- Haskell-Cafe - Haskell.org

Can I use Haskell for web programming
by Maurício 23 Jan '06

23 Jan '06

Hi, Can I use Haskell to do what people do with, say, PHP? More and more I have the need for that, and I've been looking into Ruby on Rails. Do you thing Haskell could be a choice? Of course, I don't need something exactly like PHP (for instance, I don't care if I can't insert code in the middle of xhtml pages. If I have to generate everything from Haskell code, I would probably like it. Also, CGI can be a choice). But I need reasonable efficiency and to be able to find someone to host my site. What solutions do you suggest me? Thanks, Maurício

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RE: [Haskell-cafe] Re: Hashtable woes
by Simon Marlow 23 Jan '06

23 Jan '06

On 23 January 2006 15:09, Chris Kuklewicz wrote: > That is good to hear. The benchmark's tests take 1,250,000 > pre-generated > strings as the keys. At the end, the string keys are 18 characters > long, drawn randomly from a set of 4 characters. So the hash > computations are a nontrivial hit. > > Using -A400m I get 39s down from 55s. That is the best > Data.HashTable time I > have seen. (Using -A10m and -A100m were a little slower). > > Using my over optimized c-code hashtable I get 12.3 seconds. The > associative arrays in OCaml and D are still faster. So you see why I > long for GHC 6.6. > > Is Jan-Willem Maessen's Hash available anywhere? I could benchmark > it. Jan-Willem's HashTable attached. It uses unsafeThaw/unsafeFreeze tricks to avoid the GC overheads, for this you need an up to date GHC due to a bug in the garbage collector: grab a STABLE snapshot (6.4.1 won't work). Or remove the unsafeThaw/unsafeFreeze to use it with 6.4.1, and be prepared to bump the heap size. In GHC 6.6 the unsafeThaw/unsafeFreeze tricks aren't required, because the GC is essentially doing it for you - we put a write barrier in the IOArray implementation. Cheers, Simon

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RE: [Haskell-cafe] GHC integers pre-allocation
by Simon Peyton-Jones 23 Jan '06

23 Jan '06

I believe that we statically allocate all ASCII chars, and Ints between -16 and +16. Have a look in ghc/rts/StgMiscClosures.cmm Simon ________________________________ From: haskell-cafe-bounces(a)haskell.org [mailto:haskell-cafe-bounces@haskell.org] On Behalf Of Monique Monteiro Sent: 22 January 2006 23:26 To: haskell-cafe(a)haskell.org Subject: [Haskell-cafe] GHC integers pre-allocation Hi all, does anyone know if GHC implements any kind of pre-allocation of integers/caracteres ? If yes, which range of values does it use? Thanks in advance, Monique Monteiro

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First steps in Haskell
by Daniel Carrera 23 Jan '06

23 Jan '06

Hello all, I'm trying to write the simplest possible Haskell program, and I'm not getting anywhere. I have installed Hugs, GHC and GHCI. I want to run the following program: fac :: Integer -> Integer fac 0 = 1 fac n | n > 0 = n * fac (n-1) This is what I see: $ hugs Hugs.Base> fac :: Integer -> Integer ERROR - Undefined variable "fac" Hugs.Base> fac 0 = 1 ERROR - Syntax error in input (unexpected `=') $ ghci Prelude> fac :: Integer -> Integer <interactive>:1:0: Not in scope: `fac' Prelude> fac 0 = 1 <interactive>:1:6: parse error on input `=' $ # Write the program to fac.hs $ ghc fac.hs fac.hs:1:0: The main function `main' is not defined in module `Main' When checking the type of the main function `main' This is a real problem for Haskell. I expect that a lot of people try Haskell and give up because they can't even write the simplest function. It's hard not to be put off by this. I love the theory behind Haskell, but the practice of it seems to be a real problem. I hope someone will show me how to make this program work. Even better, I hope someone will fix the compilers and interpreters if they need fixing, or fix the documentation if that's what needs fixing. Best, Daniel. -- /\/`) http://oooauthors.org /\/_/ http://opendocumentfellowship.org /\/_/ \/_/ I am not over-weight, I am under-tall. /

