[Haskell-cafe] Re: iteratee: Do I need to roll my own?
I'm looking at iteratee as a way to replace my erroneous and really inefficient lazy-IO-based backend for an expect like Monad DSL I've been working for about 6 months or so now on and off. The problem is I want something like: expect some String send some response to block or perhaps timeout, depending on the environment, looking for some String on an input Handle, and it appears that iteratee works in a very fixed block size. Actually, it doesn't. It works with what enumerator gives him. In case of `enum_fd'[1] this is a fixed block, but generally this is a ``value'' of some ``collection''[2]. And it is up to programmer to decide of what should become a value. [1] http://okmij.org/ftp/Haskell/Iteratee/IterateeM.hs [2] http://okmij.org/ftp/papers/LL3-collections-enumerators.txt While a fixed block size is ok, if I can put back unused bytes into the enumerator somehow (I may need to put a LOT back in some cases, but in the common case I will not need to put any back as most expect-like scripts typically catch the last few bytes of data sent before the peer is blocked waiting for a response...) I don't quite get this ``last few bytes'' thing. Could you explain? I was about writing that there is no problem with putting data back to Stream, and referring to head/peek functions... But then I thought, that the ``not consuming bytes from stream'' approach may not work well in cases, when the number of bytes needed (by your function to accept/reject some rule) exceeds the size of underlying memory buffer (4K in current version of `iteratee' library[3]). [3] http://hackage.haskell.org/packages/archive/iteratee/0.3.4/doc/html/src/Data-Iteratee-IO-Fd.html Do you think that abstracting to the level of _tokens_ - instead of bytes - could help here? (Think of flex and bison.) You know, these enumerators/iteratees things can be layered into _enumeratees_[1][4]... It's just an idea. [4] http://ianen.org/articles/understanding-iteratees/ Otherwise, I'm going to want to roll my own iteratee style library where I have to say NotDone howMuchMoreIThinkINeed so I don't over consume the input stream. What's the problem with over-consuming a stream? In your case? BTW, this `NotDone' is just a ``control message'' to the chunk producer (an enumerator): IE_cont k (Just (GimmeThatManyBytes n)) Does that even make any sense? I'm kind of brainstorming in this email unfortunately :-) What's the problem with brainstorming? :) Cheers. -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] cabal through PHPProxy
i'm using PHPProxy to go on the internet (www.phpproxy.fr). How can i tell cabal to use this? ... PHPProxy is a web based proxy. To use it, you have to type the http address you want in a field on the page. You still need some web access in order to access a web-based proxy... Is www.phpproxy.fr the only outer site you can connect directly to? I am just curious of what kind of LAN you have got. :) How do you update your OS, anyway? How do you download files? * * * Try the following: # Download phpproxy wget -c 'http://idea.hosting.lv/a/phpproxy/phpproxy-0.6.tar.gz' # Unpack tar -xzf phpproxy-0.6.tar.gz # Launch PHPProxy client cd phpproxy-0.6 python phpproxy.py # In another terminal, try running cabal with `http_proxy' http_proxy=http://localhost:8080/ cabal update --verbose=3 Please, report your progress. Good luck! -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Takusen and iteratee problem
Today I stuck with the following problem: I want to read a file with iteratee package, and but it to database through Takusen package, but it doesn't work. The `Takusen` was built with `mtl` package, and `iteratee` - with `transformers`, so they are conflicting when used simultaneously. And what error message is displayed? -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Cabal update problem
after updating to cabal-install-0.8.0/Cabal-1.8.0.2 with GHC 6.10.4, I always get an error when updating the package list: cabal update Downloading the latest package list from hackage.haskell.org cabal: Codec.Compression.Zlib: premature end of compressed stream Would you please send the output of `cabal update -v3' command? -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Iteratee, parsec co.
