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minimal complete definition (Data.Monoid)
by Marc A. Ziegert 18 Oct '05

18 Oct '05

i've just played a bit with monoids, especially with Ross Paterson's nice version of "class (Monoid b)=>Monoid(a->b)" mapped to Arrows, and Implicit Parameters (i tried to simulate dynamic instances). for me, i came to the conclusion, that it is easier and nicer to generalise some functions, to be able to set the used monoid-functions via parameter. (not implicit parameter!) minimizing the overhead, i read this in the libraries: [docu] class Monoid a where The monoid class. A minimal complete definition must supply mempty and mappend, and these should satisfy the monoid laws. [/docu] is that really the only minimal complete definition, that is implemented? how about mconcat? [code] mempty = mconcat [] mappend a b = mconcat [a,b] [/code] the mconcat may be not optimised, if there are only the "minimal complete definition" mempty and mappend; so, it is good, that mconcat is one of the class-functions... but writing only the optimized mconcat is a "minimal complete definition", too. by the way: instead of Ross Paterson's "Data.Monoid"(Date: 2005-09-13 15:52:31 GMT), i would prefer another class: [code] import Prelude hiding (sequence) import qualified Control.Monad import Control.Arrow class Sequence m where sequence :: [m a] -> m [a] instance Monad m => Sequence m where sequence = Control.Monad.sequence instance (Arrow f) => Sequence (f a) where sequence [] = pure (const []) sequence [f] = f >>> pure (:[]) sequence (f:fr) = (f &&& sequence fr) >>> pure (uncurry (:)) --Ross Paterson's Monoid: rp_concat :: (Monoid b) => [a->b] -> a->b rp_concat = mconcat . sequence rp_concat' :: (Arrow f,Monoid b) => [f a b] -> f a b rp_concat' fs = sequence fs >>> pure mconcat [/code]

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RE: Cabal doesn't echo commands with -v on Windows
by Simon Peyton-Jones 18 Oct '05

18 Oct '05

Windows GHC 6.4.1 is definitely seg-faulting when it runs Cabal. (Cabal outputs less trace stuff than it should, but that's a separate and less urgent matter.) We're investigating. Simon | -----Original Message----- | From: libraries-bounces(a)haskell.org [mailto:libraries-bounces@haskell.org] On Behalf Of Bayley, | Alistair | Sent: 18 October 2005 10:21 | To: 'Krasimir Angelov' | Cc: Haskell libraries | Subject: RE: Cabal doesn't echo commands with -v on Windows | | > From: Krasimir Angelov [mailto:kr.angelov@gmail.com] | > | > Cabal passes -v flag to the executed external commands only when the | > verbose level is > 4. | | I posted this to ghc-users yesterday, and asked how I could get it to | produce GHC -v output. | | sh-2.04$ runhaskell Setup.hs build -v5 | Preprocessing library haskell-src-exts-0.2... | c:\happy\happy-1.13\bin\happy.exe -agc -oLanguage\Haskell\Hsx\Parser.hs | Language\Haskell\Hsx\Parser.ly | shift/reduce conflicts: 5 | Building haskell-src-exts-0.2... | [segfault: instruction at 0 ref'd memory at 0] | sh-2.04$ | | | Do you think it might still be a flushing problem? | | Alistair. | | ----------------------------------------- | ***************************************************************** | Confidentiality Note: The information contained in this message, and any | attachments, may contain confidential and/or privileged material. It is | intended solely for the person(s) or entity to which it is addressed. Any | review, retransmission, dissemination, or taking of any action in | reliance upon this information by persons or entities other than the | intended recipient(s) is prohibited. If you received this in error, please | contact the sender and delete the material from any computer. | ***************************************************************** | | _______________________________________________ | Libraries mailing list | Libraries(a)haskell.org | http://www.haskell.org/mailman/listinfo/libraries

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RE: Cabal doesn't echo commands with -v on Windows
by Bayley, Alistair 18 Oct '05

18 Oct '05

> From: Krasimir Angelov [mailto:kr.angelov@gmail.com] > > Cabal passes -v flag to the executed external commands only when the > verbose level is > 4. I posted this to ghc-users yesterday, and asked how I could get it to produce GHC -v output. sh-2.04$ runhaskell Setup.hs build -v5 Preprocessing library haskell-src-exts-0.2... c:\happy\happy-1.13\bin\happy.exe -agc -oLanguage\Haskell\Hsx\Parser.hs Language\Haskell\Hsx\Parser.ly shift/reduce conflicts: 5 Building haskell-src-exts-0.2... [segfault: instruction at 0 ref'd memory at 0] sh-2.04$ Do you think it might still be a flushing problem? Alistair. ----------------------------------------- ***************************************************************** Confidentiality Note: The information contained in this message, and any attachments, may contain confidential and/or privileged material. It is intended solely for the person(s) or entity to which it is addressed. Any review, retransmission, dissemination, or taking of any action in reliance upon this information by persons or entities other than the intended recipient(s) is prohibited. If you received this in error, please contact the sender and delete the material from any computer. *****************************************************************

