Re: [Haskell-cafe] Re: Re: 0/0 1 == False
Ben Franksen wrote: Kalman Noel wrote: (2) lim a_n = ∞ [...] (2) means that the sequence does not converge, because you can always find a value that is /larger/ than what you hoped might be the limit. (2) usually rather mean that for each positive limit A there is a number N such that a_N A for /all/ n N. You're right here. I tried to come up with a more wordy, informal description, but failed on that. Your definition of (2) is usually termed as '(a_n) contains a subsequence that tends toward +infinity'. May you elaborate? I don't see where a subsequence comes into play here. Kalman -- Get a free email account with anti spam protection. http://www.bluebottle.com/tag/2 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] threads + IORefs = Segmentation fault?
Hi David,
Which version of GHC are you using?
I tried to recompile some GHC 6.6.1 progs using GHC 6.8.2 and I also got
segfaults. I haven't figured out yet if this is because my changes to
make it work with GHC 6.8.2 are incorrect, or if this is an issue with
6.8.2.
Cheers,
Peter
On Fri, 2008-01-18 at 18:22 -0500, David Roundy wrote:
Hi all,
I'm working on some new progress-reporting code for darcs, and am getting
segmentation faults! :( The code uses threads + an IORef global variable
to do this (with lots of unsafePerformIO). So my question for the gurus
who know more about this than I do: is this safe? I thought it would be,
because only one thread ever modifies the IORef, and the others only read
it. I don't really care if they read a correct value, as long as they
don't segfault.
The code (to summarize) looks like:
{-# NOINLINE _progressData #-}
_progressData :: IORef (Map String ProgressData)
_progressData = unsafePerformIO $ newIORef empty
updateProgressData :: String - (ProgressData - ProgressData) - IO ()
updateProgressData k f = when (progressMode) $ modifyIORef _progressData
(adjust f k)
setProgressData :: String - ProgressData - IO ()
setProgressData k p = when (progressMode) $ modifyIORef _progressData (insert
k p)
getProgressData :: String - IO (Maybe ProgressData)
getProgressData k = if progressMode then lookup k `fmap` readIORef
_progressData
else return Nothing
The key function is
beginTedious :: String - IO ()
beginTedious k = do tid - forkIO $ handleProgress k
debugMessage $ Beginning ++ k
setProgressData k $ ProgressData { sofar = 0,
latest = Nothing,
total = Nothing,
handler = Just tid }
which is called before an action that may be so tedious for our users that
they need their day brightened by messages such as Applying patch
137/1436. The handleProgress function alternates between threadDelay and
reading the progress data to see whether any progress has been made and
printing messages. Meanwhile the main thread calls functions that update
_progressData.
Anyhow, the point is that I'm getting segfaults, even after recompiling
everything from scratch! Is this in fact that unsafe? Do I really need to
switch to MVars, even though no locking is required?
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[Haskell-cafe] Re: threads + IORefs = Segmentation fault?
David Roundy [EMAIL PROTECTED] wrote:
{-# NOINLINE _progressData #-}
_progressData :: IORef (Map String ProgressData)
_progressData = unsafePerformIO $ newIORef empty
updateProgressData :: String
- (ProgressData - ProgressData)
- IO ()
updateProgressData k f = when (progressMode) $ modifyIORef
_progressData (adjust f k)
The question I'm asking myself is why you would want to modify a
reference to an always empty Map, which would be the case if
unsafePerformIO performs its action every time. If it doesnt' (and
experience suggest that it doesn't, as does the faithful usage of
{-# NOINLINE #-}, BUT YOU'LL NEVER, EVER, KNOW), I'm wondering why you
don't create the IORef in beginTedious and pass it around. Possibly
even with an implicit parameter.
And, yes, without multiple writing threads locking is unnecessary, and
mostly even with multiple writing threads, if they don't read, too.
/me mandates the renaming of unsafePerformIO to
iReallyReallyThoughtReallyHardAboutThisAndThereReallyIsNoDifferentWayThanToUseThisDreadedUnsafePerformIO.
OTOH, I have no idea what causes the segfault.
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Re: [Haskell-cafe] threads + IORefs = Segmentation fault?
Using ghc 6.6, but I've since isolated the bug as being unrelated to the
IORefs and threading, it was in an FFI binding that somehow never died
until I was testing this new code.
David
On Sat, Jan 19, 2008 at 01:27:47PM +0100, Peter Verswyvelen wrote:
Hi David,
Which version of GHC are you using?
I tried to recompile some GHC 6.6.1 progs using GHC 6.8.2 and I also got
segfaults. I haven't figured out yet if this is because my changes to
make it work with GHC 6.8.2 are incorrect, or if this is an issue with
6.8.2.
Cheers,
Peter
On Fri, 2008-01-18 at 18:22 -0500, David Roundy wrote:
Hi all,
I'm working on some new progress-reporting code for darcs, and am getting
segmentation faults! :( The code uses threads + an IORef global variable
to do this (with lots of unsafePerformIO). So my question for the gurus
who know more about this than I do: is this safe? I thought it would be,
because only one thread ever modifies the IORef, and the others only read
it. I don't really care if they read a correct value, as long as they
don't segfault.