| 3. Why Seek FileOffset is error message? Are you talking about John Lato's implementation [1]? Well, `Seek' is not an error message. It is one of constructors for ErrMsg, and ErrMsg is [2] ---- a message to the stream producer (e.g., to rewind the stream) -- or an error indication. You know the overall idea behind Seek, don't you? It is an instrument to implement random IO [3]. Compare Oleg's code [4] data SeekException = SeekException FileOffset deriving Show instance Typeable SeekException where typeOf _ = mkTyConApp (mkTyCon SeekException) [] instance Exception SeekException and [2] type ErrMsg = SomeException data Stream el = EOF (Maybe ErrMsg) | Chunk [el] deriving Show with John Lato's implementation [1]: data StreamG c el = EOF (Maybe ErrMsg) | Chunk (c el) data ErrMsg = Err String | Seek FileOffset deriving (Show, Eq) John makes Err and Seek to be the distinct constructors of ErrMsg. Errors (Err) in `iteratee' package are always Strings. Oleg's ErrMsg is SomeException. One of its instances (SeekException) is a ``rewind the stream'' message to the stream producer. And the user is free to have as many different ErrMsg'es as he needs to do the job. [1] http://inmachina.net/~jwlato/haskell/iteratee/src/Data/Iteratee/Base.hs [2] http://okmij.org/ftp/Haskell/Iteratee/IterateeM.hs [3] http://okmij.org/ftp/Streams.html#random-bin-IO [4] http://okmij.org/ftp/Haskell/Iteratee/RandomIO.hs -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] safe lazy IO or Iteratee?
John Lato jwl...@gmail.com wrote: Both designs appear to offer similar performance in aggregate, although there are differences for particular functions. I haven't yet had a chance to test the performance of the CPS variant, although Oleg has indicated he expects it will be higher. @jwlato: Do you mind creating `IterateeCPS' tree in http://inmachina.net/~jwlato/haskell/iteratee/src/Data/, so we can start writing CPS performance testing code? AFAICS, you have benchmarks for IterateeM-driven code already: http://inmachina.net/~jwlato/haskell/iteratee/tests/benchmarks.hs John Millikin jmilli...@gmail.com wrote: I wrote some criterion benchmarks for IterateeM vs IterateeCPS, and the CPS version was notably slower. I don't understand enough about CPS to diagnose why, but the additional runtime was present in even simple cases (reading from a file, writing back out). @jmillikin: Could you please publish those benchmarks? Thanks. -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] mtl and transformers
Bas van Dijk v.dijk@gmail.com wrote: I always make a ghci.sh bash script in each of my projects that calls ghci -hide-all-packages -package x -package y -package z. However a cabal ghci or cabal interactive command that does this automatically would be ideal. I see there already is a ticket[1] about it. regards, Bas [1] http://hackage.haskell.org/trac/hackage/ticket/382 Shell script can be replaced with .ghci file. See http://neilmitchell.blogspot.com/2010/01/using-ghci-files-to-run-projects.html (Just my two cents.) -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] mtl and transformers
Günther Schmidt:
Could not find module `Control.Monad.Trans':
it was found in multiple packages: transformers-0.1.4.0
mtl-1.1.0.2
Ivan Lazar Miljenovic:
There's a way of specifying it at the top of whichever file you're
using, but so far my workaround in this situation is to use ghc-pkg
hide on whichever of those packages I don't use in my code.
Günther Schmidt:
ghc-pkg hide works fine, thanks!
As an alternative, you can use `LANGUAGE PackageImports' pragma:
| {-# LANGUAGE PackageImports #-}
|
| import transformers Control.Monad.Trans
See
http://thread.gmane.org/gmane.comp.lang.haskell.libraries/12134/focus=12155
PS: Have fun with iteratees!
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Re: [Haskell-cafe] Continuable and serializable parsers.
Serguey Zefirov sergu...@gmail.com wrote:
1) How to write a parser that could be restarted? Like, it will be
represented by a function that returns something along the lines
data ParseStepResult input result =
Success (Maybe (input - ParseStepResult input result)) (Maybe result)
| Failure
(ie, parsers using stream combinators like Fudgets have that property)
ie, either a continuation of parsing process and result or failure flag.
