[Haskell-cafe] Bit streams
OK, so today I tried to write my first program using the Binary library. And I've hit a snag: It appears the library will only handle data that is byte-aligned. So if I try to write three Bool values, it uses three bytes, not three bits. Before I sit down and spend 3 months designing my own library from scratch, does anybody know of an existing library that allows you to do what Binary does, but with single-bit precision? [I presume Binary is byte-aligned for efficiency...] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell's type system
ronwalf: I'm trying to wrap my head around the theoretical aspects of haskell's type system. Is there a discussion of the topic separate from the language itself? Since I come from a rather logic-y background, I have this (far-fetched) hope that there is a translation from haskell's type syntax to first order logic (or an extension there-of). Is this done? Doable? A quick link to get you started on the topic, I'm sure others will add more material. Haskell's type system is based on System F, the polymorphic lambda calculus. By the Curry-Howard isomorphism, this corresponds to second-order logic. The GHC compiler itself implements Haskell and extensions by encoding them in System Fc internally, which extends System F with support for non-syntactic type equality.. JHC, I believe, encodes Haskell into a pure type system internally, some sort of higher order dependently-typed polymorphic lambda calculus. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On Tue, 2008-06-17 at 18:45 +0200, Karoly Negyesi wrote: Hi, The PHP community is discussing the adding of closures and lambdas to the language, see the proposal at http://wiki.php.net/rfc/closures If someone with knowledge of both languages could take a quick look it would be great. I program in Perl for a living, so hopefully you'll understand when I say (a) I would *never* want to use an implementation of closures like that. (b) Closures as proposed are *far* better than not having closures. jcc ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: Mueval 0.3
Hiya everyone. So I've uploaded Mueval 0.3 (release early, release often) http://hackage.haskell.org/cgi-bin/hackage-scripts/package/mueval-0.3. What's new? Well, I changed the printing output to be cleaner, and I made printing the inferred type optional (through a --print-type flag). In addition, I've made sure it can run (for me, at least) under -N4, and the watchdog threads should be sturdier. (Plus extra tests.) However, I've been hearing that a number of people (3 at last count) have been having a lot of trouble with the ResourceLimits stuff. So, I have a few requests of people who install mueval: * First, does it work out of the box, with no tweaking of the resource limits? * Second, if it doesn't work out of the box, which resource limits did you need to disable or increase? * Thirdly, if you changed the resource limits, could you run ./build.sh and tell me whether all the tests pass? Finally, I've been pondering removing the rlimits entirely since they are both very unportable, empirically derived, and apparently don't even work consistently on Linux. Any thoughts? -- gwern PABX MEMEX 868 1* TSCI @ shelter Yukon el ASLET signature.asc Description: Digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] blas bindings, why are they so much slower the C?
here is the C:
#include cblas.h
#include stdlib.h
int main() {
int size = 1024;
int ii = 0;
double* v1 = malloc(sizeof(double) * (size));
double* v2 = malloc(sizeof(double) * (size));
for(ii = 0; ii size*size; ++ii) {
double _dd = cblas_ddot(0, v1, size, v2, size);
}
free(v1);
free(v2);
}
this is the haskell:
module Main where
import Data.Vector.Dense.IO
main = do
let size = 1024
v1::IOVector Int Double - newListVector size [0..]
v2::IOVector Int Double - newListVector size [0..]
mapM_ (\ ii - do v1 `getDot` v2) [0..size*size]
time ./testdot
real0m0.017s
user0m0.010s
sys 0m0.010s
time ./htestdot
real0m4.692s
user0m4.670s
sys 0m0.030s
so like 250x difference
htestdot.prof is no help
Tue Jun 17 20:46 2008 Time and Allocation Profiling Report (Final)
htestdot +RTS -p -RTS
total time =3.92 secs (196 ticks @ 20 ms)
total alloc = 419,653,032 bytes (excludes profiling overheads)
COST CENTREMODULE %time %alloc
main Main 88.3 83.0
CAFMain 11.7 17.0
individualinherited
COST CENTRE MODULE
no.entries %time %alloc %time %alloc
MAIN MAIN
1 0 0.00.0 100.0 100.0
CAF Main
216 7 11.7 17.0 100.0 100.0
main Main
222 1 88.3 83.088.3 83.0
CAF GHC.Float
187 1 0.00.0 0.00.0
CAF GHC.Handle
168 3 0.00.0 0.00.0
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
(a) I would *never* want to use an implementation of closures like that. (b) Closures as proposed are *far* better than not having closures. Could you elaborate on a) ? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell's type system
On Tue, Jun 17, 2008 at 2:40 PM, Ron Alford [EMAIL PROTECTED] wrote: I'm trying to wrap my head around the theoretical aspects of haskell's type system. Is there a discussion of the topic separate from the language itself? Since I come from a rather logic-y background, I have this (far-fetched) hope that there is a translation from haskell's type syntax to first order logic (or an extension there-of). Is this done? Doable? Sort of, via the Curry-Howard Correspondence. Haskell's type system corresponds to a constructive logic (no law of excluded middle). Arbitrary quantifiers are also introduced via the RankNTypes (I think that's what it's called) extension. Haskell's type system is a straightforward polymorphic type system for the lambda calculus, so researching the Curry-Howard Correspondence will probably get you what you want. Luke ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
I believe C# already has lambdas, and Java is supposed to be getting them. PHP is playing catchup, is all. (Oh, and Eiffel has 'agents', and I think I saw something about C++ Next Degeneration, and ...) Heck, the idea has only been around in computing since the 1950s... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Something like scan1
Is there a generalisation of scan1, such that eg. foo (+) [0,1] (1,2) = [0,1,1,2,3,5,8,13,...] ? I came up with it while thinking about the equivalence of laziness and strictness resp. pull and push. To be more specific, I was thinking about ArrowLoop and how that beast generalises over time-varying values. It's some kind of helixoid fixed point (which might not help at all if your visualisation is incompatible with mine). -- (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] Lambda and closures in PHP -- could someone please comment?
On Wed, 2008-06-18 at 06:36 +0200, Karoly Negyesi wrote:
(a) I would *never* want to use an implementation of closures like that.
(b) Closures as proposed are *far* better than not having closures.
Could you elaborate on a) ?
I dislike the habit of implicit declaration --- strongly --- and the
consequent need for the lexical keyword (although at this point PHP's
stuck with it). I can see myself forgetting to use lexical far more
often than accidentally leaving off a `my' in Perl I should have used (I
hardly ever shadow variable names anyway, so if I forget `my' is usually
a use strict 'vars' error).
I dislike curly braces. Syntax that extends as far to the right as
possible tends to end up with fewer delimiters and a cleaner appearance.
It's basically a way to replace a bunch of closing braces with a
single ) or (in Haskell, implicit) ;
lintPat p0 $ \ ty0 - lintPat p1 $ \ ty1 - lint e
vs
lintPat($p0, sub { my ($ty0) = @_; lintPat($p1, sub { my ($ty1) = @_;
lint($e) })})
Four closing delimiters seems excessive.
Nit: `function' is verbose. ML uses fun or fn (I forget which and am
too lazy to google). Perl's regular keyword is sub, so they use that.
There are worse fates than duck typing (C++ comes to mind :), and given
a language with neither lexical closures/anonymous functions nor HM
typing, I'd complain about the lack of lambdas first. But, still, no HM
means no type classes. That ultimately becomes limiting. (I still
haven't seen a decent implementation of monads in a dynamically typed
language). But PHP is probably pretty much stuck with it.
Not to criticize, mind you --- the proposal looks excellent for what it
does. But I like what Haskell does worlds better.
