for `>>=' at <no location info> `a' is a rigid type variable bound by the instance declaration at baby.hs:1:23 In the first argument of `Right', namely `x' In the expression: Right x In the definition of `>>=': Right x >>= _ = Right x Failed, modules loaded: none. why this happen? and how could I make this code compile ? thanks for any help~

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  • Could someone explain gtk2hs drag and drop to me, the listDND.hs demo just isn't doing it for me?

    - by Tom Carstens
    As the title says, I just don't get DND (or rather I understand the concept and I understand the order of callbacks, I just don't understand how to setup DND for actual usage.) I'd like to say that I've done DND stuff before in C, but considering I never really got that working... So I'm trying (and mostly succeeding, save DND) to write a text editor (using gtksourceview, because it has built in code highlighting.) Reasons are below if you want them. Anyways, there's not really a good DND demo or tutorial available for gtk2hs (listDND.hs just doesn't translate well in my head.) So what I'm asking is for code that demonstrates simple DND on a window widget (for example.) Ideally, it should accept drops from other windows (such as Thunar) and print out the information in string form. I think I can take it from there... Reasons: I'm running a fairly light weight setup, dwm and a few gtk+2 programs. I really don't want to have to pull in gtk+3 to get the current gedit from the repos (Arch Linux.) Currently, I'm using geany for all of my text editing needs, however, geany is a bit heavy for editing config files. Further, geany doesn't care for my terminal of choice (st;) so I don't even get the benefit of using it as an IDE. Meaning I'd like a lightweight text editor with syntax highlighting. I could configure emacs or vim or something, but that seems to me to be more of a hack then a proper solution. Thus my project was born. It's mostly working (aside from DND, all that's left is proper multi-tab support.) Admittedly, I could probably work this out if I wrote it in C, but there isn't that much state in a text editor so Haskell's been working fine with almost no need for mutable variables.

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  • Creating a multi-page PDF doc

    - by codemercenary
    Hi, has anyone already created a PDF document in an iPad app. i see that there are new functions in the UIKit to do this, but I can't find any code example for this. BOOL UIGraphicsBeginPDFContextToFile ( NSString *path, CGRect bounds, NSDictionary *documentInfo ); void UIGraphicsBeginPDFPage ( void ); I found an example that is supposed to work on the iPhone, but this gives me errors: Fri Apr 30 11:55:32 wks104.hs.local PDF[1963] <Error>: CGFont/Freetype: The function `create_subset' is currently unimplemented. Fri Apr 30 11:55:32 wks104.hs.local PDF[1963] <Error>: invalid Type1 font: unable to stream font. Fri Apr 30 11:55:32 wks104.hs.local PDF[1963] <Error>: FT_Load_Glyph failed: error 6. Fri Apr 30 11:55:32 wks104.hs.local PDF[1963] <Error>: FT_Load_Glyph failed: error 6. Fri Apr 30 11:55:32 wks104.hs.local PDF[1963] <Error>: FT_Load_Glyph failed: error 6. Fri Apr 30 11:55:32 wks104.hs.local PDF[1963] <Error>: FT_Load_Glyph failed: error 6.

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  • Simple Question:Output of below Java program

    - by Abhishek Jain
    public class abc1 { private String s; public abc1(String s){this.s=s;} public static void main(String args[]) { HashSet<Object> hs=new HashSet<Object>(); abc1 a1= new abc1("abc"); abc1 a2= new abc1("abc"); String s1= new String("abc"); String s2= new String("abc"); hs.add(a1); hs.add(a2); hs.add(s1); hs.add(s2); System.out.println(hs.size()); } } Why above program output is 3?