I think you're looking for `iteratees'.
| newtype IterateeG c el m a
| = IterateeG {runIter :: StreamG c el - m (IterGV c el m a)}
|
| data IterGV c el m a
| = Done a (StreamG c el) | Cont (IterateeG c el m a) (Maybe ErrMsg)
|
| data StreamG c el = EOF (Maybe ErrMsg) | Chunk (c el)
See
http://okmij.org/ftp/Streams.html
http://hackage.haskell.org/package/iteratee
See also
http://www.haskell.org/haskellwiki/Enumerator_and_iteratee
http://therning.org/magnus/archives/735/comment-page-1#comment-188128
http://comonad.com/reader/2009/iteratees-parsec-and-monoid/
http://inmachina.net/~jwlato/haskell/iter-audio/
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[Haskell-cafe] changelogs for packages on Hackage
It would be nice if Hackage displayed ``recent changes'' of a package. [severity: wishlist] You see, I am subscribed to the ``hackage - recent additions'' feed [http://hackage.haskell.org/packages/archive/recent.rss] and receive entries that look like this: Cabal 1.8.0.2 Added by DuncanCoutts, Wed Dec 16 04:19:24 UTC 2009. A framework for packaging Haskell software This is sweet. But how can I tell what's new in Cabal since 1.6.0.3? (`Cabal' is just an example here.) * * * -- these are snowflakes Dear Santa, This year, I have been a very good boy (in his thirties). I have not pillaged, and I have often helped my children with their homework. And I always say `thank you', which makes me polite and so I deserve lots of presents this year! Please bring this stuff for me and the people in Haskell community. -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] changelogs for packages on Hackage
Valery V. Vorotyntsev wrote: It would be nice if Hackage displayed ``recent changes'' of a package. [severity: wishlist] You see, I am subscribed to the ``hackage - recent additions'' feed [http://hackage.haskell.org/packages/archive/recent.rss] and receive entries that look like this: Cabal 1.8.0.2 Added by DuncanCoutts, Wed Dec 16 04:19:24 UTC 2009. A framework for packaging Haskell software This is sweet. But how can I tell what's new in Cabal since 1.6.0.3? (`Cabal' is just an example here.) Duncan Coutts duncan.cou...@googlemail.com wrote: Yep it's a fair point. http://hackage.haskell.org/trac/hackage/ticket/299 Some packages have a changelog file in them that we could display, though most don't. For those that do have a changelog, how we avoid displaying all of history is a bit tricky. For those that do not, ideally we could derive a changelog by looking at the difference in the API. The latter requires a tool we've not written yet. We could mimic Debian's approach. Debian policy requires changelogs of standard format. [1] These changelogs are updated with debchange(1) tool and can be parsed with parsechangelog(1p). [2,3] See example. [4] [1] http://www.debian.org/doc/debian-policy/ch-source.html#s-dpkgchangelog [2] http://manpages.debian.net/cgi-bin/man.cgi?query=debchange [3] http://manpages.debian.net/cgi-bin/man.cgi?query=parsechangelog [4] http://packages.debian.org/changelogs/pool/main/x/xterm/current/changelog -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Iteratee question
On Thu, Nov 26, 2009 at 10:17 AM, o...@okmij.org wrote: You are correct: i2 and i3 can process a chunk of elements at a time, if an enumerator supplies it. That means an iteratee like i2 or i3 can do more work per invocation -- which is always good. Since you have to get the results as a list, you pretty much have to use stream2list. It should be noted that stream2list isn't very efficient: it returns the accumulated list only when it is done -- which happens when the stream is terminated, normally or abnormally. So, stream2list has a terrible latency, and is useful only at the last stage of processing. I found it is most useful for testing (to see the resulting stream) and for writing Unit tests (to compare the produced results with the expected). For incremental processing, it is better to stay within Iteratees. Although I think i2 and i3 should be close in performance (only benchmarking can tell for sure, of course), i3 is more extensible because stream2list is at the end of the chain. If later on further processing is required (or, the latency imposed by stream2list becomes noticeable), the chain can be easily extended. The advantage of the arrangement of i3 is that if some Iteratee further down the chain decided that it has had enough (elements), Iter.take can quickly skip the remaining elements without the need to convert them. Thanks for clarification! -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Iteratee question