jcc
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Compiling large code with old machine
Samuel Silva silva.samuel at gmail.com writes: Hello I'm using GHC to compile around 700K of Haskell Code generated by HaXml. How I compile this code. My machine is Windows-XP(512MB RAM, 1.5GHz) running GHC-6.8.2. Samuel, You may not want to take this approach. I'm assuming you are generating haskell types from a (large) DTD. I went this way (admittedly quite a few years ago) for svg. In the end it was much easier to hand generate a few combinators to produced the svg. I don't know what your application is but it may worth thinking about an alternative to 700k loc. Dominic. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Bit Streams
OK, so today I tried to write my first program using the Binary library. And I've hit a snag: It appears the library will only handle data that is byte-aligned. So if I try to write three Bool values, it uses three bytes, not three bits. Before I sit down and spend 3 months designing my own library from scratch, does anybody know of an existing library that allows you to do what Binary does, but with single-bit precision? [I presume Binary is byte-aligned for efficiency...] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/binary-strict ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
Not to criticize, mind you --- the proposal looks excellent for what it does. But I like what Haskell does worlds better. Obviously you like Haskell better given this mailing list :) I am not here to compare PHP and Haskell, I was just asking advice from people who know closures and lambdas very well and it seems that I got it in the words of the proposal looks excellent for what it does. Thanks a lot. Karoly Negyesi ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Jules ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell's type system
On Tue, Jun 17, 2008 at 04:40:51PM -0400, Ron Alford wrote: I'm trying to wrap my head around the theoretical aspects of haskell's type system. Is there a discussion of the topic separate from the language itself? Since I come from a rather logic-y background, I have this (far-fetched) hope that there is a translation from haskell's type syntax to first order logic (or an extension there-of). Is this done? Doable? I'll give you some terms to Google for. The ideal type system for Haskell (ignoring type classes) is System F. Haskell'98 doesn't quite get there, but recent extensions such as boxy types and FPH do. System F corresponds to second order propositional logic: types correspond to propositions in this logic, and Haskell programs as the corresponding proofs (by the Curry-Howard isomorphism). The type system of Haskell'98 is a bit weird from a logical perspective, and sort of corresponds to the rank 1.5 predicative fragment of second order propositional logic (I say rank 1.5 because although no abstraction over rank 1 types is allowed normally, limited abstractions over rank 1 types is allowed through let-polymorphism -- so this is *almost* first order logic but not quite: slightly more powerful). Regarding type classes, I'm not 100% what the logical equivalent is, although one can regard a type such as forall a. Eq a = a - a as requiring a proof (evidence) that equality on a is decidable. Where this sits formally as a logic I'm not sure though. Edsko ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Paul: Uncivilised you say. Well, I would have thought the civilised thing would be to share your concerns discretely with the list moderator. Instead you've chosen to make a public show of it. The Chinese have a saying, and I paraphrase - when you point the finger of accusation at someone/something you have three pointing back at yourself. Paul ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANNOUNCE: cabal-install 0.5
cabal-install 0.5 = cabal-install version 0.5 is out: http://haskell.org/cabal/download.html or get it from hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/cabal-install If you are already using a cabal-install pre-release then you can just: $ cabal update $ cabal install cabal-install New features in cabal-install = Command line improvements - The most immediately noticeable thing is that the command line interface now has all the commands that runhaskell Setup.hs has. Of course it still has the features to download and install packages from hackage. It also gained an upload command. So it now provides a command line interface to the whole Cabal/Hackage system. There’s no need to use runhaskell Setup.hs ever again. There is also bash command line completion support included which I find is a great time saver. Installing and upgrading The next big thing is that it includes a new package dependency resolution system that finds correct and sensible solutions more of the time and has better default behaviour. The new behaviour should be similar to other package managers that people are used to. For example, suppose you’ve got xmonad-0.5 installed and version 0.7 is the latest on hackage, then $ cabal install xmonad will install xmonad-0.7. The older version, xmonad-0.5, will remain installed. The behaviour of install is to upgrade as little as possible to satisfy your request, but sometimes you want to upgrade all the dependencies too. Supposing now that we have xmonad-0.7 installed, but we’re still using X11-1.4.1 and the latest version on hackage is X11-1.4.2, then $ cabal upgrade xmonad will install X11-1.4.2 and *re-install* xmonad-0.7, this time built against the newer X11-1.4.2. So in general, the install command will install the latest version of things but will try and use any existing installed versions of dependencies while the upgrade command will also try to use the latest versions of all dependencies. As a special case, cabal upgrade on its own will try to upgrade all the packages that you have installed. For both command there is a --dry-run flag so you can see what would be installed without actually doing it. Hugs Yes, it even works with hugs. That is, cabal-install built by ghc can manage the installation of packages for hugs. In principle cabal-install should be able to be run by hugs but currently the zlib binding is using a function that hugs does not support. Note that for hugs, Cabal does not know what packages are already installed because there is no equivalent of the package database that ghc has. So that means cabal-install cannot do very sensible installation planning. It should work ok so long as all the dependencies are already installed. Windows --- Yes, it even works on Windows. The one caveat is that cabal-install cannot currently upgrade itself because Windows makes it hard for a process to overwrite its own executable file. It needs more complex trickery with the Win32 API. In the meantime the workaround is to rename the cabal.exe file first eg to cabal-foo.exe, then run cabal-foo install cabal-install. Build reporting --- One feature that made it into this release is build reporting. cabal-install keeps logs of all packages that you install (at least packages from hackage, not local ones). It records a bit of information about each package, in particular whether the outcome was successful or not. You can see these build reports in ~/.cabal/packages/$server/build-reports.log. For example, there is one from my machine for xmonad: package: xmonad-0.7 os: linux arch: x86_64 compiler: ghc-6.8.2 client: cabal-install-0.5.1 flags: -testing small_base dependencies: X11-1.4.2 base-3.0.1.0 containers-0.1.0.1 directory-1.0.0.0 mtl-1.1.0.0 process-1.0.0.0 unix-2.3.0.0 install-outcome: InstallOk docs-outcome: NotTried tests-outcome: NotTried The plan in the longer term is to let people upload these build reports to hackage so we can get a wider range of testing data about the packages on hackage. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bit streams
On Jun 17, 2008, at 10:05 PM, Andrew Coppin wrote: OK, so today I tried to write my first program using the Binary library. And I've hit a snag: It appears the library will only handle data that is byte-aligned. So if I try to write three Bool values, it uses three bytes, not three bits. Before I sit down and spend 3 months designing my own library from scratch, does anybody know of an existing library that allows you to do what Binary does, but with single-bit precision? [I presume Binary is byte-aligned for efficiency...] Andrew, Maybe you could look at the generic encode/decode in this paper: people.cs.uu.nl/johanj/publications/ComparingGP.pdf When you look at some more literature about generic programming the (bit-aligned) encode and decode are quite common examples. It shouldn't be that hard to de-generify them, if you even want that. -- Sebastiaan. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Problem building GHC 6.8.3
Sorry, probably stupid questions for knowledgeable folks, but after having built for a couple of hours, make died with if ifBuildable/ifBuildable base; then \ cd base setup/Setup haddock --html-location='../$pkg' \ --hyperlink-source; \ fi Preprocessing library base-3.0.2.0... Running hscolour for base-3.0.2.0... Preprocessing library base-3.0.2.0... Running Haddock for base-3.0.2.0... Warning: The documentation for package rts-1.0 is not installed. No links to it will be generated. Setup: Haddock's internal GHC version must match the configured GHC version make[1]: *** [doc.library.base] Fehler 1 make[1]: Leaving directory `/home/dafis/HasCom/ghc-6.8.3/libraries' make: *** [stage1] Fehler 2 So, what is Haddock's internal GHC version? Is it the version, haddock was built with? And what is the configured GHC version, is it the one I'm trying to build or the one I'm building with? If the former, I seem to have landed in a circulus vitiosus, if the latter, that is the GHC, haddock was built with, too. For the record: [EMAIL PROTECTED]:~/HasCom/ghc-6.8.3 haddock --version Haddock version 2.1.0, (c) Simon Marlow 2006 Ported to use the GHC API by David Waern 2006-2008 How should I proceed now? Thanks, Daniel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bit streams
Andrew Coppin [EMAIL PROTECTED] wrote: It appears the library will only handle data that is byte-aligned. So if I try to write three Bool values, it uses three bytes, not three bits. The original Binary library, circa 1998, was based on bit-streams rather than bytes. You might be able to dig up a copy and bring it back to life. http://citeseer.ist.psu.edu/wallace98bits.html ftp://ftp.cs.york.ac.uk/pub/malcolm/ismm98.html Regards, Malcolm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell's type system
On Jun 17, 2008, at 11:08 PM, Don Stewart wrote: Haskell's type system is based on System F, the polymorphic lambda calculus. By the Curry-Howard isomorphism, this corresponds to second-order logic. just nitpicking a little this should read second-order propositional logic, right? daniel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Paul: Uncivilised you say. Well, I would have thought the civilised thing would be to share your concerns discretely with the list moderator. Hmm, I wonder who exactly this list moderator is supposed to be. We are usually adult enough around here to not need someone to look after us. I think Jules was well entitled to raise his objections about the tone of your email in public. Instead you've chosen to make a public show of it. The Chinese have a saying, and I paraphrase - when you point the finger of accusation at someone/something you have three pointing back at yourself. Well, at least not this finger... -- Dr. Janis Voigtlaender http://wwwtcs.inf.tu-dresden.de/~voigt/ mailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
Hallo, Jules Bean wrote: PR Stanley wrote: With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Thanks Jules, I was starting to worry about Haskell-café. -alex http://www.ventonegro.org/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bit streams
Hello Andrew, Wednesday, June 18, 2008, 12:05:31 AM, you wrote: what Binary does, but with single-bit precision? [I presume Binary is http://haskell.org/haskellwiki/Library/AltBinary it's not maintained, so consider it as last hope :) -- 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: Compiling large code with old machine
Hello Dominic, Wednesday, June 18, 2008, 11:17:07 AM, you wrote: I'm using GHC to compile around 700K of Haskell Code generated by HaXml. may worth thinking about an alternative to 700k loc. i think he means bytes, not lines :) -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] Bit streams
Hello Malcolm, Wednesday, June 18, 2008, 4:36:40 PM, you wrote: The original Binary library, circa 1998, was based on bit-streams rather than bytes. You might be able to dig up a copy and bring it back to life. http://citeseer.ist.psu.edu/wallace98bits.html ftp://ftp.cs.york.ac.uk/pub/malcolm/ismm98.html well, i've seen ghc-compatible Binary library flying around which supported bit fields. it was in pre-hackage days, but it should be pretty easy to find this module -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Paul: Uncivilised you say. Well, I would have thought the civilised thing would be to share your concerns discretely with the list moderator. Hmm, I wonder who exactly this list moderator is supposed to be. We are usually adult enough around here to not need someone to look after us. I think Jules was well entitled to raise his objections about the tone of your email in public. Paul: As you say, we are adult enougharound here to not need someone to look after us. So I don't need you or any other interfearing busybody to tell me what I can and can't say on Haskell Cafe. I expressed an opinion in a tongue-in-cheek way and at the end of my message expressed in clear terms that those were merely my views. Now, if you, Jules, Alex or some other wannabe Hitler have a problem with my freedom of expression then your best solution is to saddle up and get the hell out yourselves. This is the wrong place for setting up your tinpot dictatorship, Doctor! I am grateful for the help I've been getting from the list and my understanding of FP has vastly improved since my membership of this list but I refuse to tolerate bullies who use the list as a way of lifting themselves out of their own shitty lives. Now I am angry! Instead you've chosen to make a public show of it. The Chinese have a saying, and I paraphrase - when you point the finger of accusation at someone/something you have three pointing back at yourself. Well, at least not this finger... Paul: you're not making sense. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
With respect, I will not engage in further communication on that level. PR Stanley wrote: PR Stanley wrote: With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Paul: Uncivilised you say. Well, I would have thought the civilised thing would be to share your concerns discretely with the list moderator. Hmm, I wonder who exactly this list moderator is supposed to be. We are usually adult enough around here to not need someone to look after us. I think Jules was well entitled to raise his objections about the tone of your email in public. Paul: As you say, we are adult enougharound here to not need someone to look after us. So I don't need you or any other interfearing busybody to tell me what I can and can't say on Haskell Cafe. I expressed an opinion in a tongue-in-cheek way and at the end of my message expressed in clear terms that those were merely my views. Now, if you, Jules, Alex or some other wannabe Hitler have a problem with my freedom of expression then your best solution is to saddle up and get the hell out yourselves. This is the wrong place for setting up your tinpot dictatorship, Doctor! I am grateful for the help I've been getting from the list and my understanding of FP has vastly improved since my membership of this list but I refuse to tolerate bullies who use the list as a way of lifting themselves out of their own shitty lives. Now I am angry! Instead you've chosen to make a public show of it. The Chinese have a saying, and I paraphrase - when you point the finger of accusation at someone/something you have three pointing back at yourself. Well, at least not this finger... Paul: you're not making sense. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Dr. Janis Voigtlaender http://wwwtcs.inf.tu-dresden.de/~voigt/ mailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On Wed, Jun 18, 2008 at 1:42 PM, PR Stanley [EMAIL PROTECTED] wrote: Now, if you, Jules, Alex or some other wannabe Hitler have a problem with my freedom of expression then your best solution is to saddle up and get the hell out yourselves. This is the wrong place for setting up your tinpot dictatorship, Doctor! Just more evidence... http://en.wikipedia.org/wiki/Godwin's_law Luke ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
Now, if you, Jules, Alex or some other wannabe Hitler have a problem with my freedom of expression then your best solution is to saddle up and get the hell out yourselves. This is the wrong place for setting up your tinpot dictatorship, Doctor! Just more evidence... http://en.wikipedia.org/wiki/Godwin's_law Paul: I think you're missing a big painfully obvious point here, Mr smarty pants. No, actually, I think I'll leave it at that. I just can't be bothered. However, I'll say this - anyone sticking his bloody big hooter into my business in the future will get a similar reaction! Paul Luke ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: Blimey! Talk about rearranging the deckchairs :-) Today's xkcd seems apropos: http://xkcd.com/438/ It seems to me that if a PHP developer sees the Haskell community as a resource for advice on programming language implementation, we should take this as a compliment to the Haskell community. Repaying that compliment with your language sucks rocks strikes me as unwise. I'm familiar with a lot of arguments for why PHP is a poorly-designed language, and have found them sufficiently persuasive that I haven't bothered to learn PHP. But I don't see any point to repeating those arguments on this list. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Something like scan1
On Wed, 18 Jun 2008, Achim Schneider wrote: Is there a generalisation of scan1, such that eg. foo (+) [0,1] (1,2) = [0,1,1,2,3,5,8,13,...] ? What is the (1,2) for? I could think of foo f = List.unfoldr (\ xt@(x:xs) - Just (x, xs ++ [f xt])) foo sum [0,1] = [0,1,1,2,3,5,8,13,21,34,... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell data types and Storable class
On Wed, 18 Jun 2008, Galchin, Vasili wrote:
Hello,
I am reading the FFI spec. Something is unclear to me. Let's assume we
have
data A = {b:B, ...}
and
data B ={ .}
both of which belong to class Storable. In the A instance of Storable I want
to do a poke and peek of b into and out-of, respectively, B. How do I
write the poke and peek function of b in the instance Storable A?
