May 2016 - Haskell-Cafe

The maths behind the Fastest Fibb In The West.
by Michael Litchard 07 May '16

07 May '16

I've been working on a project that needs a good fibonacci generator, and I'm to the point where can now improve upon this one: https://wiki.haskell.org/The_Fibonacci_sequence#Fastest_Fib_in_the_West thanks to this guy: https://groups.google.com/forum/#!topic/haskell-cafe/HUgbAUCvCp4 He suggested breaking up a guard into two diffeent functions, which I can do, but I don't know what to call them because I don't know why the operations are different. I'm referring to this section: fib' (f, g) p | p = (f*(f+2*g), f^2 + g^2) | otherwise = (f^2+g^2, g*(2*f-g)) I'd like to know the reason why each guard does two entirely different things, so I know what to call the functions when I seperate them out.

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I have a question
by Eunsu Kim 06 May '16

06 May '16

Hi I don’t want to receive this mail anymore. what should do? thanks

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Re: [Haskell-cafe] Code critique request
by Michael Litchard 06 May '16

06 May '16

Thank you David, for taking all that time on my project. I got so much more than I was expecting. I take it my concern was focused in the wrong place? Time-space complexity of mapM fibb is okay? On Fri, May 6, 2016 at 1:37 PM, David McBride <toad3k(a)gmail.com> wrote: > A lot of your functions return Either FizError a when they obviously can't > have an error? I prefer to keep the functions as pure as they can be, and > then lift them into Either in the few cases where I'd need them to be in > that type. > > How about fibb :: Integer -> Integer, fizzbuzz :: Integer -> Text, then > in the above code: > mapM (Right <$> fizzbuzz) =<< ... =<< mapM (Right <$> fibb) =<< ... > > This also greatly simplifies many of your tests and benchmarks. For > example src-test/PropTests/Fibonacci.hs, testfib changes from > > testfib n = > case (fibb n) of > Left _ -> False > Right n' -> isFib n' > > to > > testfib = isFib . fibb > > in src-test/UnitTests/Fibonacci.hs, fibs changes from > > fibs = [Right 1,Right 1,Right 2,Right 3,Right 5,Right 8,Right 13,Right > 21,Right 34,Right 55] > > to > > fibs = [1,1,2,3,5,8,13,21,34,55] > > among others. > > In fizzbuzz, I would, instead of converting it to maybe and then using > fromMaybe, use the option function from semigroups which is the option > equivalent to maybe, and contains all the functionality of fromMaybe. > fizzbuzz :: Integer -> Text > fizzbuzz i = option (show i) id fizzbuzz' > > Your type annotation on c = 2 and subsequent comments are unnecessary if > fibb has a type annotation, which it does. I would also recommend adding > types for divs and fib' as the types are non obvious and I had to use > typeholes to find them. > > In fibb, I would change map (toEnum . fromIntegral) to map (>0) (or /= > 0). It is easier to understand, faster, and will not blow up on negative > numbers (I realize there can't be, but it was not obvious to me). > > You wrote an unfoldl, but I'm pretty sure you could replace that with > reverse (unfoldr ...). Due to the fact that you are appending with (++) in > your implementation anyways, it is much more efficient. My final version > of fibb looks like this, and passes your tests. > fibb = snd . foldl' fib' (1, 0) . map (>0) . reverse . unfoldr divs > > boolToEither can be written with an if statement instead of case > boolToEither bool a b = if bool then Right b else Left a > > Stylistically, I would put argument validation into src-exe and into the > main function, allowing it to bail with an argument error before ever > getting to your fizzbuzz code, which should not concern itself with program > argument validation. I realize you are intending to demonstrate monads > using either in your blog, so carry on if that's the case. > > Some general advice I would give, is that if a function isn't doing as > little as it can, try pulling out some of the stuff it doesn't need to do > out into a shallower part of your program. > > For example, when I look at the fibb where fib' function, fib' :: (a, a) > -> Bool -> (a, a), where depending on the bool, and nothing else, it does > two completely different things. Maybe it should be two different > functions, with the bool checking outside? I'm not familiar enough with > what you are trying to do to say that that can be done, but that is my > first instinct. > > As to the structure of your project, it looks great. I may have learned a > few things... > > > On Fri, May 6, 2016 at 2:29 PM, Michael Litchard <michael(a)schmong.org> > wrote: > >> I've got this fizzbuzz project I am using for a blog series, among other >> things. In this version, the fizzbuzz function is fed from a Fibonacci >> generator. I'm particularly concerned with the efficiency of the Fibonacci >> generator, but all scrutiny is welcomed. >> >> I'll included a link to the entire project, but below are the parts I >> think would be sufficient to spot trouble with how I am generating >> Fibonacci numbers. >> >> -- Driver function performs following-- (1) checks that input is proper-- (2) creates integer list for fibonacci generator-- (3) calculates first x in fibonnaci sequence-- (4) generates fizzbuzz output using (3) >> >> fizzBuzzFib :: [Text] -> Either FizzError [Text] >> fizzBuzzFib str = >> mapM fizzbuzz =<< >> mapM fibb =<< -- Possible problem here(\x -> Right [1 .. x]) =<< >> convertToPInt =<< >> mustHaveOne str >> >> fibb :: Integer -> Either FizzError Integer >> fibb n = Right $ snd . foldl' fib' (1, 0) . map (toEnum . fromIntegral) $ unfoldl divs n >> where >> unfoldl f x = >> case f x of >> Nothing -> [] >> Just (u, v) -> unfoldl f v ++ [u] >> >> divs 0 = Nothing >> divs k = Just (uncurry (flip (,)) (k `divMod` 2)) >> >> fib' (f, g) p >> | p = (f*(f+c*g), f^c + g^c) >> | otherwise = (f^c+g^c, g*(c*f-g)) >> where >> c :: Integer -- See codebase for reasons >> c = 2 >> >> The whole project, for your critiquing eye:https://github.com/mlitchard/swiftfizz >> >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe >> >> >