The code (to summarize) looks like:
{-# NOINLINE _progressData #-}
_progressData :: IORef (Map String ProgressData)
_progressData = unsafePerformIO $ newIORef empty
updateProgressData :: String - (ProgressData - ProgressData) - IO ()
updateProgressData k f = when (progressMode) $ modifyIORef _progressData
(adjust f k)
setProgressData :: String - ProgressData - IO ()
setProgressData k p = when (progressMode) $ modifyIORef _progressData
(insert k p)
getProgressData :: String - IO (Maybe ProgressData)
getProgressData k = if progressMode then lookup k `fmap` readIORef
_progressData
else return Nothing
The key function is
beginTedious :: String - IO ()
beginTedious k = do tid - forkIO $ handleProgress k
debugMessage $ Beginning ++ k
setProgressData k $ ProgressData { sofar = 0,
latest = Nothing,
total = Nothing,
handler = Just tid }
which is called before an action that may be so tedious for our users that
they need their day brightened by messages such as Applying patch
137/1436. The handleProgress function alternates between threadDelay and
reading the progress data to see whether any progress has been made and
printing messages. Meanwhile the main thread calls functions that update
_progressData.
Anyhow, the point is that I'm getting segfaults, even after recompiling
everything from scratch! Is this in fact that unsafe? Do I really need to
switch to MVars, even though no locking is required?
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Department of Physics
Oregon State University
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Re: [Haskell-cafe] threads + IORefs = Segmentation fault?
You should use an MVar if you want it to be thread safe.
On Jan 19, 2008 1:36 PM, David Roundy [EMAIL PROTECTED] wrote:
Using ghc 6.6, but I've since isolated the bug as being unrelated to the
IORefs and threading, it was in an FFI binding that somehow never died
until I was testing this new code.
David
On Sat, Jan 19, 2008 at 01:27:47PM +0100, Peter Verswyvelen wrote:
Hi David,
Which version of GHC are you using?
I tried to recompile some GHC 6.6.1 progs using GHC 6.8.2 and I also got
segfaults. I haven't figured out yet if this is because my changes to
make it work with GHC 6.8.2 are incorrect, or if this is an issue with
6.8.2.
Cheers,
Peter
On Fri, 2008-01-18 at 18:22 -0500, David Roundy wrote:
Hi all,
I'm working on some new progress-reporting code for darcs, and am
getting
segmentation faults! :( The code uses threads + an IORef global
variable
to do this (with lots of unsafePerformIO). So my question for the
gurus
who know more about this than I do: is this safe? I thought it would
be,
because only one thread ever modifies the IORef, and the others only
read
it. I don't really care if they read a correct value, as long as they
don't segfault.
The code (to summarize) looks like:
{-# NOINLINE _progressData #-}
_progressData :: IORef (Map String ProgressData)
_progressData = unsafePerformIO $ newIORef empty
updateProgressData :: String - (ProgressData - ProgressData) - IO
()
updateProgressData k f = when (progressMode) $ modifyIORef
_progressData (adjust f k)
setProgressData :: String - ProgressData - IO ()
setProgressData k p = when (progressMode) $ modifyIORef _progressData
(insert k p)
getProgressData :: String - IO (Maybe ProgressData)
getProgressData k = if progressMode then lookup k `fmap` readIORef
_progressData
else return Nothing
The key function is
beginTedious :: String - IO ()
beginTedious k = do tid - forkIO $ handleProgress k
debugMessage $ Beginning ++ k
setProgressData k $ ProgressData { sofar = 0,
latest =
Nothing,
total =
Nothing,
handler = Just
tid }
which is called before an action that may be so tedious for our users
that
they need their day brightened by messages such as Applying patch
137/1436. The handleProgress function alternates between threadDelay
and
reading the progress data to see whether any progress has been made
and
printing messages. Meanwhile the main thread calls functions that
update
_progressData.
Anyhow, the point is that I'm getting segfaults, even after
recompiling
everything from scratch! Is this in fact that unsafe? Do I really need
to
switch to MVars, even though no locking is required?
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Department of Physics
Oregon State University
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Re: [Haskell-cafe] First go at reactive programming
Reactive-0.3 seems to have a dependency on TypeCompose-0.3. Earlier version does not work (for lack of Data.Pair). This probably should be specified in Cabal file. I aslo fixed all the LANGUAGE problems and now encountered the following error in TypeCompose: [4 of 9] Compiling Control.Compose ( src/Control/Compose.hs, dist/build/Control/Compose.o ) src/Control/Compose.hs:561:0: parse error on input `deriving' I tried to restored the commented out deriving Monoid and got pass that. Not sure if that is right though. Back to reactive-0.3, I encountered: src/Data/Future.hs:60:27: Module `Control.Monad' does not export `forever' Forever is in the latest library, but not in my GHC 6.6. I am not sure how to get this fixed. Any suggestion? http://www.haskell.org/ghc/docs/latest/html/libraries/base/Control-Monad.html Steve On Jan 19, 2008 1:31 AM, Conal Elliott [EMAIL PROTECTED] wrote: Hi Steve, Thanks for letting me know about the LANGUAGE problem. Yes, I used 6.8-friendly (6.6-unfriendly) LANGUAGE pragmas. In retrospect, probably not such a great idea, since there seem to be many folks still on 6.6. I just changed the sources (commenting out the LANGUAGE pragmas and inserting -fglasgow-exts pragmas), darcs-pushed, and put a new version (0.3) on hackage. Please give it another try. Cheers, - Conal On Jan 18, 2008 7:58 PM, Steve Lihn [EMAIL PROTECTED] wrote: Tried to install reactive-0.2 on GHC-6.6, but failed. Building reactive-0.2... src/Data/Reactive.hs:1:13: cannot parse LANGUAGE pragma Is the package for GHC 6.8? Is there an older version (0.0?) for GHC 6.6 that I can play with your example? (Or advise how to hack that file to get it work on 6.6) Thanks, Steve ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: need help for cabal-install