On Fri, Nov 27, 2009 at 4:04 AM, John Lato jwl...@gmail.com wrote: My apologies for not replying; I have been traveling and am only now working through my email. Oleg's response is much better than anything I would have written. I'd like to add one point. stream2list is very inefficient as he mentioned, however only for large values of 'n'. For small n it should be fine. Assuming you're using Word8 elements, small means 4096. This is because the default chunk size reading from a file is 2048 elements, so for any n 4096 you have at most two concatenations in producing the stream2list. Sincerely, John Lato PS for one example of a binary data parser, please see http://inmachina.net/~jwlato/haskell/iter-audio/ This is similar to the audio codec included with iteratee, but much more efficient. In particular, the functions convFunc and unroller in Sound.Iteratee.Codecs.Common are pretty highly optimized. Wonderful! Sample code is very helpful to get familiar with iteratees. Thank you, John. Thanks to both of you. -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haskell-mode.el mailing list (+ dpatch)
On Wed, Nov 25, 2009 at 10:37 AM, Svein Ove Aas svein@aas.no wrote: http://trac.haskell.org/haskellmode-emacs/ http://projects.haskell.org/cgi-bin/mailman/listinfo/haskellmode-emacs Hurray! Thanks, Svein. -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] haskell-mode.el mailing list (+ dpatch)
Is there anybody except me feeling the need for mailing list and issue tracker for emacs' haskell-mode? Mailing list is a forum to discuss ideas _and_ the area of patch authors' self-advertisement. And issue tracker is a TODO list; it may be useful or annoying, and I think we can live without one for a while. But I vote for haskell-mode.el mailing list. Examples: http://www.haskell.org/mailman/listinfo/xmonad http://code.google.com/p/xmonad/issues/list -- Description of the attached dpatch: * make `inferior-haskell-find-project-root' respect export lists A hierarchical module (one or more dots in module name) with an export list cannot be loaded (`C-c C-l') unless there is .cabal file available. That is because regexp current in `inferior-haskell-find-project-root' does not match module headers with export lists. Like this one: module Codec.Binary.MSCP ( -- * Data structures FileHeader(..), CDR(..), -- * Parsing readFile ) where This patch makes the regexp less strict. Have fun! -- vvv #part type=application/octet-stream filename=/tmp/XXX/respect-export-lists.dpatch disposition=attachment description=respect-export-lists.dpatch #/part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: haskell-mode.el mailing list (+ dpatch)
-- Description of the attached dpatch: * make `inferior-haskell-find-project-root' respect export lists No joke this time. Sorry for the glitch. -- vvv Tue Nov 24 23:48:05 EET 2009 Valery V. Vorotyntsev valery...@gmail.com * make `inferior-haskell-find-project-root' respect export lists A hierarchical module (one or more dots in module name) with an export list cannot be loaded (`C-c C-l') unless there is .cabal file available. That is because regexp current in `inferior-haskell-find-project-root' does not match module headers with export lists. Like this one: module Codec.Binary.MSCP ( -- * Data structures FileHeader(..), CDR(..), -- * Parsing readFile ) where This patch makes the regexp less strict. New patches: [make `inferior-haskell-find-project-root' respect export lists Valery V. Vorotyntsev valery...