You will write a Storable instance for B and then just use the class
methods 'poke' and 'peek' in the instance for A.
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
It seems to me that if a PHP developer sees the Haskell community as a resource for advice on programming language implementation, we should take this as a compliment to the Haskell community. Repaying that compliment with your language sucks rocks strikes me as unwise. I'm familiar with a lot of arguments for why PHP is a poorly-designed language, and have found them sufficiently persuasive that I haven't bothered to learn PHP. But I don't see any point to repeating those arguments on this list. Paul: So, you've never bothered to learn PHP. Well, I happen to know the language very well and therefore feel I am in a good position to express my views about it. Unlike you, I don't base my judgment on rumours and hearsay. It is true that PHP fails to capture the spirit of the classical concept of a function. Type checking in PHP is equally poor. These are not just my opinions. Are we not to say anything critical about a programming language even if it happens to be substantively relevant lestwe should offend someone? God, if you want to stick up for your mates here at least come up with a convincing cover. Paul ___ 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] Lambda and closures in PHP -- could someone please comment?
On Tue, Jun 17, 2008 at 4:45 PM, Karoly Negyesi [EMAIL PROTECTED] wrote:
Hi,
The PHP community is discussing the adding of closures and lambdas to
the language, see the proposal at http://wiki.php.net/rfc/closures
If someone with knowledge of both languages could take a quick look it
would be great.
Thanks a lot
Karoly Negyesi
Ps. I am not a member of the PHP internals team, I am just a PHP
developer but I am very very interested in getting these in my
favourite language.
Whew. Well I suspect you weren't expecting that kind of reaction. Or
maybe you were... I used to be a Perl developer, and it didn't take
long before I got a level 12 resistence to flame...
Anyway, the proposal looks mostly okay. I don't know that much PHP,
but I find the lexical keyword to be a nuisance. What are the
semantics if the lexical keyword is omitted?(i.e. does the
variable become function-local, global, what?) If it is consistent
with the rest of the language, it'll do.
There is a much more important point with closures: their
implementation cannot be half-assed! I'm not claiming that the patch
is--I have not reviewed it--but there is nothing worse than coming up
with a design that relies on a language feature you only later find
out has been nerfed in some way. Story of my life in C#. And nerfed
closures are especially bad, because it's so hard to predict the code
path.
What I mean by this is the following must all be supported:
* A closure must only keep alive the varables it references, not the
whole pad on which they are allocated (Python messed up here)
* A closure must be able to call itself recursively (via a
higher-order function typically) (Squeak messed up here IIRC)
* Multiple references to the same body of code with different bindings
must be able to exist at the same time (duh, that's kinda what makes
it a closure)
* Closures must be nestable.
Looking over the Zend internal perspective section, it looks like
that implementation will mostly work. There are a couple of red
flags, though:
* I would recommend only saving $this in the op_array structure if the
closure actually references $this -- if that is possible to deduce at
the time. Otherwise you might run into unexpected poor memory
performances in certain cases. (This kind of thing can make an
*asymptotic* difference in memory performance; i.e. bringing the
memory usage of an algorithm from O(1) to O(n), for example)
* I'm worried that nested closures do not work properly with this
implementation sketch. Here's a test case:
$f = function ($y) {
return function ($z) {
return $y + $z;
}
};
$f(1)(2) # should give 3
And congratulations, PHP, for adopting a most essential and powerful feature!
Luke
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Something like scan1
Henning Thielemann [EMAIL PROTECTED] wrote: On Wed, 18 Jun 2008, Achim Schneider wrote: Is there a generalisation of scan1, such that eg. foo (+) [0,1] (1,2) = [0,1,1,2,3,5,8,13,...] ? What is the (1,2) for? Specifying the relative indexes an element depends on. Ideally, it should be generalised for n-ary functions. I could think of foo f = List.unfoldr (\ xt@(x:xs) - Just (x, xs ++ [f xt])) foo sum [0,1] = [0,1,1,2,3,5,8,13,21,34,... I should elaborate: foo (+) [0,1,4] (1,2) = _|_, as 4 isn't 0+1 foo (+) [0,1] (2,3) = [0,1,_|_,1,_|_,_|_] foo (+) [0,1,1,2,3,5] (1,2) = [0,1,1,2,3,5,8,13,...] foo (+) [1] (1,1) = [1,2,4,8,16,32,...] If you allow for inverse functions, you could even say foo (+-) [0,...,3,..] (1,2) = [0,0,0,...,0,0,1,1,2,3,5,...] It seems like I'm searching for some primitive that lets me combine lists and currying. Think of passing a matrix, with each column (or row, if you prefer) separately uniquely typed, into a function. -- (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] Lambda and closures in PHP -- could someone please comment?
On 18 Jun 2008, at 18:19, Seth Gordon wrote: It seems to me that if a PHP developer sees the Haskell community as a resource for advice on programming language implementation, we should take this as a compliment to the Haskell community. Repaying that compliment with your language sucks rocks strikes me as unwise. Not necessarily. It can be that they'd implement closures in PHP, make a dog's dinner of it (as they always do), and then we would be blamed for giving them wrong advises. Anyway, it seems that PR Stanley was forced to use PHP, no wonder he's a little mad at it. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
It seems to me that if a PHP developer sees the Haskell community as a resource for advice on programming language implementation, we should take this as a compliment to the Haskell community. Repaying that compliment with your language sucks rocks strikes me as unwise. Not necessarily. It can be that they'd implement closures in PHP, make a dog's dinner of it (as they always do), and then we would be blamed for giving them bad advice. Anyway, it seems that PR Stanley was forced to use PHP, no wonder he's a little mad at it. Paul: How did you know? :-) You know, the funny thing is that all these so-called civilised people can find time and energy to have a go at me but can't be bothered to help the chap with the original query. ___ 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] Re: Something like scan1
On Wed, 18 Jun 2008, Achim Schneider wrote: Henning Thielemann [EMAIL PROTECTED] wrote: On Wed, 18 Jun 2008, Achim Schneider wrote: Is there a generalisation of scan1, such that eg. foo (+) [0,1] (1,2) = [0,1,1,2,3,5,8,13,...] ? What is the (1,2) for? Specifying the relative indexes an element depends on. Ideally, it should be generalised for n-ary functions. foo f prefix (n,m) = let k = length prefix xs = prefix ++ zipWith f (xss!!(k-n)) (xss!!(k-m)) xss = List.tails xs in xs ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On Wed, 2008-06-18 at 16:00 +0100, PR Stanley wrote: It seems to me that if a PHP developer sees the Haskell community as a resource for advice on programming language implementation, we should take this as a compliment to the Haskell community. Repaying that compliment with your language sucks rocks strikes me as unwise. Not necessarily. It can be that they'd implement closures in PHP, make a dog's dinner of it (as they always do), and then we would be blamed for giving them bad advice. Anyway, it seems that PR Stanley was forced to use PHP, no wonder he's a little mad at it. Paul: How did you know? :-) You know, the funny thing is that all these so-called civilised people can find time and energy to have a go at me but can't be bothered to help the chap with the original query. I could, and I think you're full of it, too. So there. jcc ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] blas bindings, why are they so much slower the C?
On Tue, Jun 17, 2008 at 9:00 PM, Anatoly Yakovenko
[EMAIL PROTECTED] wrote:
here is the C:
#include cblas.h
#include stdlib.h
int main() {
int size = 1024;
int ii = 0;
double* v1 = malloc(sizeof(double) * (size));
double* v2 = malloc(sizeof(double) * (size));
for(ii = 0; ii size*size; ++ii) {
double _dd = cblas_ddot(0, v1, size, v2, size);
}
free(v1);
free(v2);
}
Your C compiler sees that you're not using the result of cblas_ddot,
so it doesn't even bother to call it. That loop never gets run. All
your program does at runtime is call malloc and free twice, which is
very fast :-)
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bit streams
On Tue, Jun 17, 2008 at 1:05 PM, Andrew Coppin [EMAIL PROTECTED] wrote: Before I sit down and spend 3 months designing my own library from scratch, does anybody know of an existing library that allows you to do what Binary does, but with single-bit precision? The binary-strict library includes this functionality. It also has several other useful pieces of functionality. It's rather a shame the binary and binary-strict developers haven't merged their efforts :-( ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Problem building GHC 6.8.3
On Wed, Jun 18, 2008 at 5:28 AM, Daniel Fischer [EMAIL PROTECTED] wrote: Sorry, probably stupid questions for knowledgeable folks Not stupid at all, but possibly the wrong mailing list. glasgow-haskell-users would usually be a better place to ask. Setup: Haddock's internal GHC version must match the configured GHC version You're using Haddock 2.0 or newer. It's not actually possible to build GHC with it; you must use Haddock 0.9. Many other packages apparently break with Haddock 2, but GHC is certainly rather visible :-) It is possible to have Haddock 0.9 and 2.0 installed simultaneously under different names or in different locations, but you'll have to patch GHC's sources in order to specify which Haddock to use. It's a small patch; look on Trac for it. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
It seems to me that if a PHP developer sees the Haskell community as a resource for advice on programming language implementation, we should take this as a compliment to the Haskell community. Repaying that compliment with your language sucks rocks strikes me as unwise. Not necessarily. It can be that they'd implement closures in PHP, make a dog's dinner of it (as they always do), and then we would be blamed for giving them bad advice. Anyway, it seems that PR Stanley was forced to use PHP, no wonder he's a little mad at it. Paul: How did you know? :-) You know, the funny thing is that all these so-called civilised people can find time and energy to have a go at me but can't be bothered to help the chap with the original query. I could, and I think you're full of it, too. So there. Paul: I rest my case! :-) you cowardly hypocrit! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On 18 Jun 2008, at 9:46 am, Jules Bean wrote: This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. Reactions/arguments like the ones on this thread are perfect for Haskell - recursive and exponential. :) Could we have closure too? :-) Sorry, couldn't resist that one! Iain frequent firestarter and purveyor of bad puns ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Bit Streams
dominic.steinitz: OK, so today I tried to write my first program using the Binary library. And I've hit a snag: It appears the library will only handle data that is byte-aligned. So if I try to write three Bool values, it uses three bytes, not three bits. Before I sit down and spend 3 months designing my own library from scratch, does anybody know of an existing library that allows you to do what Binary does, but with single-bit precision? [I presume Binary is byte-aligned for efficiency...] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/binary-strict The bitsyntax library perhaps? or a StateT over Binary for carrying arround the bit packet to write. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] blas bindings, why are they so much slower the C?
