[Haskell-cafe] Re: hmatrix
Anatoly Yakovenko wrote: do you have any plans to provide an interface for inplace updates? Yes, I will try to write a simple version of Data.Array.ST... I can try to help you, although I still dont quite grok monads. Wouldn't it be more efficient to use StorableArray, so you can cast from and to C? I am not sure how vectors and matrixes are represented in C, but I imagine it should be possible to manipulate them without resorting to copying between haskell and C. That's right, the correspondence with StorableArray is direct, and efficient conversion can be easily added to the library. I mentioned the idea of Data.Array.ST to have also the possibility of writing pure code, without IO, internally implemented with inplace updates. Alberto ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: hmatrix
Hello Alberto, Tuesday, June 3, 2008, 11:27:54 AM, you wrote: Yes, I will try to write a simple version of Data.Array.ST... That's right, the correspondence with StorableArray is direct, and efficient conversion can be easily added to the library. I mentioned the idea of Data.Array.ST to have also the possibility of writing pure code, without IO, internally implemented with inplace updates. STRef/STArray operations are just IORef/IOArray operations imported in some way/ you can easily import any other operations to ST monad as far as you use rank-2 types to guarantee that impureness will not escape the runST call. look into unsafeIOtoST function providing unmovable STUArray variant may be a good idea -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: hmatrix
Bulat Ziganshin wrote: Hello Alberto, Tuesday, June 3, 2008, 11:27:54 AM, you wrote: Yes, I will try to write a simple version of Data.Array.ST... That's right, the correspondence with StorableArray is direct, and efficient conversion can be easily added to the library. I mentioned the idea of Data.Array.ST to have also the possibility of writing pure code, without IO, internally implemented with inplace updates. STRef/STArray operations are just IORef/IOArray operations imported in some way/ you can easily import any other operations to ST monad as far as you use rank-2 types to guarantee that impureness will not escape the runST call. look into unsafeIOtoST function Good! So you can easily hide the IO operations in the ST monad. I will definitely look into it. providing unmovable STUArray variant may be a good idea Many thanks Bulat! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc 6.8.2 issue
On Mon, 2008-06-02 at 23:11 -0500, Galchin, Vasili wrote: at this point rebuild and install the unix package ... [EMAIL PROTECTED]:~/FTP/Haskell/bytestring-mmap-0.2.0$ runhaskell Setup.lhs clean cleaning... [EMAIL PROTECTED]:~/FTP/Haskell/bytestring-mmap-0.2.0$ runhaskell Setup.lhs configure Configuring bytestring-mmap-0.2.0... [EMAIL PROTECTED]:~/FTP/Haskell/bytestring-mmap-0.2.0$ runhaskell Setup.lhs build Setup.lhs: error reading dist/setup-config; run setup configure command? dist/setup-config is not being populated at the end. In your response below, are you saying that teh segfaults occur because ghc itself relies on the unix package? Something like that yes. You're running runhaskell Setup.lhs and that loads and runs code from the Cabal library. The Cabal library depends on the process library which depends on the unix library. So by replacing the same version of the unix package you're breaking everything else which depends on it, including Cabal and thus runhaskell Setup.lhs. So the solution is to not do that. Don't re-install the exact same version of any of the core libs that come with ghc. Adding new versions is fine, replacing existing versions is not fine because it breaks all the other packages that were already built against that package. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [ANN] bloomfilter 1.0 - Fast immutable and mutable Bloom filters
Thomas Hartman [EMAIL PROTECTED] writes:
What kind of speed do you get on your laptop for Data.Set? How much
faster is the bloom filter?
I tried to modify examples/Words.hs to use Data.Set insted. The
results look like this (first Bloom, second Data.Set, both compiled
with -O2):
nmd:..filter/examples % ./Words
57025 words
0.013326ss to count words
Bloom { 4194304 bits }
0.050608ss to construct filter
0.034806ss to query every element
nmd:..filter/examples % ./WordsS
57025 words
0.013291ss to count words
False
0.755115ss to construct filter
0.423289ss to query every element
In order to avoid printing the entire set, while still evaluating it,
I replaced the printing of the set with printing the result of a
search for a non-existing element - I should really use a strict
insert, I guess. Anyway, this hopefully gives an indication - looks
like a factor of 10 in this case, but it will depend on the size of
the data - more data, greater improvement.
BTW, Nice work, Bryan! I have plans for this.
-k
--
If I haven't seen further, it is by standing in the footprints of giants
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Re: [Haskell-cafe] ghc 6.8.2 issue
On Tue, 2008-06-03 at 00:04 -0500, Galchin, Vasili wrote: Duncan, By installing localling, I runhaskell Setup.hs configure --prefix=$HOME plus add local path to LD_LIBRARY_PATH and LD_RUN_PATH? On Linux, does ghc use .so's or is it linked statically? ghc is linked statically but when you do things like runhaskell Setup.hs you're asking ghc to dynamically load packages. runhaskell/runghc is basically a form of ghci, and ghci does dynamic code loading. If you've broken some of the packages that ghci loads and runs code from then you'll run into problems, mysterious segfaults and the like. As I understand it, in the next version of ghc it will track the ABI of each package so we would be able to detect when people replace packages with ones with the same version but with a different ABI (as you've been doing) and refuse to link or run in those cases rather than running and ending up with segfaults. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: appending an element to a list
Abhay Parvate wrote:
I somehow thought it would be easy to talk about complexity of calculating
individual elements in an infinite list should be sufficient, but that seems
to be involved, and my over-generalization doesn't seem to work. Thanks for
the link; particularly it has reference to Wadler's papers exactly on this
problem.
Note however that Wadler's and similar formalisms are still a
unsatisfactory in that they are quite clumsy to work with, it's quite
tedious/impossible to analyze examples with a lot of lazy evaluation.
But they are a good guideline.
In his book about purely functional data structures [1], Okasaki takes a
different approach; each node of a data structure is given a debit, a
cost to evaluate it. For instance, consider
xs = x1 : x2 : x3 : ... : xn : []
111 ... 11 0
ys = y1 : y2 : y3 : ... : ym : []
111 ... 11 0
The numbers below indicate the time it takes to evaluate the node to
weak head normal form. For demonstration purposes, I arbitrarily chose 1
for each (:) here.
The combined list will then have debits like
xs ++ ys = x1 : x2 : x3 : ... : xn : y1 : y2 : y3 : ... : ym : []
222 ... 22111 ... 11 0
In other words, the ys list is copied verbatim but each element of xs
incurs an additional cost of 1, corresponding to one step in the
evaluation of the concatenation with (++).
In order to force/inspect a constructor/node, you have to pay off its
debits first. In the above example, head (xs ++ ys) would have to pay
2 units of time (one unit for head xs and one for the (++)). Now, the
thing about debits is that we can relocate them to the top and only
overestimate the total running time if we do that. For instance, we
could push all debits to the top
xs ++ ys = x1 : x2 : x3 : ... : xn : y1 : y2 : y3 : ... : ym : []
2n+m 00 ... 00000 ... 00 0
so that evaluating head (xs ++ ys) is now estimated to cost (2n+m)
units of time while the rest is free/fully evaluated.
The above example is rather useless, but consider the case n == m and
xs = x1 : x2 : x3 : ... : xn : []
000 ... 00 0
ys = y1 : y2 : y3 : ... : yn : []
000 ... 00 0
i.e. two fully evaluated lists of the same length. Then, we have
xs ++ reverse ys =
x1 : x2 : x3 : ... : xn : yn : y{n-1} : ... : y1 : []
111 ... 11n0 ... 00 0
because reversing the list ys is monolithic, i.e. looking at its head
already forces the tail of the list. But now, we can distribute the
debits upwards
xs ++ reverse ys =
x1 : x2 : x3 : ... : xn : yn : y{n-1} : ... : y1 : []
222 ... 2200 ... 00 0
and thereby amortize the cost of reversing the second lists over the n
elements of the first list. This is used in the implementation of purely
functional queues, see also Okasaki's book.
