Re[2]: [Haskell-cafe] Type system madness
Hello Andrew, Thursday, July 12, 2007, 10:15:00 PM, you wrote: While BOMs (Byte Order Mark) are pretty irrelevant to byte-oriented encodings like UTF-8, I think programs that fail on their presence can be considered buggy. Yay! Haskell's text I/O system is buggy. :-P definitely. for example, on windows it doesn't support unicode filenames nor files bigger than 4gb, so i use my own lib, a thin layer around Windows API -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Newbie question about tuples
Am Donnerstag, 12. Juli 2007 20:14 schrieb Andrew Coppin: The only thing the libraries provide, as far as I can tell, is the fact that tuples are all Functors. (In other words, you can apply some function to all the elements to get a new tuple.) I think that's about it. I doubt you can use that to define lifting functions... Actually, they aren't (Functors). (,) takes two type arguments, (,,) takes three, etc. class Functor f requires f to take one type argument. So something like instance Functor (,) where ... won't compile. Besides, what should fmap (+1) (3, 4, foo) do? (Somewhere in the libraries there is an instance Functor (,) a where fmap f (x, y) = (x, f y) but that's probably not what you expected.) HTH, Lukas ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Defaulting to Rational [was: Number overflow]
Henning Thielemann [EMAIL PROTECTED] writes: On Thu, 12 Jul 2007, Jon Fairbairn wrote: (ie limited precision, but unbounded magnitude). If we were to use BigFloat the base would need to be a power of ten to get the desired results for things like Don's example) People will be confused, that 'sin pi' won't lead to a result since the correct result is zero and it will need forever to normalize that number. Surely the first few digits can be computed? I thought sin pi was a computable numer, anyway. Note that in my representation I didn't specify what form the small part would take; I'm not sufficiently familiar with computing on proper reals to know the best choice for that, but as I undestand it, once we reach the point of showing a number to a finite precision, we /can/ compute the necessary digits. They will be confused, that the result of 'sqrt 2 ^ 2' cannot be shown in usual decimal notation, since the formatting algorithm cannot decide between starting with 2. and 1.. Again, if it's being shown to finite precision, it can look at the next digit after the last one to be shown and use that to decide what to start with. There's no reason why show should be defined to truncate rather than defined to round after the last digit, is there? In short, the Real number type will leed to all difficulties known from computable reals. All the real ones, anyway :-). -- Jón Fairbairn [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Functional dependencies *not* part of the next Haskell standard?
| I think the implementation is some 90% complete though, in GHC head. | Certainly you can write many associated types programs already -- the | missing part is finishing off associated type synonyms, iirc. ...and we have a working implementation of that too, thanks to Tom Schrijvers. It's not in the HEAD yet, but it will be in a few weeks. Simon ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Type system madness
On Thu, 2007-07-12 at 19:15 +0100, Andrew Coppin wrote: While BOMs (Byte Order Mark) are pretty irrelevant to byte-oriented encodings like UTF-8, I think programs that fail on their presence can be considered buggy. Yay! Haskell's text I/O system is buggy. :-P Works for me, but feel free to file a bug or provide a more specific report. -k ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
Jim Burton wrote: Very timely! It's sad that haskell-cafe has so much noise now. I disagree with that characterisation. I don't mean to be pedantic, but I don't think haskell-cafe has lots of noise. I think it has lots of signal! Quite different. We don't have a problem (in my perception, at least) with the quality of either posts of responses. Not a general one, anyway. The only problem is that the volume is increasing; which is a problem if that makes it hard for valuable contributors to keep contributing. As well as being nice, can't you sometimes tell people to RTFM? The problems people have with haskell are often conceptual, and the manual doesn't help them, because they don't (yet) understand the language well enough to understand the manual. I very, very rarely see a question here about 'how to use a library funciton' or similar which could, in fact, be easily looked up in a manual. People do quite often respond to posts with links to the online library documentation, which is great. Or, You've asked that before, That's certainly a fair thing to say, if it's true. I don't see that happening very often. One way of protecting the community is to protect this list from drowning in noise and being a bit rough with newbies who don't do any research at all before asking is perfectly acceptable in my view. I disagree with that on two separate levels: (a) I don't think being rough with newbies is the right response. (b) I also don't think it would achieve the goal you state. Being rough with one newbie will not, in my experience, particularly prevent the next question asked by the next newbie :) All IMHO, obviously. Jules ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] RE: Maintaining the community
Simon Peyton-Jones wrote: [...] We need at least one forum in which it's acceptable to ask anything, no matter how naive, and get polite replies. (RTFM isn't polite; but The answer is supposed to be documented here (\url); let us know if that doesn't answer your qn is fine.) I'd be sorry to lose that. I fully agree and I don't mean RTFM literally. The answer is supposed to be documented here (\url)... is a very acceptable form of it...one can be brisk without being rude and I'm always grateful when someone points me in the direction of the right manual - if it's currently beyond my ken and I need to read something else first then that's my problem. I'm not going to waste your time by expecting you to read it for me and give quick answers to deep questions. -- View this message in context: http://www.nabble.com/Maintaining-the-community-tf4071917.html#a11577502 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] Very freaky
On Thu, Jul 12, 2007 at 10:11:07PM +0100, Andrew Coppin wrote: Felipe Almeida Lessa wrote: On 7/12/07, Andrew Coppin [EMAIL PROTECTED] wrote: How come the set of all sets doesn't exist? http://www.google.com/search?q=set+of+all+sets leads to http://en.wikipedia.org/wiki/Set_of_all_sets which has the answer, I think. Ouch. Clearly, set theory is way more complicated than people make out. (I always thought a set was just a collection of objects...) If a set is just a *finite* collection of objects, then things are usually fairly straightforward. It's those pesky infinite sets that complicate things...especially the ones which aren't constructible. Phil -- http://www.kantaka.co.uk/ .oOo. public key: http://www.kantaka.co.uk/gpg.txt ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell monads for newbies (was Functional dependencies *not* part of the next Haskell standard?)
On 7/12/07, Andrew Coppin [EMAIL PROTECTED] wrote: Monads take a while to get used to, but they're not so scary after that... The problem with monads is that there is a gazillion tutorials to explain them, each with their own analogy that works well for the author but not necessarily for you. It adds to the complexity of something that is indeed, not so difficult after all. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Multiple instancing of functions with FFI
Hi Darrell, On Mon, Jul 09, 2007 at 05:48:47PM -0700, Lewis-Sandy, Darrell wrote: I am having trouble exporting multiple instances of a polymorphic function similar to the example in the Haskell 98 Foreign Function Interface 1.0 addendum (page 6). My specific code is below: Thanks for the detailed bug report! I've put it in the bug tracker here: http://hackage.haskell.org/trac/ghc/ticket/1533 milestoned to be fixed in the next release, and also added a test to the testsuite for it. foreign export stdcall addByte (+):: Int8-Int8-Int8 foreign export stdcall addInt (+):: Int16-Int16-Int16 foreign export stdcall addLong (+):: Int32-Int32-Int32 In the mean time, as a workaround, you can use addByte :: Int8-Int8-Int8 addByte = (+) addInt :: Int16-Int16-Int16 addInt = (+) addLong :: Int32-Int32-Int32 addLong = (+) foreign export stdcall addByte addByte :: Int8-Int8-Int8 foreign export stdcall addInt addInt :: Int16-Int16-Int16 foreign export stdcall addLong addLong :: Int32-Int32-Int32 Thanks Ian ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Newbie question about tuples
I'm beginning to see that my old implementation in C++ clutters my Haskell
design.
You see, in C++ I can write:
// A vector is an array of fixed-length N and elements of type T
templatetypename T, int N struct Vector
{
T Element[N];
friend T dot(const Vector a, const Vector b)
{
T result = 0;
for( int i=0; iN; ++i )
{
result += a.Element[i] * b.Element[i];
}
return result;
}
};
So basically a wrapper around a fixed-size array of any length.
Implementations of (+), (-), dot, length, normalize, etc... then work on
vectors of any size, without the overhead of storing the size, and with
compile-time checking that only vectors of the same size can be used, etc...
This also fits in nicely when creating a MatrixT,N,M class.
I don't think Haskell has something like a fixed-length array or constant
expressions that *must* be resolved at compile-time (like the N in the C++
template)? Or like Digital Mars D's static if statement (which is a
control-flow statement that *must* succeed at compile time)?
Tuples allow a different type for each element (they are more like
anonymous structs), so are not really suitable for what I want to do.
Now in C++ when implementing this (together with fixed-size matrices), you
can get a lot of overhead because the code needs to compute many
intermediate results; it has a hard time to unroll all the loops (although I
think the latest compilers are much better). Now when implementing something
like this in Haskell, I would guess that its laziness would allow to
interleave many of the math operations, reordering them to be as optimal
as possible, removing many intermediate results (like processing streams).
So you would automatically get something like the C++ Expression Templates
http://ubiety.uwaterloo.ca/~tveldhui/papers/Expression-Templates/exprtmpl.ht
ml... Well at least I hope so :)
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Lukas Mai
Sent: Friday, July 13, 2007 09:20
To: haskell-cafe@haskell.org
Subject: Re: [Haskell-cafe] Newbie question about tuples
Am Donnerstag, 12. Juli 2007 20:14 schrieb Andrew Coppin:
The only thing the libraries provide, as far as I can tell, is the fact
that tuples are all Functors. (In other words, you can apply some
function to all the elements to get a new tuple.) I think that's about
it. I doubt you can use that to define lifting functions...
Actually, they aren't (Functors). (,) takes two type arguments, (,,)
takes three, etc. class Functor f requires f to take one type argument.
So something like
instance Functor (,) where ...
won't compile. Besides, what should fmap (+1) (3, 4, foo) do?
(Somewhere in the libraries there is an
instance Functor (,) a where fmap f (x, y) = (x, f y)
but that's probably not what you expected.)