On Jan 19, 2008 9:18 AM, Duncan Coutts [EMAIL PROTECTED] wrote: I think you're just missing a --user: $ cabal install --prefix=$HOME --user foo The prefix can also be set in the $HOME/.cabal/config file. Syntax? Something like: prefix: /path/to/my/ghc ? BTW, In the development version of cabal-install --user is the default and the default user prefix is $HOME/.cabal (though both can be changed in the config file). Is this newer than 12 hours ago? I tried cabal install --prefix=/path package (without --user). That did not seem to work... Steve ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: need help for cabal-install
On Fri, 2008-01-18 at 23:44 -0500, Chris Ball wrote: Hi Steve, Now with cabal install, I can not figure out where to specify the --prefix. Cabal always complains failed to install package. I think you're just missing a --user: $ cabal install --prefix=$HOME --user foo The prefix can also be set in the $HOME/.cabal/config file. BTW, In the development version of cabal-install --user is the default and the default user prefix is $HOME/.cabal (though both can be changed in the config file). I'd also recommend anyone trying out cabal-install to ignore the old version on hackage and go straight for the development version. It's a tad harder to get installed since it also needs the development version of the Cabal lib, but it has so many issues fixed. darcs get --partial http://darcs.haskell.org/cabal cd cabal make setup ./setup configure --prefix=$HOME/.cabal --user ./setup build ./setup install cd .. darcs get --partial http://darcs.haskell.org/cabal-install cd cabal-install runghc Setup.hs configure --prefix=$HOME/.cabal --bindir=$HOME --user runghc Setup.hs build runghc Setup.hs install This assumes $HOME/bin is on your path and that you already have the zlib and HTTP packages installed. Then get the latest hackage package list with: cabal update For a quick guide see: cabal --help There's also bash command line completion support: source bash-completion/cabal Then give it a try. Report any complaints or requests in the hackage trac: http://hackage.haskell.org/trac/hackage/ Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell-Support in Ohloh
Op 17-jan-2008, om 1:21 heeft Joachim Breitner het volgende geschreven: They explicitly write that they want haskell support, and the oldest open bug report on their page is about this: http://labs.ohloh.net/ohcount/ticket/205 So if anyone feels like programming some ruby (I guess they want it to be in that language as well) and wants to give the haskell community a chance for wider audience, give it a shot. I used this rainy saturday to make a patch. It only took three lines of Ruby or so, and some more work getting ohcount to build on my machine and to make some unit tests. I submitted the patch to their trac, http://labs.ohloh.net/ohcount/ticket/205 . Reinier ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: need help for cabal-install
Just tried to test drive another feature and got the nasty error: cabal list Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize' to increase it. On Jan 19, 2008 9:27 AM, Steve Lihn [EMAIL PROTECTED] wrote: On Jan 19, 2008 9:18 AM, Duncan Coutts [EMAIL PROTECTED] wrote: I think you're just missing a --user: $ cabal install --prefix=$HOME --user foo The prefix can also be set in the $HOME/.cabal/config file. Syntax? Something like: prefix: /path/to/my/ghc ? BTW, In the development version of cabal-install --user is the default and the default user prefix is $HOME/.cabal (though both can be changed in the config file). Is this newer than 12 hours ago? I tried cabal install --prefix=/path package (without --user). That did not seem to work... Steve ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] shootout using 6.6?
Don Stewart wrote: ... Yay, constructor specialisation! http://shootout.alioth.debian.org/gp4/benchmark.php?test=binarytreeslang=all And it's nice to see GHC 6.8.2 is now nearly ten times faster than GCC for this benchmark : http://shootout.alioth.debian.org/gp4/benchmark.php?test=threadringlang=all Scary to think how fast GHC might become in 6.10 :) Richard. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] How best to make GHC 6.6 and 6.8 co-exist on one server/account
Hi, It appears some of the latest hackages are moving towards 6.8 to take advantage of the new features, while quite a few remains at 6.6. The compatibility between the two versions has been problematic. I only have 6.6 installed, but now thinking to add 6.8 to my account (so I can switch between them, depending what works where). What is the best practice to make 6.8 co-exist with 6.6 ? Specific questions are: 1) I installed 6.6 under prefix=$HOME/ghc. If I install 6.8 to the same prefix, it will overwrite 6.6. Correct? How do I get around it? 2) I installed additional tools and packages under $HOME/htools using 6.6. (Which I begin to wonder if that is necessary.) Do I have to use a different directory for 6.8? I noticed that, for each package, the path is $HOME/htools/lib/package-ver/ghc-6.6.1/ etc etc. It seems that 6.8 will create subdirectories, so they can co-exist peacefully. Correct? Thanks, Steve ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: need help for cabal-install
On Sat, 2008-01-19 at 09:30 -0500, Steve Lihn wrote: Just tried to test drive another feature and got the nasty error: cabal list Stack space overflow: current size 8388608 bytes. Use `+RTS -Ksize' to increase it. Oops, silly error on my part. darcs pull and it's fixed. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: need help for cabal-install