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  • Haskell's cabal dependency problem with happy

    - by wirrbel
    I have problems installing ghc-mod on my linux machine. cabal worries about "happy" not being available in versione = 1.17: $ cabal install ghc-mod Resolving dependencies... [1 of 1] Compiling Main ( /tmp/haskell-src-exts-1.14.0-1357/haskell-src-exts-1.14.0/Setup.hs, /tmp/haskell-src-exts-1.14.0-1357/haskell-src-exts-1.14.0/dist/setup/Main.o ) Linking /tmp/haskell-src-exts-1.14.0-1357/haskell-src-exts-1.14.0/dist/setup/setup ... Configuring haskell-src-exts-1.14.0... setup: The program happy version =1.17 is required but it could not be found. Failed to install haskell-src-exts-1.14.0 cabal: Error: some packages failed to install: ghc-mod-3.1.3 depends on haskell-src-exts-1.14.0 which failed to install. haskell-src-exts-1.14.0 failed during the configure step. The exception was: ExitFailure 1 hlint-1.8.53 depends on haskell-src-exts-1.14.0 which failed to install. However, it even is installed in v. 1.19, as you can see here: $ cabal install happy Resolving dependencies... [1 of 1] Compiling Main ( /tmp/happy-1.19.0-1124/happy-1.19.0/Setup.lhs, /tmp/happy-1.19.0-1124/happy-1.19.0/dist/setup/Main.o ) Linking /tmp/happy-1.19.0-1124/happy-1.19.0/dist/setup/setup ... Configuring happy-1.19.0... Building happy-1.19.0... Preprocessing executable 'happy' for happy-1.19.0... [ 1 of 18] Compiling NameSet ( src/NameSet.hs, dist/build/happy/happy-tmp/NameSet.o ) [ 2 of 18] Compiling Target ( src/Target.lhs, dist/build/happy/happy-tmp/Target.o ) [ 3 of 18] Compiling AbsSyn ( src/AbsSyn.lhs, dist/build/happy/happy-tmp/AbsSyn.o ) [ 4 of 18] Compiling ParamRules ( src/ParamRules.hs, dist/build/happy/happy-tmp/ParamRules.o ) [ 5 of 18] Compiling GenUtils ( src/GenUtils.lhs, dist/build/happy/happy-tmp/GenUtils.o ) [ 6 of 18] Compiling ParseMonad ( src/ParseMonad.lhs, dist/build/happy/happy-tmp/ParseMonad.o ) [ 7 of 18] Compiling Lexer ( src/Lexer.lhs, dist/build/happy/happy-tmp/Lexer.o ) [ 8 of 18] Compiling Parser ( dist/build/happy/happy-tmp/Parser.hs, dist/build/happy/happy-tmp/Parser.o ) [ 9 of 18] Compiling AttrGrammar ( src/AttrGrammar.lhs, dist/build/happy/happy-tmp/AttrGrammar.o ) [10 of 18] Compiling AttrGrammarParser ( dist/build/happy/happy-tmp/AttrGrammarParser.hs, dist/build/happy/happy-tmp/AttrGrammarParser.o ) [11 of 18] Compiling Grammar ( src/Grammar.lhs, dist/build/happy/happy-tmp/Grammar.o ) [12 of 18] Compiling First ( src/First.lhs, dist/build/happy/happy-tmp/First.o ) [13 of 18] Compiling LALR ( src/LALR.lhs, dist/build/happy/happy-tmp/LALR.o ) [14 of 18] Compiling Paths_happy ( dist/build/autogen/Paths_happy.hs, dist/build/happy/happy-tmp/Paths_happy.o ) [15 of 18] Compiling ProduceCode ( src/ProduceCode.lhs, dist/build/happy/happy-tmp/ProduceCode.o ) [16 of 18] Compiling ProduceGLRCode ( src/ProduceGLRCode.lhs, dist/build/happy/happy-tmp/ProduceGLRCode.o ) [17 of 18] Compiling Info ( src/Info.lhs, dist/build/happy/happy-tmp/Info.o ) [18 of 18] Compiling Main ( src/Main.lhs, dist/build/happy/happy-tmp/Main.o ) Linking dist/build/happy/happy ... Installing executable(s) in /home/hope/.cabal/bin Installed happy-1.19.0 Any ideas? cabal-install version 1.16.0.2 using version 1.16.0 of the Cabal library

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  • How can my-program.hs get its version number from my-program.cabal at build time?

    - by Dave Hinton
    I would like my cabalised program to have a --version switch. I would like it to report the same version as is present in the .cabal file. If I have to update the version number separately in my Haskell source code as well as in the .cabal file, I will eventually get them out of sync. So, how can my program, while being compiled under cabal, get its version number from the .cabal file?