HTH, Lukas
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Re: [Haskell-cafe] Maintaining the community
As we sit here riding the Haskell wave: http://www.cse.unsw.edu.au/~dons/tmp/cafe.png with nearly 2000 (!) people reading haskell-cafe@, perhaps its time to think some more about how to build and maintain this lovely Haskell community we have. my replies to some of the issues raised in this thread: - gmane.org is great. i still read my main mailing lists via a mail reader, but i read some lists i follow less thoroughly via gmane's news interface, and people often refer to gmane's web interface if they want to refer to whole threads rather than individual messages. no need to change the haskell.org setup - you can already choose! - haskell-cafe is meant to be the general forum, that shouldn't change. but i think there is potential to spin off one or two more specialist lists (not too many, or they'll dry out, and not too specific, or they won't attract the haskell-cafe style of membership and content; we also do not want to start cross-postings to keep the synergies of a multitopic forum). the most obvious one being 'haskell-performance' for shootout entries, 'how do i improve this?', 'what is wrong here?', and 'why isn't haskell slow?' style of questions, profiling, spacetime leaks, compiler benchmarks, optimizations, transformations, representations, libs, tools, papers, etc. another possible candidate, judging from mails and blog postings, might be 'haskell-math', for numeric and algebra libs, apps, tools, classes, theory, and math-related algorithms and data structures, and general discussions. - with higher volume, the style of messages sometimes reminds me more of newsgroup postings than of a mailinglist. but there are several hard-earned lessons from newsgroup experience: - don't try to police threads, unless you're willing to go to a fully moderated forum (which is exactly what -cafe isn't). it tends to be ineffective, and often counterproductive wrt to the general feel of the forum and the number of messages - you cannot manage volume by adding messages. there are only two things you can do with a thread you don't like: do not add to it, and ignore it - there are lots of faq, and it sometimes feels as if a question has just been answered when a newcomer asks it again!-) but unless you have a faq you can point to that comes very close to providing the answer, there is nothing you can do about that. the wiki is evolving, and i hope that the search engine fixes that have ben applied to robots.txt will ultimately make its contents easier to find. but if you want to avoid answering questions again and again on the list, you need to improve the cache of answers. personally, i tend to be more willing to answer questions on the list than to fiddle with wiki markup and conventions, but there is no reason why people who are happier with wiki editing cannot extract content from list answers to the wiki, especially if its a faq answer rather than a research result. memoization, organization and generation of answers do not all have to be done by the same set of persons. once there is a useful collection of faq answers, it should be made easier to find: the default signature of -cafe mails should be augmented to include pointers to: http://www.haskell.org/haskellwiki/Category:FAQ http://www.haskell.org/haskellwiki/Category:Glossary doing so should soon lead to useful results when googling for 'haskell faq', as well. note how one of these is rather less exhaustive than one would expect, given the number of faqs.. faq should include pointers to the list of mailing lists, the lists and repos of libraries, the language spec, list of tutorials, papers, tools, and implementations, and to the guide about homework questions, among the obvious technical answers. there is also the registration message, which could point to a wiki page dedicated to mailinglist newcomers and their most likely information needs. which should be crosslinked with the faq answers. well, enough additional traffic for now..:-) claus ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Maintaining the community
On Fri, 13 Jul 2007, Dave Bayer wrote: As a newcomer I was stunned that this otherwise very sophisticated community was using an email list rather than a bulletin board. The shear torrent of email was impacting my mail program performance. This is a cultural thing, and assuming that it's a lack of sophistication on our part is a bad idea - on the contrary, some of the better reasons to avoid a web-based board are entirely about enabling sophistication. Boards need polling. Boards force a single user interface on everyone. Boards don't enable local archives. Etc etc etc. With mail, you can pick a client to suit your needs. A bulletin board has the capabibility to evolve, e.g. into multiple entry points. So does a mailing list when you own the domain it's hosted on. -- [EMAIL PROTECTED] Sometimes you gotta fight fire with fire. Most of the time you just get burnt worse though. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Maintaining the community
On Fri, 13 Jul 2007, Simon Peyton-Jones wrote: We need at least one forum in which it's acceptable to ask anything, no matter how naive, and get polite replies. (RTFM isn't polite; but The answer is supposed to be documented here (\url); let us know if that doesn't answer your qn is fine.) I'd be sorry to lose that. Agreed. That said, it might be worth developing a scary maths FAQ that's an explanation largely of why all the maths and why it may irritate a lot of people to get in a flap about it all. It seems to come up increasingly often, and... well, it's not just the community being elitist or shutting people out! -- [EMAIL PROTECTED] The task of the academic is not to scale great intellectual mountains, but to flatten them. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] AngloHaskell 2007, dates and venue confirmed
Hi, We are pleased to announce AngloHaskell 2007 http://www.haskell.org/haskellwiki/AngloHaskell Dates: 10th-11th of August (Friday-Saturday) Location: Cambridge, with talks at Microsoft Research on Friday All the details are on the wiki page, along with free registration. Everyone is invited, we will have a day of talks at MSR, then a day of other activities. There will be plenty of chance for general discussions on anything. If anyone in Cambridge is able to accommodate a few people for the Friday or Saturday night, please add your name to the wiki, and accept our thanks in advance. All that is needed is floor space. Thanks Neil and Philippa ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
claus.reinke: personally, i tend to be more willing to answer questions on the list than to fiddle with wiki markup and conventions, but there is no reason why people who are happier with wiki editing cannot extract content from list answers to the wiki, especially if its a faq answer rather than a research result. I've got a few tools that make wiki editing easier (shortcuts to open up a new wiki page for editing in vim, syntax highlighting, console access). These make wiki editing roughly as cheap as composing an email. I tried an experiment this week of just taking someone's post (Conor's idiom brackets), and putting directly on the wiki first, then letting the author know that's happened. How do people feel about allowing posts in -cafe to be placed on the wiki, without extensive prior negotiation? What copyright do -cafe@ posts have? If there was a rough consensus that this is ok, we could probably get a lot more material directly on the wiki, since I for one would act first, putting some interesting Clause Reinke posts there semi-verbatim, rather than pondering whether to write an email to the author to seek permission, or cojole them into doing it. Should we feel free to put mailing list material onto the wiki? -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Newbie question about tuples
On Friday 13 July 2007, peterv wrote:
I'm beginning to see that my old implementation in C++ clutters my Haskell
design.
You see, in C++ I can write:
// A vector is an array of fixed-length N and elements of type T
templatetypename T, int N struct Vector
{
T Element[N];
friend T dot(const Vector a, const Vector b)
{
T result = 0;
for( int i=0; iN; ++i )
{
result += a.Element[i] * b.Element[i];
}
return result;
}
};
So basically a wrapper around a fixed-size array of any length.
Implementations of (+), (-), dot, length, normalize, etc... then work on
vectors of any size, without the overhead of storing the size, and with
compile-time checking that only vectors of the same size can be used,
etc... This also fits in nicely when creating a MatrixT,N,M class.
I don't think Haskell has something like a fixed-length array or constant
expressions that *must* be resolved at compile-time (like the N in the C++
template)?
I'm surprised no one has posted anything on type-level programming yet. You
might google for that. And GHC 6.8 will have true type-level functions (with
guaranteed termination, of course) which will help. But I'm sure a good
google will turn up a clearer explanation than I can provide; I've never
needed or wanted to understand the type-level stuff.
Jonathan Cast
http://sourceforge.net/projects/fid-core
http://sourceforge.net/projects/fid-emacs
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Re: Re[12]: [Haskell-cafe] Toy compression algorithms [was: A very edgy language]
G'day. Quoting Bulat Ziganshin [EMAIL PROTECTED]: sorry, but you really misunderstand how PPM works and why it's so efficient. I understand PPM. I really do. I think what you don't understand is why LZW does as well as it does considering how simple it is. It's because it's a poor but cheap approximation to what PPM does. Part of the misunderstanding is that you're looking at what PPM does algorithmically, whereas I'm talking about what it's equivalent to mathematically. It turns out that pretty much all known text compression algorithms are equivalent in the sense that they give the same compression ration on the same text to within a (possibly large) constant factor. BZip, for example, gives a compression ratio that's almost always within 5% or so of the best PPM variants given an input text. How could that be, since they're so different? The answer is that they're actually _not_ that different, mathematically speaking. Cheers, Andrew Bromage ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Maintaining the community
Claus Reinke claus.reinke at talk21.com writes: will ultimately make its contents easier to find. but if you want to avoid answering questions again and again on the list, you need to improve the cache of answers. Bingo. On less technical forums, e.g. FlyerTalk, the do a search equivalent to RTFM is rampant and people goal-tend without actually doing a test search to find out if that search might not be coming up for some reason. Others say do a search but demonstrate an effective keyword combination and the resulting useful resource. Here, the Wiki is fantastic but extraordinarily spotty (any healthy wiki will always have much new growth, but the current gaps are surprising), and newcomers like myself can and have been contributing to it. If somehow the surge in Haskell Cafe interest could be harnessed to feed Wiki content, that would be great. Something like I noticed the Wiki entry for list comprehensions is just a stub, so I edited it to answer your question. Is the answer clear? Your beginner perspective is invaluable; how can it be improved? The only way to establish such a tradition is by example. I'll start giving it a try. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Defaulting to Rational [was: Number overflow]
On Friday 13 July 2007, Jon Fairbairn wrote:
Henning Thielemann [EMAIL PROTECTED] writes:
On Thu, 12 Jul 2007, Jon Fairbairn wrote:
(ie limited precision, but unbounded magnitude). If we were
to use BigFloat the base would need to be a power of ten to
get the desired results for things like Don's example)
People will be confused, that 'sin pi' won't lead to a result since the
correct result is zero and it will need forever to normalize that number.
Surely the first few digits can be computed?
That was my first thought, too.
We can't define
data Real = Real{
wholePart :: Integer,
fractionPart :: [Int]}
because you can't yield e.g. sin pi as an infinite list of digits, but you can
define
data Real = Real{
exponent :: Int,
mantissa :: Int - [Int]}
where mantissa rounds the number when it's called. But unless these can be
memoized fairly well, I would expect performance to be *quite* surprising to
new users. . .
I thought
sin pi was a computable numer, anyway. Note that in my
representation I didn't specify what form the small part
would take; I'm not sufficiently familiar with computing on
proper reals to know the best choice for that, but as I
undestand it, once we reach the point of showing a number to
a finite precision, we /can/ compute the necessary digits.
They will be confused, that the result of 'sqrt 2 ^ 2' cannot be shown in
usual decimal notation, since the formatting algorithm cannot decide
between starting with 2. and 1..
Again, if it's being shown to finite precision, it can look
at the next digit after the last one to be shown and use
that to decide what to start with. There's no reason why
show should be defined to truncate rather than defined to
round after the last digit, is there?
In short, the Real number type will leed to all
difficulties known from computable reals.
All the real ones, anyway :-).
Jonathan Cast
http://sourceforge.net/projects/fid-core
http://sourceforge.net/projects/fid-emacs
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Re: [Haskell-cafe] Maintaining the community
Hi I tried an experiment this week of just taking someone's post (Conor's idiom brackets), and putting directly on the wiki first, then letting the author know that's happened. How do people feel about allowing posts in -cafe to be placed on the wiki, without extensive prior negotiation? What copyright do -cafe@ posts have? If you email to a public mailing list, you clearly don't have a problem with verbatim copying, since you already know its going to appear in loads of different archives. You also don't have a problem with selected copying, because quoting is how mailing lists work. I'd just assume that all posts to haskell-cafe are for the good of mankind, and then let them be reused at will. Should we feel free to put mailing list material onto the wiki? Yes! Some people do email this list with disclaimers such as if this email was not specifically addressed to you, and you accidentally remember something from it, we reserve the right to lobotomise you at a future date - but I think usually those are company policy rather than personal choice. Thanks Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
On Fri, 13 Jul 2007, Donald Bruce Stewart wrote: How do people feel about allowing posts in -cafe to be placed on the wiki, without extensive prior negotiation? What copyright do -cafe@ posts have? Currently, snagging the whole post for non-archive purposes isn't necessarily legit. If there was a rough consensus that this is ok, we could probably get a lot more material directly on the wiki, since I for one would act first, putting some interesting Clause Reinke posts there semi-verbatim, rather than pondering whether to write an email to the author to seek permission, or cojole them into doing it. General is it okay if I put your interesting stuff up? permission works. So does linking to existing archives. -- [EMAIL PROTECTED] There is no magic bullet. There are, however, plenty of bullets that magically home in on feet when not used in exactly the right circumstances. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
* Malcolm Wallace wrote: If anything, Usenet is even worse than mailing lists for volume, especially of spam. Also, very few sites maintain their nntp servers adequately these days - e.g. comp.lang.haskell has never made it to where I work. I beg to differ. Of course, I'm an Usenet admin and involved in Usenet administration since years. Saing no Usenet is usually a sign of the famous not invented here syndrom. I'd sugest to keep the 30+ years experience with large volume distributed mass communication, instead of throwing good and infrastructure and user interfaces away. Wikis, Webformus and a lot of other Web 2.0 hypes are doomed to redo every mistake which is solved since 20+ years. MMDV. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] CGI test
On Jul 12, 2007, at 19:59 , Andrew Coppin wrote: Hugh Perkins wrote: ... Thanks for trying - but that doesn't actually work. (For starters, you need to prepend the HTTP status code to the data from the CGI script...) Actually, as it turns out, the script I want to test needs to accept POST data, and the parsing is really quite complicated, and I want it to not crash out if I type the URL wrong, and... Basically, the more I look at this, the more I realise that it really truely *is* going to be faster to just use a real web server. I thought I could just implement a tiny subset of it to get a working system, but it turns out the subset I need isn't so tiny... Sorry guys. As an earlier poster hinted, there is a version of Haskell Web Server that can run CGI programs: http://www.cs.chalmers.se/~bringert/darcs/hws-cgi/ /Björn___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HDBC-ODBC build/install problem.