[1]: Chris Okasaki. Purely Function Data Structures.
http://www.cs.cmu.edu/~rwh/theses/okasaki.pdf
(This is the thesis on which the book is based.)
Regards,
apfelmus
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Re[2]: [Haskell-cafe] Re: hmatrix
Hello Alberto, Tuesday, June 3, 2008, 12:56:50 PM, you wrote: Good! So you can easily hide the IO operations in the ST monad. I will definitely look into it. from implementation POV ST monad is nothing but renamed IO monad which exports only subset of its operations which are guaranteed to safe. or, saying in other words, it's just type hackery around IO monad that provides safe operations it's possible to define ST monad and its operations as following: newtype ST s a = forall s. ST_Constructor (IO a) unsafeIOtoSt action = ST_Constructor action runST (ST_Constructor action) = unsafePerformIO action newtype STRef s a = forall s. STRef (IORef a) readSTRef (STRef ref) = unsafeIOtoSt (readIORef ref) and so on. GHC uses technically (but not ideologically!) different implementation where both monads are specializations of one generic type. while Hugs afair uses exactly this approach. you may also look at ArrayRef lib which reimplements arrays/refs for both compilers in more unified way anyway, because ST is just IO monad modulo type tricks, you can execute any IO action inside ST by lifting it with unsafeIOtoSt -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Rotating backdrop (aka learning Haskell)
First version is available at: http://www.kierun.org/backdropper-1.0.tbz2 It is minimal but does the trick of randomly rotating backgrounds. Features to add are only rotate during work hours, making sure that all images are shown within a day and a nice GUI. Criticism welcome. -- [EMAIL PROTECTED] -= H+ =- www.kierun.org PGP: 009D 7287 C4A7 FD4F 1680 06E4 F751 7006 9DE2 6318 pgp1DQpdVc35O.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Implementing ParseChart with Data.Map
I actually made my own copy of Data.Map and added an extra: alterLookúp :: Ord k = (Maybe a - (b,Maybe a)) - k - Map k a - (b,Map k a) function. I also changed my data type to: type ParseChart k v = Map k (Map v ()) so I don't have to copy the Data.Set module also. Unfortunately this doesn't give much better performance - 5734 msec instead of 5828 msec. Fortunately I found that there is a way to avoid to use Map at all in one common case. This gave me time about 5024 msec. Regards, Krasimir On 6/3/08, Yitzchak Gale [EMAIL PROTECTED] wrote: Krasimir Angelov wrote: but notice that the set is still traversed twice. Neil Mitchell wrote: I don't see any way of reducing that Yeah, it looks like the Data.Set (and Data.IntSet) library is missing the functions insertMember :: Ord a = a - Set a - (Bool, Set a) deleteMember :: Ord a = a - Set a - (Bool, Set a) analagous to splitMember. It should be easy to write those functions. If you do that for yourself, consider making a patch of them and submitting the patch as a library proposal. But anyway, a set lookup is very cheap, even for a set that is quite large. You may want to try just doing the extra lookup, it might be good enough for you. At least you eliminated the Map lookup. Regards, Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Implementing ParseChart with Data.Map
Krasimir Angelov wrote: but notice that the set is still traversed twice. Neil Mitchell wrote: I don't see any way of reducing that Yeah, it looks like the Data.Set (and Data.IntSet) library is missing the functions insertMember :: Ord a = a - Set a - (Bool, Set a) deleteMember :: Ord a = a - Set a - (Bool, Set a) analagous to splitMember. It should be easy to write those functions. If you do that for yourself, consider making a patch of them and submitting the patch as a library proposal. But anyway, a set lookup is very cheap, even for a set that is quite large. You may want to try just doing the extra lookup, it might be good enough for you. At least you eliminated the Map lookup. Regards, Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Implementing ParseChart with Data.Map
Hello Krasimir, Krasimir Angelov wrote: Hi, I have to write ParseChart implementation with Data.Map/Set. The chart is type like this: type Chart k v = Map k (Set v) now I need operation like: insert :: k - v - Chart k v - Maybe (Chart k v) where the result is (Just _) if the (k,v) is actually added to the chart or Nothing if it was already there and nothing have to be done. The straight forward implementation is: case Map.lookup k chart of Nothing - Just (Map.insert k (Set.singleton v) chart) Just set | Set.member v set - Nothing | otherwise- Just (Map.insert k (Set.insert v set) chart) You can do this quite easily with the AVL library, something like this (untested code) import Data.Cordering import Data.Tree.AVL type Chart k v = AVL (k, AVL v) insert :: (Ord k, Ord v) = k - v - Chart k v - Maybe (Chart k v) insert k v tk = case genOpenPathWith cmpk tk of EmptyBP pthk- Just $! insertPath pthk (k, singleton v) tk FullBP pthk tv - case genOpenPath (compare v) tv of EmptyBP pthv - let tv' = insertPath pthv v tv in tv' `seq` (Just $! writePath pthk (k, tv') tk) FullBP _ _ - Nothing where cmpk (k',tv) = case compare k k' of LT - Lt EQ - Eq tv GT - Gt ..or something like that (maybe you don't want all that strictness) The insertPath writePath functions do involve a second traversal but do not repeat all the comparisons. Also, provided not too much has happened in between, they should be very fast as the nodes on the path are probably still in cache. The important thing is that in the case where Nothing is returned you'll have burned very little heap. Regards -- Adrian Hey ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] hs-plugins compile error
Hi,
What is the status of hs-plugins? I recently tried to install the
version plugins-1.2 on hackage, using a Gnu/Linux box with Fedora 9
and ghc-6.8.2, but didn't get past the configure stage (see config.log
below).
The installation script is invoking gcc with a -V command line argument
but according to gcc documentation -V requires an argument.
Has anyone managed to get hs-plugins to work? If so, what platform,
which version of ghc and gcc, and where did you find the hs-plugins
source?
Best wishes,
John O'Donnell
... from config.log...