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  • Compiled Haskell libraries with FFI imports are invalid when imported into GHCI

    - by John Millikin
    I am using GHC 6.12.1, in Ubuntu 10.04 When I try to use the FFI syntax for static storage, only modules running in interpreted mode (ie GHCI) work properly. Compiled modules have invalid pointers, and do not work. I'd like to know whether anybody can reproduce the problem, whether this an error in my code or GHC, and (if the latter) whether it's a known issue. I'm using sys_siglist because it's present in a standard library on my system, but I don't believe the actual storage used matters (I discovered this while writing a binding to libidn). If it helps, sys_siglist is defined in <signal.h> as: extern __const char *__const sys_siglist[_NSIG]; I thought this type might be the problem, so I also tried wrapping it in a plain C procedure: #include<stdio.h> const char **test_ffi_import() { printf("C think sys_siglist = %X\n", sys_siglist); return sys_siglist; } However, importing that doesn't change the result, and the printf() call prints the same pointer value as show siglist_a. My suspicion is that it's something to do with static and dynamic library loading. Update: somebody in #haskell suggested this might be 64-bit specific; if anybody tries to reproduce it, can you mention your architecture and whether it worked in a comment? Code as follows: -- A.hs {-# LANGUAGE ForeignFunctionInterface #-} module A where import Foreign import Foreign.C foreign import ccall "&sys_siglist" siglist_a :: Ptr CString -- -- B.hs {-# LANGUAGE ForeignFunctionInterface #-} module B where import Foreign import Foreign.C foreign import ccall "&sys_siglist" siglist_b :: Ptr CString -- -- Main.hs {-# LANGUAGE ForeignFunctionInterface #-} module Main where import Foreign import Foreign.C import A import B foreign import ccall "&sys_siglist" siglist_main :: Ptr CString main = do putStrLn $ "siglist_a = " ++ show siglist_a putStrLn $ "siglist_b = " ++ show siglist_b putStrLn $ "siglist_main = " ++ show siglist_main peekSiglist "a " siglist_a peekSiglist "b " siglist_b peekSiglist "main" siglist_main peekSiglist name siglist = do ptr <- peekElemOff siglist 2 str <- maybePeek peekCString ptr putStrLn $ "siglist_" ++ name ++ "[2] = " ++ show str I would expect something like this output, where all pointer values identical and valid: $ runhaskell Main.hs siglist_a = 0x00007f53a948fe00 siglist_b = 0x00007f53a948fe00 siglist_main = 0x00007f53a948fe00 siglist_a [2] = Just "Interrupt" siglist_b [2] = Just "Interrupt" siglist_main[2] = Just "Interrupt" However, if I compile A.hs (with ghc -c A.hs), then the output changes to: $ runhaskell Main.hs siglist_a = 0x0000000040378918 siglist_b = 0x00007fe7c029ce00 siglist_main = 0x00007fe7c029ce00 siglist_a [2] = Nothing siglist_b [2] = Just "Interrupt" siglist_main[2] = Just "Interrupt"

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  • Why do compiled Haskell libraries see invalid static FFI storage?