On Jul 12, 2007, at 23:35 , Edward Ing wrote: Hi, I am trying to make HaskellDB work with HDBC-ODBC. I did builds of HDBC/HDBC-ODBC. But when I am building HaskellDB-HDBC-ODBC, I get the following message. -- [1 of 1] Compiling Database.HaskellDB.HDBC.ODBC ( Database/HaskellDB/HDBC/ODBC.hs, dist\build/Database/HaskellDB/HDBC/ODBC.o ) C:\Program Files\Haskell\HDBC-odbc-1.1.2.0\ghc-6.6.1/Database/HDBC/ ODBC/Connection.hi Declaration for connectODBC: Failed to load interface for `Database.HDBC.ODBC.ConnectionImpl': Use -v to see a list of the files searched for. Cannot continue after interface file error -- From this, I know the problem is the linkage between Database.HDBC.ODBC.Connection and Database.HDBC.ODBC.ConnectionImple. (Also I looked at the code to see the reference.) I did a little further investigation. I looked at the package registry area (C:\Program Files\Haskell\HDBC-odbc-1.1.2.0\ghc-6.6.1\Database\HDBC\ODBC) and notice that ConnectionImpl.hi is not there. I went back to the build directory and did find ConnectoinImpl.hi and ConnectionImpl.o. It seems like runghc Setup.hs install, did not install ConnectionImpl.hi. I looked into the file named .installed-pkg-config and I saw this: exposed-modules: Database.HDBC.ODBC hidden-modules: Database.HDBC.ODBC.Connection Database.HDBC.ODBC.Statement Database.HDBC.ODBC.Types Database.HDBC.ODBC.Utils Database.HDBC.ODBC.TypeConv import-dirs: C:\\Program Files\\Haskell\\HDBC-odbc-1.1.2.0\ \ghc-6.6.1 library-dirs: C:\\Program Files\\Haskell\\HDBC-odbc-1.1.2.0\ \ghc-6.6.1 hs-libraries: HSHDBC-odbc-1.1.2.0 extra-libraries: odbc32 -- No mention of ConnectionImple.hi. It looks like the setup up script did not install ConnectionImpl.hi. Did ConnectionImpl.o get bound into libHSHDBC-odbc-1.1.2.0.a even though ConnectionImpl.hi did not get successfully installed? Does anyone know why the install target does not install ConnectionImpl.hi and how I can get around this problem? (Where is the odbc32 to be found anyways?) Here are a few things I did try which did NOT work: 1. Copy ConnectionImpl.hi over manually. HaskellDB-HDBC-ODBC builds, but at runtime there is a link error. 2. Manually alter .installed-pkg-config to add ConnectionImpl.hi as hidden module. Please comment on why these would not work ( I will learn from this.) Help would be appreciated. Hi Edward, the right approach would be to add it to other-modules in HDBC- odbc.cabal file, where it should have been all along. This is a bug in HDBC-odbc, I recommend that you send a patch to the maintainer. Approach 1 doesn't work since that does not include the .o file in the installed .a archive. Approach 2 doesn't work for several reasons, which exactly depend on what else you did, and which .installed-pkg-config file you changed. /Björn___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Maintaining the community
| Very timely! It's sad that haskell-cafe has so much noise now. | | I disagree with that characterisation. I don't mean to be pedantic, but | I don't think haskell-cafe has lots of noise. I think it has lots of | signal! Quite different. | | We don't have a problem (in my perception, at least) with the quality of | either posts of responses. Not a general one, anyway. The only problem | is that the volume is increasing; which is a problem if that makes it | hard for valuable contributors to keep contributing FWIW I agree with Jules's response here. Yes, the traffic is increasing, but much of it is in long threads with multiple response, and email readers are good at letting you skip that if you don't want to read it. Furthermore, we have the much-lower-bandwidth '[EMAIL PROTECTED]' list, for those who want to see announcements and discussion starters, but don't want the full haskell-cafe experience. We need at least one forum in which it's acceptable to ask anything, no matter how naive, and get polite replies. (RTFM isn't polite; but The answer is supposed to be documented here (\url); let us know if that doesn't answer your qn is fine.) I'd be sorry to lose that. Simon ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
Jules Bean wrote: Jim Burton wrote: Very timely! It's sad that haskell-cafe has so much noise now. I disagree with that characterisation. I don't mean to be pedantic, but I don't think haskell-cafe has lots of noise. I think it has lots of signal! Quite different. I think you're right actually. I was exaggerating the problem due to having woken up as a bad tempered spartan. [...] One way of protecting the community is to protect this list from drowning in noise and being a bit rough with newbies who don't do any research at all before asking is perfectly acceptable in my view. I disagree with that on two separate levels: (a) I don't think being rough with newbies is the right response. (b) I also don't think it would achieve the goal you state. Being rough with one newbie will not, in my experience, particularly prevent the next question asked by the next newbie :) All IMHO, obviously. Jules You notice I said people who do no research at all? It might be unfriendly and counter to the way things happen here, but I think the most helpful response is to tell them to do some research. -- View this message in context: http://www.nabble.com/Maintaining-the-community-tf4071917.html#a11577694 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] Functional dependencies *not* part of the next Haskell standard?
| I think the implementation is some 90% complete though, in GHC head. | Certainly you can write many associated types programs already -- the | missing part is finishing off associated type synonyms, iirc. ...and we have a working implementation of that too, thanks to Tom Schrijvers. It's not in the HEAD yet, but it will be in a few weeks. so it will be a part of 6.8? great news! afaiu, ATS, rather than AT, is direct substitution for FD? Functional dependencies desugar to indexed type families, an extension of the original associated, in GHC head already. For the full story, see the wiki page. http://haskell.org/haskellwiki/GHC/Indexed_types which includes an example of porting functional dependencies to associated types http://haskell.org/haskellwiki/GHC/Indexed_types#A_associated_type_synonym_example It's really simple to replace a functional dependency with a type function. A class declaration class C a b | a - b becomes: class FD a ~ b = C a b where type FD a and an instance instance C [x] x becomes instance C [x] x where type FD [x] = x That's it: only class and instance declarations have to be modified. Now you can start to drop dependent parameters, if you want. There are a few examples in my slides as well (if you don't mind the pptx): http://www.cs.kuleuven.be/~toms/Research/talks/Tyfuns.pptx Cheers, Tom -- Tom Schrijvers Department of Computer Science K.U. Leuven Celestijnenlaan 200A B-3001 Heverlee Belgium tel: +32 16 327544 e-mail: [EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
Malcolm Wallace wrote: Yes, the sheer volume of posts is definitely becoming a problem (for me, at least). All your suggestions for keeping the community polite and helpful are good. But I wonder if there are also any useful technical tips for users like myself, who would like to be able to keep up, but feel they are gradually drowning? Non-specific, I'm afraid, but technical advice: Get a decent mailreader, and learn how to use it well. Spending two hours or so learning the keybindings/advanced features of your mail reader will pay itself back 100 times over. Some people find that news readers are better than mail readers (really this is a feature of the programs, not the protocols; but they the programs tend to have different emphases). I believe the folks at gmane have setup a working two-way mail to news gateways for the haskell lists. Most people find it good to have a threading feature. (A few people have broken email clients which break threads when they reply, fortunately not too many on this list. If you're one of them, please fix it!). Couple this with the ability to either 'really delete', or just 'hide' a thread from view if it's not interesting to you and you start to work through the volume. It's stupid, but the the single feature that helps mail reading for me most of all is simply the fact that SPACE doubles up as 'page down in this email' and 'advance to next email in thread'. You can get through messages very fast this way. I use thunderbird, FWIW. And I don't think it's a panacea, but it works for me. In the past I've used mutt with some success. The emacs-based mailreaders are very powerful, but you will need to spend some time learning the keys. There are plenty of other mail readers out there. (Mind you, some of them are truly dire). Jules ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Maintaining the community
Malcolm Wallace Malcolm.Wallace at cs.york.ac.uk writes: Yes, the sheer volume of posts is definitely becoming a problem (for me, at least). As a newcomer I was stunned that this otherwise very sophisticated community was using an email list rather than a bulletin board. The shear torrent of email was impacting my mail program performance. Then I chased somes repies leading to earlier threads, and found bulletin-board stye access to our list at http://thread.gmane.org/gmane.comp.lang.haskell.cafe/ I much prefer this access, even if I wish the window spit vertically rather than horizontally. A bulletin board has the capabibility to evolve, e.g. into multiple entry points. Are there statistics on who reads which way? Posting stats should be obvious with a little script, for anyone who still has a hoard of messagess at homne. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
Besides traffic, which is something I'm quite used to (try to read the Python mailing list), I think dons made a quite good point. On 7/12/07, Donald Bruce Stewart [EMAIL PROTECTED] wrote: That is, to help people progress from newbie, to intermediate, to expert, and thus ensure the culture is maintained (avoiding `Eternal September'). This graphic[1] sums the main issue up nicely, in my view: http://headrush.typepad.com/photos/uncategorized/buildingausercommunity.jpg I consider myself an intermediate-going-to-advanced Haskeller. I mean, I can go on with my own legs most of time, even if that means to read a couple of times some good papers on the subject, so I don't need to ask lots of questions on the list. OTOH, I also rarely feel confident to give some answer that I know. Mostly because I only *feel* that I know -- however I'm not certain of that -- and sometimes because I think that I can't give the complete answer -- so I leave it to someone else. So from now on I'll try to answer more times. But, anyway, that's a big problem. I'm not the only one on this situation. And probably there'll always be someone. Dons' tips are really nice (i.e. necessary), but I wonder if they are sufficient. Cheers, -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
On 13/07/07, Jim Burton [EMAIL PROTECTED] wrote: As well as being nice, can't you sometimes tell people to RTFM? Or, You've asked that before, or That's an FAQ, search the archive? I suppose you could, but speaking as someone who doesn't know much but tries to answer questions when he does know - I would feel put off from answering questions in that case. If the easy questions become second-class citizens, I would be less likely to answer them. I don't want to give the impression that *I* am encouraging the degeneration of the list. So I would vote for only saying read the manual/FAQ/etc after the question has been answered. (That being said, I can never find what I'm looking for on the Haskell wiki; and as mentioned in other threads Google doesn't index it. So finding the relevant answers can be tricky.) Cheers, Dougal ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] Functional dependencies *not* part of the next Haskell standard?
Hello Simon, Friday, July 13, 2007, 11:37:59 AM, you wrote: | I think the implementation is some 90% complete though, in GHC head. | Certainly you can write many associated types programs already -- the | missing part is finishing off associated type synonyms, iirc. ...and we have a working implementation of that too, thanks to Tom Schrijvers. It's not in the HEAD yet, but it will be in a few weeks. so it will be a part of 6.8? great news! afaiu, ATS, rather than AT, is direct substitution for FD? -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
Donald Bruce Stewart wrote: As we sit here riding the Haskell wave: [...] * Give tips on how to answer questions Answering politely, and in detail, explaining common misunderstandings is better than one word replies. * Adopt a near-zero-tolerance Be Nice policy when people answer questions We are very good here already, both on email and IRC. Very timely! It's sad that haskell-cafe has so much noise now. I haven't been around very long at all but it has gone downhill dramatically even in the last 6 months (I think I could put a date on it but lets not get into that). As well as being nice, can't you sometimes tell people to RTFM? Or, You've asked that before, or That's an FAQ, search the archive? One way of protecting the community is to protect this list from drowning in noise and being a bit rough with newbies who don't do any research at all before asking is perfectly acceptable in my view. It goes without saying that everything you say about the quality of the help here is true but I don't think you should treat us with kid gloves. -- View this message in context: http://www.nabble.com/Maintaining-the-community-tf4071917.html#a11576127 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] Very freaky
On Thursday 12 July 2007 22:57, Steve Downey wrote: Almost, I think. A functor is a mapping from the arrows, or morphisms, in a category to arrows in a category. Oops, yes, indeed. Good catch, thanks. :-) Alexis. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
On Fri, Jul 13, 2007 at 09:35:09AM +0100, Malcolm Wallace wrote: Yes, the sheer volume of posts is definitely becoming a problem (for me, at least). The Haskell lists are quite peculiarly named; the haskell@ list is pretty much what would be haskell-announce@ anywhere else, and haskell-cafe@ what would be haskell@ elsewhere. A haskell-cafe@ list elsewhere would probably be where the haskell@ people discuss things which aren't actually related to Haskell (like e.g. the demon.local newsgroup). I think the number of posts in the wrong place would be lower if these were more conventionally named (although there aren't a lot of them anyway). I think it would make sense to: * Rename haskell@ to haskell-announce@, and redirect mails from haskell@ to haskell-announce@ for some period. * After that, rename haskell-cafe@ to haskell@ in a similar manner. * At any point, create [EMAIL PROTECTED] This would have the advantage that people might not be so intimidated at making their first post here, and posts wouldn't be answered with category theory or scary type extensions. The disadvantages are that it makes an artificial barrier (when is someone ready to post to haskell@ instead?) and it doesn't split the discussion up by topic (if you want to see all the discussion about X, you need to follow both lists so you have the same amount of mail to read). I'm not sure if this is a good idea. * At any point, create topic-specific lists, e.g. a list for discussion type system extensions (not sure if that's a good one, as often an extension is the /answer/ to a question how do I do foo?). This needs people to work out which lists would allow us to make a significant dent to the haskell-cafe traffic. Thanks Ian, also drowning ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
* Magnus Therning wrote: One obvious solution is to split the list into several, more specialised lists. It's far from obvious, at least to me, how to do that with this list though. Switch to Usenet. The new haskell group will die, if the traffic will not increase. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
On Fri, Jul 13, 2007 at 09:35:09 +0100, Malcolm Wallace wrote: [EMAIL PROTECTED] (Donald Bruce Stewart) writes: As we sit here riding the Haskell wave: http://www.cse.unsw.edu.au/~dons/tmp/cafe.png with nearly 2000 (!) people reading haskell-cafe@, perhaps its time to think some more about how to build and maintain this lovely Haskell community we have. Yes, the sheer volume of posts is definitely becoming a problem (for me, at least). All your suggestions for keeping the community polite and helpful are good. But I wonder if there are also any useful technical tips for users like myself, who would like to be able to keep up, but feel they are gradually drowning? One obvious solution is to split the list into several, more specialised lists. It's far from obvious, at least to me, how to do that with this list though. Personally I try to read the first post in every conversation thread. If it doesn't grab be then I delete the whole thread. Not an ideal strategy, but it helps me keeping my day job ;-) /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) [EMAIL PROTECTED] Jabber: [EMAIL PROTECTED] http://therning.org/magnus pgpwDnERALoFN.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
[EMAIL PROTECTED] (Donald Bruce Stewart) writes: As we sit here riding the Haskell wave: http://www.cse.unsw.edu.au/~dons/tmp/cafe.png with nearly 2000 (!) people reading haskell-cafe@, perhaps its time to think some more about how to build and maintain this lovely Haskell community we have. Yes, the sheer volume of posts is definitely becoming a problem (for me, at least). All your suggestions for keeping the community polite and helpful are good. But I wonder if there are also any useful technical tips for users like myself, who would like to be able to keep up, but feel they are gradually drowning? Regards, Malcolm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[12]: [Haskell-cafe] Toy compression algorithms [was: A very edgy language]
Hello ajb, Friday, July 13, 2007, 12:10:54 PM, you wrote: it seems that you either misunderstood PPM or make too wide assumptions. More likely I'm not explaining myself well. in classical fixed-order ppm each char probability found in context of previous N chars. i.e. when encoding abcdef.. with order 3, 'd' encoded in context of 'abc', 'e' encoded in context of 'bcd' and so on Let's suppose that abcdef is a context in PPM, and we're starting from the start state (which usually isn't the case, of course). Then to encode it, you encode the probability of finding an a in the start state, followed by the probability of finding a b in the a state, followed by the probability of finding a c in the ab state... sorry, but you really misunderstand how PPM works and why it's so efficient. it searches probability of each symbol in context of previous N chars where N is fixed. lzw can be directly compared with ppm modification you described here, but this modification isn't ppm itself. also, because ppm encodes each symbol separately, making its probabilities flat effectively disables compression - the key why flat probabilities still work in lzw is that it encodes whole word with this flat model -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Functional dependencies *not* part of the next Haskell standard?