On Sat, 2008-01-19 at 09:27 -0500, Steve Lihn wrote: On Jan 19, 2008 9:18 AM, Duncan Coutts [EMAIL PROTECTED] wrote: I think you're just missing a --user: $ cabal install --prefix=$HOME --user foo The prefix can also be set in the $HOME/.cabal/config file. Syntax? Something like: prefix: /path/to/my/ghc ? Yes, but using ghc's path would be a really bad idea. Actually there's user-prefix: and global-prefix: for the prefixes to use when using --user or --global installs. BTW, In the development version of cabal-install --user is the default and the default user prefix is $HOME/.cabal (though both can be changed in the config file). Is this newer than 12 hours ago? I tried cabal install --prefix=/path package (without --user). That did not seem to work... Remember, --user is default unless overridden by --global. So if you are trying to install as root that probably will not work since it'll probably have been built against packages that were in your user's package db but are not in your root users package db. We've not concentrated very much on global installs yet for cabal-install. We've been trying to make ordinary user installs Just Worktm. There was a bug a couple days ago where the prefix given on the command line was being overridden from the one given in the config file. That's now fixed. The command line overrides the saved config settings. So if it's still not working for you, you'll have to give more details. Details of what command you were using exactly and what the error message was. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How best to make GHC 6.6 and 6.8 co-exist on one server/account
On Sat, 2008-01-19 at 10:47 -0500, Steve Lihn wrote: Hi, It appears some of the latest hackages are moving towards 6.8 to take advantage of the new features, while quite a few remains at 6.6. The compatibility between the two versions has been problematic. I only have 6.6 installed, but now thinking to add 6.8 to my account (so I can switch between them, depending what works where). It should all work. I've got 3 ghc versions installed. What is the best practice to make 6.8 co-exist with 6.6 ? Specific questions are: 1) I installed 6.6 under prefix=$HOME/ghc. If I install 6.8 to the same prefix, it will overwrite 6.6. Correct? How do I get around it? That could be ok. Check what the layout if $HOME/ghc is. If it looks like: bin/ lib/ lib/ghc-6.6/ then that's fine and you'll be able to install another ghc to the same prefix, since the sub-dirs are versioned. You'll end up with $HOME/bin/ghc being the latest ghc, and the older version available as $HOME/ghc/bin/ghc-6.6. 2) I installed additional tools and packages under $HOME/htools using 6.6. (Which I begin to wonder if that is necessary.) Do I have to use a different directory for 6.8? I noticed that, for each package, the path is $HOME/htools/lib/package-ver/ghc-6.6.1/ etc etc. It seems that 6.8 will create subdirectories, so they can co-exist peacefully. Correct? Yes. The aim is to be able to have multiple haskell implementations, multiple versions of each haskell implementations and multiple versions of each library built for any/all haskell implementation/version and to have them all co-exist peacefully. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] First go at reactive programming
Thanks for the TypeCompose=0.3 tip. I've fixed my local Reactive.cabal and will push at some point. Oh yeay -- I'd forgotten about the deriving change in 6.8 vs 6.6. Urg. I didn't realize that 'forever' isn't in 6.2. You can use the 6.8def: -- | @'forever' act@ repeats the action infinitely. forever :: (Monad m) = m a - m () forever a = a forever a I'm wondering how hard to try to get these libs to work with both 6.6 and 6.8. My hope has been that people will switch to 6.8, but perhaps there are obstacles I don't know about. Is there something that keeps you from upgrading? - Conal On Jan 19, 2008 6:14 AM, Steve Lihn [EMAIL PROTECTED] wrote: Reactive-0.3 seems to have a dependency on TypeCompose-0.3. Earlier version does not work (for lack of Data.Pair). This probably should be specified in Cabal file. I aslo fixed all the LANGUAGE problems and now encountered the following error in TypeCompose: [4 of 9] Compiling Control.Compose ( src/Control/Compose.hs, dist/build/Control/Compose.o ) src/Control/Compose.hs:561:0: parse error on input `deriving' I tried to restored the commented out deriving Monoid and got pass that. Not sure if that is right though. Back to reactive-0.3, I encountered: src/Data/Future.hs:60:27: Module `Control.Monad' does not export `forever' Forever is in the latest library, but not in my GHC 6.6. I am not sure how to get this fixed. Any suggestion? http://www.haskell.org/ghc/docs/latest/html/libraries/base/Control-Monad.html Steve On Jan 19, 2008 1:31 AM, Conal Elliott [EMAIL PROTECTED] wrote: Hi Steve, Thanks for letting me know about the LANGUAGE problem. Yes, I used 6.8-friendly (6.6-unfriendly) LANGUAGE pragmas. In retrospect, probably not such a great idea, since there seem to be many folks still on 6.6. I just changed the sources (commenting out the LANGUAGE pragmas and inserting -fglasgow-exts pragmas), darcs-pushed, and put a new version ( 0.3) on hackage. Please give it another try. Cheers, - Conal On Jan 18, 2008 7:58 PM, Steve Lihn [EMAIL PROTECTED] wrote: Tried to install reactive-0.2 on GHC-6.6, but failed. Building reactive-0.2... src/Data/Reactive.hs:1:13: cannot parse LANGUAGE pragma Is the package for GHC 6.8? Is there an older version (0.0?) for GHC 6.6 that I can play with your example? (Or advise how to hack that file to get it work on 6.6) Thanks, Steve ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell-Support in Ohloh