@gmail.com**20091124214805 Ignore-this: 13944cebba542b12a6b02a7c8ef43c81 A hierarchical module (one or more dots in module name) with an export list cannot be loaded (`C-c C-l') unless there is .cabal file available. That is because regexp current in `inferior-haskell-find-project-root' does not match module headers with export lists. Like this one: module Codec.Binary.MSCP ( -- * Data structures FileHeader(..), CDR(..), -- * Parsing readFile ) where This patch makes the regexp less strict. ] hunk ./inf-haskell.el 285 (goto-char (point-min)) (let ((case-fold-search nil)) (when (re-search-forward - ^module[ \t]+\\([^- \t\n]+\\.[^- \t\n]+\\)[ \t]+where\\ nil t) + ^module[ \t]+\\([^- \t\n]+\\.[^- \t\n]+\\)[ \t]+ nil t) (let* ((dir default-directory) (module (match-string 1)) (pos 0)) Context: [Emacs regexes are not perl regexes! svein@aas.no**20091120123455 Ignore-this: 7adddfb072ffabb8e02457fd9f1d7179 ] [Add missing `:group's to defcustoms. Dave Love f...@gnu.org**2009105701 Ignore-this: c5126608a89343c907e6a03f77143a82 ] [Resolve conflict with mdo patch. Dave Love f...@gnu.org**20091110143208 Ignore-this: 48568e05d3b1d48d5a3c8014e5287fe3 ] [Allow non-ASCII names. Dave Love f...@gnu.org**20091105212057 Ignore-this: f46f407a19ae2a597f44317e4915e5ba The code already used char-classes unconditionally, though I didn't think they're supported in XEmacs. ] [Various fixes for Emacs 21. Dave Love f...@gnu.org**20091105211507 Ignore-this: caae466ff29882fa42f44e081d0a8909 ] [Fix treatment of missing syntax-ppss. Dave Love f...@gnu.org**2009111819 Ignore-this: 284f4d7440592d4b7f4697d1bf2483c7 ] [Comment/doc/message fixes. Dave Love f...@gnu.org**20091105212607 Ignore-this: 15a2aa347da042465d652328b91324a1 ] [Parse the unicode syntax for (::) vandijk.r...@gmail.com**20091106085644 Ignore-this: f4d582279acbaf613b5d77b6788c8189 ] [Fixed bug in haskell-decl-scan.el when using unicode syntax vandijk.r...@gmail.com**2009110615 Ignore-this: 6e8eecb8bd1d7d5ddfc0496bee4d4f3f ] [Indent mdo as do svein@aas.no**20091109214749 Ignore-this: 8cf3b448fcde1d8219c4c97ba1955c85 ] [TAG 2.6.4 svein@aas.no**20091107110901 Ignore-this: d2d4c16df56f5bb4b749e886a99e0550 ] Patch bundle hash: db4c47fb09199c61b1611bfbb46a9e0277c82c0a ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Iteratee question
I am writing a binary data parser and use `iteratee' package. The following pattern appears quite often in my code: results - map someConversion `liftM` replicateM nbytes Iter.head The meaning is: take `nbytes' from stream, apply `someConversion' to every byte and return the list of `results'. But there's more than one way to do it[1]: i1, i2, i3 :: Monad m = Int - IterateeG [] Word8 m [String] i1 n = map conv `liftM` replicateM n Iter.head i2 n = map conv `liftM` joinI (Iter.take n stream2list) i3 n = joinI $ Iter.take n $ joinI $ mapStream conv stream2list [1] http://en.wikipedia.org/wiki/There's_more_than_one_way_to_do_it If you try the program[2] I've hpasted, you will see that these three iteratees have equal results. [2] http://hpaste.org/fastcgi/hpaste.fcgi/view?id=12464#a12464 Of those i1, i2, i3 which one is better and why? Or is there another - preferable - way of applying iteratees to this task? My naïve guess is that i1 will have worse performance with big n's. It looks like `i1' is reading bytes one by one, while `i2' takes whole chunks of data... I'm not sure though. I would appreciate it a lot if you improve my understanding. -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Fwd: cabal-install sends invalid proxy password
Hello, I was surprised to discover that `cabal-install' -- a popular utility for installing Hackage packages -- cannot work with HTTP proxies. Despite all the necessary code linked in. `cabal update' command returns HTTP 407 (Proxy Authentication Required) error. The problem is explained below and patches follow. See http://article.gmane.org/gmane.comp.lang.haskell.libraries/10420 No response so far. (I start to suspect that there is just one proxied haskeller subscribed to `libraries' and `cabal-dev' lists:) -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Arrow without `'
On 1/23/08, David Menendez [EMAIL PROTECTED] wrote:
On Jan 23, 2008 12:20 PM, Valery V. Vorotyntsev [EMAIL PROTECTED] wrote:
I've built GHC from darcs, and...