Simon Peyton-Jones wrote: | I think the implementation is some 90% complete though, in GHC head. | Certainly you can write many associated types programs already -- the | missing part is finishing off associated type synonyms, iirc. ...and we have a working implementation of that too, thanks to Tom Schrijvers. It's not in the HEAD yet, but it will be in a few weeks. Excellent news! Jules ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Functional dependencies *not* part of the next Haskell standard?
bulat.ziganshin: Hello Simon, Friday, July 13, 2007, 11:37:59 AM, you wrote: | I think the implementation is some 90% complete though, in GHC head. | Certainly you can write many associated types programs already -- the | missing part is finishing off associated type synonyms, iirc. ...and we have a working implementation of that too, thanks to Tom Schrijvers. It's not in the HEAD yet, but it will be in a few weeks. so it will be a part of 6.8? great news! afaiu, ATS, rather than AT, is direct substitution for FD? Functional dependencies desugar to indexed type families, an extension of the original associated, in GHC head already. For the full story, see the wiki page. http://haskell.org/haskellwiki/GHC/Indexed_types which includes an example of porting functional dependencies to associated types http://haskell.org/haskellwiki/GHC/Indexed_types#A_associated_type_synonym_example -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
Lutz Donnerhacke [EMAIL PROTECTED] wrote: Switch to Usenet. The new haskell group will die, if the traffic will not increase. If anything, Usenet is even worse than mailing lists for volume, especially of spam. Also, very few sites maintain their nntp servers adequately these days - e.g. comp.lang.haskell has never made it to where I work. Regards, Malcolm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Newbie question about tuples
with guaranteed termination, of course
Just out of curiosity (not Haskell related): I always get confused when
people speak about guaranteed termination; what about the halting problem?
In which context can one check for guaranteed termination, as the halting
problem says it's not *generally* possible?
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Jonathan Cast
Sent: Friday, July 13, 2007 16:21
To: haskell-cafe@haskell.org
Subject: Re: [Haskell-cafe] Newbie question about tuples
On Friday 13 July 2007, peterv wrote:
I'm beginning to see that my old implementation in C++ clutters my Haskell
design.
You see, in C++ I can write:
// A vector is an array of fixed-length N and elements of type T
templatetypename T, int N struct Vector
{
T Element[N];
friend T dot(const Vector a, const Vector b)
{
T result = 0;
for( int i=0; iN; ++i )
{
result += a.Element[i] * b.Element[i];
}
return result;
}
};
So basically a wrapper around a fixed-size array of any length.
Implementations of (+), (-), dot, length, normalize, etc... then work on
vectors of any size, without the overhead of storing the size, and with
compile-time checking that only vectors of the same size can be used,
etc... This also fits in nicely when creating a MatrixT,N,M class.
I don't think Haskell has something like a fixed-length array or
constant
expressions that *must* be resolved at compile-time (like the N in the C++
template)?
I'm surprised no one has posted anything on type-level programming yet. You
might google for that. And GHC 6.8 will have true type-level functions
(with
guaranteed termination, of course) which will help. But I'm sure a good
google will turn up a clearer explanation than I can provide; I've never
needed or wanted to understand the type-level stuff.
Jonathan Cast
http://sourceforge.net/projects/fid-core
http://sourceforge.net/projects/fid-emacs
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Re: [Haskell-cafe] Re: Maintaining the community
Dave Bayer wrote: Malcolm Wallace Malcolm.Wallace at cs.york.ac.uk writes: Yes, the sheer volume of posts is definitely becoming a problem (for me, at least). As a newcomer I was stunned that this otherwise very sophisticated community was using an email list rather than a bulletin board. The shear torrent of email was impacting my mail program performance. I find it incredibly surprising whenever I discover than an otherwise sophisticated community has adopted a bulletin board rather than email ;) Then I chased somes repies leading to earlier threads, and found bulletin-board stye access to our list at http://thread.gmane.org/gmane.comp.lang.haskell.cafe/ I much prefer this access, even if I wish the window spit vertically rather than horizontally. A bulletin board has the capabibility to evolve, e.g. into multiple entry points. Conversely, a bulletin board cannot be read offline, traps users into a single UI (in every case I've used, slow, ugly, and lacking in functionality) over which they have no control. Modern email programs have sophisticated sorting, filtering, scoring, processes (not just the MUA, but other programs during the delivery chain of my emails score them and sort them); and they allow me to read messages while offline, search them locally, etc etc. They have customisable key bindings, they allow me to read all of my mailing lists in one place, they are scriptable, may support plugins... all of this under full user control. Of course, having a bulletin board interface available for those who prefer it is a very nice thing. Jules ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
Hello, On Friday 13 July 2007 16:45, Ian Lynagh wrote: ... * At any point, create [EMAIL PROTECTED] This would have the advantage that people might not be so intimidated at making their first post here, and posts wouldn't be answered with category theory or scary type extensions. The disadvantages are that it makes an artificial barrier (when is someone ready to post to haskell@ instead?) Just an idea: How about haskell-first-post@ to encourage the second post to go to [EMAIL PROTECTED] Or is that too dictator-like? ... I'm not sure if this is a good idea. I'm not sure either ... ... Best regards Thorkil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Newbie question about tuples
peterv [EMAIL PROTECTED] wrote in article [EMAIL PROTECTED] in gmane.comp.lang.haskell.cafe: I don't think Haskell has something like a fixed-length array or constant expressions that *must* be resolved at compile-time (like the N in the C++ template)? Or like Digital Mars D's static if statement (which is a control-flow statement that *must* succeed at compile time)? Actually, Haskell can do it one better: you can have fixed-length arrays whose length is known only at run time. That is, you can have the compiler check that you will only be adding arrays with the same length, but find out what that length is (and pass it around non-redundantly) at run time. (You can encode the same idea, more verbosely, using generics in Java and C#.) Please see (among other work): http://ofb.net/~frederik/vectro/ http://www.cs.rutgers.edu/~ccshan/prepose/ http://www.eecs.usma.edu/webs/people/okasaki/icfp99.ps -- Edit this signature at http://www.digitas.harvard.edu/cgi-bin/ken/sig http://www.unaids.org/en/HIV_data/epi2006/ UNAIDS/WHO AIDS Epidemic Update: December 2006 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
On Friday 13 July 2007, Donald Bruce Stewart wrote: claus.reinke: personally, i tend to be more willing to answer questions on the list than to fiddle with wiki markup and conventions, but there is no reason why people who are happier with wiki editing cannot extract content from list answers to the wiki, especially if its a faq answer rather than a research result. I've got a few tools that make wiki editing easier (shortcuts to open up a new wiki page for editing in vim, syntax highlighting, console access). These make wiki editing roughly as cheap as composing an email. I tried an experiment this week of just taking someone's post (Conor's idiom brackets), and putting directly on the wiki first, then letting the author know that's happened. How do people feel about allowing posts in -cafe to be placed on the wiki, without extensive prior negotiation? Well, anything /I/ write is OK. . . What copyright do -cafe@ posts have? Legally? I'd imagine it's pretty restrictive; morally, I think we should encourage people to wave whatever rights they have (like with the wiki). If there was a rough consensus that this is ok, we could probably get a lot more material directly on the wiki, since I for one would act first, putting some interesting Clause Reinke posts there semi-verbatim, rather than pondering whether to write an email to the author to seek permission, or cojole them into doing it. Should we feel free to put mailing list material onto the wiki? We should. We may not, yet, but that should change. Jonathan Cast http://sourceforge.net/projects/fid-core http://sourceforge.net/projects/fid-emacs ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Looking for final year project - using Haskell, or another functional language
I actually meant that simply as beyond opengl bindings, but added 'better' to make reference to Hugh's suggestion. The website sure could be better though ;) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Claus Reinke Sent: Thursday, July 12, 2007 7:23 PM To: haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] Looking for final year project - using Haskell,or another functional language Building on what Hugh was getting at, beyond better opengl bindings, i'm curious: just what do you think is missing in haskell's opengl binding? just be sure to ignore http://www.haskell.org/HOpenGL/ , which should be moved to the wiki or to /dev/null. instead, look at the implementation, mailing list and and api docs (which need to be read side-by-side with the specs): http://darcs.haskell.org/packages/OpenGL http://www.haskell.org/mailman/listinfo/hopengl http://www.haskell.org/ghc/docs/latest/html/libraries/OpenGL/Graphics-Re ndering-OpenGL-GL.html the mailing list has occasional progress info like this http://www.haskell.org/pipermail/hopengl/2006-November.txt Implement the entire opengl 1.3 interface specifications in Haskell. http://www.haskell.org/ghc/docs/latest/html/libraries/OpenGL/Graphics-Re ndering-OpenGL-GL-BasicTypes.html This module corresponds to section 2.3 (GL Command Sytax) of the OpenGL 2.1 specs. claus ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe NOTICE: If received in error, please destroy and notify sender. Sender does not intend to waive confidentiality or privilege. Use of this email is prohibited when received in error. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Re: Newbie question about tuples
Super. This is really a great mailing list :) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Chung-chieh Shan Sent: Friday, July 13, 2007 16:54 To: haskell-cafe@haskell.org Subject: [Haskell-cafe] Re: Newbie question about tuples peterv [EMAIL PROTECTED] wrote in article [EMAIL PROTECTED] in gmane.comp.lang.haskell.cafe: I don't think Haskell has something like a fixed-length array or constant expressions that *must* be resolved at compile-time (like the N in the C++ template)? Or like Digital Mars D's static if statement (which is a control-flow statement that *must* succeed at compile time)? Actually, Haskell can do it one better: you can have fixed-length arrays whose length is known only at run time. That is, you can have the compiler check that you will only be adding arrays with the same length, but find out what that length is (and pass it around non-redundantly) at run time. (You can encode the same idea, more verbosely, using generics in Java and C#.) Please see (among other work): http://ofb.net/~frederik/vectro/ http://www.cs.rutgers.edu/~ccshan/prepose/ http://www.eecs.usma.edu/webs/people/okasaki/icfp99.ps -- Edit this signature at http://www.digitas.harvard.edu/cgi-bin/ken/sig http://www.unaids.org/en/HIV_data/epi2006/ UNAIDS/WHO AIDS Epidemic Update: December 2006 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.476 / Virus Database: 269.10.4/898 - Release Date: 12/07/2007 16:08 No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.476 / Virus Database: 269.10.4/898 - Release Date: 12/07/2007 16:08 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Newbie question about tuples
peterv wrote: with guaranteed termination, of course Just out of curiosity (not Haskell related): I always get confused when people speak about guaranteed termination; what about the halting problem? In which context can one check for guaranteed termination, as the halting problem says it's not *generally* possible? The simplest answer to that is 'rule out recursion'. Mind you, that rules out an awful lot of important programs. There are better answers involving restricting the kind of recursion you allow. Google for 'total programming' and also for 'epigram'. Jules ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