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Code critique request
by Michael Litchard 06 May '16

06 May '16

I've got this fizzbuzz project I am using for a blog series, among other things. In this version, the fizzbuzz function is fed from a Fibonacci generator. I'm particularly concerned with the efficiency of the Fibonacci generator, but all scrutiny is welcomed. I'll included a link to the entire project, but below are the parts I think would be sufficient to spot trouble with how I am generating Fibonacci numbers. -- Driver function performs following-- (1) checks that input is proper-- (2) creates integer list for fibonacci generator-- (3) calculates first x in fibonnaci sequence-- (4) generates fizzbuzz output using (3) fizzBuzzFib :: [Text] -> Either FizzError [Text] fizzBuzzFib str = mapM fizzbuzz =<< mapM fibb =<< -- Possible problem here(\x -> Right [1 .. x]) =<< convertToPInt =<< mustHaveOne str fibb :: Integer -> Either FizzError Integer fibb n = Right $ snd . foldl' fib' (1, 0) . map (toEnum . fromIntegral) $ unfoldl divs n where unfoldl f x = case f x of Nothing -> [] Just (u, v) -> unfoldl f v ++ [u] divs 0 = Nothing divs k = Just (uncurry (flip (,)) (k `divMod` 2)) fib' (f, g) p | p = (f*(f+c*g), f^c + g^c) | otherwise = (f^c+g^c, g*(c*f-g)) where c :: Integer -- See codebase for reasons c = 2 The whole project, for your critiquing eye:https://github.com/mlitchard/swiftfizz

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Trouble building library with cabal-install 1.24
by Amy de Buitléir 06 May '16

