- Haskell - Haskell.org

PEPM 2008: abstracts due Oct 12
by Oege.de.Moor＠comlab.ox.ac.uk 11 Sep '07

11 Sep '07

PEPM 2008 ACM SIGPLAN Workshop on Partial Evaluation and Program Manipulation January 7-8, 2008, San Francisco Keynotes by Ras Bodik (Berkeley) and Monica Lam (Stanford) Co-located with POPL http://www.program-transformation.org/PEPM08/WebHome PEPM is a leading venue for the presentation of cutting-edge research in program analysis, program generation and program transformation. Its proceedings are published by ACM Press; full details of the scope, submission process, and program committee can be found at the above URL. The program committee would particularly welcome submissions from researchers in functional programming on any topic relating to analysis, optimisation and synthesis of Haskell programs Abstracts are due on October 12, and the deadline for full paper submission is October 17. Prospective authors are welcome to contact the program chairs, Robert Glueck (glueck(a)acm.org) and Oege de Moor (oege(a)comlab.ox.ac.uk) with any queries they might have.

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Numeric programming on toy problems in Haskell
by Philip K.F. Hölzenspies 11 Sep '07

11 Sep '07

Dear Tomi, all, I agree with everyone on this list that there is a good reason for being picky about numeric types. However, when you're simply trying to understand a small problem or puzzle, the rather intricate numeric part of the type system can be prohibitively complex. I'm no Haskell guru, but I don't consider myself a novice anymore. Still, I tend to waste time on numeric stuff when trying to understand a simple and small problem. To avoid this, I wrote a Number module that provides a type Number that is of all of the standard numeric type classes. Especially for toy problems - I keep repeating this, because my Number module is NOT FIT for production code - it is the lazy man's solution to all the fuss about numbers. I'm lazy, me like. You can have a look at the Number module here: http://www.cs.utwente.nl/~holzensp/Number.hs Now, whenever I've hacked together a small program, it nearly always works. When it doesn't, it generally complains about some numeric value somewhere. I just stick a "toNumber" in front, et voilà! :D Regards, Philip PS. I know, people will want to kill me for putting all numbers back together in a sluggish single type, but in my defense: aren't we all a tiny bit lazy every once in a while?

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ANN: The Monad.Reader - Issue 8
by Wouter Swierstra 10 Sep '07

10 Sep '07

I am pleased to announce that the latest issue of The Monad.Reader is now available: http://www.haskell.org/haskellwiki/The_Monad.Reader Issue 8 consists of the following two articles: * Brent Yorgey Generating Multiset Partitions * Conrad Parker Type-Level Instant Insanity The Monad.Reader is a quarterly magazine about functional programming. It is less-formal than journal, but somehow more enduring than a wiki page or blog post. If you'd like to submit something to the next issue of The Monad.Reader, please get in touch. I haven't fixed the deadline for the next issue just yet; I hope to send out an official call for copy in the coming weeks. I'd also like to point out that you can now order TMR apparel from: http://www.cafepress.com/TheMonadReader. Enjoy! Wouter This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.

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ANNOUNCE: Haskell mode plugins for Vim
by Claus Reinke 10 Sep '07