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Cabal doesn't echo commands with -v on Windows
by Simon Peyton-Jones 18 Oct '05

18 Oct '05

Cabal with -v should echo the commands it is executing. But on Windows it doesn't. See the error log below. (This is when compiling the FastPackedString Cabal package, in fact.) Simon M thinks it might be a buffering issue. Flush before calling any command? Simon sh-2.04$ runghc Setup.hs -v build Preprocessing library fps-0.1... Building fps-0.1... <Windows pops up the GHC-has-crashed window>

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holy frijoles: constant factors matter.
by John Meacham 14 Oct '05

14 Oct '05

these differences in jhc runtimes were the result of a single line change. < total time = 44.32 secs (2216 ticks @ 20 ms) < total alloc = 9,372,965,276 bytes (excludes profiling overheads) --- > total time = 36.74 secs (1837 ticks @ 20 ms) > total alloc = 6,621,233,076 bytes (excludes profiling overheads) the odd thing is, the change should not have changed the order of the algorithm at all. the change was (effectivly) Map.fromAscList . map f . Map.toAscList being changed to Map.map f both are O(n). but those constant factors matter. a lot. in any case, the reason I mention it is because if there were routines for converting between Set and Map that preserved the binary tree structure, I think their use could dramatically speed up many routines. In jhc (and other programs), I convert between them all the time and I'd hate to have to fall back on type Set a = Map a (). Map already has a keysSet, but it does the same inefficient thing building an intermediate list. all that is needed is a setToMap :: (a -> b) -> Set a -> Map a b the keysSet could be made more efficient in the next point release, but I guess adding setToMap would have to wait til the next major one. John -- John Meacham - ⑆repetae.net⑆john⑈

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RE: Network Exception
by Simon Marlow 13 Oct '05

13 Oct '05

On 12 October 2005 17:14, Arias wrote: > My name Iván Arias, I'm trying to connect to a server using the > Network library, the code that I'm using is something like this: > > --- BEGIN --- > module Main where > import System.IO > import Network > > main = do > handle <- connectTo "localhost" ( PortNumber 8080 ) > hClose handle > --- END --- > > It compiles correctly, but when I try to run this code, it throws an > exception at connectTo. The exception message is this: > > - getServiceEntry: does not exists (No such service entry) I can't see any reason that would happen. Is that the actual code you are using? Cheers, Simon

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RE: [Haskell] setSocketOption unusable?
by Simon Marlow 13 Oct '05

13 Oct '05

[ moved to libraries(a)haskell.org from haskell(a)haskell.org] On 12 October 2005 21:01, John Goerzen wrote: > I'm wanting to set the SO_RCVTIMEO and SO_SNDTIMEO options on a socket > from Haskell. socket(7) say that these take a struct timeval ad a > parameter. (Other options, such as SO_LONGER, also could have this > problem.) > > In Haskell, we see: > > setSocketOption :: Socket -> SocketOption -> Int -> IO () > > Now, there are SocketOption constructors (RecvTimeOut and SendTimeOut) > for what I want. But there is no way to give it a proper timeval (and > yes, I checked the source.) > > setSocketOption definately wants an Int, and is passing the length of > the Int to setsockopt(2) as well, so it appears to me that there is > absolutely no way to correctly specify SO_RCVTIMEO or SO_SNDTIMEO > through Haskell's socket layer. > > Is that correct? > > If so, how can we fix it? Looks like that interface is fairly broken to me. SocketOption should be an albebraic type with the appropraite parameters to each constructor. Fortunately everything is exported non-abstractly from Network.Socket so you can implement your own setSocketOption. If you come up with some code, I'll incorporate it, or just submit a bug report. Cheers, Simon

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Network Exception
by Arias 12 Oct '05

12 Oct '05

Hi, My name Iván Arias, I'm trying to connect to a server using the Network library, the code that I'm using is something like this: --- BEGIN --- module Main where import System.IO import Network main = do handle <- connectTo "localhost" ( PortNumber 8080 ) hClose handle --- END --- It compiles correctly, but when I try to run this code, it throws an exception at connectTo. The exception message is this: - getServiceEntry: does not exists (No such service entry) Do somebody know why this happens and how to fix it? Thanks