gcc version 4.3.0 20080428 (Red Hat 4.3.0-8) (GCC)
configure:1852: $? = 0
configure:1854: gcc -V /dev/null 5
gcc: '-V' option must have argument
configure:1857: $? = 1
configure:1880: checking for C compiler default output file name
configure:1883: gccconftest.c 5
conftest.c:9:13: warning: missing terminating character
conftest.c:10: error: stray '\33' in program
conftest.c:10: error: expected identifier or '(' before '[' token
conftest.c:10:4: error: invalid suffix h on integer constant
conftest.c:10:9: warning: missing terminating character
conftest.c:10: error: missing terminating character
configure:1886: $? = 1
configure: failed program was:
| /* confdefs.h. */
|
| #define PACKAGE_NAME
| #define PACKAGE_TARNAME
| #define PACKAGE_VERSION
| #define PACKAGE_STRING
| #define PACKAGE_BUGREPORT
| #define LEADING_UNDERSCORE 0
| #define TOP /home/jtod/system/installs/hs-plugins/hs-plugins-1.2
| ESC[?1034h
| #define WITH_GHC ghc
| #define GHC_LIB_PATH /usr/local/lib/ghc-6.8.2
| /* end confdefs.h. */
|
| int
| main ()
| {
|
| ;
| return 0;
| }
configure:1925: error: C compiler cannot create executables
-Original Message-
From: [EMAIL PROTECTED] on behalf of Edsko de Vries
Sent: Mon 2008-06-02 20:23
To: Don Stewart
Cc: haskell-cafe@haskell.org
Subject: Re: [Haskell-cafe] hs-plugins compile error
Hi Don,
Is this the kind of thing you mean (I'm not really a darcs user; this is
the patch created by darcs record):
[Hide some names to remove ambiguity errors
Edsko de Vries [EMAIL PROTECTED]**20080602202001] {
hunk ./src/System/Plugins/Env.hs 76
-import Distribution.Package
+import Distribution.Package hiding (packageName)
hunk ./src/System/Plugins/PackageAPI.hs 43
-import Distribution.Package
+import Distribution.Package hiding (depends, packageName)
hunk ./src/System/Plugins/ParsePkgConfCabal.hs 9
-import Distribution.Package
+import Distribution.Package hiding (depends)
}
Edsko
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Re: [Haskell-cafe] [ANNOUNCE] git-darcs-import 0.1
2008/6/3 Darrin Thompson [EMAIL PROTECTED]: On Sun, Jun 1, 2008 at 2:44 PM, Bertram Felgenhauer [EMAIL PROTECTED] wrote: Hi, I'm pleased to announce yet another tool for importing darcs repositories to git. Unlike darcs2git [1] and darcs-to-git [2], it's written in Haskell, on top of the darcs2 source code. The result is a much faster program - it can convert the complete ghc 6.9 branch (without libraries) in less than 15 minutes on my slightly dated machine (Athlon XP 2500+), which is quite fast [3]. Incremental updates work, too. What's the appeal of this? I personally love git, but I thought all the cool kids at this school used darcs and that was that. Disclaimer: I'm no expert, this is what I've heard. Anyone please confirm or deny the following? Basically, git is waaay faster than Darcs on a number of use cases. So, maybe the point of using this converter is when you just cannot use Darcs any more (too old/big project, merging huge branch with loads of conflicts, I don't know). Another point may be broadcast-ability: It is possible to expose two repositories: one Darcs, one Git. If I use Git and not Darcs (please don't sue me), it will be simpler for me to get the source from the Git snapshot, provided there is one. Well, if I want to contribute back... maybe I should switch. I think the True Heresy (and most useful, if practical) would be to convert back and forth between the two version control systems, accepting patches from both :-) Loup ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] hs-plugins compile error
On Tue, Jun 03, 2008 at 03:07:33PM +0100, John O'Donnell wrote: Hi, What is the status of hs-plugins? I recently tried to install the version plugins-1.2 on hackage, using a Gnu/Linux box with Fedora 9 and ghc-6.8.2, but didn't get past the configure stage (see config.log below). The installation script is invoking gcc with a -V command line argument but according to gcc documentation -V requires an argument. Has anyone managed to get hs-plugins to work? If so, what platform, which version of ghc and gcc, and where did you find the hs-plugins source? It's working fine for me (after applying the patch I submitted), on Debian Lenny (which currently comes with ghc 6.8.2, gcc 4.2.4) and the source from Hackage. Source from the darcs repository also works fine (after applying the same patch). I *am* getting an application crash sometimes when I close my application, but I have not yet been able to track that down so I'm not 100% sure it's due to hs-plugins. Edsko ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [ANNOUNCE] git-darcs-import 0.1
On Sun, Jun 1, 2008 at 2:44 PM, Bertram Felgenhauer [EMAIL PROTECTED] wrote: Hi, I'm pleased to announce yet another tool for importing darcs repositories to git. Unlike darcs2git [1] and darcs-to-git [2], it's written in Haskell, on top of the darcs2 source code. The result is a much faster program - it can convert the complete ghc 6.9 branch (without libraries) in less than 15 minutes on my slightly dated machine (Athlon XP 2500+), which is quite fast [3]. Incremental updates work, too. What's the appeal of this? I personally love git, but I thought all the cool kids at this school used darcs and that was that. -- Darrin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] hs-plugins compile error
Thanks, Edsko. My version of gcc is 4.3.0. It may well be that some other piece of software in the Fedora 9 distribution is incompatible with the hs-plugins installation script. Has anyone installed hs-plugins on Fedora? I was able to get it to compile on Fedora 4, using ghc-6.4, two or three years ago, but it's never worked on any of my systems since then. John -Original Message- From: Edsko de Vries [mailto:[EMAIL PROTECTED] Sent: Tue 2008-06-03 15:35 To: John O'Donnell Cc: Edsko de Vries; Don Stewart; haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] hs-plugins compile error On Tue, Jun 03, 2008 at 03:07:33PM +0100, John O'Donnell wrote: Hi, What is the status of hs-plugins? I recently tried to install the version plugins-1.2 on hackage, using a Gnu/Linux box with Fedora 9 and ghc-6.8.2, but didn't get past the configure stage (see config.log below). The installation script is invoking gcc with a -V command line argument but according to gcc documentation -V requires an argument. Has anyone managed to get hs-plugins to work? If so, what platform, which version of ghc and gcc, and where did you find the hs-plugins source? It's working fine for me (after applying the patch I submitted), on Debian Lenny (which currently comes with ghc 6.8.2, gcc 4.2.4) and the source from Hackage. Source from the darcs repository also works fine (after applying the same patch). I *am* getting an application crash sometimes when I close my application, but I have not yet been able to track that down so I'm not 100% sure it's due to hs-plugins. Edsko ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Rewrite class with fundeps in pure h98?
I thought that I should be able to write something like the toHtml
function below with pure H98, but when I went to write it I ended up
needing fundeps. Is there a way to express this without using any
extensions?
The idea was to take a remotely Dom-like tree and flatten it into a
string, but not require any particular string type. Mostly I'm ripping
off HStringTemplate for the fun of it.
{-# OPTIONS -fglasgow-exts #-}
module Control.WebWidget where
import Data.Monoid
import Data.String
data (IsString s, Monoid s) = Dom s =
Element s [Attr s] [Dom s] |
Text s
data (IsString s, Monoid s) = Attr s = Attr s s
class (Monoid s, IsString s) = HTML d s | d - s where
toHtml :: d - s
instance (Monoid s, IsString s) = HTML (Dom s) s where
toHtml (Element name attrs children) =
mconcat [
fromString ,
name,
mconcat $ map toHtml attrs,
fromString ,
mconcat $ map toHtml children,
fromString /,
name,
fromString ]
toHtml (Text s) = s
instance (Monoid s, IsString s) = HTML (Attr s) s where
toHtml (Attr key value) =
mconcat [
fromString ',
key,
fromString '=',
value,
fromString ' ]
--
Darrin
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Re: [Haskell-cafe] Implementing ParseChart with Data.Map
Duncan Coutts wrote: modify :: k - Map k e - (e, Maybe e - Map k e) so it's a lookup that returns the element at k and also a continuation that lets you rebuild a new map with an altered element. I guess that doesn't account for the element not existing. There's probably a generalisation that does. isn't it just adding the necessary Maybe?: modify :: k - Map k e - (Maybe e, Maybe e - Map k e) ? -Isaac ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN (2 Libs) -- hvac 0.1b, a lightweight web framework and HStringTemplate 0.3
I just tried out hvac. I was trying to run the hvac examples after following the readme in the samples directory. sudo lighttpd -D -f lh.conf [sudo] password for thartman: 2008-06-03 09:30:02: (log.c.75) server started so that's okay, but http://localhost:3000/hvac-board/board/1 in firefox attempted to open a binary file 1. Same result for http://localhost:3000/hvac-board I don't know if this is an hvac issue or a fastcgi issue (seems more likely) but any advice? Thomas. 2008/3/22 Sterling Clover [EMAIL PROTECTED]: 1) hvac 0.1b: transactional, declarative framework for lightweight web applications. 