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GHC integers pre-allocation
by Monique Monteiro 22 Jan '06

22 Jan '06

Hi all, does anyone know if GHC implements any kind of pre-allocation of integers/caracteres ? If yes, which range of values does it use? Thanks in advance, Monique Monteiro

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Haskell': Kicking off the process of defining the next Haskell standard.
by Isaac Jones 21 Jan '06

21 Jan '06

let haskell' = succ haskell98 in Announcing the Haskell' ("Haskell-Prime") process. A short time ago, I asked for volunteers to help with the next Haskell standard. A brave group has spoken up, and we've organized ourselves into a committee in order to coordinate the community's work. It will be the committee's task to bring together the very best ideas and work of the broader community in an "open-source" way, and to fill in any gaps in order to make Haskell' as coherent and elegant as Haskell 98. Our task is broadly defined by our mission statement: The Haskell programming language is more-or-less divided into two "branches". The Haskell 98 standard is the "stable" branch of the language, and that has been a big success. A lot of progress has been made over the last few years in the "research" branch of the Haskell language. It is constantly advancing, and we feel that it is time for a new standard which reflects those advancements. Haskell' will be a conservative refinement of Haskell 98. It will be the work of this committee to adopt a set of language extensions and modifications and to standardize a new set of libraries. We will strive to only include tried-and-true language features, and to define them at least as rigorously as Haskell 98 was defined. This standard will reflect the realities of developing practical applications in the Haskell language. We will work closely with the rest of the Haskell community to create this standard. Your Haskell' Committee is as follows (slightly munged email addresses follow): * Manuel M T Chakravarty <chak at cse.unsw.edu.au> * John Goerzen <jgoerzen at complete.org> * Bastiaan Heeren <bastiaan at cs.uu.nl> * Isaac Jones <ijones at galois.com> * John Launchbury <john at galois.com> * Andres Loeh <loeh at iai.uni-bonn.de> * Simon Marlow <simonmar at microsoft.com> * John Meacham <john at repetae.net> * Ravi Nanavati <ravi at bluespec.com> * Henrik Nilsson <nhn at cs.nott.ac.uk> * Ross Paterson <ross at soi.city.ac.uk> * Simon Peyton-Jones <simonpj at microsoft.com> * Don Stewart <dons at cse.unsw.edu.au> * Audrey Tang <autrijus at gmail.com> * Simon J. Thompson <S.J.Thompson at kent.ac.uk> * Malcolm Wallace <Malcolm.Wallace at cs.york.ac.uk> * Stephanie Weirich <sweirich at cis.upenn.edu> The editors are Isaac Jones and John Launchbury. Feel free to contact any of us with any concerns or questions. If you don't know who to direct your questions to, email Isaac Jones ijones(a)syntaxpolice.org. Community involvement is vital to our task, and there will be a way for members of the community to make formal proposals. In the opening phases, please use these more informal resources to help us coordinate Haskell': * The haskell-prime mailing list. All technical discussion will take place here, or (if other meetings take place) be reported here. Anyone can subscribe, and any subscriber can post questions and comments, and participate in discussions. Anyone can read the list archives. http://haskell.org/mailman/listinfo/haskell-prime * A wiki / issue tracking system to document consensus and to track ongoing tasks. This system is publicly readable, but only committee writable so that we may present it as the "official" output of the committee. If you ever feel that the wiki is not accurate as to the consensus, please alert the committee! http://hackage.haskell.org/trac/haskell-prime * A darcs code repository for experiments, proposed libraries,and complex examples. darcs is a decentralized system, so anyone can use it, but patches should be sent to Isaac Jones: http://hackage.haskell.org/trac/haskell-prime/wiki/SourceCode Please join us in making Haskell' a success. your, Haskell' Committee p.s. Please feel free to forward this announcement to appropriate forums.