06 May '16

I'm trying to use cabal-install 1.24. To start fresh, I removed ~/.cabal and ~/.ghc, and then used the old cabal(-install) executable to do cabal update and cabal install cabal-install. Unfortunately, it seems that cabal-install is building everything except my library! $ cabal --version cabal-install version 1.24.0.0 compiled using version 1.24.0.0 of the Cabal library $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.10.3 $ cat cabal.project.local tests: True program-options ghc-options: -Werror $ cabal new-build --enable-test -v Project settings changed, reconfiguring... creating /home/eamybut/néal/creatur/dist-newstyle creating /home/eamybut/néal/creatur/dist-newstyle/cache creating /home/eamybut/.cabal/store/ghc-7.10.3 Reading installed packages... /usr/local/ghc-7.10.3/bin/ghc-pkg dump '--package-db=/home/eamybut/.cabal/store/ghc-7.10.3/package.db' -v0 /usr/local/ghc-7.10.3/bin/ghc --print-libdir -Werror In order, the following will be built: cond-0.4.1.1 (lib:cond) (requires build) primitive-0.6.1.0 (lib:primitive) (requires build) random-1.1 (lib:random) (requires build) MonadRandom-0.4.2.3 (lib:MonadRandom) (requires build) regex-base-0.93.2 (lib:regex-base) (requires build) regex-posix-0.95.2 (lib:regex-posix) (requires build) tf-random-0.5 (lib:tf-random) (requires build) QuickCheck-2.8.2 (lib:QuickCheck) (requires build) xml-1.3.14 (lib:xml) (requires build) test-framework-0.8.1.1 (lib:test-framework) (requires build) test-framework-hunit-0.3.0.2 (lib:test-framework-hunit) (requires build) test-framework-quickcheck2-0.3.0.3 (lib:test-framework-quickcheck2) (requires build) creatur-5.9.12 (lib:creatur test:creatur-tests) *test (first run) creating /home/eamybut/néal/creatur/dist-newstyle/build creating /home/eamybut/néal/creatur/dist-newstyle/tmp Extracting /home/eamybut/.cabal/packages/hackage.haskell.org/cond/0.4.1.1/cond-0.4.1.1.tar. gz to /home/eamybut/néal/creatur/dist-newstyle/tmp/cond-4543... Extracting Extracting Extracting /home/eamybut/.cabal/packages/hackage.haskell.org/primitive/0.6.1.0/primitive-0. 6.1.0.tar.gz /home/eamybut/.cabal/packages/hackage.haskell.org/random/1.1/random-1.1.tar.gz /home/eamybut/.cabal/packages/hackage.haskell.org/regex-base/0.93.2/regex-base-0 .93.2.tar.gz Updating cond.cabal with the latest revision from the index. to /home/eamybut/néal/creatur/dist-newstyle/tmp/primitive-4543... to /home/eamybut/néal/creatur/dist-newstyle/tmp/random-4543... to /home/eamybut/néal/creatur/dist-newstyle/tmp/regex-base-4543... creating dist Updating primitive.cabal with the latest revision from the index. Updating random.cabal with the latest revision from the index. Updating regex-base.cabal with the latest revision from the index. Configuring cond-0.4.1.1... creating dist creating dist creating dist /home/eamybut/.cabal/bin/cabal act-as-setup --build-type=Simple -- configure Configuring primitive-0.6.1.0... Configuring random-1.1... Configuring regex-base-0.93.2... --verbose=2 --builddir=dist --ghc --prefix=/home/eamybut/.cabal/store/ghc-7.10.3/cond-0.4.1.1-d6f8f52c204603b82b24 b34eb8efb77ce69172f7e29c5da408121c1e840e7bca --bindir=/home/eamybut/.cabal/store/ghc-7.10.3/cond-0.4.1.1-d6f8f52c204603b82b24 b34eb8efb77ce69172f7e29c5da408121c1e840e7bca/bin /home/eamybut/.cabal/bin/cabal act-as-setup --build-type=Simple -- configure /home/eamybut/.cabal/bin/cabal act-as-setup --build-type=Simple -- configure /home/eamybut/.cabal/bin/cabal act-as-setup --build-type=Simple -- configure --libdir=/home/eamybut/.cabal/store/ghc-7.10.3/cond-0.4.1.1-d6f8f52c204603b82b24 b34eb8efb77ce69172f7e29c5da408121c1e840e7bca/lib --verbose=2 --builddir=dist --ghc --verbose=2 --builddir=dist --ghc --verbose=2 --builddir=dist --ghc --libsubdir= --prefix=/home/eamybut/.cabal/store/ghc-7.10.3/primitive-0.6.1.0-b7ddd297d5514a8 7874afe52df39e3953f43ebb68440dbf31be727064e02c914 --prefix=/home/eamybut/.cabal/store/ghc-7.10.3/random-1.1-b26d9915a884bbc1b303e6 d2667f43890fe97c8ce038e14ab1c9b19e493af5c1 --prefix=/home/eamybut/.cabal/store/ghc-7.10.3/regex-base-0.93.2-b143cb5bc118558 645f7ba3efa292084e0faa0371afb4065baebdd6202d7600d --libexecdir=/home/eamybut/.cabal/store/ghc-7.10.3/cond-0.4.1.1-d6f8f52c204603b8 2b24b34eb8efb77ce69172f7e29c5da408121c1e840e7bca/libexec --bindir=/home/eamybut/.cabal/store/ghc-7.10.3/primitive-0.6.1.0-b7ddd297d5514a8 7874afe52df39e3953f43ebb68440dbf31be727064e02c914/bin --bindir=/home/eamybut/.cabal/store/ghc-7.10.3/random-1.1-b26d9915a884bbc1b303e6 d2667f43890fe97c8ce038e14ab1c9b19e493af5c1/bin --bindir=/home/eamybut/.cabal/store/ghc-7.10.3/regex-base-0.93.2-b143cb5bc118558 645f7ba3efa292084e0faa0371afb4065baebdd6202d7600d/bin --datadir=/home/eamybut/.cabal/store/ghc-7.10.3/cond-0.4.1.1-d6f8f52c204603b82b2 4b34eb8efb77ce69172f7e29c5da408121c1e840e7bca/share --libdir=/home/eamybut/.cabal/store/ghc-7.10.3/primitive-0.6.1.0-b7ddd297d5514a8 7874afe52df39e3953f43ebb68440dbf31be727064e02c914/lib --libdir=/home/eamybut/.cabal/store/ghc-7.10.3/random-1.1-b26d9915a884bbc1b303e6 d2667f43890fe97c8ce038e14ab1c9b19e493af5c1/lib --libdir=/home/eamybut/.cabal/store/ghc-7.10.3/regex-base-0.93.2-b143cb5bc118558 645f7ba3efa292084e0faa0371afb4065baebdd6202d7600d/lib --datasubdir= --libsubdir= --libsubdir= --libsubdir= --docdir=/home/eamybut/.cabal/store/ghc-7.10.3/cond-0.4.1.1-d6f8f52c204603b82b24 b34eb8efb77ce69172f7e29c5da408121c1e840e7bca/share/doc --libexecdir=/home/eamybut/.cabal/store/ghc-7.10.3/primitive-0.6.1.0-b7ddd297d55 14a87874afe52df39e3953f43ebb68440dbf31be727064e02c914/libexec --libexecdir=/home/eamybut/.cabal/store/ghc-7.10.3/random-1.1-b26d9915a884bbc1b3 03e6d2667f43890fe97c8ce038e14ab1c9b19e493af5c1/libexec --libexecdir=/home/eamybut/.cabal/store/ghc-7.10.3/regex-base-0.93.2-b143cb5bc11 8558645f7ba3efa292084e0faa0371afb4065baebdd6202d7600d/libexec --htmldir=/home/eamybut/.cabal/store/ghc-7.10.3/cond-0.4.1.1-d6f8f52c204603b82b2 4b34eb8efb77ce69172f7e29c5da408121c1e840e7bca/share/doc/html --datadir=/home/eamybut/.cabal/store/ghc-7.10.3/primitive-0.6.1.0-b7ddd297d5514a 87874afe52df39e3953f43ebb68440dbf31be727064e02c914/share --datadir=/home/eamybut/.cabal/store/ghc-7.10.3/random-1.1-b26d9915a884bbc1b303e 6d2667f43890fe97c8ce038e14ab1c9b19e493af5c1/share --datadir=/home/eamybut/.cabal/store/ghc-7.10.3/regex-base-0.93.2-b143cb5bc11855 8645f7ba3efa292084e0faa0371afb4065baebdd6202d7600d/share --haddockdir=/home/eamybut/.cabal/store/ghc-7.10.3/cond-0.4.1.1-d6f8f52c204603b8 2b24b34eb8efb77ce69172f7e29c5da408121c1e840e7bca/share/doc/html --datasubdir= --datasubdir= --datasubdir= --sysconfdir=/home/eamybut/.cabal/store/ghc-7.10.3/cond-0.4.1.1-d6f8f52c204603b8 2b24b34eb8efb77ce69172f7e29c5da408121c1e840e7bca/etc --docdir=/home/eamybut/.cabal/store/ghc-7.10.3/primitive-0.6.1.0-b7ddd297d5514a8 7874afe52df39e3953f43ebb68440dbf31be727064e02c914/share/doc --docdir=/home/eamybut/.cabal/store/ghc-7.10.3/random-1.1-b26d9915a884bbc1b303e6 d2667f43890fe97c8ce038e14ab1c9b19e493af5c1/share/doc --docdir=/home/eamybut/.cabal/store/ghc-7.10.3/regex-base-0.93.2-b143cb5bc118558 645f7ba3efa292084e0faa0371afb4065baebdd6202d7600d/share/doc --enable-library-vanilla --enable-library-profiling --enable-shared --htmldir=/home/eamybut/.cabal/store/ghc-7.10.3/primitive-0.6.1.0-b7ddd297d5514a 87874afe52df39e3953f43ebb68440dbf31be727064e02c914/share/doc/html --htmldir=/home/eamybut/.cabal/store/ghc-7.10.3/random-1.1-b26d9915a884bbc1b303e 6d2667f43890fe97c8ce038e14ab1c9b19e493af5c1/share/doc/html --htmldir=/home/eamybut/.cabal/store/ghc-7.10.3/regex-base-0.93.2-b143cb5bc11855 8645f7ba3efa292084e0faa0371afb4065baebdd6202d7600d/share/doc/html --disable-executable-dynamic --disable-profiling --profiling-detail=default --haddockdir=/home/eamybut/.cabal/store/ghc-7.10.3/primitive-0.6.1.0-b7ddd297d55 14a87874afe52df39e3953f43ebb68440dbf31be727064e02c914/share/doc/html --haddockdir=/home/eamybut/.cabal/store/ghc-7.10.3/random-1.1-b26d9915a884bbc1b3 03e6d2667f43890fe97c8ce038e14ab1c9b19e493af5c1/share/doc/html --haddockdir=/home/eamybut/.cabal/store/ghc-7.10.3/regex-base-0.93.2-b143cb5bc11 8558645f7ba3efa292084e0faa0371afb4065baebdd6202d7600d/share/doc/html --library-profiling-detail=default --enable-optimization --disable-debug-info --sysconfdir=/home/eamybut/.cabal/store/ghc-7.10.3/primitive-0.6.1.0-b7ddd297d55 14a87874afe52df39e3953f43ebb68440dbf31be727064e02c914/etc --sysconfdir=/home/eamybut/.cabal/store/ghc-7.10.3/random-1.1-b26d9915a884bbc1b3 03e6d2667f43890fe97c8ce038e14ab1c9b19e493af5c1/etc --sysconfdir=/home/eamybut/.cabal/store/ghc-7.10.3/regex-base-0.93.2-b143cb5bc11 8558645f7ba3efa292084e0faa0371afb4065baebdd6202d7600d/etc --disable-library-for-ghci --disable-split-objs --disable-executable-stripping --enable-library-vanilla --enable-library-profiling --enable-shared --enable-library-vanilla --enable-library-profiling --enable-shared --enable-library-vanilla --enable-library-profiling --enable-shared --disable-library-stripping --package-db=clear --package-db=global --disable-executable-dynamic --disable-profiling --profiling-detail=default --disable-executable-dynamic --disable-profiling --profiling-detail=default --disable-executable-dynamic --disable-profiling --profiling-detail=default --package-db=/home/eamybut/.cabal/store/ghc-7.10.3/package.db --library-profiling-detail=default --enable-optimization --disable-debug-info --library-profiling-detail=default --enable-optimization --disable-debug-info --library-profiling-detail=default --enable-optimization --disable-debug-info --ipid=cond-0.4.1.1-d6f8f52c204603b82b24b34eb8efb77ce69172f7e29c5da408121c1e840e 7bca --disable-library-for-ghci --disable-split-objs --disable-executable-stripping --disable-library-for-ghci --disable-split-objs --disable-executable-stripping --disable-library-for-ghci --disable-split-objs --disable-executable-stripping --dependency=base=base-4.8.2.0-0d6d1084fbc041e1cded9228e80e264d --disable-library-stripping --package-db=clear --package-db=global --disable-library-stripping --package-db=clear --package-db=global --disable-library-stripping --package-db=clear --package-db=global --disable-tests --disable-coverage --exact-configuration --disable-benchmarks --package-db=/home/eamybut/.cabal/store/ghc-7.10.3/package.db --package-db=/home/eamybut/.cabal/store/ghc-7.10.3/package.db --package-db=/home/eamybut/.cabal/store/ghc-7.10.3/package.db --with-ghc=/usr/local/ghc-7.10.3/bin/ghc --ipid=primitive-0.6.1.0-b7ddd297d5514a87874afe52df39e3953f43ebb68440dbf31be7270 64e02c914 --ipid=random-1.1-b26d9915a884bbc1b303e6d2667f43890fe97c8ce038e14ab1c9b19e493af5 c1 --flags=splitbase --flags=newbase --with-ghc-pkg=/usr/local/ghc-7.10.3/bin/ghc-pkg --ghc-option=-Werror --dependency=base=base-4.8.2.0-0d6d1084fbc041e1cded9228e80e264d --dependency=base=base-4.8.2.0-0d6d1084fbc041e1cded9228e80e264d --ipid=regex-base-0.93.2-b143cb5bc118558645f7ba3efa292084e0faa0371afb4065baebdd6 202d7600d --dependency=ghc-prim=ghc-prim-0.4.0.0-6cdc86811872333585fa98756aa7c51e --dependency=time=time-1.6-3b93b66397d7b7d84c3a87826ae1549fc4e47935065267f486fdc 3425d250cd5 --dependency=array=array-0.5.1.0-960bf9ae8875cc30355e086f8853a049 --dependency=transformers=transformers-0.5.2.0-c4818cc3cc5467e714fd3fd12dcbf7740 9ca3ca7292b47a5830cfcb4fb5911e2 --disable-tests --disable-coverage --exact-configuration --disable-benchmarks --dependency=base=base-4.8.2.0-0d6d1084fbc041e1cded9228e80e264d Redirecting build log to {handle: /home/eamybut/.cabal/logs/cond-0.4.1.1.log} --disable-tests --disable-coverage --exact-configuration --disable-benchmarks --with-ghc=/usr/local/ghc-7.10.3/bin/ghc --dependency=bytestring=bytestring-0.10.6.0-9a873bcf33d6ce2fd2698ce69e2c1c66 --with-ghc=/usr/local/ghc-7.10.3/bin/ghc --with-ghc-pkg=/usr/local/ghc-7.10.3/bin/ghc-pkg --ghc-option=-Werror --dependency=containers=containers-0.5.6.2-59326c33e30ec8f6afd574cbac625bbb --with-ghc-pkg=/usr/local/ghc-7.10.3/bin/ghc-pkg --ghc-option=-Werror --dependency=mtl=mtl-2.2.1-f8863ab628c53078d6adbcf7634212242d99bcdf1c73497f1131e 24fcafd4187 --disable-tests --disable-coverage --exact-configuration --disable-benchmarks Redirecting build log to {handle: /home/eamybut/.cabal/logs/random-1.1.log} --with-ghc=/usr/local/ghc-7.10.3/bin/ghc Redirecting build log to {handle: --with-ghc-pkg=/usr/local/ghc-7.10.3/bin/ghc-pkg --ghc-option=-Werror /home/eamybut/.cabal/logs/primitive-0.6.1.0.log} Redirecting build log to {handle: /home/eamybut/.cabal/logs/regex-base-0.93.2.log} Building regex-base-0.93.2... /home/eamybut/.cabal/bin/cabal act-as-setup --build-type=Simple -- build --verbose=2 --builddir=dist Redirecting build log to {handle: /home/eamybut/.cabal/logs/regex-base-0.93.2.log} Building random-1.1... /home/eamybut/.cabal/bin/cabal act-as-setup --build-type=Simple -- build --verbose=2 --builddir=dist Redirecting build log to {handle: /home/eamybut/.cabal/logs/random-1.1.log} Building primitive-0.6.1.0... /home/eamybut/.cabal/bin/cabal act-as-setup --build-type=Simple -- build --verbose=2 --builddir=dist Redirecting build log to {handle: /home/eamybut/.cabal/logs/primitive-0.6.1.0.log} Building cond-0.4.1.1... /home/eamybut/.cabal/bin/cabal act-as-setup --build-type=Simple -- build --verbose=2 --builddir=dist Redirecting build log to {handle: /home/eamybut/.cabal/logs/cond-0.4.1.1.log} Extracting /home/eamybut/.cabal/packages/hackage.haskell.org/xml/1.3.14/xml-1.3.14.tar.gz to /home/eamybut/néal/creatur/dist-newstyle/tmp/xml-4543... Updating