#include cblas.h
#include stdlib.h
int main() {
int size = 1024;
int ii = 0;
double* v1 = malloc(sizeof(double) * (size));
double* v2 = malloc(sizeof(double) * (size));
for(ii = 0; ii size*size; ++ii) {
double _dd = cblas_ddot(0, v1, size, v2, size);
}
free(v1);
free(v2);
}
Your C compiler sees that you're not using the result of cblas_ddot,
so it doesn't even bother to call it. That loop never gets run. All
your program does at runtime is call malloc and free twice, which is
very fast :-)
C doesn't work like that :). functions always get called. but i did
find a problem with my C code, i am incorrectly calling the dot
production function:
#include cblas.h
#include stdlib.h
#include stdio.h
#include string.h
int main() {
int size = 1024;
int ii = 0;
double dd = 0.0;
double* v1 = malloc(sizeof(double) * (size));
double* v2 = malloc(sizeof(double) * (size));
for(ii = 0; ii size; ++ii) {
v1[ii] = 0.1;
v2[ii] = 0.1;
}
for(ii = 0; ii size*size; ++ii) {
dd += cblas_ddot(size, v1, 0, v2, 0);
}
free(v1);
free(v2);
printf(%f\n, dd);
return 0;
}
time ./testdot
10737418.240187
real0m2.200s
user0m2.190s
sys 0m0.010s
So C is about twice as fast. I can live with that.
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
* A closure must only keep alive the varables it references, not the
whole pad on which they are allocated (Python messed up here)
Getting off subject, but I didn't know this about python. I'm not
saying you're incorrect, but my experimentation shows:
% cat t.py
class A(object):
def __init__(self, name): self.name = name
def __del__(self): print self.name, 'gone'
def f():
x = A('x')
y = A('y')
def g():
print x.name, 'alive'
return g
% python
Python 2.5.1 (r251:54869, Apr 18 2007, 22:08:04)
[GCC 4.0.1 (Apple Computer, Inc. build 5367)] on darwin
Type help, copyright, credits or license for more information.
import t
g = t.f()
y gone
g()
x alive
g.func_closure
#- (cell at 0xefb50: A object at 0xefb90,)
del g
x gone
%
So it looks to me like 'y' is not preserved by the closure returned by
'f', and you can see that in its func_closure which keeps the
reference to one A object, but not two.
Python closures do have a unique quirk, which is that variables
bound in a nested function are read-only. This is something that a
schemer might take issue with, but a haskeller probably wouldn't
notice :) And for the longest time python had its two space
namespace thing going on, so it wasn't even really lexically scoped,
but that's many years ago now.
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: [...] Paul: I rest my case! :-) you cowardly hypocrit! Please take your own advice now, and rest your case. Like it or not (I think most people do like it), haskell-cafe has norms of behaviour that make it different to many pl mailing lists. Your sarky comments would have gone unnoticed if they had been accompanied with something constructive. Name calling is out. Jim ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/Lambda-and-closures-in-PHPcould-someone-please-comment--tp17918732p17986275.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Bit Streams
On Wed, Jun 18, 2008 at 12:46 AM, Dominic Steinitz [EMAIL PROTECTED] wrote: OK, so today I tried to write my first program using the Binary library. And I've hit a snag: It appears the library will only handle data that is byte-aligned. So if I try to write three Bool values, it uses three bytes, not three bits. There's a BitGet[1] and BitPut in the Hackage version of binary-strict. However, these versions work on strict ByteStrings. Putting, for one, is pretty inefficient. In the darcs version[2] of binary-strict, there's a fully lazy BitPut[3]. There was a request for a lazy BitGet, but I never wrote it. Most of the time, bit fields are small and you can use the lazy Get from binary to extract a ByteString and parse that with strict BitGet. However, the BitPut should be just fine (including doing things like writing ByteStrings by shifting each byte etc). If it's missing anything obvious, ping me and I'll see what I can do. Cheers, [1] http://darcs.imperialviolet.org/darcsweb.cgi?r=binary-strict;a=headblob;f=/src/Data/Binary/Strict/BitGet.hs [2] http://darcs.imperialviolet.org/binary-strict/ [3] http://darcs.imperialviolet.org/darcsweb.cgi?r=binary-strict;a=headblob;f=/src/Data/Binary/BitPut.hs -- Adam Langley [EMAIL PROTECTED] http://www.imperialviolet.org ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On Wed, 2008-06-18 at 09:46 +0100, Jules Bean wrote: PR Stanley wrote: With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Jules Hear, hear... Hans van Thiel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] blas bindings, why are they so much slower the C?
On Wed, Jun 18, 2008 at 9:16 AM, Anatoly Yakovenko [EMAIL PROTECTED] wrote: C doesn't work like that :) Yes it can. You would have to check the disassembly to be sure, but C compilers can, and do, perform dead code elimination. AGL -- Adam Langley [EMAIL PROTECTED] http://www.imperialviolet.org ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: [...] Paul: I rest my case! :-) you cowardly hypocrit! Paul: Why did you remove Jonathan Cast's message? Afraid somebody might understand why I responded the way I did? Please take your own advice now, and rest your case. Like it or not (I think most people do like it), haskell-cafe has norms of behaviour that make it different to many pl mailing lists. Your sarky comments would have gone unnoticed if they had been accompanied with something constructive. Name calling is out. Paul: and who the bloody hell are you to tell me what's in or out? If you want the matter to rest then shut up yourself. I'm getting sick of you hypocrites who allow yourselves the audacity to attack me, totally gratuitously, yet when I try to defend myself you take the moral high ground. Tell me, why did you remove Jonathan Cast's message? Is he too big for you? Why don't you tell all the other people who have been busy attacking me to modify their language? Are you afraid of upsetting the Haskell Cafe Mafia? Well, guess what, you damn thugs, I 'aint taking this lying down. You come back with more and I'll give you even more! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: With respect, do you not think it'd be wiser for the community [snip] *disgusted* This is exactly the sort of message that haskell-cafe does not normally contain. Let's not start now. This is a civilized mailing list. Either comment on the nice gentlemen's PHP closure proposal from a language point of view, or don't say anything. Jules Hear, hear... Paul: You can shut up too, you bloody troll! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] blas bindings, why are they so much slower the C?
Anatoly Yakovenko wrote:
#include cblas.h
#include stdlib.h
int main() {
int size = 1024;
int ii = 0;
double* v1 = malloc(sizeof(double) * (size));
double* v2 = malloc(sizeof(double) * (size));
for(ii = 0; ii size*size; ++ii) {
double _dd = cblas_ddot(0, v1, size, v2, size);
}
free(v1);
free(v2);
}
Your C compiler sees that you're not using the result of cblas_ddot,
so it doesn't even bother to call it. That loop never gets run. All
your program does at runtime is call malloc and free twice, which is
very fast :-)
C doesn't work like that :).
C compilers can do what they like ;)
GCC in particular is pretty good at removing dead code, including entire
loops. However it shouldn't eliminate the call to cblas_ddot unless it
thinks cblas_ddot has no side effects at all, which would be surprising
unless it's inlined somehow.
Jules
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] blas bindings, why are they so much slower the C?
On Wed, Jun 18, 2008 at 09:16:24AM -0700, Anatoly Yakovenko wrote:
#include cblas.h
#include stdlib.h
int main() {
int size = 1024;
int ii = 0;
double* v1 = malloc(sizeof(double) * (size));
double* v2 = malloc(sizeof(double) * (size));
for(ii = 0; ii size*size; ++ii) {
double _dd = cblas_ddot(0, v1, size, v2, size);
}
free(v1);
free(v2);
}
Your C compiler sees that you're not using the result of cblas_ddot,
so it doesn't even bother to call it. That loop never gets run. All
your program does at runtime is call malloc and free twice, which is
very fast :-)
C doesn't work like that :). functions always get called. but i did
find a problem with my C code, i am incorrectly calling the dot
production function:
See a recent article in lwn on pure and const functions to see how gcc
is able to perform dead code elimination and CSE, provided its given
annotations on the relevant functions. I'd certainly hope that your
blas library is properly annotated!
#include cblas.h
#include stdlib.h
#include stdio.h
#include string.h
int main() {
int size = 1024;
int ii = 0;
double dd = 0.0;
double* v1 = malloc(sizeof(double) * (size));
double* v2 = malloc(sizeof(double) * (size));
for(ii = 0; ii size; ++ii) {
v1[ii] = 0.1;
v2[ii] = 0.1;
}
for(ii = 0; ii size*size; ++ii) {
dd += cblas_ddot(size, v1, 0, v2, 0);
}
free(v1);
free(v2);
printf(%f\n, dd);
return 0;
}
time ./testdot
10737418.240187
real0m2.200s
user0m2.190s
sys 0m0.010s
So C is about twice as fast. I can live with that.