Hello, On Friday 13 July 2007 17:08, Neil Mitchell wrote: Hi * At any point, create [EMAIL PROTECTED] This would have the advantage that people might not be so intimidated at making their first post here, and posts wouldn't be answered with category theory or scary type extensions. The disadvantages are that it makes an artificial barrier (when is someone ready to post to haskell@ instead?) Just an idea: How about haskell-first-post@ to encourage the second post to go to [EMAIL PROTECTED] Or is that too dictator-like? Why not [EMAIL PROTECTED], for people who aren't using Haskell to do things, but are working through tutorials. The idea with haskell-first-post@ would be to make it extremely easy for people to select which list to post to. For example, with a learning list, I would be uncertain myself. Whether it would also be easy for answerers to figure out how to behave, I don't know. In any case, it is important (as others have also said) not to lose the situation that mixes new-comers with experts. A number of questions relate directly to books such as SOE, and these could be easily answered there. Thanks Neil Best regards Thorkil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
Hi * At any point, create [EMAIL PROTECTED] This would have the advantage that people might not be so intimidated at making their first post here, and posts wouldn't be answered with category theory or scary type extensions. The disadvantages are that it makes an artificial barrier (when is someone ready to post to haskell@ instead?) Just an idea: How about haskell-first-post@ to encourage the second post to go to [EMAIL PROTECTED] Or is that too dictator-like? Why not [EMAIL PROTECTED], for people who aren't using Haskell to do things, but are working through tutorials. A number of questions relate directly to books such as SOE, and these could be easily answered there. Thanks Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
On Fri, Jul 13, 2007 at 02:30:49AM -0700, Jim Burton wrote: Very timely! It's sad that haskell-cafe has so much noise now. I haven't been around very long at all but it has gone downhill dramatically even in the last 6 months just look for the date of my first post... to improve the list, might i suggest - push chatter to IRC - take this service off of email entirely. try a web forum system (you may have to slum it and use php). i don't recommend nntp, that just forces us to use gmane since very few isps provide nntp now. a web forum would allow you to segment interest sections while retaining a global search etc. if you use code like slash, you can just moderate noise makers off the page. you can set up a yahoo group in ten minutes. - just get used to noise if indeed you want haskell to grow in popularity. use digest-mode, read on gmane, or use client email filters to remove individual noise generators - please don't split the lists, people will still just email cafe anyway, and it causes tension when a moderator-type continually asks them to take the issue to haskell-* - in the worst case, get volunteer moderators to filter submissions to the list. this will reduce traffic dramatically but also remove the immediacy of direct email. a web forum would probably be easier. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
Hi Don
On 13 Jul 2007, at 14:47, Donald Bruce Stewart wrote:
I tried an experiment this week of just taking someone's post
(Conor's idiom
brackets), and putting directly on the wiki first, then letting the
author know that's happened.
Seemed entirely reasonable to me. If I have a spare moment, I might
even finally get around to registering so I can add the other thing I
usually bundle (for inserting effectful computations which don't
contribute an argument to the main function).
data Ig = Ig
instance Idiomatic i f g = Idiomatic i f (Ig - i x - g) where
idiomatic fi Ig xi = idiomatic (fi * xi)
so that iI f a Ig (putStrLn Boo!) b Ii
isdo {a' - a; putStrLn Boo!; b' - b; return (f a b)}
If I'm writing for a mailing list, I'm certainly willing (if
surprised) to be exploited in this way.
If there is any legalistic need for explicit permission, then we
should have a permanent permission system on an opt-in basis, perhaps
recorded in some suitable central and accessible place (like,
erm, ...). I'm in.
Cheers
Conor
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Re: [Haskell-cafe] Maintaining the community
On Fri, 13 Jul 2007, brad clawsie wrote: to improve the list, might i suggest - push chatter to IRC This is problematic for some kinds of techie chatter, where email makes it easier to get all the maths down. - take this service off of email entirely. try a web forum system (you may have to slum it and use php). i don't recommend nntp, that just forces us to use gmane since very few isps provide nntp now. a web forum would allow you to segment interest sections while retaining a global search etc. if you use code like slash, you can just moderate noise makers off the page. you can set up a yahoo group in ten minutes. A global search might be an idea to add to our existing archives, otherwise I'm still not convinced. -- [EMAIL PROTECTED] Society does not owe people jobs. Society owes it to itself to find people jobs. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
Perhaps an information retrieval pipedream, but what if we attempted an automated FAQ answerer? I'm sure some keywords pop-up often enough in certain chunks of first posts (heterogenous lists, existential error messages, SOE and graphics, category functor monad, etc). It could respond with the standard links to the Wiki pages and research papers. Of course we would want to keep it on a leash for a while during training and taming. If we integrate it with the list, it might even belay the list message, giving the user a chance to read its response before selecting: * not quite helpful, send to list anyway * never send me this rubbish again Or we could avoid such invasive methods all together and just auto-post a rather comprehensive answer. Just a neat thought -- and another potentially nifty and well-sought tool written in Haskell. On 7/13/07, Philippa Cowderoy [EMAIL PROTECTED] wrote: On Fri, 13 Jul 2007, brad clawsie wrote: to improve the list, might i suggest - push chatter to IRC This is problematic for some kinds of techie chatter, where email makes it easier to get all the maths down. - take this service off of email entirely. try a web forum system (you may have to slum it and use php). i don't recommend nntp, that just forces us to use gmane since very few isps provide nntp now. a web forum would allow you to segment interest sections while retaining a global search etc. if you use code like slash, you can just moderate noise makers off the page. you can set up a yahoo group in ten minutes. A global search might be an idea to add to our existing archives, otherwise I'm still not convinced. -- [EMAIL PROTECTED] Society does not owe people jobs. Society owes it to itself to find people jobs. ___ 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] Maintaining the community
FYI, Gmail *can* kill threads, the Geniuses just deemed it unworthy of a UI presence. This is news to me and related to earlier comments in this thread. HTH http://mail.google.com/support/bin/answer.py?hl=enanswer=47787 On 7/13/07, Nicolas Frisby [EMAIL PROTECTED] wrote: Perhaps an information retrieval pipedream, but what if we attempted an automated FAQ answerer? I'm sure some keywords pop-up often enough in certain chunks of first posts (heterogenous lists, existential error messages, SOE and graphics, category functor monad, etc). It could respond with the standard links to the Wiki pages and research papers. Of course we would want to keep it on a leash for a while during training and taming. If we integrate it with the list, it might even belay the list message, giving the user a chance to read its response before selecting: * not quite helpful, send to list anyway * never send me this rubbish again Or we could avoid such invasive methods all together and just auto-post a rather comprehensive answer. Just a neat thought -- and another potentially nifty and well-sought tool written in Haskell. On 7/13/07, Philippa Cowderoy [EMAIL PROTECTED] wrote: On Fri, 13 Jul 2007, brad clawsie wrote: to improve the list, might i suggest - push chatter to IRC This is problematic for some kinds of techie chatter, where email makes it easier to get all the maths down. - take this service off of email entirely. try a web forum system (you may have to slum it and use php). i don't recommend nntp, that just forces us to use gmane since very few isps provide nntp now. a web forum would allow you to segment interest sections while retaining a global search etc. if you use code like slash, you can just moderate noise makers off the page. you can set up a yahoo group in ten minutes. A global search might be an idea to add to our existing archives, otherwise I'm still not convinced. -- [EMAIL PROTECTED] Society does not owe people jobs. Society owes it to itself to find people jobs. ___ 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] HDBC-ODBC build/install problem.
This solved the particular problem as you suggested, but I ran into other problems and stuck at another one. So I have another question. When I am using DBDirect from haskelldb to connect through HDBC-odbc. I get the following error message (I got pass the compile problems) DBDirect.exe: user error (Couldn't load Database.HaskellDB.HDBC.ODBC.driver from package haskelldb-hdbc-odbc-0.10) I looked into the package directories and the *.o and *.a file is there. Also I looked into the installed.pkg-config file and found. exposed: True exposed-modules: Database.HaskellDB.HDBC.ODBC So it appears to me that Database.HaskellDB.HDBC.ODBC has been installed properly. Does the build of DBDirect have to be configured some way? I did not configure anything for DBDirect. Has it anything to do with hs-plugins? Your help would be appreciated. Edward Ing On 7/13/07, Bjorn Bringert [EMAIL PROTECTED] wrote: On Jul 12, 2007, at 23:35 , Edward Ing wrote: Hi Edward, the right approach would be to add it to other-modules in HDBC- odbc.cabal file, where it should have been all along. This is a bug in HDBC-odbc, I recommend that you send a patch to the maintainer. /Björn ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Simple newbie question - Int and Integer
Gregory Propf gregorypropf at yahoo.com writes: So what the hell is the difference between them? Int and Integer. They aren't synonyms clearly. What's going on? http://www.haskell.org/haskellwiki/Learn_Haskell_in_10_minutes is a good starting point for answering this and similar questions. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Very freaky
This is the best intro to category theory I have ever heard. I finally
understand. Thank you.
Dan Piponi wrote:
I thought I'd dive in with a comment to explain why category theory is
an important subject and why it often crops up in Haskell programming.
The key thing is this: in many branches of mathematics people draw
what are known as commutative diagrams:
http://mathworld.wolfram.com/CommutativeDiagram.html
So what do these diagrams represent? The letters at the 'vertices'
(known as objects) often represent sets and the arrows represent
functions. But in different branches of mathematics the same diagrams
appear with the objects and arrows having a quite different
interpretation. For example you could use a diagram like 1 - 2 to
mean 12. Or you could use X - Y to mean X implies Y. Or in {1,2} -
{4,5,6} the arrow might mean containment and so on. But here's a
remarkable fact: you can often take a definition in one branch of
mathematics and write it diagrammatically. You can then reinterpret
that diagram in a different branch of mathematics as different
definition. Sometimes the new definition isn't interesting, but often
it is. So now you can define things in multiple branches of
mathematics at the same time. It gets better. Statements of theorem
can also sometimes be written in purely diagrammatic language so a
theorem that holds in one branch of mathematics turns out to be an
interesting theorem in another. Sometimes the entire proof can be
written diagrammatically meaning you can solve problems in different
branches of mathematics at the same time. This whole
'multidisciplinary' subject is known as Category Theory.
To a good approximation (and there is a certain amount of choice over
which approximation you pick) Haskell also forms a category. The
objects are types and the arrows are functions. But as I've also
hinted above, objects can represent propositions and arrows can
represent implication. So that suggests theorems about logic might
carry over to theorems about Haskell. They do, as has been mentioned
in another thread. But that's a special case of a much wider
phenomenon where constructions in different parts of mathematics can
feed into Haskell.
So knowing category theory can help you to bring to bear mathematical
knowledge from other fields when writing Haskell code. A big example
of that payoff has been the notion of a monad. But there are many
more.
It also works the other way too. As you acquire a grasp of Haskell you
get insight into other parts of mathematics and computer science, even
if you don't yet know it! Haskell has certainly helped me this way.