2) HStringTemplate 0.3 1) hvac 0.1b hvac (short for http view and controller) has been my project for the last little while, and is finally in a fairly usable state, so I'm opening up the repo (darcs get http://community.haskell.org/~sclv/hvac/) for folks to play with and to get some feedback. While not quite yet ready for hackage, the package as provided should be fully cabal installable. Documentation is available at http://community.haskell.org/~sclv/hvac/html_docs/hvac/ The aim of hvac is to provide an environment that makes the creation of lightweight fastcgi based web applications as simple as possible, with an emphasis on concise, declarative style code, correct concurrent transactional logic, and transparency in adding caching combinators. There are two included example programs, naturally neither of which is feature complete. They share a common login module of about 50 lines of code, excluding imports, templates, and database schema. The first program is a classic, greenspun-style message board with basic login functionality. It totals roughly 40 lines and tends to use just under 4mb of resident memory on my system. The second is a wiki based on Pandoc and the PandocWiki code. The code totals roughly 30 lines (rendering borrowed from PandocWiki aside) and uses about 5mb of memory. hvac processes all requests in the STM monad, with some bells attached to properly interleave STM with session, database and filesystem operations such that they all conceptually occur together in a single transaction per request. Currently it is only fully tested with sqlite, but it should operate, modulo a few tweaks, with any database accessible via HDBC. hvac is particularly designed to use the HStringTemplate library as an output layer, in a simple declarative fashion. As the StringTemplate grammar is explicitly sub-turing, this ensures a clean separation of program logic from presentation, while providing a nonetheless fairly powerful language to express typical display tasks. The included cache combinators, still experimental, should allow a simple and fine-grained control over the level of caching of various disk-bound operations. Phantom types are used to ensure that no functions that modify state may be cached. To give a flavor of hvac code, the following is the complete (twenty lines!) source of the wiki controller (due to sql statements, some lines are rather long): wikiController tmpl = h |/ login * login_plug tmpl | (h |/ wiki |\\ \pageName -h |// POST * withValidation [ (contents, return) ] (\ [contents] - do pageId - selectVal id from pages where name=? [toSql pageName] maybe (addErrors [(Login,must be logged in.)] continue) (\user - case fromSql pageId of Just (_::Int) - execStat insert into page_hist(pageId,contents,author) values(?,?,?) [pageId, toSql contents, toSql . userName $ user] Nothing - do execStat insert into pages(name,locked) values(?,?) [toSql pageName, toSql (0::Int)] pid - selectVal max(id) from pages [] execStat insert into page_hist(pageId,contents,author) values(?,?,?) [pid, toSql contents, toSql . userName $ user]) = getSes continue) | do pageId - selectVal id from pages where name=? [toSql pageName] (join $ renderf (tmpl showPage) (pageName, pageName) $ pageContents |= selectRow * from page_hist where pageId=? order by time desc limit 1 [pageId] )) | (redirect . ( ++ /wiki/Index) = scriptName) Future directions for work on hvac include: Stress testing for correctness of transactional logic and benchmarks. Exploration of various efficiency tweaks. Unit tests. Further development of the cache combinator API. Improvement of the example apps and addition of a few others (a blog maybe). Expansion of the library of validator functions. Exploration of transferring hvac to the standard FastCGI bindings (currently it uses a custom modified version to work properly with STM). Improvement of the database layer, particularly with regards to common paging functions. Creation of a set of simple combinators for generating CRUD
[Haskell-cafe] Re: Rewrite class with fundeps in pure h98?
Darrin Thompson wrote: I thought that I should be able to write something like the toHtml function below with pure H98, but when I went to write it I ended up needing fundeps. Is there a way to express this without using any extensions? The idea was to take a remotely Dom-like tree and flatten it into a string, but not require any particular string type. data (IsString s, Monoid s) = Dom s = Element s [Attr s] [Dom s] | Text s data (IsString s, Monoid s) = Attr s = Attr s s class (Monoid s, IsString s) = HTML d s | d - s where toHtml :: d - s instance (Monoid s, IsString s) = HTML (Dom s) s where instance (Monoid s, IsString s) = HTML (Attr s) s where The H98 way is to make a class for type constructors: class HTML d where toHTML :: (Monoid s, IsString s) = d s - s instance HTML Dom where ... instance HTML Attr where ... Btw, naming the class HTML is feels wrong, something like Serialize is probably a better fit. Regards, apfelmus ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What is the maturity of Haskell Web Frameworks
Note however that hpaste runs off an earlier version of HAppS, which has changed radically from v8 to v9. I seem to remember discussion of porting hpaste to the latest HAppS as a demo app... are there still plans to do that? Thomas. 2008/6/2 Don Stewart [EMAIL PROTECTED]: aditya_siram: I am building a web-app that, in broad strokes, allows a leader to assign tasks to team members and allows team members to accept/reject/pick tasks that they want to do. I really like Haskell and I would like to use it to implement the solution. Are frameworks like Happs ready? Not so much in terms of documentation, but in functionality and stability. HAppS is nice (see hpaste.org for example, which is nice and simple, and has been running for over a year). Another nice option in Haskell is using something like HStringTemplate or the xhtml combinators with fastcgi hooked into GHC's concurrency mechanisms. You can find *many* more things here, http://hackage.haskell.org/packages/archive/pkg-list.html#cat:Network http://hackage.haskell.org/packages/archive/pkg-list.html#cat:Web ___ 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] What is the maturity of Haskell Web Frameworks
note to the curious that this is a git and not a darcs repo git clone http://code.haskell.org/hpaste.git thomas. 2008/6/3 Don Stewart [EMAIL PROTECTED]: A new version of happs was written on a Monday a couple of months ago, using fastcgi and takusen. We're running it at galois, and you can find the code on code.haskell.org/hpaste. So not quite what you wanted, but another data point. -- Don tphyahoo: Note however that hpaste runs off an earlier version of HAppS, which has changed radically from v8 to v9. I seem to remember discussion of porting hpaste to the latest HAppS as a demo app... are there still plans to do that? Thomas. 2008/6/2 Don Stewart [EMAIL PROTECTED]: aditya_siram: I am building a web-app that, in broad strokes, allows a leader to assign tasks to team members and allows team members to accept/reject/pick tasks that they want to do. I really like Haskell and I would like to use it to implement the solution. Are frameworks like Happs ready? Not so much in terms of documentation, but in functionality and stability. HAppS is nice (see hpaste.org for example, which is nice and simple, and has been running for over a year). Another nice option in Haskell is using something like HStringTemplate or the xhtml combinators with fastcgi hooked into GHC's concurrency mechanisms. You can find *many* more things here, http://hackage.haskell.org/packages/archive/pkg-list.html#cat:Network http://hackage.haskell.org/packages/archive/pkg-list.html#cat:Web ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] More on performance
I wrote up the second part of the tour of understanding low level performance in GHC here, http://reddit.com/r/programming/info/6lx36/comments/ Follows on from the discussion last week about various performance related things. Enjoy. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: [ANNOUNCE] git-darcs-import 0.1
On 2008-06-03, Peter Hercek [EMAIL PROTECTED] wrote: Loup Vaillant wrote: 2008/6/3 Darrin Thompson [EMAIL PROTECTED]: --cut-- What's the appeal of this? I personally love git, but I thought all the cool kids at this school used darcs and that was that. Disclaimer: I'm no expert, this is what I've heard. Anyone please confirm or deny the following? Basically, git is waaay faster than Darcs on a number of use cases. Other reason can be git rebase. Of course there is a question how good practice it is ... but it is being used. Darcs patches are pretty much an implicit rebase. -- Aaron Denney -- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What is the maturity of Haskell Web Frameworks
Ah yes, the url was incorrect. Well spotted. tphyahoo: note to the curious that this is a git and not a darcs repo git clone http://code.haskell.org/hpaste.git thomas. 2008/6/3 Don Stewart [EMAIL PROTECTED]: A new version of happs was written on a Monday a couple of months ago, using fastcgi and takusen. We're running it at galois, and you can find the code on code.haskell.org/hpaste. So not quite what you wanted, but another data point. -- Don tphyahoo: Note however that hpaste runs off an earlier version of HAppS, which has changed radically from v8 to v9. I seem to remember discussion of porting hpaste to the latest HAppS as a demo app... are there still plans to do that? Thomas. 2008/6/2 Don Stewart [EMAIL PROTECTED]: aditya_siram: I am building a web-app that, in broad strokes, allows a leader to assign tasks to team members and allows team members to accept/reject/pick tasks that they want to do. I really like Haskell and I would like to use it to implement the solution. Are frameworks like Happs ready? Not so much in terms of documentation, but in functionality and stability. HAppS is nice (see hpaste.org for example, which is nice and simple, and has been running for over a year). Another nice option in Haskell is using something like HStringTemplate or the xhtml combinators with fastcgi hooked into GHC's concurrency mechanisms. You can find *many* more things here, http://hackage.haskell.org/packages/archive/pkg-list.html#cat:Network http://hackage.haskell.org/packages/archive/pkg-list.html#cat:Web ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What is the maturity of Haskell Web Frameworks
A new version of happs was written on a Monday a couple of months ago, using fastcgi and takusen. We're running it at galois, and you can find the code on code.haskell.org/hpaste. So not quite what you wanted, but another data point. -- Don tphyahoo: Note however that hpaste runs off an earlier version of HAppS, which has changed radically from v8 to v9. I seem to remember discussion of porting hpaste to the latest HAppS as a demo app... are there still plans to do that? Thomas. 2008/6/2 Don Stewart [EMAIL PROTECTED]: aditya_siram: I am building a web-app that, in broad strokes, allows a leader to assign tasks to team members and allows team members to accept/reject/pick tasks that they want to do. I really like Haskell and I would like to use it to implement the solution. Are frameworks like Happs ready? Not so much in terms of documentation, but in functionality and stability. HAppS is nice (see hpaste.org for example, which is nice and simple, and has been running for over a year). Another nice option in Haskell is using something like HStringTemplate or the xhtml combinators with fastcgi hooked into GHC's concurrency mechanisms. You can find *many* more things here, http://hackage.haskell.org/packages/archive/pkg-list.html#cat:Network http://hackage.haskell.org/packages/archive/pkg-list.html#cat:Web ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: type-level integers using type families
On Thu, May 29, 2008 at 5:15 AM, Peter Gavin [EMAIL PROTECTED] wrote: Has anyone else tried implementing type-level integers using type families? When I started to work on thetype-level and parameterized data packages, I considered using type-families and GADTs, but I found quite a few problems which have been nicely summarized by Benedikt in this thread. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Rewrite class with fundeps in pure h98?