Could anybody tell me, what's the purpose of Arrow[1] not having `'
method?
It's derived from the Category superclass.
Yes, it is.
The right question: how to build `arrows' in such circumstances?
Here go 2 changes I made to `CoState.hs' accompanied by the
error messages. :) Unfortunately, I'm not arrow-capable enough to
make _proper_ changes to the code and satisfy GHC... Any help?
~~
Change #1:
$ darcs w Control/Arrow/Transformer/CoState.hs
What's new in Control/Arrow/Transformer/CoState.hs:
{
hunk ./Control/Arrow/Transformer/CoState.hs 23
+import Control.Category (())
}
--
Error #1:
Control/Arrow/Transformer/CoState.hs:29:7:
`' is not a (visible) method of class `Arrow'
Failed, modules loaded: Control.Arrow.Operations.
~~
Change #2:
$ darcs diff -u Control/Arrow/Transformer/CoState.hs
--- old-arrows/Control/Arrow/Transformer/CoState.hs 2008-01-24
14:54:29.852296559 +0200
+++ new-arrows/Control/Arrow/Transformer/CoState.hs 2008-01-24
14:54:29.852296559 +0200
@@ -20,12 +20,13 @@
import Control.Arrow
import Control.Arrow.Operations
+import Control.Category (())
newtype CoStateArrow s a b c = CST (a (s - b) (s - c))
instance Arrow a = Arrow (CoStateArrow s a) where
arr f = CST (arr (f .))
- CST f CST g = CST (f g)
+-- CST f CST g = CST (f g)
first (CST f) = CST (arr unzipMap first f arr zipMap)
zipMap :: (s - a, s - b) - (s - (a,b))
--
Error#2:
Control/Arrow/Transformer/CoState.hs:27:0:
Could not deduce (Control.Category.Category (CoStateArrow s a))
from the context (Arrow a)
arising from the superclasses of an instance declaration
at Control/Arrow/Transformer/CoState.hs:27:0
Possible fix:
add (Control.Category.Category
(CoStateArrow s a)) to the context of
the instance declaration
or add an instance declaration for
(Control.Category.Category (CoStateArrow s a))
In the instance declaration for `Arrow (CoStateArrow s a)'
Failed, modules loaded: Control.Arrow.Operations.
Thank you.
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[Haskell-cafe] Fwd: Arrow without `'
The problem has been resolved. Kudos to Ross Paterson. -- Forwarded message -- From: Valery V. Vorotyntsev [EMAIL PROTECTED] Date: Jan 24, 2008 3:34 PM Subject: Re: Arrow without `' To: [EMAIL PROTECTED] On 1/24/08, Ross Paterson [EMAIL PROTECTED] wrote: The right question: how to build `arrows' in such circumstances? To build with the darcs version of the base library (built with GHC), you'll need the darcs version of the arrows library, which I think is right now: darcs get http://darcs.haskell.org/packages/arrows Yes, after pulling the latest change from repo installation went smoothly. Thank you very much, Ross! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Arrow without `'
Hi, friends,
I've built GHC from darcs, and...
Could anybody tell me, what's the purpose of Arrow[1] not having `'
method?
1. http://darcs.haskell.org/packages/base/Control/Arrow.hs
$ ghci
GHCi, version 6.9.20080104: http://www.haskell.org/ghc/ :? for help
Loading package base ... linking ... done.