(And I should confess that this is one of my primary motivations for
learning it.)
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[Haskell-cafe] When is extra-libraries config in .cabal
I am building and running some haskelldb/HDBC/HSQL libraries on Windows XP (using the MinGW minimals system (MSYS)) with GHC environment. I ran into runtime link problems, foreign functions would not found. eg. atoi,from C standard; recv from sockets. To solve the problem, I added dll's to the build configuration field extra-libraries, MSVCRT (c runtime), KERNEL32, WSOCK32 (sockets). This solved the problem. 1. But is there a better way to solve the problem? I am expecting that those libraries are available through the OS and do not need explicit loading. I am confuse by what does the loading of the libraries. 2. Does a UNIX/POSIX system not have this problem? Information for understanding this problem would be great. Edward Ing ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
Ian Lynagh [EMAIL PROTECTED] wrote: I think the number of posts in the wrong place would be lower if these were more conventionally named (although there aren't a lot of them anyway). There are very few inappropriate posts to the haskell@ list. I very much doubt that the list names are a problem. * At any point, create [EMAIL PROTECTED] This would pretty-much guarantee that no-one with the necessary expertise to answer questions was actually listening to them. :-( Regards, Malcolm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] [Math] Category theory research programs?
Hi Haskell, Sorry to contribute to the noise but given that we've been talking about categories lately, I was wondering if anyone had any opinions on good universities for studying category theory. I'm trying to figure out where to apply for my phd. I want to either be at a place with a strong category theory program or a strong differential geometry program. Thanks, Creighton ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Type system madness
On Fri, Jul 13, 2007 at 10:26:38AM +0200, Ketil Malde wrote: On Thu, 2007-07-12 at 19:15 +0100, Andrew Coppin wrote: While BOMs (Byte Order Mark) are pretty irrelevant to byte-oriented encodings like UTF-8, I think programs that fail on their presence can be considered buggy. Yay! Haskell's text I/O system is buggy. :-P Works for me, but feel free to file a bug or provide a more specific report. He's not trying to report a bug; he's just complaining about base's long-known lack of support for non-latin1 encodings. (IIUC) 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] Maintaining the community
Donald Bruce Stewart wrote: As we sit here riding the Haskell wave: http://www.cse.unsw.edu.au/~dons/tmp/cafe.png with nearly 2000 (!) people reading haskell-cafe@, perhaps its time to think some more about how to build and maintain this lovely Haskell community we have. Just yesterday I received an email: I posted it to Haskell-Cafe and received loads of brilliant responses. Wow, those guys are awesome. I'm definitely going to learn Haskell now. Which is *exactly* the kind of (view of the) community we want to build and encourage, so we can keep the Haskell project growing into the future. Hear, hear. I'm a Haskell newbie. I've not posted much, but my copy of The Haskell School of Expression just arrived from Amazon, and I'm stoked. I think the main thing we need to remember is to help train new experts in the community, to be fluent in the culture, ensuring that expertise and a knowledge of the culture diffuses through the new people arriving. All important. I've spent a fair amount of time in the Ruby community. I got started on Ruby around 2001, and found the community welcoming and helpful, even when I was asking what were likely many dopey questions. The general climate was sufficient to make me want to be more involved; I went and started ruby-doc.org to do my share to help the community grow, and tried to stay active on Ruby lists to help others as I had been helped. This was quite different from my experiences when learning other languages. To be fair, I don't really recall to what extent I was using Usenet and discussion groups when learning Perl, PHP, or Java, but I don't think there was the same emphasis on niceness and the promotion of an explicit community culture. I think Haskell has a reputation for being hard, of being a dense, academic, egghead language. In short, it's scary. The more people who try it who can report good responses from the community and code success stories the more people there will be who can help each batch of newcomers. Thanks, James Britt ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] Newbie question about tuples
Hello peterv, Friday, July 13, 2007, 5:03:00 PM, you wrote: think the latest compilers are much better). Now when implementing something like this in Haskell, I would guess that its laziness would allow to interleave many of the math operations, reordering them to be as optimal as possible, removing many intermediate results (like processing streams). don't forget that laziness by itself makes programs an orders of magnitude slower :) -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [Math] Category theory research programs?
are you applying to computer science programs or math programs? for category theory, you might look at where the Ken Shans of the world went to grad school. for diff geo, there are a host of great places. and I don't know exactly what you mean by diff geo. You could be into gauge theory, in which case places like Imperial College, Cambridge, Oxford, Columbia, Duke, MIT come to mind (advisors like Donaldson, Hamilton, Morgan, Bryant, dozens I'm neglecting to mention). The other standard top US schools (Harvard, Princeton, Stanford, Berkeley, Chicago, Michigan) are all pretty strong in both algebra and geometry, of course (Yau, Givental, Eliashberg, etc, are at these schools). Other places like UT Austin, Northwestern, UIUC, UCLA, and even UW (University of Washington) come to mind. In Canada, UBC. Also, you may find that your interests are closer to (say) algebraic geometry, which is intimately connected to the kind of diff geo that's done in relation to physics these days. In which case you might want to consider Chicago and Northwestern strongly, as these schools have amazing alg geo groups these days. Of course Harvard is the historical leader here (some have left, but Mumford, Mazur, Yau, Griffiths, Harris, Siu, Richard Taylor, etc), and Princeton is also incredibly strong. Pretty much any of these schools will give you a plenty strong background in category theory to understand it for haskell, I'd say (perhaps this is overstatement, but (for example) algebraic geometers tend to become quite expert at category theory). On Fri, 13 Jul 2007, Creighton Hogg wrote: Hi Haskell, Sorry to contribute to the noise but given that we've been talking about categories lately, I was wondering if anyone had any opinions on good universities for studying category theory. I'm trying to figure out where to apply for my phd. I want to either be at a place with a strong category theory program or a strong differential geometry program. Thanks, Creighton ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] When is extra-libraries config in .cabal
On Fri, 2007-07-13 at 12:05 -0400, Edward Ing wrote: I am building and running some haskelldb/HDBC/HSQL libraries on Windows XP (using the MinGW minimals system (MSYS)) with GHC environment. I ran into runtime link problems, foreign functions would not found. eg. atoi,from C standard; recv from sockets. To solve the problem, I added dll's to the build configuration field extra-libraries, MSVCRT (c runtime), KERNEL32, WSOCK32 (sockets). This solved the problem. 1. But is there a better way to solve the problem? I am expecting that those libraries are available through the OS and do not need explicit loading. I am confuse by what does the loading of the libraries. 2. Does a UNIX/POSIX system not have this problem? On unix the C compiler generally links to the standard C library without you having to ask for it explicitly. I'm not sure that if we automatically linked to msvcrt that everyone would be happy. Many people seem to think msvcrt is to be avoided in preference of 'native' win32 calls. Information for understanding this problem would be great. This is a slightly tricky problem because the names of the libraries to link to are different on different operating systems. We don't have a proper solution to this at the moment. I'm posting this to the cabal-devel list in case anyone has any good practical realistic suggestions. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Maintaining the community
Philippa Cowderoy wrote: On Fri, 13 Jul 2007, Dave Bayer wrote: As a newcomer I was stunned that this otherwise very sophisticated community was using an email list rather than a bulletin board. The shear torrent of email was impacting my mail program performance. This is a cultural thing, and assuming that it's a lack of sophistication on our part is a bad idea - on the contrary, some of the better reasons to avoid a web-based board are entirely about enabling sophistication. Boards need polling. Boards force a single user interface on everyone. Boards don't enable local archives. Etc etc etc. With mail, you can pick a client to suit your needs. Indeed, and if you prefer newsgroups, you can even get a newsgroup interface with gmane.org. Incidentally, I've generally found gmane.org to be one of best ways to manage volume -- like someone said: Usenet/NNTP has already solved many of the issues with high volume. -- Bardur Arantsson [EMAIL PROTECTED] DISCLAIMER: No humor intended as to not annoy the humor impaired. All speculative humor is purely in the mind of the insane reader and has no bearing on reality. Author cannot be held liable for any damages due to enjoyment (or lack thereof) of said humor. Offer void in Massachusetts and Utah. Only while supplies last. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Type system madness
On 2007-07-13, Stefan O'Rear [EMAIL PROTECTED] wrote: He's not trying to report a bug; he's just complaining about base's long-known lack of support for non-latin1 encodings. (IIUC) Which is a bug. Base needs to support (in an /obvious/ way) (1) direct I/O of octets (bytes), with no character interpretation set (2) I/O of text in UTF-8. In addition, it would be nice to support (3) (On Unix) use of locale to determine text encoding but users can work around this themselves, and will often need to, even if (3) is supported. (2) can also be layered atop (1), but something is wrong if you have to write your own layer to do simple text input and output. It's even worse if you can't without going to the FFI. (1) can currently be done, but it's not at all clear how to do so, or once you have figured out how to do so, why it works. (This may be a bit out of date, but seeing this brought up again, I think not.) -- Aaron Denney -- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Maintaining the community
Donald Bruce Stewart wrote: What copyright do -cafe@ posts have? I'm not a lawyer but everything you write down is automatically copyrighted in most countries assuming that it meets some low requirement of skill, originality and work. Which is likely to be the case for posts that are eligible to make it into the wiki. For mailing lists, archiving and quoting are considered fair use. Explicit permission from the author is required to put posts on the wiki since that means to license them under the Simple Permissive License. Regards, apfelmus ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Maintaining the community
On 2007-07-13, brad clawsie [EMAIL PROTECTED] wrote: - take this service off of email entirely. try a web forum system (you may have to slum it and use php). i don't recommend nntp, that just forces us to use gmane since very few isps provide nntp now. a web forum would allow you to segment interest sections while retaining a global search etc. if you use code like slash, you can just moderate noise makers off the page. you can set up a yahoo group in ten minutes. Switching to a web forum system will kill any interest I have in following this community. I suspect I'm not alone. It's usenet done /wrong/. E-mail, the gmane web interface, and the gmane nntp interface combine into a very serviceable system, where I can choose my client, and on two of those paths, my client keeps track of what I read, rather than pushing that onto an overloaded server. The one thing that I can suggest is putting a note about other ways of access on the mailing list pages, and heck, on community introduction pages. -- Aaron Denney -- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] reading existential types
On Mon, Jul 09, 2007 at 09:41:32PM +0100, Claus Reinke wrote:
hiding concrete types in existentials sometimes only defers problems
instead of solving them, but exposing class interfaces instead of types is a
useful way to mitigate that effect. it just so happens that this particular
problem, reading an existential type, slightly exceeds that pattern, as
'read' needs to know the hidden type to do its job ('read' does not
determine the type from the input form, but uses the type to determine what
form.the input should have).
a workaround is to try to read all possible types, then hide the type again
once a match is found. the main disadvantage of this method is that we need
a list of all the types that could possibly be hidden
As a follow up, mainly meant to thank you, I wanted to let you know
that I adopted this approach in a piece of software I'm writing.
It's a status bar for the XMonad Window Manager, the tiling WM written
in Haskell.[1]
Actually it is a text based status bar that can be used with any
WM, but we love XMonad particularly...;-)
More information about this status bar can be found here:
http://www.haskell.org/pipermail/xmonad/2007-July/001442.html
with link to the source code, a screen shot and eve a link to a
binary.
I obviously credited you for the help and the code![2]
One again, thank you.