I suspect that it is your initialization that is the difference. For
one thing, you've initialized the arrays to different values, and in
your C code you've fused what are two separate loops in your Haskell
code. So you've not only given the C compiler an easier loop to run
(since you're initializing the array to a constant rather than to a
sequence of numbers), but you've also manually optimized that
initialization. In fact, this fusion could be precisely the factor of
two. Why not see what happens in Haskell if you create just one
vector and dot it with itself? (of course, that'll also make the blas
call faster, so you'll need to be careful in your interpretation of
your results.)
David
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] blas bindings, why are they so much slower the C?
On Wed, Jun 18, 2008 at 06:03:42PM +0100, Jules Bean wrote:
Anatoly Yakovenko wrote:
#include cblas.h
#include stdlib.h
int main() {
int size = 1024;
int ii = 0;
double* v1 = malloc(sizeof(double) * (size));
double* v2 = malloc(sizeof(double) * (size));
for(ii = 0; ii size*size; ++ii) {
double _dd = cblas_ddot(0, v1, size, v2, size);
}
free(v1);
free(v2);
}
Your C compiler sees that you're not using the result of cblas_ddot,
so it doesn't even bother to call it. That loop never gets run. All
your program does at runtime is call malloc and free twice, which is
very fast :-)
C doesn't work like that :).
C compilers can do what they like ;)
GCC in particular is pretty good at removing dead code, including entire
loops. However it shouldn't eliminate the call to cblas_ddot unless it
thinks cblas_ddot has no side effects at all, which would be surprising
unless it's inlined somehow.
Or unless it's been annotated as pure, which it should be.
David
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
PR Stanley wrote: PR Stanley wrote: [...] Paul: I rest my case! :-) you cowardly hypocrit! Paul: Why did you remove Jonathan Cast's message? Afraid somebody might understand why I responded the way I did? Please take your own advice now, and rest your case. Like it or not (I think most people do like it), haskell-cafe has norms of behaviour that make it different to many pl mailing lists. Your sarky comments would have gone unnoticed if they had been accompanied with something constructive. Name calling is out. Paul: and who the bloody hell are you to tell me what's in or out? If you want the matter to rest then shut up yourself. I'm getting sick of you hypocrites who allow yourselves the audacity to attack me, totally gratuitously, yet when I try to defend myself you take the moral high ground. Tell me, why did you remove Jonathan Cast's message? Is he too big for you? Why don't you tell all the other people who have been busy attacking me to modify their language? Are you afraid of upsetting the Haskell Cafe Mafia? Well, guess what, you damn thugs, I 'aint taking this lying down. You come back with more and I'll give you even more! I snipped Jonathan's message just because I was commenting on the tone of your response. Sorry if you think I presented your reply out of context, but my point is that I don't think there is any need for this in any context here. I do have a right to say that, even as someone who hardly ever posts but prefers to read the list...it's owned by everybody. This isn't the same thing as censorship and you'll notice I said norms, not rules of behaviour. No one's going to stop you making yourself look silly if you insist on doing it. As for Jonathan being too big for me, erm, who is he again? :-) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/Lambda-and-closures-in-PHPcould-someone-please-comment--tp17918732p17987734.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
At 18:17 18/06/2008, you wrote: PR Stanley wrote: PR Stanley wrote: [...] Paul: I rest my case! :-) you cowardly hypocrit! Paul: Why did you remove Jonathan Cast's message? Afraid somebody might understand why I responded the way I did? Please take your own advice now, and rest your case. Like it or not (I think most people do like it), haskell-cafe has norms of behaviour that make it different to many pl mailing lists. Your sarky comments would have gone unnoticed if they had been accompanied with something constructive. Name calling is out. Paul: and who the bloody hell are you to tell me what's in or out? If you want the matter to rest then shut up yourself. I'm getting sick of you hypocrites who allow yourselves the audacity to attack me, totally gratuitously, yet when I try to defend myself you take the moral high ground. Tell me, why did you remove Jonathan Cast's message? Is he too big for you? Why don't you tell all the other people who have been busy attacking me to modify their language? Are you afraid of upsetting the Haskell Cafe Mafia? Well, guess what, you damn thugs, I 'aint taking this lying down. You come back with more and I'll give you even more! I snipped Jonathan's message just because I was commenting on the tone of your response. Sorry if you think I presented your reply out of context, but my point is that I don't think there is any need for this in any context here. I do have a right to say that, even as someone who hardly ever posts but prefers to read the list...it's owned by everybody. This isn't the same thing as censorship and you'll notice I said norms, not rules of behaviour. No one's going to stop you making yourself look silly if you insist on doing it. As for Jonathan being too big for me, erm, who is he again? :-) Paul: So, now I am silly! I'd still prefer that to a coward and a hypocrite ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Bit Streams
Dominic Steinitz wrote: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/binary-strict Ooo... looks interesting. Pity I can't look at any documentation for it. (Is that *really* Haddoc failing with a parse error on a pragma? Surely not...) I'll take a look at this. Thanks. Andrew. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Bit Streams
agl: On Wed, Jun 18, 2008 at 12:46 AM, Dominic Steinitz [EMAIL PROTECTED] wrote: OK, so today I tried to write my first program using the Binary library. And I've hit a snag: It appears the library will only handle data that is byte-aligned. So if I try to write three Bool values, it uses three bytes, not three bits. There's a BitGet[1] and BitPut in the Hackage version of binary-strict. However, these versions work on strict ByteStrings. Putting, for one, is pretty inefficient. In the darcs version[2] of binary-strict, there's a fully lazy BitPut[3]. There was a request for a lazy BitGet, but I never wrote it. Most of the time, bit fields are small and you can use the lazy Get from binary to extract a ByteString and parse that with strict BitGet. However, the BitPut should be just fine (including doing things like writing ByteStrings by shifting each byte etc). If it's missing anything obvious, ping me and I'll see what I can do. Cheers, [1] http://darcs.imperialviolet.org/darcsweb.cgi?r=binary-strict;a=headblob;f=/src/Data/Binary/Strict/BitGet.hs [2] http://darcs.imperialviolet.org/binary-strict/ [3] http://darcs.imperialviolet.org/darcsweb.cgi?r=binary-strict;a=headblob;f=/src/Data/Binary/BitPut.hs Adam, Would you recommend binary-strict over bitsyntax now? Or are none yet entirely satisfactory -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
Hallo, PR Stanley wrote: Now, if you, Jules, Alex or some other wannabe Hitler have a problem with my freedom of expression then your best solution is to saddle up and get the hell out yourselves. This is the wrong place for setting up your tinpot dictatorship, Doctor! I am grateful for the help I've been getting from the list and my understanding of FP has vastly improved since my membership of this list but I refuse to tolerate bullies who use the list as a way of lifting themselves out of their own shitty lives. Now I am angry! Wow, Godwin's in record time. Please don't confuse freedom of speech with name-calling, or distasteful, non-constructive comments about someone else's programming language. Stop making yourself look like a fool. -alex http://www.ventonegro.org/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Bit Streams
On Wed, Jun 18, 2008 at 10:52 AM, Don Stewart [EMAIL PROTECTED] wrote: Would you recommend binary-strict over bitsyntax now? Or are none yet entirely satisfactory Probably, yes. Bitsyntax was, after all, the first Haskell code I ever wrote :) It works, but I think the monad style of binary-strict is better. AGL -- Adam Langley [EMAIL PROTECTED] http://www.imperialviolet.org ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Bit Streams
On Wed, Jun 18, 2008 at 10:43 AM, Andrew Coppin [EMAIL PROTECTED] wrote: Dominic Steinitz wrote: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/binary-strict Ooo... looks interesting. Pity I can't look at any documentation for it. (Is that *really* Haddoc failing with a parse error on a pragma? Surely not...) I'll take a look at this. Yeah, I just ran into that myself, and solved it by removing the haddock comments for those types. I think Haddock is a bit oversensitive when it comes to parsing. It would be nice if it would at least try to continue when it failed to parse something. Of course, that might be easier said than done! While I'm on the subject, what is the future for binary-strict? I recently wanted it since I wanted to catch parse errors, but didn't wind up using it because I would have had to rewrite a whole bunch of Binary instances to be separate Binary.Put Binary.Strict.Get instances, and I'm lazy. So I did 'length (show result) `seq` return result which doesn't win any beauty contests but seems to work. Inclusion in the official Data.Binary would be nice, especially if it could be a drop-in replacement, say by changing the Data.Binary instance definitions to Strict.Binary or something. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Bit Streams
On Wed, Jun 18, 2008 at 11:00 AM, Adam Langley [EMAIL PROTECTED] wrote: On Wed, Jun 18, 2008 at 10:52 AM, Don Stewart [EMAIL PROTECTED] wrote: Would you recommend binary-strict over bitsyntax now? Or are none yet entirely satisfactory Probably, yes. Bitsyntax was, after all, the first Haskell code I ever wrote :) It works, but I think the monad style of binary-strict is better. If you provide Applicative and Alternative instances for your getter monads (perhaps you already do?), that will get us very close to the kind of notational succinctness that Erlang's bit-level pattern matching gives, using entirely general Haskell mechanisms, and without the fuglitude of TH. That, I think, would be just lovely. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Fast sorting with Bytestring