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 On 20/01/2008, Reinier Lamers wrote: Op 17-jan-2008, om 1:21 heeft Joachim Breitner het volgende geschreven: They explicitly write that they want haskell support, and the oldest open bug report on their page is about this: http://labs.ohloh.net/ohcount/ticket/205 So if anyone feels like programming some ruby (I guess they want it to be in that language as well) and wants to give the haskell community a chance for wider audience, give it a shot. I used this rainy saturday to make a patch. It only took three lines of Ruby or so, and some more work getting ohcount to build on my machine and to make some unit tests. I submitted the patch to their trac, http://labs.ohloh.net/ohcount/ticket/205 . Is it just me or does that patch not actually include the line counting code..? Jeremy -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFHkixQ5plcd8tF/AQRAqQeAJ420viuL4fdi3EqvtRZkbTSoJsmQQCgkYqG oofypoHigdBzSNtM2xB1nw0= =3tv8 -END PGP SIGNATURE- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] functional graphs
I don't get where the graph edges (Node,Node) are specified. Do you just assume that every two nodes have an edge between them and calculate the edge label from the function? Also, is there a real world / motivating use for a graph defined this way? thomas. 2008/1/18, Christian Maeder [EMAIL PROTECTED]: Hi, Given a complete graph as a list of nodes whose edge labels are given by a function over two nodes: data CGraph a b = CGraph [a] (a - a - b) Can I define an instance for the fgl Graph class? import Data.Graph.Inductive.Graph instance Graph CGraph where empty = CGraph [] -- and now? I had no idea how to define empty (except using undefined). I thought of requiring a context for the node labels of type a, but this type is not mentioned in the class header. So it looked to me like the impossibility to define sets (requiring an Ord) as monads. (i.e. instance Monad Data.Set.Set) Any working proposals for my graph problem? Cheers Christian ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] First go at reactive programming
-- | @'forever' act@ repeats the action infinitely. forever :: (Monad m) = m a - m () forever a = a forever a Great. The code compiled successfully by inserting this in various places. I'm wondering how hard to try to get these libs to work with both 6.6 and 6.8. My hope has been that people will switch to 6.8, but perhaps there are obstacles I don't know about. Is there something that keeps you from upgrading? I am asking this question in another thread. The problem is -- I've got many modules compiled under 6.6, some with much agony. If I switch to 6.8, I have to recompile them again. Two issues I image: (1) It may take lots of effort to recompile all the modules. I have forgetten how I got around some of the modules! Too bad... Got to take notes next time... (2) If I got stuck in 6.8, it may not be easy to switch back. It does not appear straightforward to me. I'd like to hear how other people approach these issues before I jump into it. Don't want to break the working environment that I spent months to set up! -- Finally, get to test the Reactive sample code. (1) Levi's first post compiled successfully and worked like charm. Congrat. (2) Levi's second post did not compile. There is a type error... react.hs:33:65: Couldn't match expected type `Handle' against inferred type `RequestHandler' In the first argument of `handleConnection', namely `r' In the first argument of `fmap', namely `(handleConnection r)' In the second argument of `(.)', namely `fmap (handleConnection r)' Thanks. Steve ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Throwback of inferred types
Is it possible to get throwback of inferred types into Emacs or an IDE for Haskell? -- Dr Jon D Harrop, Flying Frog Consultancy Ltd. http://www.ffconsultancy.com/products/?e ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] First go at reactive programming
On 2008.01.19 12:22:43 -0500, Steve Lihn [EMAIL PROTECTED] scribbled 1.5K characters: ... I am asking this question in another thread. The problem is -- I've got many modules compiled under 6.6, some with much agony. If I switch to 6.8, I have to recompile them again. Two issues I image: (1) It may take lots of effort to recompile all the modules. I have forgetten how I got around some of the modules! Too bad... Got to take notes next time... These days, every package you'd want to install (with the exception of GHC, Darcs, and the large graphics toolkits) should be available on Hackage or at least in Cabalized form. If they aren't, then that's a bug or at least missing feature. The whole point of Cabal was so you don't have to take notes! (2) If I got stuck in 6.8, it may not be easy to switch back. Well, uh, is that really a bad thing? Do you worry about device drivers 'because if I got stuck in the 2.x series of Linux kernels, it may not be easy to switch back [to 1.x]'? No; 6.8.x is the future. The older GHCs will fall behind, people will rightfully upgrade, things will bitrot, and so on. There's no real benefit to willfully using outdated software - the most painful parts of the 6.8.x upgrade are past. It does not appear straightforward to me. I'd like to hear how other people approach these issues before I jump into it. Don't want to break the working environment that I spent months to set up! I began darcs send'ing patches for stuff broken by 6.8.x; by this point, all the major stuff I use is fixed, at least out of Darcs (although many packages are woefully outdated on Hackage. I've been working on this). ... Thanks. Steve -- gwern Information II captain SAS BRLO unclassified of Audiotel Taiwan RSOC pgpg7mEkHNDX2.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Throwback of inferred types