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Re: Type Eigenvariable
by oleg＠pobox.com 20 Jan '06

20 Jan '06

Bill Wood wrote: > is |nabla x, nabla y. phi(x,y)| logically equivalent to > |forall x, forall y. x <> y only-if phi(x,y)|? I use |P only-if Q| for > |P materially implies Q| First of all, I should remark that Miller and Tiu introduce two calculi (with names that are hardly speakable, even in TeX). One of them is the sequent calculus with globally and locally scoped eigen-variables and the _open_ world of predicates. The other, calculus of definitions, uses the _closed_ world of predicates (the authors neglect to emphasize the closedness, btw). Universal and existentials quantifiers deal with eigenvariables of the global scope; only nabla can affect the locally scoped eigen variables. Also, the only rules that can irrevocable destroy/create locally scoped variables are "False --> X" and "X --> True". Because of these properties, nabla quantification in the open world neither implies nor implied by the universal quantification (ditto for the existential). So, the answer to your question for the open world calculus is no. In the closed world, the matters are muddier and depend on the predicates in the closed world. If we manage to reduce our sequent to the form, "X --> Y" where X has no definition, then, by closed world property, we proved the sequent (regardless of how many locally-scoped variables we have there). So, we can in some cases replace quantifiers. I must acknowledge Chung-chieh Shan for helpful discussions on these matters.

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Type Eigenvariable [was: Simple IO Regions]
by oleg＠pobox.com 20 Jan '06

20 Jan '06

A good explanation is in Section `1. Eigenvariables and generic reasoning' of @inproceedings{MillerTiu, author = {Dale Miller and Alwen Fernanto Tiu}, title = {A Proof Theory for Generic Judgments: An extended abstract}, booktitle = {LICS}, year = {2003}, pages = {118-127}, url = \url{http://users.rsise.anu.edu.au/~tiu/lics03sub.pdf}, crossref = {DBLP:conf/lics/2003}, bibsource = {DBLP, http://dblp.uni-trier.de} } @proceedings{DBLP:conf/lics/2003, title = {18th IEEE Symposium on Logic in Computer Science (LICS 2003), 22-25 June 2003, Ottawa, Canada, Proceedings}, booktitle = {LICS}, publisher = {IEEE Computer Society}, year = {2003}, isbn = {0-7695-1884-2}, key = {LICS}, } The section explains in which sense eigen-variables are _variables_. The paper argues, btw, for the separation of those senses and for a new quantifier to mean uniqueness only. In short, when we write forall x. forall y. body then x may well be equal to y (in body). And so, forall x. forall y. B[x,y] ====> forall z. B[z,z] OTH, when we write |nabla x. nabla y. body| then x and y are guaranteed to be different, and so the implication above no longer holds. Alwen Tiu's web page http://users.rsise.anu.edu.au/~tiu/ lists the journal version of the paper.

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Re: [Haskell-cafe] Packed String parameters
by Scherrer, Chad 19 Jan '06

19 Jan '06

Thanks, Bulat. Taking a look at Hal's FastIO library now... Hal, it looks like your library could be helpful, especially if there is a way to construct a FastIO.Handle from stdin. Can this be done, or do I need to start with an actual file? Thanks, Chad -------------------------------------------------------- Hello Chad, Thursday, January 19, 2006, 1:09:38 AM, you wrote: SC> parameter. The input file is over 1 million lines long. Any ideas? see at the BlockIO and FastIO libraries http://cryp.to/blockio/blockio-2004-10-10.tar.gz http://www.isi.edu/~hdaume/haskell/FastIO.tar.gz -- Best regards, Bulat mailto:bulatz at HotPOP.com

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Re: [Haskell] Simple IO Regions
by mark＠ixod.org 19 Jan '06

19 Jan '06

Brandon Moore <brandonm(a)yahoo-inc.com> writes: (snip) > The term I've heard is "skolem constant", which is a freshly invented > thing distinct from everything else. (snip) There's a nice easy-going example in chapter 8 of http://www.cl.cam.ac.uk/Teaching/2000/LogicProof/notes.pdf where quantifiers are removed from first-order formulae. (this aside moved from haskell to haskell-cafe) -- Mark

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