Prelude :m + Control.Arrow
Prelude Control.Arrow :i Arrow
class (Control.Category.Category a) = Arrow a where
arr :: (b - c) - a b c
pure :: (b - c) - a b c
first :: a b c - a (b, d) (c, d)
second :: a b c - a (d, b) (d, c)
(***) :: a b c - a b' c' - a (b, b') (c, c')
() :: a b c - a b c' - a b (c, c')
-- Defined in Control.Arrow
instance Arrow (-) -- Defined in Control.Arrow
instance (Monad m) = Arrow (Kleisli m) -- Defined in Control.Arrow
Prelude Control.Arrow Leaving GHCi.
I can't build[2] arrows-0.3 package without `' in Arrow.
2.
[EMAIL PROTECTED]:~/src/arrows$ darcs w
{
hunk ./Control/Arrow/Operations.hs 36
+import Control.Category (())
hunk ./Control/Arrow/Transformer/CoState.hs 23
+import Control.Category (())
}
[EMAIL PROTECTED]:~/src/arrows$ runhaskell Setup build
Preprocessing library arrows-0.3...
Building arrows-0.3...
[ 3 of 12] Compiling Control.Arrow.Transformer.CoState (
Control/Arrow/Transformer/CoState.hs,
dist/build/Control/Arrow/Transformer/CoState.o )
Control/Arrow/Transformer/CoState.hs:29:7:
`' is not a (visible) method of class `Arrow'
The question arises should I?, but this is one of lambdabot's[3]
depencies.
3. http://code.haskell.org/lambdabot/
Thanks a lot!
--
vvv
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Re: [Haskell-cafe] Code folding in Emacs
On 1/14/08, Johan Tibell [EMAIL PROTECTED] wrote: It would be pretty neat for Haskell hacking if the Emacs Haskell mode could do the following. Imagine you have written some code like so: [...] Binding a haskell-fold-source function to a key chain would enable you to get a quick overview of your module showing only the comments and type signatures. I've used the little function from http://emacs.wordpress.com/2007/01/16/quick-and-dirty-code-folding/ but it doesn't work well together with indented type signatures like in the example above. AFAIU the problem, .. data StupidTypeNameIntendedToBeLong = Foo functionWithLngName :: Foo - Bar functionWithLngName = undefined .. you don't like the way haskell-mode indents the `- Bar' line. If this is the case, you could `newline-and-indent' (`C-j') right after `::'. anotherFunctionWithLongName :: Foo - Bar anotherFunctionWithLongName = undefined And what's this haskell-fold-source function you were talking about? -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Literate HTML
On 12/11/07, Neil Mitchell [EMAIL PROTECTED] wrote: I couldn't get it working either, so have raised a feature request bug. Which has been merged into #1232: http://hackage.haskell.org/trac/ghc/ticket/1967#comment:1 -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: emacs haskellers: r-stripping files becomes popular
On 11/16/07, Valery V. Vorotyntsev [EMAIL PROTECTED] wrote: Add the following lines to your ~/.emacs: Adding buffer name to confirmation message: --- BEGIN --- (defun delete-trailing-whitespace-if-confirmed () Delete all the trailing whitespace across the current buffer, asking user for confirmation. (if (and (save-excursion (goto-char (point-min)) (re-search-forward [[:space:]]$ nil t)) (y-or-n-p (format Delete trailing whitespace from %s? (buffer-name (delete-trailing-whitespace))) --- END --- (add-hook 'before-save-hook 'delete-trailing-whitespace-if-confirmed) -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] emacs haskellers: r-stripping files becomes popular
On 11/16/07, Denis Bueno [EMAIL PROTECTED] wrote: For one thing, if you happen to write code shared with other people who do not use this hook, then you may end up causing *huge* numbers of spurious differences in diff(1) output. There may be an easy way to deal with this, but, it is a problem. Yes, you are right. That's why user is being asked for confirmation. And `diff -w' removes the noise, but still, yes, that can be a problem. :) -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] emacs haskellers: r-stripping files becomes popular
On 11/16/07, Brent Yorgey [EMAIL PROTECTED] wrote: Nice! Is there a way to have this only run if the current buffer is in haskell-mode? I'd add it myself but I've not yet taken the plunge to being an elisp hacker. Try adding ``(eq major-mode 'haskell-mode)'' after the `and' .. .. but why would you tolerate whitespace in other modes? -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] emacs haskellers: r-stripping files becomes popular
Add the following lines to your ~/.emacs: --- BEGIN OF ELISP CODE --- ;(global-set-key (kbd f9 s) 'delete-trailing-whitespace) (defun delete-trailing-whitespace-if-confirmed () Delete all the trailing whitespace across the current buffer, asking user for confirmation. (if (and (save-excursion (goto-char (point-min)) (re-search-forward [[:space:]]$ nil t)) (y-or-n-p Delete trailing whitespace? )) (delete-trailing-whitespace))) (add-hook 'before-save-hook 'delete-trailing-whitespace-if-confirmed) --- END OF ELISP CODE --- Have fun! -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: Math.OEIS 0.1
On 10/22/07, Henning Thielemann [EMAIL PROTECTED] wrote: Cute! +1 http://programming.reddit.com/info/5yuhf/comments/ -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] On the verge of ... giving up!