On 2008.01.19 17:30:50 +, Jon Harrop [EMAIL PROTECTED] scribbled 0.2K characters: Is it possible to get throwback of inferred types into Emacs or an IDE for Haskell? -- Dr Jon D Harrop, Flying Frog Consultancy Ltd. Sure. I once hacked together quite a while ago a little function for haskell-mode which looked like: , | (defun getHaskellFunctionTypeSignature () | (interactive) | (progn | (setq file-name buffer-file-name) | (setq functionName (thing-at-point 'word)) | (shell-command (concat echo :t functionName | ghci -v0 -cpp -fglasgow-exts -w file-name |grep functionName) t))) | (global-set-key \C-c\l 'getHaskellFunctionTypeSignature) ` And I think haskell-mode has a better way of doing things somewhere in its inf-haskell.el. -- gwern Information II captain SAS BRLO unclassified of Audiotel Taiwan RSOC pgpHVN2nHWUXN.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Throwback of inferred types
Visual Haskell does that, but IMHO not as good as the F# plugin for Visual Studio. Currently I just use Emacs and Haskell Mode and the :t command, but this only works for top level functions (is this correct? Maybe some syntax exists to refer to an inner function?), so yeah, it would be really handy to have a good IDE that shows you the inferred types on the fly. -Original Message- From: [EMAIL PROTECTED] [mailto:haskell-cafe- [EMAIL PROTECTED] On Behalf Of Jon Harrop Sent: Saturday, January 19, 2008 6:31 PM To: haskell-cafe@haskell.org Subject: [Haskell-cafe] Throwback of inferred types Is it possible to get throwback of inferred types into Emacs or an IDE for Haskell? -- Dr Jon D Harrop, Flying Frog Consultancy Ltd. http://www.ffconsultancy.com/products/?e ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Re: Re: 0/0 1 == False
Kalman Noel wrote: Ben Franksen wrote: Kalman Noel wrote: (2) lim a_n = ∞ [...] (2) means that the sequence does not converge, because you can always find a value that is /larger/ than what you hoped might be the limit. (2) usually rather mean that for each positive limit A there is a number N such that a_N A for /all/ n N. You're right here. I tried to come up with a more wordy, informal description, but failed on that. Your definition of (2) is usually termed as '(a_n) contains a subsequence that tends toward +infinity'. May you elaborate? I don't see where a subsequence comes into play here. I'll show (2) = (2'), where (2'): (a_n) contains a subsequence that tends toward +infinity = : Assume (2) holds. Construct a subsequence (b_m) of (a_n) by chosing, for each natural number m, an index n_m such that b_m = n_(n_m) is larger than m (which is possible by (2)). Then (b_m) is a subsequence of (a_n) that tends toward infinity (as I defined it). = : Assume (2') holds. Let A 0 be any positive number (that you hope might be the limit). We want to show that we can find N such that a_N A. To do so, chose a M, such that b_M A (which is possible by assumption). Then there exists an N such that a_N = b_M, because (b_n) is a subsequence of (a_n). q.e.d Cheers Ben ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Throwback of inferred types
The problem is that this only works when the complete source file compiles correctly no? I would find it most useful to get type inference information on the fly, even when not all of the code compiles correctly yet. -Original Message- From: [EMAIL PROTECTED] [mailto:haskell-cafe- [EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Saturday, January 19, 2008 6:42 PM To: Jon Harrop; haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] Throwback of inferred types On 2008.01.19 17:30:50 +, Jon Harrop [EMAIL PROTECTED] scribbled 0.2K characters: Is it possible to get throwback of inferred types into Emacs or an IDE for Haskell? -- Dr Jon D Harrop, Flying Frog Consultancy Ltd. Sure. I once hacked together quite a while ago a little function for haskell-mode which looked like: , | (defun getHaskellFunctionTypeSignature () | (interactive) | (progn | (setq file-name buffer-file-name) | (setq functionName (thing-at-point 'word)) | (shell-command (concat echo :t functionName | ghci -v0 -cpp | -fglasgow-exts -w file-name |grep functionName) t))) | (global-set-key \C-c\l 'getHaskellFunctionTypeSignature) ` And I think haskell-mode has a better way of doing things somewhere in its inf-haskell.el. -- gwern Information II captain SAS BRLO unclassified of Audiotel Taiwan RSOC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] functional graphs
Hi Christian, On Jan 18, 2008 1:55 PM, Christian Maeder [EMAIL PROTECTED] wrote: data CGraph a b = CGraph [a] (a - a - b) Can I define an instance for the fgl Graph class? I had no idea how to define empty (except using undefined). Well, presumably the function does not need to be defined on values not in the list, so returning an error is fair enough-- empty = CGraph [] (const $ error Node not in graph) I suppose you want to use the index in the list as the Node (= Int), which should be fine, but you'll run into problems with mkGraph, because you don't have an Eq constraint on a, so you can't implement the function to pass to CGraph. Since mkGraph is required to have the type mkGraph :: [LNode a] - [LEdge b] - CGraph a b for *all* a and b, you don't have a way to add an Eq constraint anywhere, either. So, no dice... However, if you'd be able to live with data CGraph a b = CGraph [LNode a] (Node - Node - b) then you should be able to write the instance like this-- instance Graph CGraph where empty = CGraph [] (const $ error Node not in graph) isEmpty (CGraph xs _) = null xs labNodes (CGraph xs _) = xs mkGraph nodes edges = CGraph nodes f where f x y = fromMaybe (error Edge not found) (lookup (x,y) edges') edges' = map (\(x,y,l) - ((x,y),l)) edges match x (CGraph nodes f) = case lookup x nodes of Nothing - (Nothing, CGraph nodes f) Just l - let nodes' = filter ((/= x) . fst) nodes left = map (\(y,_) - (f y x, y)) nodes' right = map (\(y,_) - (f x y, y)) nodes' in (Just (left, x, l, right), CGraph nodes' f) - Benja ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] functional graphs
Hi, On Jan 19, 2008 6:05 PM, Thomas Hartman [EMAIL PROTECTED] wrote: Do you just assume that every two nodes have an edge between them [...]? Since that's what complete graph means, I assume so =-) - Benja ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] threads + IORefs = Segmentation fault?