All the best,
Andrea
[1] http://xmonad.org/
[2] http://gorgias.mine.nu/repos/xmobar/Runnable.hs
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RE: Re[2]: [Haskell-cafe] Newbie question about tuples
Yes but doesn't GHC have a good strictness analyzer (or how is this called?)? I haven't looked at the generated assembly code yet (if this is at all readable; but good C/C++ compilers *do* generate reasonably readable assembly code) -Original Message- From: Bulat Ziganshin [mailto:[EMAIL PROTECTED] Sent: Friday, July 13, 2007 6:43 PM To: peterv Cc: 'Lukas Mai'; haskell-cafe@haskell.org Subject: Re[2]: [Haskell-cafe] Newbie question about tuples Hello peterv, Friday, July 13, 2007, 5:03:00 PM, you wrote: think the latest compilers are much better). Now when implementing something like this in Haskell, I would guess that its laziness would allow to interleave many of the math operations, reordering them to be as optimal as possible, removing many intermediate results (like processing streams). don't forget that laziness by itself makes programs an orders of magnitude slower :) -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] Looking for final year project - using Haskell, or another functional language
Yes, for a newbie like me it was actually the reason to abandon Haskell initially; none of the examples at http://www.haskell.org/HOpenGL compiled! Another very cool albeit difficult project would be automatic retargeting of Haskell code to the graphics processor unit (GPU), or IBM Synergistic Processor Unit (SPU aka Cell processor, if you can get your hands on such a board...). I think IBM has been working on something like that for imperative languages, but it would be interesting to see how far you one can go with Haskell. If this is not yet done of course... -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Stefan O'Rear Sent: Friday, July 13, 2007 3:37 AM To: wp Cc: Haskell-Cafe@haskell.org Subject: Re: [Haskell-cafe] Looking for final year project - using Haskell, or another functional language On Fri, Jul 13, 2007 at 02:31:58AM +0100, wp wrote: just be sure to ignore http://www.haskell.org/HOpenGL/ , which should be moved to the wiki or to /dev/null. sorry for the basic question: why is hopengl so bad? HOpenGL, the library, isn't bad at all. It's the website that's absolutely horrible. Stefan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lazy Lists and IO - Redux
[Ronald Guida, 07/11/07] Suppose I have a function f that reads a lazy list, such that f only consumes as much of the list as it needs to. Laziness allows me to apply f to an infinite list without creating an infinite loop. Now I want to connect the console to f, such that the list of inputs to f comes from the console, one item at a time. How do I do this? [Stefan O'Rear] Not very nicely. Apparently, the solution gets ugly. [Stefan O'Rear] Option 1. Ignore purity [using unsafeInterleaveIO] Option 2. Ignore lists [Felipe Almeida Lessa] Option 3. Use continuations I would like to understand *why* it gets ugly, and I think I figured it out. [Ronald Guida, 07/11/07] To create a specific example, lets suppose I want to read and accumulate the contents of a list, and I want to stop when the sum reaches or exceeds a specified cutoff. I can write this as a function that reads elements from an infinite list: [Snipped: Ronald Guida's newb implementation of accumUntilCutoff] [Stefan O'Rear, 07/11/07, Improved implementation] accumUntilCutoff :: (Ord a, Num a) = a - [a] - (a, [a]) accumUntilCutoff cutoff xs = findAcceptLast ((= cutoff) . fst) (zip (scanl (+) 0 xs) (inits xs)) findAcceptLast :: (a - Bool) - [a] - a findAcceptLast pred lst = fromMaybe (last lst) (find pred lst) First, if I start with an arbitrary pure function, then I can build a dependency graph to determine what to evaluate. Since pure functions are referentially transparent, I am free to evaluate the nodes of my dependency graph in any order, provided that I respect the dependencies. On the one hand, suppose I want to read a list with IO. In order to use IO, or any monad for that matter, I have to pass a baton[1] from one operation to the next. If a create a complicated function that involves a monad, then every time I use the bind operator, I am adding an edge to my dependency graph. Since I receive a baton from the outside, and I have to return it, I end up threading that baton through my dependency graph. Now when my function is evaluated, the evaluation order, at least for monadic actions, is locked down. On the other hand, I can compare a lazy list function, such as accumUntilCutoff, to a multi-layer perceptron[2]. The input layer of this perceptron receives the contents of a lazy list. List processing functions, such as init, zipWith, and map, construct hidden layers of neurons. For example, zipWith (+) xs $ tail xs builds a hidden layer such that each neuron computes the sum of two adjacent inputs. The major contrast between a lazy list function and a multi-layer perceptron is that for some functions, such as filter, takeWhile, dropWhile, and find, I can't build the corresponding neural interconnections until runtime, since these connections depend on the actual *data* that is presented to the inputs. A complicated function, like accumUntilCutoff, is almost a multi-layer perceptron, except for the fact that parts of the dependency graph are constructed at runtime based on the input data. This makes it very hard to thread a baton through the dependency graph. So I want to make accumUntilCutoff read its input, lazily, from the console. That means: 1. I need to provide a way to hand the IO baton to accumUntilCutoff and get it back at the end. 2. The baton must be passed, sequentially, to each element of the input list, up to and including the last element that I need. Here is my key observation -- Suppose that: 1. I have two functions f and g that both process a lazy list. 2. I feed the same lazy list from the console to both functions. 3. Function f consumes part of the list, and g consumes more than f. 4. I choose to print the result of f, then interact with the user, and later, based on user input, possibly print the result of g. Then: 1. In order to print the result of f, I must pass the baton through f, so the baton will be sequenced through a prefix of my lazy list. 2. In order to determine whether to evaluate g, I must get the baton back from f and use it to interact with the user. 3. If I later need to print the result of g, then I need to pass the baton through g, and the baton must be sequenced *starting in the middle* through my lazy list of user input. As a result, I have to interleave IO operations. Example pseudo-code: 1. main :: IO 2. main = do 3. putStrLn Hello. 4. xs - getLazyListOfNumbersFromUser 5. let ys = zipWith (+) xs $ tail xs 6. print (ys !! 0)-- depends on xs !! 0 and 1 7. b - askUserBool Would you like to continue? 8. if b 9. then print (ys !! 1) -- depends on xs !! 1 and 2 10. else return () 11.putStrLn Goodbye. We *must* ask the user for the first two elements of xs because we have to print the result before asking the user a question. We *can't* ask the user for the third element of xs at this time because the user gets to decide whether we need it. As a result, we must interleave
Re: [Haskell-cafe] Maintaining the community
On Fri, Jul 13, 2007 at 12:11:58PM +1000, Donald Bruce Stewart wrote: As we sit here riding the Haskell wave: http://www.cse.unsw.edu.au/~dons/tmp/cafe.png [..] That is, to help people progress from newbie, to intermediate, to expert, and thus ensure the culture is maintained (avoiding `Eternal September'). This graphic[1] sums the main issue up nicely, in my view: http://headrush.typepad.com/photos/uncategorized/buildingausercommunity.jpg I feel somehow in the Nothing area and I feel somehow ashamed for that: I used to ask a lot when I was a newbie, but now I'm not answering very much. I ask some questions sometimes, and that's it. At first, when I was learning, I tried to help others who seemed even more novice then I was, but usually the experts used to jump in, and show, with their wonderfully conceived examples, how basically ridiculous my code was and how many better ways there are to do things. I did not want to sound clever, and, moreover, I was just trying to make my code as simple as clear as I, newbie, I would have wanted to see. Nevertheless it's not very rewarding to publicly face your ignorance at ever single message you dare to send. So you just quit. Now, I'm telling this because I believe that the expert ones are in part responsible for the gap the picture shows. But only when I'll be an expert I'll be able to prove that. In the meanwhile I'd better shut up! ;-) Just my 2 cents. all the best, andrea ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Type system madness
Donald Bruce Stewart wrote: By the way Andrew, have you noticed that you're generating 50% of the traffic on this list? Perhaps we can work a bit more on improving the signal/noise ratio. My inbox can only take so much of this... ;) o_O My God... even the Haskell mailing list is complaining I talk about Haskell too much... That's *advanced*! (Everybody in the main forum I inhabit has now taken to auto-deleting any post that mentions the word Haskell. Except for Mr C++, who seems to seek out such threads so he can tell me how superior C++ is to Haskell...) Oh well, the problem is easily fixed... *sigh* ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] problem with IO, strictness, and let
Stefan O'Rear wrote: The problem is that you're closing the file twice. When you call any function of the getContents family, you assign to that function the responsibility to close the file, no sooner than it is no longer needed. Don't call hClose yourself, Bad Things will happen. Care to elaborate on bad things? (I.e., will this just crash the program with an error, or will it do something more serious?) I must admit, I thought closing such a file was simply no-op. I can't remember why exactly, but somewhere or other I wrote some code that does this. (Basically I want to shut the file without reading all of it, so I can reopen it and start reading from the beginning again.) Is there a sane way to do this? Or am I going to have to start playing with explicit reads and writes? (Obviously I could just hang on to *all* of the input stream returned from getContents - but that could be quite large. The current way gives me low memory usage...) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Type system madness
Bulat Ziganshin wrote: Hello Andrew, Yay! Haskell's text I/O system is buggy. :-P definitely. for example, on windows it doesn't support unicode filenames nor files bigger than 4gb ...OK, that's quite worrying... so i use my own lib, a thin layer around Windows API Has a bug been reported for this? Have you (or anyone else) thought about offering up code to fix it? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Newbie question about tuples
Lukas Mai wrote: Am Donnerstag, 12. Juli 2007 20:14 schrieb Andrew Coppin: The only thing the libraries provide, as far as I can tell, is the fact that tuples are all Functors. (In other words, you can apply some function to all the elements to get a new tuple.) I think that's about it. I doubt you can use that to define lifting functions... Actually, they aren't (Functors). Oh. Kay... well that makes me look *very* intelligent. :-} (,) takes two type arguments, (,,) takes three, etc. class Functor f requires f to take one type argument. Ah. A kind error. Yes, you're right about that... oops. Besides, what should fmap (+1) (3, 4, foo) do? I was assuming it's only defined for (a,a), not for (a,b)... (Somewhere in the libraries there is an instance Functor (,) a where fmap f (x, y) = (x, f y) but that's probably not what you expected.) Indeed. Oh well... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Type system madness
Ketil Malde wrote: On Thu, 2007-07-12 at 19:15 +0100, Andrew Coppin wrote: While BOMs (Byte Order Mark) are pretty irrelevant to byte-oriented encodings like UTF-8, I think programs that fail on their presence can be considered buggy. Yay! Haskell's text I/O system is buggy. :-P Works for me, but feel free to file a bug or provide a more specific report. I was actually commenting on the other guy's remark that anything that chokes on a BOM can be considered buggy - not entirely seriously. ;-) If there is a bug to be reported, it is merely that [the GHC implementation of] Haskell appears to interpret files as containing 8-bit ASCII, rather than doing real character encodings. I have no idea whether anybody has filed a bug report / feature request for this. (Come to think of it, I have no idea how to check either...) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Maintaining the community
Dave Bayer wrote: Malcolm Wallace Malcolm.Wallace at cs.york.ac.uk writes: Yes, the sheer volume of posts is definitely becoming a problem (for me, at least). As a newcomer I was stunned that this otherwise very sophisticated community was using an email list rather than a bulletin board. The shear torrent of email was impacting my mail program performance. Seconded. (I also commented on it at the time, and was told use IRC or SMTP. Personally I'd prefer NNTP, but apparently I'm a minority here...) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] problem with IO, strictness, and let
On Fri, Jul 13, 2007 at 07:59:22PM +0100, Andrew Coppin wrote: Stefan O'Rear wrote: The problem is that you're closing the file twice. When you call any function of the getContents family, you assign to that function the responsibility to close the file, no sooner than it is no longer needed. Don't call hClose yourself, Bad Things will happen. Care to elaborate on bad things? (I.e., will this just crash the program with an error, or will it do something more serious?) I must admit, I thought closing such a file was simply no-op. If you close the file, the stream will suddenly end. I believe silent data corruption is worse than a crash :) (currently, hGetContents also truncates on I/O error, but that's much less common and syslog will tell you about it anyway) I can't remember why exactly, but somewhere or other I wrote some code that does this. (Basically I want to shut the file without reading all of it, so I can reopen it and start reading from the beginning again.) Is there a sane way to do this? Or am I going to have to start playing with explicit reads and writes? (Obviously I could just hang on to *all* of the input stream returned from getContents - but that could be quite large. The current way gives me low memory usage...) Did you actually try it? getContents is *lazy*. it doesn't read any more of the file than it has to. If it read the whole file immediately, you obviously DO need the whole file. This is also why closing a file after getContentsing it is Bad - getContents can't keep reading after you've closed the handle. 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] Type system madness
On Fri, Jul 13, 2007 at 08:05:36PM +0100, Andrew Coppin wrote: Ketil Malde wrote: On Thu, 2007-07-12 at 19:15 +0100, Andrew Coppin wrote: While BOMs (Byte Order Mark) are pretty irrelevant to byte-oriented encodings like UTF-8, I think programs that fail on their presence can be considered buggy. Yay! Haskell's text I/O system is buggy. :-P Works for me, but feel free to file a bug or provide a more specific report. I was actually commenting on the other guy's remark that anything that chokes on a BOM can be considered buggy - not entirely seriously. ;-) If there is a bug to be reported, it is merely that [the GHC implementation of] Haskell appears to interpret files as containing 8-bit ASCII, rather than doing real character encodings. I have no idea whether There is no such thing as 8-bit ASCII - base assumes files contain ISO-8859-1. anybody has filed a bug report / feature request for this. (Come to think of it, I have no idea how to check either...) http://hackage.haskell.org/trac/ghc/query 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] Re: Maintaining the community
Jules Bean wrote: I find it incredibly surprising whenever I discover than an otherwise sophisticated community has adopted a bulletin board rather than email ;) Erm... why? Conversely, a bulletin board cannot be read offline, traps users into a single UI (in every case I've used, slow, ugly, and lacking in functionality) over which they have no control. Oh... I suppose. Still, a newsreader doesn't appear to have those limitations. Modern email programs have sophisticated sorting, filtering, scoring, processes and they allow me to read messages while offline, search them locally, etc etc. They have customisable key bindings, they allow me to read all of my mailing lists in one place, they are scriptable, may support plugins... all of this under full user control. I'd just prefer not to have to wait through 100 emails a day to find the few that interest me. With a newsreader, I can simply mark ignore on the threads that don't interest me, and I'm done. (Also, either my ISP or Thunderbird itself keeps magically loosing certain emails, which is rather irritating...) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] CGI test
Bjorn Bringert wrote: On Jul 12, 2007, at 19:59 , Andrew Coppin wrote: Basically, the more I look at this, the more I realise that it really truely *is* going to be faster to just use a real web server. I thought I could just implement a tiny subset of it to get a working system, but it turns out the subset I need isn't so tiny... Sorry guys. As an earlier poster hinted, there is a version of Haskell Web Server that can run CGI programs: http://www.cs.chalmers.se/~bringert/darcs/hws-cgi/ Thanks. I'll take a look... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell monads for newbies (was Functional dependencies *not* part of the next Haskell standard?)