    - by John Millikin
    I am using GHC 6.12.1, in Ubuntu 10.04 When I try to use the FFI syntax for static storage, only modules running in interpreted mode (ie GHCI) work properly. Compiled modules have invalid pointers, and do not work. I'd like to know whether anybody can reproduce the problem, whether this an error in my code or GHC, and (if the latter) whether it's a known issue. Given the following three modules: -- A.hs {-# LANGUAGE ForeignFunctionInterface #-} module A where import Foreign import Foreign.C foreign import ccall "&sys_siglist" siglist_a :: Ptr CString -- -- B.hs {-# LANGUAGE ForeignFunctionInterface #-} module B where import Foreign import Foreign.C foreign import ccall "&sys_siglist" siglist_b :: Ptr CString -- -- Main.hs {-# LANGUAGE ForeignFunctionInterface #-} module Main where import Foreign import Foreign.C import A import B foreign import ccall "&sys_siglist" siglist_main :: Ptr CString main = do putStrLn $ "siglist_a = " ++ show siglist_a putStrLn $ "siglist_b = " ++ show siglist_b putStrLn $ "siglist_main = " ++ show siglist_main peekSiglist "a " siglist_a peekSiglist "b " siglist_b peekSiglist "main" siglist_main peekSiglist name siglist = do ptr <- peekElemOff siglist 2 str <- maybePeek peekCString ptr putStrLn $ "siglist_" ++ name ++ "[2] = " ++ show str I would expect something like this output, where all pointer values identical and valid: $ runhaskell Main.hs siglist_a = 0x00007f53a948fe00 siglist_b = 0x00007f53a948fe00 siglist_main = 0x00007f53a948fe00 siglist_a [2] = Just "Interrupt" siglist_b [2] = Just "Interrupt" siglist_main[2] = Just "Interrupt" However, if I compile A.hs (with ghc -c A.hs), then the output changes to: $ runhaskell Main.hs siglist_a = 0x0000000040378918 siglist_b = 0x00007fe7c029ce00 siglist_main = 0x00007fe7c029ce00 siglist_a [2] = Nothing siglist_b [2] = Just "Interrupt" siglist_main[2] = Just "Interrupt"

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  • Why I am forced to write the (Data Constructor) name with first letter in small case?

    - by Optimight
    Why I am forced to write "liOfLi" in place of "LiOfLi"? Please guide. code in baby.hs LiOfLi = [ [1,3,4,5,6,8], [ 12, 13, 15, 16, 19, 20], [23, 24, 25, 45, 56] ] ghci response: ghci :l baby [1 of 1] Compiling Main ( baby.hs, interpreted ) Failed, modules loaded: none. ghci baby.hs:29:1: Not in scope: data constructor `LiOfLi' When changing the initial letter to smaller case code in baby.hs liOfLi = [ [1,3,4,5,6,8], [ 12, 13, 15, 16, 19, 20], [23, 24, 25, 45, 56] ] ghci response: ghci :l baby [1 of 1] Compiling Main ( baby.hs, interpreted ) Ok, modules loaded: Main. Following are the SO questions I refered but I failed to understand the rules/ logic and get the answer for (my) abovementioned question. Why does Haskell force data constructor's first letter to be upper case? the variable names need to be lowercase. The official documentation related to this is at haskell.org/onlinereport/intro.html#namespaces – (the SO comment by) Chris Kuklewicz

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  • Haskell: how to get through 'no instance for' ?

    - by artemave
    I am learning Haskell. I am on the 8th chapter of this book. The main thing I've learned so far is that Haskell is very unfriendly to me and it bites my ass where possible. Moreover... Heck! Enough mourning, to business. Here is the code: module GlobRegex ( globToRegex, matchesGlob ) where import Text.Regex.Posix import Text.Regex.Posix.String import Text.Regex.Base.RegexLike data CaseOpt = Case | NoCase deriving (Eq) matchesGlob :: String -> String -> CaseOpt -> Bool matchesGlob name pat caseopt = match regex name where regex = case caseopt of NoCase -> makeRegexOpts (defaultCompOpt + compIgnoreCase) defaultExecOpt (globToRegex pat) Case -> makeRegex (globToRegex pat) globToRegex :: String -> String ... And here is how it fails to compile: Prelude Text.Regex.Posix Text.Regex.Base.RegexLike> :load globtoregex\GlobRegex. hs [1 of 1] Compiling GlobRegex ( globtoregex\GlobRegex.hs, interpreted ) globtoregex\GlobRegex.hs:14:31: No instance for (RegexLike regex [Char]) arising from a use of `match' at globtoregex\GlobRegex.hs:14:31-46 Possible fix: add an instance declaration for (RegexLike regex [Char]) In the expression: match regex name In the definition of `matchesGlob': matchesGlob name pat caseopt = match regex name where regex = case caseopt of { NoCase -> makeRegexOpts (defaultCompOpt + compIgnoreCase) defaultExecOpt (globToRegex pat) Case -> makeRegex (globToRegex pat) } globtoregex\GlobRegex.hs:17:23: No instance for (RegexMaker regex CompOption execOpt String) arising from a use of `makeRegex' at globtoregex\GlobRegex.hs:17:23-49 Possible fix: add an instance declaration for (RegexMaker regex CompOption execOpt String) In the expression: makeRegex (globToRegex pat) In a case alternative: Case -> makeRegex (globToRegex pat) In the expression: case caseopt of { NoCase -> makeRegexOpts (defaultCompOpt + compIgnoreCase) defaultExecOpt (globToRegex p at) Case -> makeRegex (globToRegex pat) } Failed, modules loaded: none. To my best understanding, Text.Regex.Posix.String provides instances for RegexLike Regex String and RegexMaker Regex CompOption ExecOption String, so it should work. On the other hand, I can see that regex in the error message is type variable, not a concrete type, so, perhaps not... Anyway, this is where I am stuck. May be there is a common pattern for resolving no instance for type of problems? Or, in Haskell terms, instance of SmartGuess typeclass for no instance for?