Hi, I played a bit around with the nice bytestring package. At some point I implemented a simple sorting program, because I needed line-sorting a file with a custom line-compare function. I was a bit surprised, that the resulting code is very fast. A lot of faster than sorting via GNU sort (with the standard line-compare function). Then I got suspicious and tested standard GNU sort against a trivial standard sort implementation in Haskell using bytestring. The Haskell implementation looks like: module Main where import qualified Data.ByteString.Lazy.Char8 as B import Data.List main = do c - B.getContents let l = B.lines c let r = sort l B.putStr $ B.unlines r Sorting a file of '[]'-strings I get: time ./sort brackets /dev/null # ~ 0.01 s time sort brackets /dev/null# ~ 14s Ok, strane ... Well, let's test with some 'normal' text: time ./sort bible /dev/null # ~ 0.4 s time sort bible /dev/null # ~ 0.56 s Ok, not that different. But with Haskell you often expect to get very slow code compared to an implementation in C. And I am surprised, that the Haskell is fast _and_ nice to read - because for example the ultra fast 'wc -l' Haskell implementation from the Haskell-Wiki uses some insider-knowledge about bytestring, and looks to a beginner not that intuitive, I guess. ./sort is the shown Haskell implementation. I used ghc 6.8.2, installed bytestring 0.9.1.0 as a user-local package (don't now I this superseeds the global bytestring package), compiled via ghc -O2. The tests are run at a Pentium M 1.3 GHz computer. As GNU sort I tested the version from coreutils 6.9. You can get the test files from: http://www.techfak.uni-bielefeld.de/~gsauthof/stuff/brackets.gz http://www.techfak.uni-bielefeld.de/~gsauthof/stuff/bible.gz (obviously, you have to gunzip them after downloading ...) Of course, the naive Haskell implementation doesn't care about locales (i.e. collating locale sequences), but this shouldn't explain the observed differences sorting the brackets file. Best regards Georg Sauthoff -- Fortune : 'Real programmers don't comment their code. It was hard to write, it should be hard to understand.' ;) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Fast sorting with Bytestring
On Wed, Jun 18, 2008 at 08:19:10PM +0200, Georg Sauthoff wrote: Hi, I played a bit around with the nice bytestring package. At some point I implemented a simple sorting program, because I needed line-sorting a file with a custom line-compare function. I was a bit surprised, that the resulting code is very fast. A lot of faster than sorting via GNU sort (with the standard line-compare function). Then I got suspicious and tested standard GNU sort against a trivial standard sort implementation in Haskell using bytestring. The Haskell implementation looks like: [snip] Ok, strane ... Well, let's test with some 'normal' text: time ./sort bible /dev/null # ~ 0.4 s time sort bible /dev/null # ~ 0.56 s Ok, not that different. But with Haskell you often expect to get very slow code compared to an implementation in C. And I am surprised, that the Haskell is fast _and_ nice to read - because for example the ultra fast 'wc -l' Haskell implementation from the Haskell-Wiki uses some insider-knowledge about bytestring, and looks to a beginner not that intuitive, I guess. ./sort is the shown Haskell implementation. I used ghc 6.8.2, installed bytestring 0.9.1.0 as a user-local package (don't now I this superseeds the global bytestring package), compiled via ghc -O2. The tests are run at a Pentium M 1.3 GHz computer. As GNU sort I tested the version from coreutils 6.9. You can get the test files from: http://www.techfak.uni-bielefeld.de/~gsauthof/stuff/brackets.gz http://www.techfak.uni-bielefeld.de/~gsauthof/stuff/bible.gz (obviously, you have to gunzip them after downloading ...) Of course, the naive Haskell implementation doesn't care about locales (i.e. collating locale sequences), but this shouldn't explain the observed differences sorting the brackets file. GNU 'sort' uses an external sort algorithm. You can, with 200M of memory, give it a 50G input file, and it will work. This might explain the difference.. Stefan signature.asc Description: Digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Fast sorting with Bytestring
On Wed, Jun 18, 2008 at 11:23:00AM -0700, Stefan O'Rear wrote: GNU 'sort' uses an external sort algorithm. You can, with 200M of memory, give it a 50G input file, and it will work. This might explain the difference.. But the input files are both 10 mb ... If I create a 'big_bible' file like 'cat bible bible | dd of=big_bible count=1 bs=SIZE_OF_BRACKETS' then the timings are: time sort big_bible /dev/null # ~ 1.2 s time ./sort big_bible /dev/null # ~ 0.8 s I.e. the difference here is like a low constant factor, and not like a factor of 1000 with the brackets. Best regards Georg Sauthoff -- Fortune : 'Real programmers don't comment their code. It was hard to write, it should be hard to understand.' ;) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Fast sorting with Bytestring
Stefan O'Rear [EMAIL PROTECTED] writes: Ok, strane ... Well, let's test with some 'normal' text: time ./sort bible /dev/null # ~ 0.4 s time sort bible /dev/null # ~ 0.56 s Ok, not that different. But with Haskell you often expect to get very slow code compared to an implementation in C. GNU 'sort' uses an external sort algorithm. You can, with 200M of memory, give it a 50G input file, and it will work. This might explain the difference.. GNU sort also handles locale-based comparison, which I suspect explains more of the difference. Try with LC_ALL=C. -k -- If I haven't seen further, it is by standing in the footprints of giants ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] type constructor confusion
hello list,
loading the code below into ghci gives me this error:
HttpMessage.hs:36:20: Not in scope: type constructor or class `HttpRequest'
The troublesome line is the definition of the cookie function at the end
of the code. I've made HttpRequest and HttpResponse constructors of
HttpMessage as I've sketched out an action that might return either
one. Given that I thought what I was doing below was defining these as
type constructors (maybe I have my vocabulary mixed up) I don't know why
ghci is returning this error.
module HttpMessage ( HttpMessage(..), HttpRequestMethod(..), cookie ) where
import Data.Map as M
data HttpHeaders = HttpHeaders !(M.Map String String )
data HttpMessage =
HttpRequest {
headers:: HttpHeaders,
body :: String,
request_method :: HttpRequestMethod,
uri:: URI,
http_version :: Float,
cookies:: !(M.Map String String)
}
| HttpResponse {
headers:: HttpHeaders,
body :: String,
status :: HttpStatus
}
data HttpRequestMethod = Get | Head | Post | Put | Delete | Unsupported
String
data HttpStatus = OK | NotFound | NotAuthorized | ServerError
data URI = URI {
protocol :: String,
domain :: String,
port :: String,
path :: String,
query:: !(M.Map String String),
anchor :: String
}
cookie :: String - HttpRequest - Maybe String
cookie n request = M.lookup n (cookies request)
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] type constructor confusion
On Jun 18, 2008, at 15:31 , Stephen Howard wrote: HttpMessage.hs:36:20: Not in scope: type constructor or class `HttpRequest' The troublesome line is the definition of the cookie function at the end of the code. I've made Right. HttpRequest is a data constructor associated with the type constructor HttpMessage. (Data constructors are effectively functions; you used it in the context of a type, not a function name.) -- 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] Re: working with Random.randoms
Thanks for the replies. This was my solution:
module RandomTest ( random_test ) where
import Random
random_test :: Int - IO String
random_test n = do
g - newStdGen
return $ take n (randomRs printable_ascii g)
where printable_ascii = ('!','~')
The struggling with the type system was supposed to be
tongue-in-cheek. I trust it, it just takes some time to get used to
it. And I appreciate Dan's comments about separating the pure code from
the non-pure, but in this case the code was succinct enough that one
more layer of functions seemed to do more harm than good when it came to
legibility.
- Stephen
Jon Fairbairn wrote:
Stephen Howard [EMAIL PROTECTED] writes:
I am a newcomer doing my obligatory struggling with
Haskell's type system,
That's your mistake. Don't struggle with the type system,
the type system is your friend; when it tells you you are
doing something wrong, it's usually right.
and I've got a nut I've not been able to crack. Given:
import Random
random_test :: Int - String
random_test n = do
g - getStdGen
take n (randoms g)::String
My immediate reaction on seeing this is that do is for
manipulating monads, but the only monad you've indicated in
the type is [] (from String = [Char]), and that's probably
an accident.
In GHCi:
Prelude :t Random.getStdGen
Random.getStdGen :: IO System.Random.StdGen
What this says is that getStdGen isn't a function, which is
to say it doesn't always return the same value (ie it isn't
pure -- it wouldn't be much use if it were!). In effect it
uses the real world to get a new value, and such things are
kept safely in the IO monad. In C, everything is in the IO
monad; there's no way of telling from the type whether
something is pure or not¹. In Haskell (apart from some
ugliness that's supposed to stay hidden) you have to
distinguish between pure and impure, and the type checker
keeps track of all this for you.
And yet, when I run these lines in GHCI by hand,
The top level of GHCi is IO (which shouldn't come as a
surprise!)
things seem to work (though the string is the same set of
random characters each time, another bit that I need to
solve
That's a somewhat obscure aspect of GHCi, I think, to do
with not reverting top-level expressions. If you do this:
Prelude :set +r
Prelude g - Random.getStdGen -- what's the type?
1954047482 7573
Prelude g - Random.getStdGen -- what's the type?
1626678354 7697
Prelude
you see that you get a different StdGen each time.
I'm guessing that randoms is returning an IO type but I'm
not sure how to go about extracting the String to return to
the calling action. Changing the type signature to Int -
IO String only gives me a different error.
If you do any IO, you've done some IO! So you need to lift
out the StdGen and pass that to the functions that you want
to use it.
main :: IO()
do gen - getStdGen
the_list - real_programme gen
print the_list
You should be able to deduce from the fact that the first
argument of real_programme here is of type StdGen (not IO
anything) and its result type is [something] that
real_programme is pure, and gen has only one value
throughout. So if you want more than one random list out of
it, you either need to use Random.split or pass more than
one gen in.
[1] Were you truly perverse, you could define your own
libraries in Haskell so that YourInt = IO Int; YourDouble =
IO Double etc, and make appropriate classes in place of Num
c (hiding the proper ones), so that
+ :: YourInt - YourInt - YourInt
and so on (you'd have to define your own Bool and if, too,
but Haskell can do that). Then the type checker would
overlook all sorts of mistakes that it could otherwise have
caught.
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Fast sorting with Bytestring
On Wed, Jun 18, 2008 at 08:56:43PM +0200, Ketil Malde wrote: Stefan O'Rear [EMAIL PROTECTED] writes: GNU 'sort' uses an external sort algorithm. You can, with 200M of memory, give it a 50G input file, and it will work. This might explain the difference.. GNU sort also handles locale-based comparison, which I suspect explains more of the difference. Try with LC_ALL=C. Well, for input 'bible' with locale en_US.utf8 GNU sort is ~ 6 times slower than with locale C. But for input 'brackets' it is ~ 433 times slower ... Best regards Georg Sauthoff -- Fortune : 'Real programmers don't comment their code. It was hard to write, it should be hard to understand.' ;) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Meaning of ribbonsPerLine at Text.PrettyPrint.HughesPJ ?
Hi,
Can anyone give a good explanation of what ribbonsPerLine means?
Maybe it would be better to simply ask for the meaning of ribbon in
this context. The documentation is totally meaningless to me:
reibbonsPerLine: Ratio of ribbon length to line length.