On Jan 19, 2008 2:36 PM, David Roundy [EMAIL PROTECTED] wrote: Using ghc 6.6, but I've since isolated the bug as being unrelated to the IORefs and threading, it was in an FFI binding that somehow never died until I was testing this new code. In case the you are creating a binding of haskell code. Did you make sure that the runtime constructor and destructor (hs_* functions) are properly called? The could be the source of the segfault. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Re: Re: 0/0 1 == False
Ben Franksen wrote: Kalman Noel wrote: Ben Franksen wrote: Kalman Noel wrote: (2) means that the sequence does not converge, because you can always find a value that is /larger/ than what you hoped might be the limit. Your definition of (2) is usually termed as '(a_n) contains a subsequence that tends toward +infinity'. I'll show (2) = (2'), where (2'): (a_n) contains a subsequence that tends toward +infinity Only now did I understand that your point was to explain why and how my definition (2) is incorrect. It's clear to me now. Kalman -- Finally - A spam blocker that actually works. http://www.bluebottle.com/tag/4 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Throwback of inferred types
On Saturday 19 January 2008 18:11:13 Peter Verswyvelen wrote: I would find it most useful to get type inference information on the fly, even when not all of the code compiles correctly yet. Yes. Is this not provided by any development environments then? -- Dr Jon D Harrop, Flying Frog Consultancy Ltd. http://www.ffconsultancy.com/products/?e ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Throwback of inferred types
Peter Verswyvelen [EMAIL PROTECTED] wrote: The problem is that this only works when the complete source file compiles correctly no? ghc could just insert appropriate calls to error everywhere it can't compile, so you can choose whether to fix the bugs by lexical or operational ordering, ecj (the eclipse compiler) does exactly that. -- (c) this sig last receiving data processing entity. Inspect headers for past copyright information. All rights reserved. Unauthorised copying, hiring, renting, public performance and/or broadcasting of this signature prohibited. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Hangman game
Hi Ronald,
Ronald Guida wrote:
I'm interested in learning how to program games. Since I have to start
somewhere, I decided to write a simple Hangman game. I'm wondering if
anyone can look at my code and give me some feedback.
Lots of fun, thanks! And nicely written.
One point is that while it's OK to do your random
calculation directly in IO for this simple case, in general
you will have many random calculations and you will
want to avoid forcing them all into IO.
You can add one more field to GameState that holds
a random generator. Let's say you call it gsRandGen.
Make sure that gsRandGen gets initialized somewhere.
Define this utility function:
rand :: MonadState GameState m = (StdGen - (a, StdGen)) - m a
rand f = do
gs - get
let (x, g) = f $ gsRandGen gs
put $ gs {gsRandGen = g}
return x
Now, instead of:
nWord - liftIO $ getStdRandom (randomR (0,length wordList - 1))
you can write:
nWord - rand $ randomR (0,length wordList - 1)
If you want, you can even remove the dependence on
StdGen by making some of your function types polymorphic,
qualified where necessary by RandomGen g = ...
Regards,
Yitz
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Re: [Haskell-cafe] Re: 0/0 1 == False
On 19 Jan 2008, at 2:52 AM, Kalman Noel wrote:
Jonathan Cast wrote:
On 12 Jan 2008, at 3:23 AM, Kalman Noel wrote:
(2) lim a_n = ∞
[...]
(2) means that the sequence does not converge,
To a value in R. Again, inf is a perfectly well defined extended
real number, and behaves like any other element of R u {-inf, inf}.
(Although that structure isn't quite a field --- 0 * inf isn't
defined, nor is inf - inf).
Out of curiosity, is there some typical application domain for
extended real
numbers?
In calculus and elementary analysis, the notion of limits at/to
infinity, improper Riemann integrals, etc., are introduced by a
succession of `special notations'. Taking the extended real numbers
as the underlying space permits these notations to be defined more
compositionally, because ∞ is now an ordinary mathematical object.
For example, if f is a nonnegative measurable function, ∫f on a
measurable set is /always/ defined (as an extended real number) and
the special case of an `integrable' function is simply one where the
integral (which is an actual mathematical value) is an element of R.
So, when we say ∫f ∈ R, that notation is compositional --- that's
real set membership there. Similarly, ∫_{-∞}^∞ f is defined (as
a Lebesgue integral) the same way any other integral is, because the
interval [-∞, ∞] is a perfectly good mathematical object.
jcc
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[Haskell-cafe] overlapping instance error -- need help using instance Monoid (Sum a) where a is a map of money values
The code below compiles as given, however if I uncomment the tSM
function I get the overlapping instance error mentioned in the subject
line.
Can someone give me advice on how to do what I want to do?
basically I want to add, for example, (USD,1) and (USD,2) and (Euro,3)
and get result
fromList [(USD,3), (Euro,3)]
the datatypes below are more verbose but the above is the basic idea
thanks!
thomas.