This was how it was originally done in HStringTemplate, as I recall. The mptcs were introduced in order to maintain lookup-maps of the correct type, and particularly to allow embedding of templates within one another. There may have been some other corner-cases involved as well. However, unless you run into them, the H98 way is certainly cleaner. --Sterl On Jun 3, 2008, at 1:17 PM, apfelmus wrote: Darrin Thompson wrote: I thought that I should be able to write something like the toHtml function below with pure H98, but when I went to write it I ended up needing fundeps. Is there a way to express this without using any extensions? The idea was to take a remotely Dom-like tree and flatten it into a string, but not require any particular string type. data (IsString s, Monoid s) = Dom s = Element s [Attr s] [Dom s] | Text s data (IsString s, Monoid s) = Attr s = Attr s s class (Monoid s, IsString s) = HTML d s | d - s where toHtml :: d - s instance (Monoid s, IsString s) = HTML (Dom s) s where instance (Monoid s, IsString s) = HTML (Attr s) s where The H98 way is to make a class for type constructors: class HTML d where toHTML :: (Monoid s, IsString s) = d s - s instance HTML Dom where ... instance HTML Attr where ... Btw, naming the class HTML is feels wrong, something like Serialize is probably a better fit. Regards, apfelmus ___ 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] ANN (2 Libs) -- hvac 0.1b, a lightweight web framework and HStringTemplate 0.3
Probably best not to keep this discussion in -cafe after this, as this is more of a debugging-type issue, but in my experience, I bet the lighttpd server is trying to serve the hvac-board fcgi file directly as a binary, rather than launching it as a fastcgi instance at all. The configurations files I've built have worked fine for me, but your milage may vary -- getting fastcgi up and running can be a bit of a bear at times. At a minimum, you should make sure that the lh.conf file points correctly to your binary in the fastcgi.server variable, and that you have all the proper fastcgi libraries installed on your system. Regards, Sterl On Jun 3, 2008, at 1:08 PM, Thomas Hartman wrote: I just tried out hvac. I was trying to run the hvac examples after following the readme in the samples directory. sudo lighttpd -D -f lh.conf [sudo] password for thartman: 2008-06-03 09:30:02: (log.c.75) server started so that's okay, but http://localhost:3000/hvac-board/board/1 in firefox attempted to open a binary file 1. Same result for http://localhost:3000/hvac-board I don't know if this is an hvac issue or a fastcgi issue (seems more likely) but any advice? Thomas. 2008/3/22 Sterling Clover [EMAIL PROTECTED]: 1) hvac 0.1b: transactional, declarative framework for lightweight web applications. 2) HStringTemplate 0.3 1) hvac 0.1b hvac (short for http view and controller) has been my project for the last little while, and is finally in a fairly usable state, so I'm opening up the repo (darcs get http://community.haskell.org/~sclv/hvac/) for folks to play with and to get some feedback. While not quite yet ready for hackage, the package as provided should be fully cabal installable. Documentation is available at http://community.haskell.org/~sclv/hvac/html_docs/hvac/ The aim of hvac is to provide an environment that makes the creation of lightweight fastcgi based web applications as simple as possible, with an emphasis on concise, declarative style code, correct concurrent transactional logic, and transparency in adding caching combinators. There are two included example programs, naturally neither of which is feature complete. They share a common login module of about 50 lines of code, excluding imports, templates, and database schema. The first program is a classic, greenspun-style message board with basic login functionality. It totals roughly 40 lines and tends to use just under 4mb of resident memory on my system. The second is a wiki based on Pandoc and the PandocWiki code. The code totals roughly 30 lines (rendering borrowed from PandocWiki aside) and uses about 5mb of memory. hvac processes all requests in the STM monad, with some bells attached to properly interleave STM with session, database and filesystem operations such that they all conceptually occur together in a single transaction per request. Currently it is only fully tested with sqlite, but it should operate, modulo a few tweaks, with any database accessible via HDBC. hvac is particularly designed to use the HStringTemplate library as an output layer, in a simple declarative fashion. As the StringTemplate grammar is explicitly sub-turing, this ensures a clean separation of program logic from presentation, while providing a nonetheless fairly powerful language to express typical display tasks. The included cache combinators, still experimental, should allow a simple and fine-grained control over the level of caching of various disk- bound operations. Phantom types are used to ensure that no functions that modify state may be cached. To give a flavor of hvac code, the following is the complete (twenty lines!) source of the wiki controller (due to sql statements, some lines are rather long): wikiController tmpl = h |/ login * login_plug tmpl | (h |/ wiki |\\ \pageName -h |// POST * withValidation [ (contents, return) ] (\ [contents] - do pageId - selectVal id from pages where name=? [toSql pageName] maybe (addErrors [(Login,must be logged in.)] continue) (\user - case fromSql pageId of Just (_::Int) - execStat insert into page_hist(pageId,contents,author) values(?,?,?) [pageId, toSql contents, toSql . userName $ user] Nothing - do execStat insert into pages(name,locked) values(?,?) [toSql pageName, toSql (0::Int)] pid - selectVal max(id) from pages [] execStat insert into page_hist(pageId,contents,author) values(?,?,?) [pid, toSql contents, toSql . userName $ user]) = getSes continue) | do pageId - selectVal id from pages where name=? [toSql pageName] (join $ renderf (tmpl showPage) (pageName, pageName) $ pageContents |= selectRow * from page_hist where pageId=? order
[Haskell-cafe] Re: [ANNOUNCE] git-darcs-import 0.1
Aaron Denney wrote: On 2008-06-03, Peter Hercek [EMAIL PROTECTED] wrote: Loup Vaillant wrote: 2008/6/3 Darrin Thompson [EMAIL PROTECTED]: --cut-- What's the appeal of this? I personally love git, but I thought all the cool kids at this school used darcs and that was that. Disclaimer: I'm no expert, this is what I've heard. Anyone please confirm or deny the following? Basically, git is waaay faster than Darcs on a number of use cases. Other reason can be git rebase. Of course there is a question how good practice it is ... but it is being used. Darcs patches are pretty much an implicit rebase. You cannot push patch B if it depends on patch A without also pushing A. And darcs currently does not alow you to reorder B before A (which is what git rebase actually does). Git rebase works quite well even in cloned repositories. See: http://bugs.darcs.net/issue891 Some discussin about it is also here: http://lists.osuosl.org/pipermail/darcs-users/2008-February/011564.html When the issue is fixed then darcs will be really patch based and will become the ultimate DSCM :-) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] HDBC-odbc 1.1.4.4 fixes Windows linking problems
Hi, HDBC-odbc version 1.1.4.4 has been uploaded to Hackage. It fixes the problems some here have encountered regarding ODBC crashes or other similar odd behavior on Windows. Thanks to Andrew Appleyard for tracking down the problem and sending me a patch. The detailed explanation, if you're interested, is a ccall vs. stdcall issue in FFI. Details here: http://git.complete.org/hdbc-odbc?a=commit;h=cca312d9891d227094494dcee518f436042e14b4 People that are not using HDBC-odbc on Windows will not find any difference or other changes in this version. -- John Goerzen Author, Foundations of Python Network Programming http://www.amazon.com/exec/obidos/tg/detail/-/1590593715 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc 6.8.2 issue
Something like that yes. You're running runhaskell Setup.lhs and that loads and runs code from the Cabal library. The Cabal library depends on the process library which depends on the unix library. So by replacing the same version of the unix package you're breaking everything else which depends on it, including Cabal and thus runhaskell Setup.lhs. So the solution is to not do that. Don't re-install the exact same version of any of the core libs that come with ghc. Adding new versions is fine, replacing existing versions is not fine because it breaks all the other packages that were already built against that package. But Duncan, let's suppose I build unix putting in a local directory with a different version number than the released version of unix. 1) How do I get the local package.conf built and populated? 2) How do I get a test case to link against this experimental local version of unix? Is there a --prefix or something like that I pass on runhaskell Setup.hs build? Regards, Vasili Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: [ANNOUNCE] git-darcs-import 0.1