I asked at #haskell and frankly, I was surprised by the answer:
fons: can anyone tell me what the heck does ribbonsPerLine mean in
Text.PrettyPrint.HughesPJ?
fons: renderStyle style{lineLength=10, ribbonsPerLine=1} $ sep [text
foo ,text bar]
lambdabot: foo bar
fons: renderStyle style{lineLength=10, ribbonsPerLine=2} $ sep [text
foo ,text bar]
lambdabot: foo\nbar
fons: ok, somehow it affects the line width ...
byorgey: fons: I can't explain it, all I know is that you must set it
to 1 or else it does bizarre things
fons: hahah, ok
fons: byorgey: that's funny considering its default value is 1.5
byorgey: if you set it to 1 then lineLength means what you think it should
byorgey: fons: EXACTLY
Cheers,
Fons
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell Weekly News: Issue 73 - June 18, 2008
--- Haskell Weekly News http://sequence.complete.org/hwn/20080618 Issue 73 - June 18, 2008 --- Welcome to issue 73 of HWN, a newsletter covering developments in the [1]Haskell community. The Google Summer of Code is in full swing, preparations are underway for ICFP and the eleventh ICFP Programming Contest, and cabal-install is oh-so-sexy. It's an exciting time to be a part of the Haskell community! Community News Andy Gill has completed his move from Portland, OR to Kansas. Luke Palmer (luqui) has [2]begun work for [3]Anygma, Peter Verswyvelen's startup using Haskell (among other languages) to ``generate easy-to-use tools for creating audio-visual 2D/3D content.'' Congrats to Andy and Luke on their new beginnings! Announcements Final CFP: 2008 Haskell Symposium. Andy Gill [4]announced the final call for papers for the [5]2008 Haskell Symposium. The deadline is the 23rd of this month; please submit a paper! cabal-install. Duncan Coutts [6]announced the release of [7]cabal-install-0.5, along with the release of Cabal-1.4 to support it. It features an improved command line interface, smarter upgrading, and is made of win. If you are still stuck in the dark ages of runhaskell Setup configure blah blah, then the imperative monkeys have already won. ICFP programming contest. Tim Chevalier [8]announced the eleventh annual [9]ICFP programming contest, to be held from Friday, July 11, 2008 to Monday, July 14, 2008. Are you ready? c.h.o trac. Ian Lynagh [10]announced that it is now possible for projects on [11]community.haskell.org to [12]create themselves a trac, providing a bug tracking system and wiki. random-access-list. Stephan Friedrichs [13]announced an [14]implementation of Chris Okasaki's random-access lists, providing typical list operations (cons, head, tail) in O(1) and indexed random-access in O(log n). GHC version 6.8.3. Ian Lynagh [15]announced a [16]new patchlevel release of [17]GHC, containing a number of bugfixes relative to 6.8.2. Printf-TH. Marc Weber [18]announced that he has taken over maintenance of the [19]Printf-TH library, which implements a printf function via [20]Template Haskell, in order to guarantee that wrong argument types or the wrong number of arguments will result in compile time errors. Mueval. Gwern Branwen [21]announced the release of the [22]mueval package, providing a standalone executable for evaluating Haskell expressions based on the GHC API. Topkata. Christoph Bauer [23]announced the release of [24]Topkata, a simple OpenGL game written in Haskell. The goal is to guide a ball through a labyrinth to the opposite corner. Haddock Trac. David Waern [25]announced a new [26]bug-tracker and wiki for the [27]Haddock project. Fortress talk. Jeff Polakow [28]announced that a [29]talk on [30]Fortress, a new OO/functional language from Sun, will take place on Wednesday, June 25 at 6:30pm in Manhattan, New York, USA. ieee-0.2. Patrick Perry [31]announced the release of [32]ieee, a library that provides approximate comparison of floating point numbers based, NaN-aware minimum and maximum, and a type class for approximate comparisons. Google Summer of Code Hoogle 4. Neil Mitchell (ndm) is [33]working on Hoogle 4, recently adding support for generating Hoogle databases to [34]Haddock, using the GHC API. This week he plans to work on database creation and text searches. DPH physics engine. Roman Cheplyaka (Feuerbach) is [35]working on a physics engine using [36]Data Parallel Haskell, recently adding rotations, represented by quaternions. Next he plans to handle collisions properly with respect to rotation, and to add documentation. Generic tries. Jamie Brandon is writing a library for efficient maps using generalized tries. He has come up with a preliminary API and is [37]asking for feedback. Cabal dependency framework. Andrea Vezzosi (Saizan) is working on a make-like dependency analysis framework for Cabal, recently refining the core model, that has built its first sources in the testing environment. The next step will be dealing with preprocessor chaining. Language.C. Benedikt Huber (visq) is working on Language.C, a standalone parser/pretty printer library for C99. The test suite is finished, the parser and pretty printer support most GNU extensions, and all failing tests of gcc.dg are documented. GHC API. Thomas Schilling (nominolo) is working on improvements to the GHC API. GHC plugins. Maximilian Conroy Bolingbroke is working on dynamically loaded plugins for GHC. Discussion Low-level array performance. Dan Doel began a [38]discussion about the [39]fannkuch benchmark and the current
[Haskell-cafe] Using cabal-install
Is there a tutorial/user's guide for cabal-install somewhere? My limited google skills haven't found one and I really need it, because there MUST be a better way to get a package and its dependencies built and the haddock documentation generated, installed and hyperlinked than manually unpacking each .tar.gz and running cabal haddock there. Thanks, Daniel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Meaning of ribbonsPerLine at Text.PrettyPrint.HughesPJ ?
byorgey: fons: I can't explain it, all I know is that you must set it to 1 or else it does bizarre things fons: hahah, ok fons: byorgey: that's funny considering its default value is 1.5 byorgey: if you set it to 1 then lineLength means what you think it should byorgey: fons: EXACTLY Excellent, thanks for solving a nagging problem I couldn't be bothered to track down. I was wondering why my pretty printing was a little messed up and slightly too wide. And isn't 100 columns a bit non-standard for a default? I thought 80 columns had more traction? I know that's what my terminals are at... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Using cabal-install
http://blog.well-typed.com/2008/06/new-cabal-and-cabal-install-releases/ Basically, build and install cabal-install, then let have it. daniel.is.fischer: Is there a tutorial/user's guide for cabal-install somewhere? My limited google skills haven't found one and I really need it, because there MUST be a better way to get a package and its dependencies built and the haddock documentation generated, installed and hyperlinked than manually unpacking each .tar.gz and running cabal haddock there. Thanks, Daniel ___ 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] Problem building GHC 6.8.3
2008/6/18 Bryan O'Sullivan [EMAIL PROTECTED]: On Wed, Jun 18, 2008 at 5:28 AM, Daniel Fischer [EMAIL PROTECTED] wrote: Sorry, probably stupid questions for knowledgeable folks Not stupid at all, but possibly the wrong mailing list. glasgow-haskell-users would usually be a better place to ask. Setup: Haddock's internal GHC version must match the configured GHC version You're using Haddock 2.0 or newer. It's not actually possible to build GHC with it; you must use Haddock 0.9. We're discussing how to fix this problem in future releases of GHC and Haddock. In the meantime, it is actually possible to build GHC with Haddock 2.1.0 by first building GHC without docs, then installing Haddock with this GHC, and then building the GHC documentation. David ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Using cabal-install
Am Mittwoch, 18. Juni 2008 22:57 schrieb Don Stewart: http://blog.well-typed.com/2008/06/new-cabal-and-cabal-install-releases/ Basically, build and install cabal-install, then let have it. I have cabal-install installed, and I'm thankful for it. My problem is, when I do cabal install foo it downloads foo and its dependencies, builds and installs, but it doesn't generate the documentation. How do I get it to build, install and link the documentation for all packages automatically, too? daniel.is.fischer: Is there a tutorial/user's guide for cabal-install somewhere? My limited google skills haven't found one and I really need it, because there MUST be a better way to get a package and its dependencies built and the haddock documentation generated, installed and hyperlinked than manually unpacking each .tar.gz and running cabal haddock there. Thanks, Daniel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bit streams
Malcolm Wallace wrote: The original Binary library, circa 1998, was based on bit-streams rather than bytes. You might be able to dig up a copy and bring it back to life. This derivative (by Hal Daume III) works with GHC 6.8.2 (I haven't tried 6.8.3): http://hackage.haskell.org/cgi-bin/hackage-scripts/package/NewBinary Not sure how to compares to the original version. It does appear to still support bit-oriented I/O though. j. (Note: I just fixed the cabal stuff to work with 6.8.2 minutes ago, so if have tried it before, it should work now). ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Using cabal-install
On Wed, 2008-06-18 at 22:44 +0200, Daniel Fischer wrote: Is there a tutorial/user's guide for cabal-install somewhere? My limited google skills haven't found one and I really need it, because there MUST be a better way to get a package and its dependencies built and the haddock documentation generated, installed and hyperlinked than manually unpacking each .tar.gz and running cabal haddock there. The feature you are looking for is not implemented yet. cabal-install should be able to generate haddock docs http://hackage.haskell.org/trac/hackage/ticket/206 Go add your comments to that ticket and tell us how you think it should work. I mean what command would you expect to run to have it work and what would it do exactly? A closely related feature and one it probably overlaps with is this one: allow installing just specific bits, like just docs http://hackage.haskell.org/trac/hackage/ticket/225 so we should also think about what the user interface / mode of interaction of this feature should be. The issue is that previously we had separate commands for each phase so it was obvious where to put various phase-specific flags. Now with cabal-install's install command it does all the phases in one go. Currently it takes just the flags that the configure command takes (plus one or two others). So do we just make the install command take the union of the flags of the other phases? And how to say that we want optional phases like docs and tests. That's basically the issue, how do we expect to interact with it? If it can be relatively consistent and memorable then that's all the better. We also want all flags that you can pass on the command line to be able to be set as defaults in the ~/.cabal/config file. Currently there's just a subset but we want to have it cover everything. In general, adding yourself to the cc list of a ticket counts as a vote for the importance of that ticket and commenting on why it's important even more so (eg how painful and time consuming the alternative is). Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Meaning of ribbonsPerLine at Text.PrettyPrint.HughesPJ ?