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  • Haskell simple compilation bug

    - by fmsf
    I'm trying to run this code: let coins = [50, 25, 10, 5, 2,1] let candidate = 11 calculate :: [Int] calculate = [ calculate (x+candidate) | x <- coins, x > candidate] I've read some tutorials, and it worked out ok. I'm trying to solve some small problems to give-me a feel of the language. But I'm stuck at this. test.hs:3:0: parse error (possibly incorrect indentation) Can anyone tell me why? I've started with haskell today so please go easy on the explanations. I've tried to run it like: runghc test.hs ghc test.hs but with: ghci < test.hs it gives this one: <interactive>:1:10: parse error on input `=' Thanks

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  • Can I free memory passed to SysAllocString?

    - by RichAmberale
    When allocating a new BSTR with SysAllocString via a wchar_t* on the heap, should I then free the original wchar_t* on the heap? So is this the right way? wchar_t *hs = new wchar_t[20]; // load some wchar's into hs... BSTR bs = SysAllocString(hs); delete[] hs; Am I supposed to call delete here to free up the memory? Or was that memory just adoped by the BSTR?

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  • What is wrong with this simple type definition? (Expecting one more argument to...)

    - by fluteflute
    basic.hs: areaCircle :: Floating -> Floating areaCircle r = pi * r * r Command: *Main> :l basic.hs [1 of 1] Compiling Main ( Sheet1.hs, interpreted ) Sheet1.hs:2:15: Expecting one more argument to `Floating' In the type signature for `areaCircle': areaCircle :: Floating -> Floating Failed, modules loaded: none. I see that areaCircle :: Floating a => a -> a loads as expected. Why is the above version not acceptable?

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  • problems with Haskell's Number Types

    - by mindeavor.
    I have the following haskell code: fac n = product [1..n] taylor3s w0 f f' f'' t h = w1 : taylor3s w1 f f' f'' (t+h) h where hp i = h^i / fac i w1 = w0 + (hp 1) * f t w0 + (hp 2) * f' t w0 + (hp 3) * f'' t w0 taylor_results = take 4 $ taylor3s 1 f f' f'' 1 0.25 where f t x = t^4 - 4*x/t f' t x = 4*t^3 - 4*(f t x)/t + 4*x/t^2 f'' t x = 12*t^2 - 4*(f' t x)/t + 8*(f t x)/t^2 - 8*x/t^3 taylor_results is supposed to be a use case of taylor3s. However, there is something wrong with the number type inferencing. When I try to compile, this is the error I get: practice.hs:93:26: Ambiguous type variable `a' in the constraints: `Integral a' arising from a use of `taylor3s' at practice.hs:93:26-51 `Fractional a' arising from a use of `f' at practice.hs:93:37 Possible cause: the monomorphism restriction applied to the following: taylor_results :: [a] (bound at practice.hs:93:0) Probable fix: give these definition(s) an explicit type signature or use -XNoMonomorphismRestriction Can someone help me with understanding what the problem is?