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RE: cabal beginner issues (other-modules, build-depends)
by Simon Marlow 12 Oct '05

12 Oct '05

On 23 September 2005 08:45, Johannes Waldmann wrote: >> Another way to look at both issues is that if ghc can figure out >> other modules and packages itself, the user shouldn't be required to >> specify them in a cabal file. ... > > Definitely. Having the list of modules in the .cabal is unnecessary > duplication of information (because it's in the sources already). > This is bound to get out-of-sync during development - > unless you use some kind of Makefile to generate the .cabal file, > which defeats the very purpose of Cabal itself. I know how to do this using GHC, but I'm not sure about other compilers. With GHC, we can generate the dependencies using 'ghc -M' and then parse the generated Makefile (a bit of a long way around, but I can't think of an easier way). Of course we'd avoid splatting an existing Makefile by redirecting the dependencies to a temporary file. How would we do this with nhc98 or Hugs? Perhaps because these systems don't actually need to know the value of other-modules we can get away with it. Comments? > Unrelated question: can someone please share an example that shows > how to put user-defined options for haddock in a .cabal? There's no good way to do it right now. You can override the whole haddock command using hooks, but you'd have to write quite a bit of code to do this. I plan to add something to allow extra Haddock args to be given (the Haddock support is a very bare-bones right now, it should get better). Cheers, Simon

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making with profiling, 6.4.1, cabal-1.1.3
by Serge D. Mechveliani 11 Oct '05

11 Oct '05

People, I need help on making for profiling, and cannot decide whether the question is on GHC or on Cabal. I have ghc-6.4.1, and Cabal-1.1.3-September-12 installed in my user directory, under Debian Linux, and need to make a project for profiling. ghci -package Cabal says ... Loading package base-1.0 ... linking ... done. ... Loading package Cabal-1.1.3 ... linking ... done. I start with a contrived example project of M1.hs, M2.hs, Main.hs: --------------------------------------- module M1 where m1 = True module M2 where import M1; m2 = m1 && m1 Main.hs: import M2l; main = putStr $ shows m2 "\n" --------------------------------------- For this, ghc --make -prof -auto-all Main works as needed -- without packages. Now, try to make a package for profiling: foo.cabal: name: foo version: 1.0 build-depends: base, haskell98, data exposed-modules: M2 other-modules: M1 ghc-options: -prof -auto-all -hisuf p_hi -osuf p_o The aim is to build foo (of M2) as a library, then to make Main under the package foo, and with profiling. Then, runhaskell Setup configure --ghc --prefix=$source/inst runhaskell Setup build produces a report ------------------------------------------------------------------- ... configure: Using compiler: /home/mechvel/ghc/6.4.1/inst/bin/ghc configure: Compiler flavor: GHC configure: Compiler version: 6.4.1 configure: Using package tool: /home/mechvel/ghc/6.4.1/inst/bin/ghc-pkg configure: No haddock found configure: Using happy: /usr/bin/happy configure: Using alex: /usr/bin/alex configure: Using hsc2hs: /home/mechvel/ghc/6.4.1/inst/bin/hsc2hs configure: No c2hs found configure: No cpphs found configure: No greencard found configure: Dependency base-any: using base-1.0 configure: Dependency haskell98-any: using haskell98-1.0 configure: Dependency data-any: using data-1.0 scico:~/t> make build runhaskell Setup.hs build Preprocessing library foo-1.0... Building foo-1.0... Chasing modules from: M2,M1 Skipping M1 ( M1.hs, dist/build/M1.p_o ) Skipping M2 ( M2.hs, dist/build/M2.p_o ) /usr/bin/ar: creating dist/build/libHSfoo-1.0.a /usr/bin/ar: dist/build/M2.o: No such file or directory make: *** [build] Error 1 ------------------------------------------------------------------- The directory ~/t/dist/build contains at this moment M1.p_hi M1.p_o M2.p_hi M2.p_o Main.p_hi Main.p_o , and indeed, no M2.o file. If I remove -hisuf p_hi -osuf p_o (by the way, why should the user think of these wise suffixes, maybe, -prof should be sufficient? ), then it reports ... /usr/bin/ld: cannot find -lHSfoo-1.0_p collect2: ld returned 1 exit status What I am missing, please? Thank you in advance for the help. ----------------- Serge Mechveliani mechvel(a)botik.ru

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