This is drifting off-topic, but... On 2008-06-03, Peter Hercek [EMAIL PROTECTED] wrote: Aaron Denney wrote: On 2008-06-03, Peter Hercek [EMAIL PROTECTED] wrote: Loup Vaillant wrote: 2008/6/3 Darrin Thompson [EMAIL PROTECTED]: --cut-- What's the appeal of this? I personally love git, but I thought all the cool kids at this school used darcs and that was that. Disclaimer: I'm no expert, this is what I've heard. Anyone please confirm or deny the following? Basically, git is waaay faster than Darcs on a number of use cases. Other reason can be git rebase. Of course there is a question how good practice it is ... but it is being used. Darcs patches are pretty much an implicit rebase. You cannot push patch B if it depends on patch A without also pushing A. And darcs currently does not alow you to reorder B before A True. This is a *feature* not a bug. You shouldn't be able to do this automatically, because it can't be done right. You need to do this sort of thing manually. If you don't, the heuristics used will bite you at some point. When they do commute, there is no problem. Git rebase works quite well even in cloned repositories. Meh. It can, if you're really really lucky. See: http://bugs.darcs.net/issue891 Some discussin about it is also here: http://lists.osuosl.org/pipermail/darcs-users/2008-February/011564.html When the issue is fixed then darcs will be really patch based and will become the ultimate DSCM :-) Rebasing is doable in git as a one-repository operation because each repository has multiple branches. As darcs has one repo per branch, it fundamentally needs to be done in multiple repos. There are naturally two repos, upstream, and your-feature-development. your-feature-development has a patch A that you want to rebase. What you should do is pull upstream into new-tracking, then pull patch A from your-feature-development into new-tracking. If it applies with no problem, great: mv your-feature-development your-feature-development-old; new-tracking your-feature-development. Of course, in this case, you could have just pulled into your-feature-development. If there weren't any other patches to save in the old your-feature-development, you can delete it instead of moving it. When there is a conflict, then you need to handle it somehow. Neither git nor darcs can do it automatically. You can just record the merge conflict and your resolution. This keeps repos that pulled from you valid, but this won't give you the clean history that you presumably want. So you need to combine the merger and cleanup into a new patch with the same log message, etc. It's true that git does make *this* process very nice. There is one thing that git rebase does easily (and correctly) that darcs doesn't do nicely: rewriting history by merging commits prior to the head. I put prior in quotes, because darcs doesn't preserve history in the first place. I don't find that a compelling use, as opposed to maintaing topic branches. -- Aaron Denney -- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: appending an element to a list
Thank you, apfelmus. That was a wonderful explanation; the debit method in [1] finally makes sense. [1]: Chris Okasaki. Purely Function Data Structures. http://www.cs.cmu.edu/~rwh/theses/okasaki.pdf ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Laziness leaks
I was looking at the real time queues in [1] and I wanted to see what would happen if I tried to write one in Haskell. The easy part was translating the real time queue from [1], p43 into Haskell. The hard part is testing to see if the rotations really happen what they should. Basically, I decided to use Debug.Trace.trace to see when rotations were actually occurring. I pushed the numbers 1 to 10 into the queue, and then I popped the queue ten times. What I found is that none of the rotations would actually take place until the first time I actually tried to /display the value/ of a popped element. What I realized is that my test driver is lazy. I figured out that I could put a bunch of 'seq' functions in the test driver to get the rotations to happen. My demonstration code is in: http://hpaste.org/8080 This leads to two questions: 1. If I find a laziness leak, is 'seq' the appropriate way to plug it? 2. Is there any way to systematically search for or detect laziness leaks? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] hs-plugins compile error
What is the status of hs-plugins? I recently tried to install the version plugins-1.2 on hackage, using a Gnu/Linux box with Fedora 9 and ghc-6.8.2, but didn't get past the configure stage (see config.log below). I am getting exactly the same error on a Gentoo box. I've tracked it down to some awkward escape character sequence in the TOP variable defined in config.h. The following patch makes it work for me, but I've no idea if this is the right way to fix this problem: hunk ./configure 1385 -TOP=`echo Directory.getCurrentDirectory = putStrLn.init.tail.show | ghc --interactive -ignore-dot-ghci -v0 | tr -d '\r'` +TOP=`echo Directory.getCurrentDirectory = putStr. | ghc --interactive -ignore-dot-ghci -v0` hunk ./configure.ac 66 -TOP=`echo Directory.getCurrentDirectory = putStrLn.init.tail.show | ghc --interactive -ignore-dot-ghci -v0 | tr -d '\r'` +TOP=`echo Directory.getCurrentDirectory = putStr | ghc --interactive -ignore-dot-ghci -v0` Regards, T. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ghc 6.8.2 issue
On 2008 Jun 3, at 16:40, Galchin, Vasili wrote: 1) How do I get the local package.conf built and populated? 2) How do I get a test case to link against this experimental local version of unix? Is there a --prefix or something like that I pass on runhaskell Setup.hs build? both cases the answer is the same: --user --prefix=whatever -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED] system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED] electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] What is the maturity of Haskell Web Frameworks
On Tue, 2008-06-03 at 10:23 -0700, Don Stewart wrote: A new version of happs was written on a Monday a couple of months ago, using fastcgi and takusen. We're running it at galois, and you can find the code on code.haskell.org/hpaste. So not quite what you wanted, but another data point. That's very interesting. I hope we will also see a version with the same feature set implemented with the latest HAppS. It would give an interesting comparison of the web frameworks to see the same app implemented in both. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: [ANN] bloomfilter 1.0 - Fast immutable and mutable Bloom filters
* Jim Snow [EMAIL PROTECTED] [080531 15:23]: Without looking at the code to verify that this is how it has really been implemented, a bloom filter is like a series of hash tables, where the hash table entries are one bit. The bit is set if there is an item that hashes to that value in the bloom filter. So, assuming a single hash table where half the bits are set, there's a 50% false positive rate and no false negatives when you do a membership test. To reduce the false positives, we can add another hash table with a different hash function. Assuming it also is half full, we can check if an item is in both tables, and our false positive rate drops to 25%. In practice, one might use something like 32 hash tables. This yields a false positive rate of 1/(2^32). Their most obvious application is to store the dictionary for a spell checker in a space-efficient way, though I have a friend who wrote a paper on using them for router caches. There was a google tech talk on bloom filters awhile ago: http://www.youtube.com/watch?v=947gWqwkhu0 One other use: LOAF is a simple extension to email that lets you append your entire address book to outgoing mail message without compromising your privacy. Correspondents can use this information to prioritize their mail, and learn more about their social networks. The LOAF home page is at http://loaf.cantbedone.org. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Laziness leaks