D.V. wrote: On 7/12/07, Andrew Coppin [EMAIL PROTECTED] wrote: Monads take a while to get used to, but they're not so scary after that... The problem with monads is that there is a gazillion tutorials to explain them, each with their own analogy that works well for the author but not necessarily for you. It adds to the complexity of something that is indeed, not so difficult after all. What was the phrase? Monads are possibly the most tutorialised concept ever...? Still, while the concept is simple, it's hard to sum up in just a few words what a monad is. (Especially given that Haskell has so many different ones - and they seem superficially to bear no resemblence to each other.) Maybe I'll give it a shot some day. ;-) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Maintaining the community
Dave Bayer wrote: Claus Reinke claus.reinke at talk21.com writes: will ultimately make its contents easier to find. but if you want to avoid answering questions again and again on the list, you need to improve the cache of answers. Bingo. Here, the Wiki is fantastic but extraordinarily spotty (any healthy wiki will always have much new growth, but the current gaps are surprising), and newcomers like myself can and have been contributing to it. Whenever I find that something isn't on the Wiki, I try to add it. (E.g., the articles on alpha/beta/eta reduction.) On the other hand, when I find something isn't there, it's usually because I'm trying to look it up because I don't understand it. ;-) To some extend, incorrect information can be worse than no information... :-( ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Maintaining the community
On Fri, Jul 13, 2007 at 08:23:41PM +0100, Andrew Coppin wrote: Dave Bayer wrote: Here, the Wiki is fantastic but extraordinarily spotty (any healthy wiki will always have much new growth, but the current gaps are surprising), and newcomers like myself can and have been contributing to it. Whenever I find that something isn't on the Wiki, I try to add it. (E.g., the articles on alpha/beta/eta reduction.) On the other hand, when I find something isn't there, it's usually because I'm trying to look it up because I don't understand it. ;-) To some extend, incorrect information can be worse than no information... :-( Conversely, it's generally easier for us to fix an incorrect page than to write a new one from scratch. 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] Maintaining the community
The following recent reply from Dave Bayer is IMHO nearly optimal for Maintaining the Community, and I applaud him for it: Dave Bayer wrote: [someone] writes: So what the hell is the difference between them? Int and Integer. They aren't synonyms clearly. What's going on? http://www.haskell.org/haskellwiki/Learn_Haskell_in_10_minutes is a good starting point for answering this and similar questions. 0) The question that was actually asked was answered, saving follow-on frustration, discouragement, and noise. The experience level of the answer matches the (inferred) experience level of the question. 1) The provocative word hell is appropriately ignored without comment, allowing leeway for occasional frustration, especially from newbies. 2) No assumption was made that the person who posed the question was being lazy, stupid, or acting in bad faith. 3) A useful link was provided to enable the questioner to answer his own question without excess frustration, and without the useless that was already answered in a previous e-mail (but who knew? I just joined the list...) was not deployed. 4) The last line pleasantly (read: effectively) encouraged optimal future interaction. The inevitably irritating phrase Next time, was wonderfully avoided. 5) Phrases like of course, wild guess, why don't you, if you just, next time, before you do ..., that provide only heat without light were not deployed in arrogance or anger. Dan Weston ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Maintaining the community
Andrew Coppin wrote: Dave Bayer wrote: Malcolm Wallace Malcolm.Wallace at cs.york.ac.uk writes: Yes, the sheer volume of posts is definitely becoming a problem (for me, at least). As a newcomer I was stunned that this otherwise very sophisticated community was using an email list rather than a bulletin board. The shear torrent of email was impacting my mail program performance. Seconded. (I also commented on it at the time, and was told use IRC or SMTP. Personally I'd prefer NNTP, but apparently I'm a minority here...) What are you on about? Use gmane.org... -- Bardur Arantsson [EMAIL PROTECTED] Nuke unborn gay whales for Jebus! Most Broadly Offensive Slogan Ever ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] problem with IO, strictness, and let
Stefan O'Rear wrote: On Fri, Jul 13, 2007 at 07:59:22PM +0100, Andrew Coppin wrote: Care to elaborate on bad things? (I.e., will this just crash the program with an error, or will it do something more serious?) I must admit, I thought closing such a file was simply no-op. If you close the file, the stream will suddenly end. I believe silent data corruption is worse than a crash :) Agreed...! o_O I can't remember why exactly, but somewhere or other I wrote some code that does this. (Basically I want to shut the file without reading all of it, so I can reopen it and start reading from the beginning again.) Is there a sane way to do this? Or am I going to have to start playing with explicit reads and writes? (Obviously I could just hang on to *all* of the input stream returned from getContents - but that could be quite large. The current way gives me low memory usage...) Did you actually try it? I am not 100% sure about this. I wrote code that had an execution path that does this, but I don't know if I ever actually *excercised* it... (The idea was to read, say, 10% of the file, and then close it and start reading from the beginning again.) How about redundantly closing the file after you've already read all of it anyway? Is that dangerous? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Lazy Lists and IO - Redux
On 7/13/07, Ronald Guida [EMAIL PROTECTED] wrote: [Ronald Guida, 07/11/07] Now I want to connect the console to f, such that the list of inputs to f comes from the console, one item at a time. How do I do this? [Stefan O'Rear] Not very nicely. Apparently, the solution gets ugly. If we have to throw in the towel for a request that is so elementary, surely it means that pure functional programming is broken. Let's not throw in the towel just yet... We just need a bunch of library functions. We hide the ugliness in the library. Rather than post an overlong mail here's some code I threw together last night building on ListT done right on the Wiki: http://hpaste.org/1657 The library itself looks ugly but scroll to the end where you see I use 'lifted' versions of foldl, foldlM, filter and takeWhile. It works with ghc, it's easy to use and the input and output are fully interleaved. The IO is almost completely decoupled from the logic. It'd be nice to put together a more complete library that does this kind of stuff. An interesting project might be to try defining a GeneralisedList type class of which [] and ListT are both instances so we don't need to distinguish between filter and filterT, say. Then we could make interleaving IO and lists fairly transparent. (And sorry if I'm duplicating what someone else said. The thread is long and I haven't read every word of all of it.) -- Dan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Type system madness
Stefan O'Rear wrote: On Fri, Jul 13, 2007 at 08:05:36PM +0100, Andrew Coppin wrote: I was actually commenting on the other guy's remark that anything that chokes on a BOM can be considered buggy - not entirely seriously. ;-) If there is a bug to be reported, it is merely that [the GHC implementation of] Haskell appears to interpret files as containing 8-bit ASCII, rather than doing real character encodings. I have no idea whether There is no such thing as 8-bit ASCII - base assumes files contain ISO-8859-1. Indeed - ASCII is actually a 7-bit standard. But all known systems use 8 bits/character, and use the extra bit in various random ways. Everybody seems to *call* this 8-bit ASCII, despite that being a rather silly name. I have no idea what ISO-8859-1 is. (But let's not start another thread about that...) anybody has filed a bug report / feature request for this. (Come to think of it, I have no idea how to check either...) http://hackage.haskell.org/trac/ghc/query Ah... OK. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Maintaining the community
Stefan O'Rear wrote: On Fri, Jul 13, 2007 at 08:23:41PM +0100, Andrew Coppin wrote: Whenever I find that something isn't on the Wiki, I try to add it. (E.g., the articles on alpha/beta/eta reduction.) On the other hand, when I find something isn't there, it's usually because I'm trying to look it up because I don't understand it. ;-) To some extend, incorrect information can be worse than no information... :-( Conversely, it's generally easier for us to fix an incorrect page than to write a new one from scratch. ...hence my usual tacktic of adding the page and putting in the comments somebody should probably check this... Sometimes it works. ;-) (It worked for the beta and eta articles - somebody quickly pointed out that I actually got the names the wrong way round! Oops... On the other hand, I updated the Existential Type article, and apparently nobody noticed that one of my examples don't actually compile due to gratuetusly invalid syntax.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] better error expression in IO function
Derek Elkins wrote: On Wed, 2007-07-11 at 17:10 -0700, Jeremy Shaw wrote: At Thu, 12 Jul 2007 09:18:14 +1000, Thomas Conway wrote: On 7/12/07, Andrew Coppin [EMAIL PROTECTED] wrote: It's fairly common to use the Either type for this. By convention, Right means correct, and by elimination Left means an error... Presumably, this is because the world is dominated by dull, conventional, right handed people. :-) Personally, I blame it on the Romans. Personally, I blame it on biology. I blame it on partial application at the type level. instance Monad (Either x) and instance MonadError (Either x) determine that x has no hope of being the normal return type and is stuck as the exception type. But I guess you can still blame the Romans for writing everything from left to right, writing Either x y rather than y x rehtiE, thus designating the first argument x as Left. Actually, it predates the Romans too: they learned that from the Greeks, and the Greeks got that from God-knows-who. (Actually, God knows, just that I don't know.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Type system madness
Bryan O'Sullivan wrote: Andrew Coppin wrote: Oh well, the problem is easily fixed... *sigh* I doubt that anybody minds having you talk about Haskell. You've been responsible for spawning a lot of interesting threads. [And that one about compression that's still going on somewhere... lol!] All I would suggest is that you take your cue from the other people who post to the list, and try a few tactics before you post: - If you have a chatty one-line comment, do 2,000 other people need to see it? Mmm. This is why I prefer NNTP. (If a thread becomes tangent, everybody just marks it ignore and they don't have to waste time downloading it or reading it.) But yeah, point taken... - If you have a question to ask, try to spend 2 minutes with Google or the Haskell wiki to find the anwer. I continue to be surprised at the things that don't seem to be on the Wiki... Google is typically no help at all with anything Haskell-related, because Haskell is so completely obscure. The various haddoc documentation is also frustratingly sparse in places. (E.g., Control.Concurrent.STM.TVar contains *nothing* but terse type signatures. And concurrent programming is already a tricky thing to get right.) Some things seem to be well known yet not actually written down anywhere - e.g., the finer points of using seq to make stuff go faster. But sure, I do like to try to puzzle a thing out first before posting here. (If something else, I kind of enjoy a challenge...) - Join us on #haskell on IRC. It's extremely chatty, and you'll be welcome. Not in my experience, no. (Maybe I ask the wrong way... but almost everybody seems to simply ignore me. Actually, usually when I go there absolutely nobody is speaking at all. What time zone do these people live in?) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Maintaining the community
brad clawsie wrote: to improve the list, might i suggest - push chatter to IRC - take this service off of email entirely. try a web forum system (you may have to slum it and use php). i don't recommend nntp, that just forces us to use gmane since very few isps provide nntp now. Just curiose, but... what does NNTP have to do with your ISP? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