10 Sep '07

recent off-list discussions have reminded me that it has been quite a while since i last announced my haskell mode plugins for vim here: http://www.cs.kent.ac.uk/~cr3/toolbox/haskell/Vim/ i know that many of you keep up to date with these - thanks everyone (but especially the gentoo haskell group:-) for the positive feedback, useful bug reports and contributions! but if you haven't had a look since the last announcement in April, you will want to update (assuming you're using vim;-), as the plugins have seen a lot of change since then. the plugins functionality is based partially on ghc(i), haddock documentation/indexes, and vim scripting, and they are now known (or can be configured) to work with a variety of unixes, windows, and browsers. the gui vim version is still recommended for popup menues and type balloons, but the plugins now also work in console vim (useful for remote editing), with console mode browsers. handling of qualified names has also improved. the plugins are now available as a single vimball archive (at the time of writing, the latest is dated 20070828), for easy installation (just open the vimball in vim and follow instructions, or see :help vimball-extract), and come with a vim help file (which the vimball archiver will automatically link into your vim's :help on extraction). alternatively, you can select individual files for download separately, and gentoo users can use the gentoo haskell overlay. here is the quick reference section from the helpfile: *haskellmode-quickref* 1.2 Quick Reference ~ |:make| load into GHCi, show errors (|quickfix| |:copen|) |_ct| create |tags| file |_si| show info for id under cursor |_t| show type for id under cursor |_T| insert type declaration for id under cursor |balloon| show type for id under mouse pointer |_?| browse Haddock entry for id under cursor |:IDoc| {identifier} browse Haddock entry for unqualified {identifier} |:MDoc| {module} browse Haddock entry for {module} |_.| qualify unqualified id under cursor |_i| add 'import <module>(<identifier>)' for id under cursor |_im| add 'import <module>' for id under cursor |_ie| make imports explit for import statement under cursor |_opt| add OPTIONS_GHC pragma |i_CTRL-X_CTRL-O| insert-mode completion based on imported ids (|haskellmode-XO|) |i_CTRL-X_CTRL-U| insert-mode completion based on documented ids (|haskellmode-XU|) |i_CTRL-N| insert-mode completion based on imported sources |:GHCi|{command/expr} run GHCi command/expr in current module |:DocSettings| show current Haddock-files-related plugin settings |:DocIndex| populate Haddock index |:ExportDocIndex| cache current Haddock index to a file |:HpasteIndex| Read index of most recent entries from hpaste.org |:HpastePostNew| Submit current buffer as a new hpaste for details, requirements, and settings, see :help haskellmode after installation, or read the helpfile online: http://www.cs.kent.ac.uk/~cr3/toolbox/haskell/Vim/vimfiles/doc/haskellmode.… the guided tour with screenshots is still at http://www.cs.kent.ac.uk/~cr3/toolbox/haskell/Vim/vim.html i only started logging changes and known issues in August: http://www.cs.kent.ac.uk/~cr3/toolbox/haskell/Vim/vimfiles/haskellmode-file… happy vimming!-) claus

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Re: Haskell development in Banking
by McBeath, Kyle 07 Sep '07

07 Sep '07

A top tier Investment bank is looking for a Haskell developer to join their quantitative analytics group. This is a permanent position in London, joining a cross asset team. You will be able to use Haskell commercially everyday, be generously compensated and be on the forefront of technology in banking. This is a great opportunity for PhD students or above with proven experience of Haskell programming. If you are interested in the position or would like further details then please send an up to date CV in word document to k.mcbeath(a)orgtel.com during the week or kylemcbeath(a)hotmail.co.uk on the weekend. Alternatively you can call me on 0207 337 2323. Kind regards, Kyle McBeath http://www.orgtel.com This email is confidential and intended solely for the addressee. If you are not the intended addressee, please notify Orgtel immediately. If received in error, you must not disclose, copy or otherwise distribute the contents of this email. If you do not want to receive further emails from us about our services, or wish to query how your personal data is held by us, please contact us via email at dataprotection(a)orgtel.co.uk You can view our privacy statement at: http://www.orgtel.com/privacy_statement.html

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Plea for separate kind annotations
by Pablo Nogueira 07 Sep '07

07 Sep '07

Just quickly, in light of some wiki tracs on Haskell prime i've read recently. I wonder if any one else is also of the opinion that kind annotations should be available and that they should be separated from type definitions in the same way as type annotations are separated from value definitions. Example: data T :: * -> * data T a = T a There are two levels of lambda calculus (values and types), with types structuring values and kinds structuring types. So why not let programmers deal with them in similar ways?