Ronald Guida wrote: I was looking at the real time queues in [1] and I wanted to see what would happen if I tried to write one in Haskell. The easy part was translating the real time queue from [1], p43 into Haskell. The hard part is testing to see if the rotations really happen what they should. Basically, I decided to use Debug.Trace.trace to see when rotations were actually occurring. I pushed the numbers 1 to 10 into the queue, and then I popped the queue ten times. What I found is that none of the rotations would actually take place until the first time I actually tried to /display the value/ of a popped element. What I realized is that my test driver is lazy. I figured out that I could put a bunch of 'seq' functions in the test driver to get the rotations to happen. My demonstration code is in: http://hpaste.org/8080 This leads to two questions: 1. If I find a laziness leak, is 'seq' the appropriate way to plug it? 2. Is there any way to systematically search for or detect laziness leaks? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe I want to point out several non-causes of laziness. For a no-magic, no-surprise understanding, it is important to know both what causes laziness and what does not. A. The lazy list at rtqRear, which is originally a strict list. It is an invariant that every thunk you put there is [] or x:y. (As a result, it is unnecessary to make RTQueue a strict record, since you want two of the fields to be lazy, and the remaining field rtqRear is de facto strict.) B. rtqueue's thunked call to rotate, i.e., rtqueue f r []= let f' = rotate f r [] in RTQueue f' [] f' Originally f' is forced before the record is returned (SML convention). In Haskell the rotate call is thunked as f' and the record is returned. But there will not be an accumulation of such rotate thunks. For example if you snoc twice in succession and the first instance builds a rotate thunk: snoc p (snoc q (RTQueue f r [])) - snoc p (rtqueue f (q:r) []) - snoc p (RTQueue f' [] f') where f' = thunk - rtqueue f' p:[] f' where f' = thunk - f' is now forced by rtqueue's pattern matching on the 3rd param So if one snoc builds a rotate thunk, the next snoc kills it. And similarly any interleaving of queue operations. (head and tail add their extra pattern matching.) Thus it can be proved that Haskell lags behind the original by just one step in this regard. This is ok unless you're done with reducing asymptotic cost and start looking at constant factor cost. A true cause of laziness is in accumulating a chain of tail's and snocs without intermediate forcing, as observed. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] A simple beginner question
Example: data SampleType = A | B Int | C String | D -- etc. sampleTypes = [A, B 5, C test] :: [SampleType] How do I find for example element A in the sampleTypes list? Do I have to create e.g.: isA :: SampleType - Bool isA A = True isA _ = False for every constructor and use find? It feels like this is not the quicker method. Thanks, Adam ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Laziness leaks
Don Stewart wrote: 2. Is there any way to systematically search for or detect laziness leaks? Profiling, and looking at the Core. Being explicit about the evaluation strategy you want is a fine idea though. Albert Y. C. Lai wrote A true cause of laziness is in accumulating a chain of tail's and snocs without intermediate forcing, as observed. So I just thought of something. If laziness leads to laziness leaks, then is there such a thing as a strictness leak? I realized that the answer is yes. A lazy leak is a situation where I'm wasting resources to delay a sequence of calculations instead of just doing them now. But in a strict language, I might waste resources to compute things that I'll never need. I would call that a strictness leak. Now I could ask the dual question, How do I detect strictness leaks, and I would probably get the same answers: profiling, looking at object code, and being explicit about the evaluation strategy. Both types of leaks share a lot in common. In both cases, I'm wasting resources. If I have a real-time system, then either type of leak can cause me to a miss a deadline. With a strict evaluation strategy, I might miss a nearby deadline because I'm busy calculating things that I don't need until the distant future. With a lazy evaluation strategy, I might miss a distant deadline because I'm lazily putting off a calculation now. If I were a college student, then this would be a laziness leak: Professor X assigns a report, due in a month. Two days before the report is due, I'll head to the drugstore, load up on caffeine, and work for 48 hours straight to get it done. And this would be a strictness leak: Professor X assigns a report, due in a month. As soon as I leave the classroom, I'll head to the drugstore, load up on caffeine, and work for 48 hours straight to get it done. And this would be an effective solution: Professor X assigns a report, due in a month. I'll select 15 days, spaced out over the next month, and allocate four hours per day to work on the report. By default, a lazy language will procrastinate. By default, a strict language will anticrastinate. Either way, I can waste resources by blindly accepting the default time management plan. So the real question is How do I avoid laziness leaks or strictness leaks and apparently, the real answers are (1) learn how to recognize when the default plan will waste resources, and (2) learn how to express reasonable evaluation strategies in code. I would ask, how do I examine the evaluation order of my code, but the answer is already available: use a debugger. Haskell already has debugging tools that do exactly what I need. (http://www.haskell.org/haskellwiki/Debugging) In particular, HOOD looks extremely interesting. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] More on performance
I think it's hard to overstate how awesome the RULES pragma is. Thanks for the example. -- ryan On 6/3/08, Don Stewart [EMAIL PROTECTED] wrote: I wrote up the second part of the tour of understanding low level performance in GHC here, http://reddit.com/r/programming/info/6lx36/comments/ Follows on from the discussion last week about various performance related things. Enjoy. -- Don ___ 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] A simple beginner question
On Tue, Jun 3, 2008 at 5:11 PM, Adam Smyczek [EMAIL PROTECTED] wrote: Example: data SampleType = A | B Int | C String | D -- etc. sampleTypes = [A, B 5, C test] :: [SampleType] How do I find for example element A in the sampleTypes list? Do I have to create e.g.: isA :: SampleType - Bool isA A = True isA _ = False for every constructor and use find? isA is already defined for every constructor, so all you have to do is find isA It feels like this is not the quicker method. Thanks, Adam ___ 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] A simple beginner question
Adam Smyczek wrote: data SampleType = A | B Int | C String | D -- etc. sampleTypes = [A, B 5, C test] :: [SampleType] How do I find for example element A in the sampleTypes list? Here's one way to do it: filter (\x - case x of A - True; otherwise - False) sampleTypes == [A] filter (\x - case x of B _ - True; otherwise - False) sampleTypes == [B 5] filter (\x - case x of C _ - True; otherwise - False) sampleTypes == [C test] Your idea works just as well: isA :: SampleType - Bool isA A = True isA _ = False filter isA sampleTypes == [A] There is a third possibility: Have you learned about the maybe function or the either function yet? maybe :: b - (a - b) - Maybe a - b either :: (a - c) - (b - c) - Either a b - c I would call these mediating morphisms, where morphism is techno- babble for function. You could write your own version of one of these for SampleType. Assuming you have: data SampleType = A | B Int | C String You could write: sampletype :: t - (Int - t) - (String - t) - SampleType - t sampletype a bf cf s = case s of A - a B n - bf n C s - cf s isA = sampletype True (const False) (const False) isB = sampletype False (const True) (const False) isC = sampletype False (const False) (const True) filter isA sampleTypes == [A] This (the mediating morphism) is probably overkill for what you want to do, though. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: A simple beginner question
Adam Smyczek [EMAIL PROTECTED] wrote:
data SampleType = A | B Int | C String | D -- etc.
deriving (Eq)
sampleTypes = [A, B 5, C test] :: [SampleType]
If you derive from Eq, you can do
isA = (==) A
filter isA sampleTypes
or ad-hoc:
filter ((==) A) sampleTypes
things like
filter (\x - case x of
{ A - True
; B b | b 2 - True
; C c | c == foo - True
; _ - False}) sampleTypes
work, too. Admittedly, I'm lambda-spoilt.
