- Beginners - Haskell.org

Re: [Haskell-beginners] Error when running `cabal install cabal-install`
by Peng Yu 23 Apr '15

23 Apr '15

> Long story short: Try > $> cabal install --extra-include-dirs=/opt/local/include --extra-lib-dirs=/opt/local/lib I tried it but it still shows the error messages. ~$ cabal install --extra-include-dirs=/opt/local/include --extra-lib-dirs=/opt/local/lib cabal-install Resolving dependencies... Configuring cabal-install-1.22.3.0... Failed to install cabal-install-1.22.3.0 Build log ( /Users/py/.cabal/logs/cabal-install-1.22.3.0.log ): cabal: Error: some packages failed to install: cabal-install-1.22.3.0 failed during the configure step. The exception was: user error ('/usr/bin/ghc' exited with an error: Undefined symbols for architecture x86_64: "_iconv", referenced from: _hs_iconv in libHSbase-4.7.0.1.a(iconv.o) (maybe you meant: _hs_iconv, _base_GHCziIOziEncodingziIconv_iconvEncodingzuloc_info , _base_GHCziIOziEncodingziIconv_iconvEncoding8_info , _base_GHCziIOziEncodingziIconv_iconvEncoding9_closure , _hs_iconv_open , _base_GHCziIOziEncodingziIconv_iconvEncodingzuloc1_closure , _hs_iconv_close , _base_GHCziIOziEncodingziIconv_iconvEncoding6_info , _base_GHCziIOziEncodingziIconv_iconvEncoding4_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding6_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding10_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding7_info , _base_GHCziIOziEncodingziIconv_iconvEncoding2_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding2_info , _base_GHCziIOziEncodingziIconv_iconvEncodingzuloc_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding3_info , _base_GHCziIOziEncodingziIconv_iconvEncoding10_info , _base_GHCziIOziEncodingziIconv_iconvEncoding9_info , _base_GHCziIOziEncodingziIconv_iconvEncoding8_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding7_closure , _base_GHCziIOziEncodingziIconv_iconvEncodingzuloc1_info , _base_GHCziIOziEncodingziIconv_iconvEncoding3_closure ) "_iconv_close", referenced from: _hs_iconv_close in libHSbase-4.7.0.1.a(iconv.o) (maybe you meant: _hs_iconv_close) "_iconv_open", referenced from: _hs_iconv_open in libHSbase-4.7.0.1.a(iconv.o) (maybe you meant: _hs_iconv_open) "_locale_charset", referenced from: _localeEncoding in libHSbase-4.7.0.1.a(PrelIOUtils.o) ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation) ) -- Regards, Peng

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Re: [Haskell-beginners] Error when running `cabal install cabal-install`
by Brandon Allbery 23 Apr '15

23 Apr '15

On Thu, Apr 23, 2015 at 6:00 PM, Clemens Lang <cal(a)macports.org> wrote: > From https://www.haskell.org/platform/ > > it sounds like the latest platform release > is 2014.2.0.0, and that's what's currently packaged in MacPorts. It took > me a > while to get it done, but it's there and all components of the platform > should be > included. I'd welcome a bug report if there's anything wrong with it. > Mrrr, I thought there was a 6.8.4-based release (with the bizarre new build system). We're packaging 6.8.3 still. -- brandon s allbery kf8nh sine nomine associates allbery.b(a)gmail.com ballbery(a)sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

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Re: [Haskell-beginners] Error when running `cabal install cabal-install`
by Brandon Allbery 23 Apr '15

23 Apr '15

On Thu, Apr 23, 2015 at 5:56 PM, Clemens Lang <cal(a)macports.org> wrote: > So if you get these link errors, the problem almost always is that you > adjusted your library search path, but not the corresponding header > search path and you're actually compiling against Apple's iconv.h but > MacPorts libiconv.dylib (or vice-versa). > Those are coming from a library already built against Apple's libiconv, but being linked against MacPorts' libiconv. -- brandon s allbery kf8nh sine nomine associates allbery.b(a)gmail.com ballbery(a)sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

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Re: [Haskell-beginners] Error when running `cabal install cabal-install`
by Peng Yu 23 Apr '15