*
module TransactionRows {- ( mkTransactionRows,TransactionRows ) -} where
import Data.Monoid
import Data.List
import qualified Data.Map as M
data Currency a = Currency a
deriving ( Show, Eq, Ord )
data Money c a = Money ( M.Map c a )
deriving Show
instance (Num a, Ord c)= Monoid ( Sum (Money c a) ) where
mempty = Sum ( Money M.empty )
Sum ( Money m1 ) `mappend` Sum ( Money m2 ) = Sum (Money m1
`plusmoney` Money m2)
plusmoney (Money m1s) (Money m2s) = Money msum
where msum = foldl' f m1s (M.toList m2s)
f m (k,v) = M.insertWith (+) k v m
mkMoney1 :: Currency String - Float - Money (Currency String) Float
mkMoney1 c a = Money $ M.singleton c a
--sumMoney :: [Money (Currency String) Float] - Money (Currency String) Float
sumMoney ms = getSum $ mconcat $ map Sum ms
-- if I uncomment this, get Overlapping instances for Monoid error
--tSM = sumMoney [mkMoney1 (Currency usd) 1 :: Money (Currency String) Float]
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Re: [Haskell-cafe] overlapping instance error -- need help using instance Monoid (Sum a) where a is a map of money values
On Jan 20, 2008 12:56 AM, Thomas Hartman [EMAIL PROTECTED] wrote:
The code below compiles as given, however if I uncomment the tSM
function I get the overlapping instance error mentioned in the subject
line.
Can someone give me advice on how to do what I want to do?
basically I want to add, for example, (USD,1) and (USD,2) and (Euro,3)
and get result
fromList [(USD,3), (Euro,3)]
the datatypes below are more verbose but the above is the basic idea
thanks!
thomas.
*
module TransactionRows {- ( mkTransactionRows,TransactionRows ) -} where
import Data.Monoid
import Data.List
import qualified Data.Map as M
data Currency a = Currency a
deriving ( Show, Eq, Ord )
data Money c a = Money ( M.Map c a )
deriving Show
instance (Num a, Ord c)= Monoid ( Sum (Money c a) ) where
mempty = Sum ( Money M.empty )
Sum ( Money m1 ) `mappend` Sum ( Money m2 ) = Sum (Money m1
`plusmoney` Money m2)
This is the overlap. Data.Monoid already defines an instance for Monoid (Sum
a), so it's going to overlap with your Monoid (Sum (Money c a)).
Unless you're planning to define more than one Monoid for Money, I suggest
skipping Sum entirely.
--
Dave Menendez [EMAIL PROTECTED]
http://www.eyrie.org/~zednenem/
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[Haskell-cafe] Basic binary IO
Hello all, I'm wondering if anyone has a reference to any binary IO and data conversion tutorials. I'm playing around with generating a BMP file in haskell, and am a little stuck on the best way to go about the simple task of creating the BMP header. The header is BM + 4 bytes for file size + 4 bytes reserved + 4 bytes for offset where data begins. I have the basis starting off at: bmpHeader = B.pack $ [ 0x42, 0x4D ] ++ [0 , 0, 0, 0] ++ [0 , 0, 0, 0] ++ [14 :: Int32] (where B is Data.ByteString) I'm wondering how I can: 1/ convert a 32 bit number (Int32, Char32) to 4 Char8 elements 2/ rotate bits/bytes in a 32 bit Char32 (or Int32) so they are explicitly little-endian (I work on a mac powerbook, and it is big-endian) 3/ convert an Integer or Int type to an Int32 type Any pointers or suggestions would be helpful. Thanks -- Jamie Love Senior Consultant Aviarc Australia Mobile: +61 400 548 048 This message has been scanned for viruses and dangerous content by MailScanner and is believed to be clean. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Basic binary IO
jamie.love: Hello all, I'm wondering if anyone has a reference to any binary IO and data conversion tutorials. A good place to start looking is Data.Binary, http://hackage.haskell.org/cgi-bin/hackage-scripts/package/binary I'm playing around with generating a BMP file in haskell, and am a little stuck on the best way to go about the simple task of creating the BMP header. The header is BM + 4 bytes for file size + 4 bytes reserved + 4 bytes for offset where data begins. I have the basis starting off at: bmpHeader = runPut $ [ 0x42, 0x4D ] ++ [0 , 0, 0, 0] ++ [0 , 0, 0, 0] ++ [14 :: Int32] bmpHeader = runPut $ do put 'B' put 'M' put (0 :: Int32) put (0 :: Int32) put (14 :: Int32) Yields the lazy bytestring, BM\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\SO (where B is Data.ByteString) I'm wondering how I can: 1/ convert a 32 bit number (Int32, Char32) to 4 Char8 elements Data.Binary.put (x :: Int32) etc. 2/ rotate bits/bytes in a 32 bit Char32 (or Int32) so they are explicitly little-endian (I work on a mac powerbook, and it is big-endian) Use the little endian 'put' primitives, putWord32le (fromIntegral (7 :: Int32)) 3/ convert an Integer or Int type to an Int32 type Any pointers or suggestions would be helpful. fromIntegral Data.Binary should support all this nicely, I hope. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] One-line haskell program with GHC
Thanks all. This really helps me a lot! On Jan 18, 2008 6:24 PM, Jonathan Cast [EMAIL PROTECTED] wrote: On 18 Jan 2008, at 2:00 PM, Clifford Beshers wrote: 2008/1/18 Sukit Tretriluxana [EMAIL PROTECTED]: Hi, I don't know if it's been asked before. I just wonder if GHC supports some sort of one-liner program that can be specify right as the argument to either ghci or runghc program. In perl, they have something like perl *-e* 'print Hello' Do we have similar thing with GHC? ghc -e 'putStrLn Yes, we do.' Although, unlike perl, you don't have to say print explicitly if you don't need it: ghc -e 'This works great!' jcc ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