xml.cabal with the latest revision from the index. creating dist Configuring xml-1.3.14... /home/eamybut/.cabal/bin/cabal act-as-setup --build-type=Simple -- configure --verbose=2 --builddir=dist --ghc --prefix=/home/eamybut/.cabal/store/ghc-7.10.3/xml-1.3.14-b04f5878120533b38458e7 afa38083e761daf4b6cf823ee2a31d1d5bba8de548 --bindir=/home/eamybut/.cabal/store/ghc-7.10.3/xml-1.3.14-b04f5878120533b38458e7 afa38083e761daf4b6cf823ee2a31d1d5bba8de548/bin --libdir=/home/eamybut/.cabal/store/ghc-7.10.3/xml-1.3.14-b04f5878120533b38458e7 afa38083e761daf4b6cf823ee2a31d1d5bba8de548/lib --libsubdir= --libexecdir=/home/eamybut/.cabal/store/ghc-7.10.3/xml-1.3.14-b04f5878120533b384 58e7afa38083e761daf4b6cf823ee2a31d1d5bba8de548/libexec --datadir=/home/eamybut/.cabal/store/ghc-7.10.3/xml-1.3.14-b04f5878120533b38458e 7afa38083e761daf4b6cf823ee2a31d1d5bba8de548/share --datasubdir= --docdir=/home/eamybut/.cabal/store/ghc-7.10.3/xml-1.3.14-b04f5878120533b38458e7 afa38083e761daf4b6cf823ee2a31d1d5bba8de548/share/doc --htmldir=/home/eamybut/.cabal/store/ghc-7.10.3/xml-1.3.14-b04f5878120533b38458e 7afa38083e761daf4b6cf823ee2a31d1d5bba8de548/share/doc/html --haddockdir=/home/eamybut/.cabal/store/ghc-7.10.3/xml-1.3.14-b04f5878120533b384 58e7afa38083e761daf4b6cf823ee2a31d1d5bba8de548/share/doc/html --sysconfdir=/home/eamybut/.cabal/store/ghc-7.10.3/xml-1.3.14-b04f5878120533b384 58e7afa38083e761daf4b6cf823ee2a31d1d5bba8de548/etc --enable-library-vanilla --enable-library-profiling --enable-shared --disable-executable-dynamic --disable-profiling --profiling-detail=default --library-profiling-detail=default --enable-optimization --disable-debug-info --disable-library-for-ghci --disable-split-objs --disable-executable-stripping --disable-library-stripping --package-db=clear --package-db=global --package-db=/home/eamybut/.cabal/store/ghc-7.10.3/package.db --ipid=xml-1.3.14-b04f5878120533b38458e7afa38083e761daf4b6cf823ee2a31d1d5bba8de5 48 --dependency=base=base-4.8.2.0-0d6d1084fbc041e1cded9228e80e264d --dependency=bytestring=bytestring-0.10.6.0-9a873bcf33d6ce2fd2698ce69e2c1c66 --dependency=text=text-1.2.2.1-ba97440de9fbd614cd8b02c1d9fda7e9073a288481e7e539c 2629ac910e67bf4 --disable-tests --disable-coverage --exact-configuration --disable-benchmarks --with-ghc=/usr/local/ghc-7.10.3/bin/ghc --with-ghc-pkg=/usr/local/ghc-7.10.3/bin/ghc-pkg --ghc-option=-Werror Redirecting build log to {handle: /home/eamybut/.cabal/logs/xml-1.3.14.log} Building xml-1.3.14... /home/eamybut/.cabal/bin/cabal act-as-setup --build-type=Simple -- build --verbose=2 --builddir=dist Redirecting build log to {handle: /home/eamybut/.cabal/logs/xml-1.3.14.log} That's the last line. No mention of actually building creatur (my library). $ find dist-newstyle dist-newstyle dist-newstyle/tmp dist-newstyle/cache dist-newstyle/cache/source-hashes dist-newstyle/cache/improved-plan dist-newstyle/cache/plan.json dist-newstyle/cache/compiler dist-newstyle/cache/elaborated-plan dist-newstyle/cache/solver-plan dist-newstyle/cache/config dist-newstyle/build $ find dist dist $ cabal info creatur * creatur (library) Synopsis: Framework for artificial life experiments. Versions available: 4.2.0, 4.3.2, 4.3.3, 5.7.3, 5.8.0, 5.8.2, 5.9.9, 5.9.10, 5.9.11 (and 51 others) Versions installed: [ Not installed ] . . . I'm using the same cabal file I've used with sandboxes.