On Wed, 2008-06-18 at 13:55 -0700, Evan Laforge wrote: byorgey: fons: I can't explain it, all I know is that you must set it to 1 or else it does bizarre things fons: hahah, ok fons: byorgey: that's funny considering its default value is 1.5 byorgey: if you set it to 1 then lineLength means what you think it should byorgey: fons: EXACTLY Excellent, thanks for solving a nagging problem I couldn't be bothered to track down. I was wondering why my pretty printing was a little messed up and slightly too wide. And isn't 100 columns a bit non-standard for a default? I thought 80 columns had more traction? I know that's what my terminals are at... Yeah. I'd vote for 80. That's what we use in pretty printing messages in Cabal. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] First Call for Papers: DSL WC
IFIP Working Conference on Domain Specific Languages (DSL WC) July 15-17, 2009, Oxford CALL FOR PAPERS Domain-specific languages are emerging as a fundamental component of software engineering practice. DSLs are often introduced when new domains such as web-scripting or markup come into existence, but it is also common to see DSLs being introduced and adopted for traditional domains such as parsing and data description. Developing software using DSLs has many benefits. DSLs are often designed based on existing notations that are already in use by experts in a given domain. As such, successful DSLs often reduce or eliminate the effort needed to transform the concept or innovation produced by the domain expert into an executable artifact or even a deliverable software product. DSL implementations can capture and mechanize a significant portion of the repetitive and mechanical tasks that a domain expert traditionally needed to perform in order to produce an executable. DSLs can in many cases capture and make widely available special expertise that only top specialists in a given domain might have. By capturing expert knowledge and reducing repetitive tasks, DSLs often also lead to software that is significantly more portable, more reliable and more understandable than it would otherwise be. DSLs can be viewed as having a dual role to general-purpose languages: whereas general purpose languages try to do everything as well as possible, DSLs are designed to find a domain where they can solve some class of problems -- no matter how small -- in the best possible way. Widely known examples of DSLs include Matlab, Verilog, SQL, LINQ, JavaScript, PERL, HTML, Open GL, Tcl/Tk, Macromedia Director, Mathematica/Maple, AutoLisp/AutoCAD, XSLT, RPM, Make, lex/yacc, LaTeX, PostScript, Excel, among many others. But while these tools have been widely successful, they still fall short of realizing the full idea behind them. The goal of this conference is to explore the extent to which incorporating modern principles of language design and software engineering can benefit existing and future domain-specific languages. The ultimate goal of using DSLs is to improve programmer productivity and software quality. Often, this is achieved by reducing the cost of initial software development as well as maintenance costs. These improvements - programs being easier to write and maintain - materialize as a result of domain-specific guarantees, analyses, testing techniques, verification techniques, and optimizations. * Paper Criteria Papers are sought addressing the research problems, fundamental principles, and practical techniques of DSLs, including but not limited to: - Foundations, including semantics, formal methods, type theory, and complexity theory - Language design, ranging from concrete syntax to semantic and typing issues - Software engineering, including domain analysis, software design, and round-trip engineering - Software processes, including metrics for software and language evaluation - Implementation techniques, including parsing, compiling, and program generation - Program analysis and automated transformation - Reverse engineering, re-engineering, design discovery, automated refactoring - Hardware/software codesign - Programming environments, including visual languages, debuggers, and testing infrastructure - Teaching DSLs and the use of DSLs in teaching - Case studies, including engineering, bioinformatics, hardware specification languages, parallel computing languages, real-time and embedded systems, and networked and distributed domains Papers will be judged on the depth of their insight and the extent to which they translate specific experience into general lessons for domain-specific language designers and implementers, and software engineers. Papers can range from the practical to the theoretical; where appropriate, they should refer to actual languages, tools, and techniques, provide pointers to full definitions and implementations, and include empirical data on results. * Important Dates - December 14th, 2008: Abstract submission due. Firm, will not have any extensions - December 21st, 2008: Paper submission deadline. Firm, will not have any extensions - February 23rd, 2009: Author notification of decisions - March 22nd, 2009: Camera ready manuscripts due * Program Committee - Jon Bentley, Avayalabs - Martin Erwig, Oregon State University - Jeff Gray, University of Alabama at Birmingham - Robert Grimm, New York University - Jim Grundy, Intel Strategic CAD Labs - Tom Henzinger, EPFL - Sam Kamin, UIUC - Dick Kieburtz, Portland State University - Ralf Lämmel, University of Koblenz - Julia Lawall, University of Copenhagen -
Re: [Haskell-cafe] Re: Bit Streams
Don Stewart wrote: dominic.steinitz: OK, so today I tried to write my first program using the Binary library. And I've hit a snag: It appears the library will only handle data that is byte-aligned. So if I try to write three Bool values, it uses three bytes, not three bits. Before I sit down and spend 3 months designing my own library from scratch, does anybody know of an existing library that allows you to do what Binary does, but with single-bit precision? [I presume Binary is byte-aligned for efficiency...] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/binary-strict The bitsyntax library perhaps? or a StateT over Binary for carrying arround the bit packet to write. -- Don The vagaries of gmane have made it appear that I asked the question. In fact, Andrew Coppin asked the question and I responded with a pointer to the library Adam Langley pulled together. Dominic. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lambda and closures in PHP -- could someone please comment?
On 18 Jun 2008, at 4:36 pm, Karoly Negyesi wrote: (a) I would *never* want to use an implementation of closures like that. Could you elaborate on a) ? It wasn't me who wrote it, but consider - non-local variables are *not* captured unless you explicitly hoist them into the lambda expression using the 'lexical' keyword. - references to non-local variables that are not so hoisted are not syntax errors, they just quietly do something else. - ordinary functions do not act as if defined by lambda expressions; 'lexical' is required in lambdas and forbidden in functions. - ordinary functions do not act as if defined by lambda expressions; the latter can outlive their lexical scope, the former can't. - what you get is a reference to a variable (as you do in Scheme) but loop variables really are variables, not names for values, so lambdas created in different iterations of the same loop point so the same loop variable, and do not remember the value it had when they were created. The proposal explains how to work around this. All of this boils down to something in which you *can* with care do the things you expect to do with closures, but the language gently leads you to the edge of the Pit and the compiler just smiles quietly as you fall over. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] blas bindings, why are they so much slower the C?
On 19 Jun 2008, at 4:16 am, Anatoly Yakovenko wrote: C doesn't work like that :). functions always get called. Not true. A C compiler must produce the same *effect* as if the function had been called, but if by some means the compiler knows that the function has no effect, it is entitled to skip the call. In particular, the C compiler I normally use offers these pragmas, amongst others: #pragma does_not_write_global_data (funcname [, funcname]) #pragma no_side_effect(funcname[, funcname]) So with a declaration like extern double cblas_ddot( int, double const *, int, double const *, int); #pragma no_side_effect (cblas_ddot) the compiler would be completely within its rights to discard any call to cblas_ddot() whose result was not used. (As it happens, it didn't, but it would have been allowed to.) If using gcc, extern double cblas_ddot( ... as before ...) __attribute__ ((const)); seems to have the same effect, certainly the test case I tried did in fact completely eliminate a call to cblas_ddot() when so declared. Since the malloc() results pointed to uninitialised memory, the C compiler was entitled to do anything it pleased anyway. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] type constructor confusion
Thanks Brandon, forgot to send my reply to the list: Ok, so I am confusing things. Good to know. So my question is how do I fulfill this scenario? - I have an action that might return either an HttpResponse or an HttpRequest, depending on if the IO in the action determined more work needed doing. It's here, though I doubt it's correct yet: requestHandler :: HttpRequest - IO HttpResponse requestHandler request = do session - sessionHandler request ret - uriHandler request case ret of HttpResponse - ret HttpRequest - resourceHandler session ret uriHandler :: HttpRequest - IO HttpMessage sessionHandler :: HttpRequest - IO HttpSession I've given the uriHandler a signature of IO HttpMessage because the HttpMessage might be either an HttpResponse or an HttpRequest, and I don't know how I should be specifying that. Ideas? - Stephen Brandon S. Allbery KF8NH wrote: On Jun 18, 2008, at 15:31 , Stephen Howard wrote: HttpMessage.hs:36:20: Not in scope: type constructor or class `HttpRequest' The troublesome line is the definition of the cookie function at the end of the code. I've made Right. HttpRequest is a data constructor associated with the type constructor HttpMessage. (Data constructors are effectively functions; you used it in the context of a type, not a function name.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell's type system
On 6/18/08, Edsko de Vries [EMAIL PROTECTED] wrote: Regarding type classes, I'm not 100% what the logical equivalent is, although one can regard a type such as forall a. Eq a = a - a as requiring a proof (evidence) that equality on a is decidable. Where this sits formally as a logic I'm not sure though. You can take the minimalist view and treat a typeclass parameter as an explicitly passed dictionary; that is: (Eq a = a - a) is isomorphic to (a - a - Bool, a - a - Bool) - a - a In fact, this is basically what GHC does. You then treat an instance declaration: instance Eq Int where (==) = eqInt# (/=) = neqInt# as just a constant Eq_Int = (eqInt#, neqInt#) -- ryan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] type constructor confusion
It sounds like you need to split up your types a bit more. data HttpRequest = HttpRequest ... data HttpResponse = HttpResponse ... data HttpMessage = MsgRequest HttpRequest | MsgResponse HttpResponse -- alternatively -- type HttpMessage = Either HttpRequest HttpResponse Now you can have functions that take/return just an HttpRequest or just an HttpResponse, as well as functions that use either one via HttpMessage. In the latter case, you do need to pattern match to decide which one you have. -- ryan On 6/18/08, Stephen Howard [EMAIL PROTECTED] wrote: Thanks Brandon, forgot to send my reply to the list: Ok, so I am confusing things. Good to know. So my question is how do I fulfill this scenario? - I have an action that might return either an HttpResponse or an HttpRequest, depending on if the IO in the action determined more work needed doing. It's here, though I doubt it's correct yet: requestHandler :: HttpRequest - IO HttpResponse requestHandler request = do session - sessionHandler request ret - uriHandler request case ret of HttpResponse - ret HttpRequest - resourceHandler session ret uriHandler :: HttpRequest - IO HttpMessage sessionHandler :: HttpRequest - IO HttpSession I've given the uriHandler a signature of IO HttpMessage because the HttpMessage might be either an HttpResponse or an HttpRequest, and I don't know how I should be specifying that. Ideas? - Stephen Brandon S. Allbery KF8NH wrote: On Jun 18, 2008, at 15:31 , Stephen Howard wrote: HttpMessage.hs:36:20: Not in scope: type constructor or class `HttpRequest' The troublesome line is the definition of the cookie function at the end of the code. I've made Right. HttpRequest is a data constructor associated with the type constructor HttpMessage. (Data constructors are effectively functions; you used it in the context of a type, not a function name.) ___ 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] Gtk2Hs and GCs
I don't see a way to fetch an existing standard GC from a widget. In other Gtk bindings I usually do this by fetching the widget's style and then grabbing one of the gc's (such as fg_gc[STATE_NORMAL]). In Gtk2Hs docs: http://www.haskell.org/gtk2hs/docs/gtk2hs-docs-0.9.12/Graphics-UI-Gtk-General-Style.html it looks like you can only get Colors, not the whole GC. I can't seem to find any other way short of making a whole new GC (as is done in Gtk2Hs/demos/graphic/Drawing.hs). Am I missing something? Is there a reason the GC's arent retrievable? Tim Newsham http://www.thenewsh.com/~newsham/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] message passing style like in Haskell?
Hi guys, This is my second attempt to learn Haskell :) Any way here's the code: module Dot where import Prelude hiding ( (.) ) (.) :: a - (a - b) - b a . f = f a infixl 9 . So for example, 99 questions: Problem 10 (*) Run-length encoding of a list. comparing: encode xs = map (\x - (length x,head x)) (group xs) to encode xs = xs.group.map token where token x = (x.length, x.head) I found starting with data and working my way to a solution seems to be easier to think with, or maybe it's just me ... What is your thought? Jinjing ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