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  • NoInitialContextException: in ejb 3

    - by JavaDeveloper
    My client class code Hashtable hs = new Hashtable(); hs.put(Context.INITIAL_CONTEXT_FACTORY, "org.jnp.interfaces.NamingContextFactory"); hs.put(Context.PROVIDER_URL, "jnp://10.20.52.41:1200"); hs.put(Context.URL_PKG_PREFIXES, "org.jboss.naming:org.jnp.interfaces"); Context context = new InitialContext(hs); System.out.println("-----"); try { Example helloWorld = (Example) context .lookup("Example"); helloWorld.display("HelloWorld"); } catch (NamingException e) { System.out.println("naming exception occoured"); e.printStackTrace(); } My session bean code public class Example implements javax.ejb.SessionBean { //method here.. } getting following exception. how to resolve? Exception in thread "main" javax.naming.NoInitialContextException: Cannot instantiate class: org.jnp.interfaces.NamingContextFactory [Root exception is java.lang.ClassNotFoundException: org.jnp.interfaces.NamingContextFactory] at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:657) at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:288) at javax.naming.InitialContext.init(InitialContext.java:223) at javax.naming.InitialContext.(InitialContext.java:197) at comtest.client.Example.main(Test.java:22) Caused by: java.lang.ClassNotFoundException: org.jnp.interfaces.NamingContextFactory at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:249) at com.sun.naming.internal.VersionHelper12.loadClass(VersionHelper12.java:46) at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:654) ... 4 more

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  • CouchDB crashes at startup when path to config file has space(s)

    - by Barry Wark
    I'm hoping to run CouchDB as a per-user Launch Agent on OS X. I'm using the coucdbx-core folder from the CouchDB Server.app as the base of my CouchDB deployment. I'd like each user to have their own couch instance (on a different port), necessitating separate config files for each instance. The logical place to put these files is in ~/Library/Application Support/ for each user. I can put the entire distribution in ~/Library/Application Support/my-app/coucdbx, and put the .ini at ~/Library/Application Support/my-app/local.ini. Starting couchdb as bin/couchdb -a ../local.ini (from ~/Library/Application Support/my-app/coucdbx) works great. But I'd like to save every user the ~50MB couchdbx and install the couchdbx-core in a shared location (e.g. within my app's .app bundle). When I do this, the path to the per-user config file contains a space, and I get the following error when starting CouchDB: $ bin/couchdb -n -a ~/Library/Application\ Support/us.physion.ovation/default.ini {"init terminating in do_boot",{{badmatch,{error,{bad_return,{{couch_app,start,[normal,["/Users/hs/prj/build-couchdb/build/etc/couchdb/default.ini","/Users/hs/prj/build-couchdb/build/etc/couchdb/local.ini"]]},{'EXIT',{{badmatch,{error,{error,enoent}}},[{couch_server_sup,start_server,1,[{file,"/Users/hs/prj/build-couchdb/dependencies/couchdb/src/couchdb/couch_server_sup.erl"},{line,56}]},{application_master,start_it_old,4,[{file,"application_master.erl"},{line,274}]}]}}}}}},[{couch,start,0,[{file,"/Users/hs/prj/build-couchdb/dependencies/couchdb/src/couchdb/couch.erl"},{line,18}]},{init,start_it,1,[]},{init,start_em,1,[]}]}} Is there any way to provide a config file at the command line, if that config file's path includes space(s)? Despite my best efforts in the mailing list archives, wiki and google, I haven't been able to find a solution or a definitive "it can't work". Any help greatly appreciated.

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  • Why do Finder and du report different file size?

    - by flipdoubt
    I am writing a geektool 3 script to show the size of a particular VMware Fusion virtual machine. Get Info in Finder says the file is "52.91 GB". I run the following du command to get the file size: > du -hs ~/Documents/Virtual\ Machines.localized/MY-PRECIOUS-7.vmwarevm | awk '{print $1}' This du -hs command returns the file size as "49G". What accounts for the difference from what Finder reports? Alternatively, I have tried replacing the -s option with the -d option like so: du -hd ~/Documents/Virtual\ Machines.localized/MY-PRECIOUS-7.vmwarevm | awk '{print $1}' This du -hd command returns the file size as "59G". What accounts for the difference between Finder, du -hd, and du -hs? Also, this du -hd command produces no output in geektool 3. What gives?

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