23 Apr '15

Indeed, I uninstalled libiconv by running the following command. sudo port uninstall --follow-dependents libiconv Then, `cabal install cabal-install` runs without a problem. Hi MacPorts Users, Is there better solution to this problem? Please see the original question regarding the conflict of MacPorts and Haskell. (I don't what to use haskell from MacPorts as I want to keep updated with the latest version of Haskell.) https://mail.haskell.org/pipermail/beginners/2015-April/015214.html On Thu, Apr 23, 2015 at 3:34 PM, Brandon Allbery <allbery.b(a)gmail.com> wrote: > On Thu, Apr 23, 2015 at 4:19 PM, Peng Yu <pengyu.ut(a)gmail.com> wrote: >> >> It is installed from <https://www.haskell.org/platform/ >> >> >. The OS is Mac OS X. > > > Yes, as I suspected. The problem is that Apple ships an old version of the > iconv library; MacPorts and Homebrew generally install a newer, incompatible > one with symbols renamed to trigger that link error (because otherwise you > find out about the mismatch when the first iconv call dumps core at > runtime). You will need to arrange for ghc not to see that other iconv, only > Apple's, since it won't work with any but Apple's. Or use a ghc from > whichever package manager you have installed, so that it works with that > package manager's iconv library. > > (This is more likely to happen with Homebrew, since most things don't look > /opt/local but just about everything looks under /usr/local.) > > -- > brandon s allbery kf8nh sine nomine associates > allbery.b(a)gmail.com ballbery(a)sinenomine.net > unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net > > _______________________________________________ > Beginners mailing list > Beginners(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners > -- Regards, Peng

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Error when running `cabal install cabal-install`
by Peng Yu 23 Apr '15

23 Apr '15

~$ cabal --version cabal-install version 1.18.0.5 using version 1.18.1.4 of the Cabal library ~$ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.8.3 I got the following error. Does anybody know how to resolve it? Thanks. ~$ cabal install cabal-install Resolving dependencies... Configuring Cabal-1.22.3.0... Failed to install Cabal-1.22.3.0 Last 10 lines of the build log ( /Users/py/.cabal/logs/Cabal-1.22.3.0.log ): cabal: Error: some packages failed to install: Cabal-1.22.3.0 failed during the configure step. The exception was: user error (Undefined symbols for architecture x86_64: "_iconv", referenced from: _hs_iconv in libHSbase-4.7.0.1.a(iconv.o) (maybe you meant: _hs_iconv, _base_GHCziIOziEncodingziIconv_iconvEncodingzuloc1_info , _base_GHCziIOziEncodingziIconv_iconvEncoding9_info , _base_GHCziIOziEncodingziIconv_iconvEncoding9_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding8_info , _base_GHCziIOziEncodingziIconv_iconvEncodingzuloc_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding10_info , _base_GHCziIOziEncodingziIconv_iconvEncoding6_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding10_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding3_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding7_info , _hs_iconv_close , _base_GHCziIOziEncodingziIconv_iconvEncodingzuloc1_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding2_info , _base_GHCziIOziEncodingziIconv_iconvEncoding8_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding3_info , _base_GHCziIOziEncodingziIconv_iconvEncoding2_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding7_closure , _base_GHCziIOziEncodingziIconv_iconvEncodingzuloc_info , _base_GHCziIOziEncodingziIconv_iconvEncoding4_closure , _base_GHCziIOziEncodingziIconv_iconvEncoding6_info , _hs_iconv_open ) "_iconv_close", referenced from: _hs_iconv_close in libHSbase-4.7.0.1.a(iconv.o) (maybe you meant: _hs_iconv_close) "_iconv_open", referenced from: _hs_iconv_open in libHSbase-4.7.0.1.a(iconv.o) (maybe you meant: _hs_iconv_open) "_locale_charset", referenced from: _localeEncoding in libHSbase-4.7.0.1.a(PrelIOUtils.o) ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation) ) cabal-install-1.22.3.0 depends on Cabal-1.22.3.0 which failed to install. ~/ports$ gvim ~/.cabal/logs/ -- Regards, Peng

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Re: [Haskell-beginners] Value from Monad
by Shishir Srivastava 22 Apr '15