On 10/19/07, Valery V. Vorotyntsev [EMAIL PROTECTED] wrote: On 10/19/07, Johan Tibell [EMAIL PROTECTED] wrote: If you have a web server somewhere you can use CGIIRC. That's what I did in a similar situation. http://cgiirc.org/ Thanks, Johan! There is one at http://ircatwork.com/ And now I'm in. Thank you very much. :) -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] On the verge of ... giving up!
On 10/18/07, Don Stewart [EMAIL PROTECTED] wrote: Please drop by the irc channel! enthusiasm is always welcome there, and we're pretty much all obsessed too! Maybe that's not The Right Thing(TM) to ask, but anyway. :) My access the world outside the office's LAN is limited to ports 80 and 443. And chat.freenode.net lives on 6667. Once upon a time I could access #haskell via IRC gateway @ irc.e.jabber.ru, but not know, for the reasons unknown. Do you know of any 443:server, forwarding connections to chat.freenode.net:6667? Thanks a lot. -- vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] 'Proper' use of the State monad
Denis Volk [EMAIL PROTECTED] writes: I am trying to make a (turn-based) game in Haskell and need to pass around quite a bit of information, so using the State monad seems most appropriate. My question is, which is a better idea: Have you read `Theseus and the Zipper'[1] yet? 1. http://en.wikibooks.org/wiki/Haskell/Zippers -vvv ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why Perl is more learnable than Haskell
Dave Feustel [EMAIL PROTECTED] writes: A serious omission in Haskell tutorials is a collection of examples of how to write Haskell solutions for problems that would use arrays in any imperative language. I see that arrays can be defined in Haskell, but I don't see their use as computationally efficient in Haskell. By replacing the string type with our ByteString representation, Haskell is able to approach the speed of C, while still retaining the elegance of the idiomatic implementation. With stream fusion enabled, it actually beats the original C program. Only by sacrificing clarity and explicitly manipulating mutable blocks is the C program able to outperform Haskell. - http://www.cse.unsw.edu.au/~dons/papers/CSL06.html The ability to fuse all common list functions allows the programmer to write in an elegant declarative style, and still produce excellent low level code. We can finally write the code we *want* to be able to write without sacrificing performance! - http://www.cse.unsw.edu.au/~dons/papers/CLS07.html Don't give up. ;-) -vvv ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [OT] Re: [Haskell-cafe] Tricks for making low level haskell hacking easier
Mathieu Boespflug [EMAIL PROTECTED] writes: On 2/10/07, Donald Bruce Stewart [EMAIL PROTECTED] wrote: metachars). A screenshot: http://www.cse.unsw.edu.au/~dons/tmp/screen-core.png Just out of curiosity, what window manager is that? Mathieu Looks like ratpoison. http://www.nongnu.org/ratpoison/ But give Ion3 a try. You'll love it. http://modeemi.cs.tut.fi/~tuomov/ion/ http://tinyurl.com/25sd9f VVV ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