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GHC.Prim: Resizable Multidimensional array
by Jake 06 May '16

06 May '16

I'm trying to create a resizable multidimensional array using the primitive array stuff in GHC.Prim. I see that the only resizable array is the ByteArray#, but the only array that supports multidimensionality is the ArrayArray# as far as I can tell. I have groups of 4 Double#s that I want to have a resizable array of, so only really the "first dimension" needs to be resizable. I was thinking if there was a way to get the pointer of a SmallArray# as an Addr# I could use the ability of ByteArray#s to store Addr#s. The other option I was considering was to simply have a mapping similar to the ones provided by Data.Ix that maps pairs of numbers to a single index, and in that way use a single ByteArray# to store everything. However, because this will be a fairly large array it seems like it is a much better idea to avoid allocating and reallocating that humongous chunk of memory when I can keep it spread out in smaller chunks by storing pointers to smaller arrays in the larger array. But maybe that isn't an important consideration? Thanks, Jake

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Taking over cmdtheline
by Gregory Crosswhite 06 May '16

06 May '16

The package cmdtheline has not been updated since Apr 30, 2013, and it is broken with the current version of GHC; it needs to have its upper bound on transformers bumped. I tried contacting the author three months ago and three weeks ago to ask him to fix the package, but I received no response. I contacted him one more time one week ago to tell him that I intended to take over the package, and still I received no response. Thus, following the instructions on Hackage for taking over a package, I am officially stating my intent to take over this package so that I can fix it. Cheers, Greg

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Fwd: Problem logging in GHC Trac
by Юрий Сыровецкий (Yuriy Syrovetskiy) 05 May '16

05 May '16

Hello I enter my login and password at https://ghc.haskell.org/trac/ghc/login and get: Internal Server Error Please contact the server administrator, webmaster@localhost Who is responsible for the site? Who can fix it? -- Yuriy Syrovetskiy, http://cblp.su

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Is Haskell IO inherently slower than C?
by Jake 04 May '16

04 May '16

I'm trying to write a program in Haskell that writes a large file at the end, and it seems like that output alone is taking way longer than it should. I don't understand why Haskell shouldn't be able to write data as quickly as C, so I wrote two test files: -- Test.hs import Control.Loop import Data.ByteString.Builder import System.IO main :: IO () main = numLoop 0 1000000 $ \_ -> hPutBuilder stdout $ char7 ' ' // test.c #include <stdio.h> int main() { int i; for (i = 0; i < 1000000; i++) { fprintf(stdout, " "); } return 0; } I compiled them both with -O2, and ran them redirecting their outputs to /dev/null. For the Haskell version I got times aroudn 0.3 seconds, while the C version was around 0.03. Is there any reason why in simple IO the Haskell version would be slower by an order of magnitude?

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Cabal confusion. Modules not being exposed still accessible for testing.
by Michael Litchard 04 May '16

04 May '16

I use reactive-banana <https://github.com/HeinrichApfelmus/reactive-banana/blob/master/reactive-ba…> as an example. My question is how can Reactive.Banana.Internal.Combinators be testable from Reactive.Banana.Test.Plumbing? My misunderstanding is that only modules named in the exposed-modules stanza could be imported. Could someone clear up my misunderstanding?

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