22 Apr '15

Thanks ! that does work now. My next question was how do i only get "34" or "3" i.e. the Maybe value without wrapped in to a 'Maybe' ? Shishir

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Value from Monad
by Shishir Srivastava 22 Apr '15

22 Apr '15

Hi, Going through the '<-' description in 'learnouahaskell' it says - *" If we have a Maybe String and we bind it with <- to a variable, that variable will be a String"* so if you write do str <- Just "3" str should be of type 'String'. My question is how do I return "34" by concatenating it to "4" because the following line of code fails - --- do str <- Just "3" return str++"4"::Maybe String --- or for that matter how can I return/print just the value of str from this do block ? Thanks, Shishir

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integer to noise function in Haskell
by Florian Gillard 22 Apr '15

22 Apr '15

I am trying to implement a basic pelin noise function, but I have some problem with the integer to noise function used to generate deterministic noise from integer inputs. the function I am trying to implement is defined there: http://libnoise.sourceforge.net/noisegen/index.html#continuousnoise and my code so far look like this: noise2d :: (Int32, Int32) -> Double noise2d (x, y) = let m = x + y * 57 n = (shiftR m 13) ^ m j = (n * (n * n * 15731 + 789221) + 1376312589) .&. 0x7fffffff in 1.0 - (fromIntegral j / 1073741824.0) the code compile but I get the same result for any input, due to the fact that n is evaluated to 0. Is there a better way to do that?

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Return function
by Shishir Srivastava 22 Apr '15

22 Apr '15

Hi, Looking at the definition of return function for a Monad, it is described as - return :: a -> m a However when I do - return (Just 3) The result is Just 3 and not Just (Just 3) If I understand the definition correctly (which doesn't seem to be the case) the return function should wrap the parameter (which in my case is 'Just 3') into the Maybe Monad and therefore should return me 'Just (Just 3)' Please can someone help explain. Thanks, Shishir Srivastava +44 (0) 750 127 5019

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Re: [Haskell-beginners] filterM function
by Shishir Srivastava 22 Apr '15

22 Apr '15

Hi Mike, Thanks for your response. I was aware that 'casting' doesn't really fit in Haskell vocab but for the lack of better word used it. My question was however more towards the usage of [Bool] in the 'if' statement of the filterM function. More precisely - How does 'if [True, False] then x else y' work , because when I do this in GHCi it throws up the following error ? *>>Couldn't match expected type `Bool' with actual type `[Bool]'* Clearly the 'if' construct does not take a list of Boolean but a single Boolean value so how does filterM use it in it's implementation. Hope have made myself clear this time. Thanks, Shishir > From: Mike Meyer <mwm(a)mired.org> > To: The Haskell-Beginners Mailing List - Discussion of primarily > beginner-level topics related to Haskell <beginners(a)haskell.org> > Cc: > Date: Wed, 22 Apr 2015 04:15:31 -0500 > Subject: Re: [Haskell-beginners] filterM function > On Wed, Apr 22, 2015 at 3:31 AM, Shishir Srivastava < > shishir.srivastava(a)gmail.com> wrote: > >> I still don't quite understand how 'flg' being a boolean [] is used in >> the last 'if statement' of implementation because when I try to do the >> same thing outside in GHCi it fails miserably even though I am casting it >> to [Int] - >> >> -- >> return (if [True, False] then "4" else "3")::[Int] >> > > "cast" is a misnomer in Haskell. When you add a type to an expression, you > aren't changing the type of the expression like a C-style cast, but picking > out a type from the set of possible types for that expression. > > Ignoring the if part and and focusing on return, which has a type Monad m > => a -> m a. [Int] is equivalent to [] Int, so [] would be the Monad, and a > is Int. While 3 can be an Int, "3", can't. So you could do return 3 :: > [Int] or equivalently return 3 :: [] Int to get [3], you can't do return > "3" :: [Int], because "3" can't be an Int. You can do return "3" :: > [String], since "3" is a string. Just to show the range of possibilities, > you can do return 3 :: IO Float, and get back 3.0 as an IO action. The > monad in the type is IO, and 3 can be interpreted as a Float. > > _______________________________________________ > Beginners mailing list > Beginners(a)haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners > >

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