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[Haskell-cafe] Re: A simple beginner question
Achim Schneider [EMAIL PROTECTED] wrote:
filter (\x - case x of
{ A - True
; B b | b 2 - True
; C c | c == foo - True
; _ - False}) sampleTypes
coming to think of it: Why can't I write
filter (\A - True
\B b | b 2 - True
\C c | c == foo - True
_ - False
) sampleTypes
? AFAICT it's syntactically unambiguous.
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Re: [Haskell-cafe] Laziness leaks
On Tue, 2008-06-03 at 20:12 -0400, Ronald Guida wrote: Don Stewart wrote: 2. Is there any way to systematically search for or detect laziness leaks? Profiling, and looking at the Core. Being explicit about the evaluation strategy you want is a fine idea though. Albert Y. C. Lai wrote A true cause of laziness is in accumulating a chain of tail's and snocs without intermediate forcing, as observed. So I just thought of something. If laziness leads to laziness leaks, then is there such a thing as a strictness leak? I realized that the answer is yes. I ask a similar question here albeit for a much narrower and more technical notion: http://lambda-the-ultimate.org/node/2273#comment-40156 and come to the same conclusion (at least for an even more narrow notion). ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A simple beginner question
There's always one more way to do things in Haskell! :) Here's yet another way to get at the payloads in a list. You don't have to know how this works to use it: data SampleType = A | B Int | C String unA :: SampleType - [()] unA A = return () unA _ = fail Not an A unB :: SampleType - [Int] unB (B b) = return b unB _ = fail Not a B unC :: SampleType - [String] unC (C c) = return c unC _ = fail Not a C -- I can check for more than one constructor... -- Note that a single type must be returned, -- so for C I return e.g. the length of the string unBorC :: SampleType - [Int] unBorC (B b) = return b unBorC (C c) = return (length c) unBorC _ = fail Not a B or C For lists, the = operator knows to ignore failure and collect anything else into a new list. The technobabble for this is that [] is a Monad. *Main let sampleTypes = [A, B 5, C test, A, A, B 7, C go] *Main sampleTypes = unA [(),(),()] *Main sampleTypes = unB [5,7] *Main sampleTypes = unC [test,go] *Main sampleTypes = unBorC [5,4,7,2] Adam Smyczek wrote: Example: data SampleType = A | B Int | C String | D -- etc. sampleTypes = [A, B 5, C test] :: [SampleType] How do I find for example element A in the sampleTypes list? Do I have to create e.g.: isA :: SampleType - Bool isA A = True isA _ = False for every constructor and use find? It feels like this is not the quicker method. Thanks, Adam ___ 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: A simple beginner question
Dan Weston [EMAIL PROTECTED] wrote: There's always one more way to do things in Haskell! :) Here's yet another way to get at the payloads in a list. You don't have to know how this works to use it: Bastard. He's going to try and find out how it works. To get back to the filters: module Main where import Control.Monad data SampleType = A | B Int | C String deriving Show noA :: SampleType - [SampleType] noA A = mzero noA e = return e noB :: SampleType - [SampleType] noB (B _) = mzero noB e = return e noAB :: SampleType - [SampleType] noAB m = [m] = noA = noB sampleTypes = [A, B 5, C test, A, A, B 7, C go] *Main sampleTypes = noA [B 5,C test,B 7,C go] *Main sampleTypes = noB [A,C test,A,A,C go] *Main sampleTypes = noAB [C test,C go] -- (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] HDBC-odbc 1.1.4.4 fixes Windows linking problems
On Tue, 03 Jun 2008, John Goerzen wrote: Hi, HDBC-odbc version 1.1.4.4 has been uploaded to Hackage. It fixes the problems some here have encountered regarding ODBC crashes or other similar odd behavior on Windows. I'm getting a 'Parse error in pattern' error. C:\Documents and Settings\Administratorghci GHCi, version 6.8.2: http://www.haskell.org/ghc/ :? for help Loading package base ... linking ... done. Prelude :m Database.HDBC.ODBC Database.HDBC Prelude Database.HDBC Database.HDBC.ODBC conn - connectODBC dictation Loading package array-0.1.0.0 ... linking ... done. Loading package containers-0.1.0.1 ... linking ... done. Loading package bytestring-0.9.0.1 ... linking ... done. Loading package old-locale-1.0.0.0 ... linking ... done. Loading package old-time-1.0.0.0 ... linking ... done. Loading package mtl-1.1.0.0 ... linking ... done. Loading package HDBC-1.1.4 ... linking ... done. Loading package HDBC-odbc-1.1.4.4 ... linking ... done. *** Exception: (unknown) Prelude Database.HDBC Database.HDBC.ODBC handleSqlError $ conn - connectODBC dictation interactive:1:0: Parse error in pattern -- Dr Bean If there is one thing we learn from the study of language learning, it is that language learners learn more than we learn. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HDBC-odbc 1.1.4.4 fixes Windows linking problems
On 4/06/2008 1:05 PM, Greg Matheson wrote: I'm getting a 'Parse error in pattern' error. C:\Documents and Settings\Administratorghci GHCi, version 6.8.2: http://www.haskell.org/ghc/ :? for help Loading package base ... linking ... done. Prelude :m Database.HDBC.ODBC Database.HDBC [...] Prelude Database.HDBC Database.HDBC.ODBC handleSqlError $ conn - connectODBC dictation interactive:1:0: Parse error in pattern Try: conn - handleSqlError $ connectODBC dictation You can only use '-' in a do expression, or at the GHCi prompt. -- Andrew ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] A simple beginner question
adam.smyczek:
Example:
data SampleType = A | B Int | C String | D -- etc.
sampleTypes = [A, B 5, C test] :: [SampleType]
How do I find for example element A in the sampleTypes list?
Do I have to create e.g.:
isA :: SampleType - Bool
isA A = True
isA _ = False
for every constructor and use find?
It feels like this is not the quicker method.
This is where the implicit filtering in a list comprehension comes in
really handy,
data T = A | B Int | C String | D
deriving Show
xs = [A, B 5, C test, D]
main = do print [ A | A - xs ] -- filter A's
print [ x | x@(C _) - xs ] -- filter C's
{-
*Main main
[A]
[C test]
-}
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Re: [Haskell-cafe] A simple beginner question
On Tue, Jun 3, 2008 at 6:48 PM, Ronald Guida [EMAIL PROTECTED] wrote:
filter (\x - case x of A - True; otherwise - False) sampleTypes
== [A]
filter (\x - case x of B _ - True; otherwise - False) sampleTypes
== [B 5]
There's a neat little mini-trick for these types of pattern matches:
filter (\x - case x of B {} - True; otherwise - False) sampleTypes
Does the same thing, but works no matter how many arguments the
constructor B takes.
Luke
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Re: [Haskell-cafe] [ANNOUNCE] git-darcs-import 0.1
Darrin Thompson wrote: On Sun, Jun 1, 2008 at 2:44 PM, Bertram Felgenhauer [EMAIL PROTECTED] wrote: I'm pleased to announce yet another tool for importing darcs repositories to git. [...] What's the appeal of this? I personally love git, but I thought all the cool kids at this school used darcs and that was that. For myself, git-darcs-import itself is an opportunity to learn more about both darcs and git. It wasn't meant to be argument in the git vs. darcs discussion, although it was inevitable that it would be seen as such. I really like darcs' concepts, but in my opinion, darcs doesn't get enough power out of the theory of patches to really shine so far. This is a hard problem, and I can't offer solutions. Ideally, you'd have semantic patches which just commute with virtually all other patches because they know what they are about. The only thing that darcs offers in that direction - besides handling conflicts, mergers and undos gracefully, which is quite useful in itself - is a keyword substitution patch type. In the meantime, I prefer git to darcs, mainly because I'm sort of attached to seeing the development history, i.e. I prefer to think of patches as (partially) ordered instead of being a cloud of patches that darcs uses as a model. Bertram ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