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Re: Entry route into Finance for quantitative functional programming developers
by McBeath, Kyle 06 Sep '07

06 Sep '07

Dear All, The global quantitative analytics group of a London based 1st tier investment bank is urgently searching for a strong quantitative developer, with proven experience of functional programming languages. The group is responsible for the research, development and implementation of quantitative models across all Rates asset classes. Initially, the main function of the job will be to contribute to the extension of their payout framework. The framework has been developed within the Equity Derivatives area and is based on Haskell. In the long term you will be responsible for the cross asset payout technology. This is great permanent opportunity to join a first tier investment bank and a very successful desk. You will be able to apply cutting edge functional programming language knowledge in a real world situation, with both great exposure to the business and multiple asset classes. A strong candidate will have a great quantitative education and have a experience of functional programming (Haskell, ML, CaML) as well as C++ experience. Any knowledge of financial products is a plus. If interested in the role or would like to discuss functional programming opportunities within finance, please send an up to date CV and give me a call. Regards, Kyle Kyle McBeath | Quantitative Development Consultant Orgtel Finance 5th Floor | 140 Leadenhall Street London | EC3V 4QT T: 0207 3372323 http://www.orgtel.com This email is confidential and intended solely for the addressee. If you are not the intended addressee, please notify Orgtel immediately. If received in error, you must not disclose, copy or otherwise distribute the contents of this email. If you do not want to receive further emails from us about our services, or wish to query how your personal data is held by us, please contact us via email at dataprotection(a)orgtel.co.uk You can view our privacy statement at: http://www.orgtel.com/privacy_statement.html

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(no subject)
by Tomi Owens 06 Sep '07

06 Sep '07

Hi there. I'm a teacher of Maths and am working my way through the Euler Project problems for fun. I have mostly been using Basic, but have read up about Haskell and think it looks like a sensible way to solve many of the problems. OK, so I've downloaded GHCi and am trying to teach myself. So far I have done this: ___ ___ _ / _ \ /\ /\/ __(_) / /_\// /_/ / / | | GHC Interactive, version 6.6.1, for Haskell 98. / /_\\/ __ / /___| | http://www.haskell.org/ghc/ \____/\/ /_/\____/|_| Type :? for help. Loading package base ... linking ... done. Prelude> let f (a,b) = a * floor (100000/b) Prelude> f(2,5) 40000 This function works just as I want it to. Now I try creating a list: Prelude> [(a2+b2,a)| a <- [1..4] , b<- [1..4], a2+b2<20, b<=a] [(2,1),(5,2),(8,2),(10,3),(13,3),(18,3),(17,4)] and this works So now I try to apply the function to the list: Prelude> map (f) [(a2+b2,a)| a <- [1..4] , b<- [1..4], a2+b2<20, b<=a] and I get this result: <interactive>:1:5: Ambiguous type variable `t' in the constraints: `Integral t' arising from use of `f' at <interactive>:1:5 `RealFrac t' arising from use of `f' at <interactive>:1:5 Probable fix: add a type signature that fixes these type variable(s) I'm sorry, but I don't quite get how to set the type signature and how it will apply to my function... Thanks, Tomi -------------------------------------------------------------------------------- Department for Education, Sport and Culture E Mail This message is for the named person's use only. It may contain confidential, proprietary or legally privileged information. No confidentiality or privilege is waived or lost by any mistransmission. If you receive this message in error, please immediately delete it and all copies of it from your system, destroy any hard copies of it and notify the sender. You must not, directly or indirectly, use, disclose, distribute, print, or copy any part of this message if you are not the intended recipient. The Department for Education, Sport and Culture and any of its establishments each reserve the right to monitor all e-mail communications through its networks. Any views expressed in this message are those of the individual sender, except where the message states otherwise and the sender is authorised to state them to be the views of any such entity. The Department for Education, Sport and Culture shall not be liable to the recipient or any third party for any loss or damage, however it appears, from this e-mail or its content. This includes loss or damage caused by viruses. It is the responsibility of the recipient to ensure that the opening of this message and its attachments shall not adversely affect systems or data. --------------------------------------------------------------------------------

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Re: [Haskell] (no subject)
by Brent Yorgey 05 Sep '07

05 Sep '07

On 9/5/07, Tomi Owens <t.owens(a)hautlieu.sch.je> wrote: > > Hi there. I'm a teacher of Maths and am working my way through the Euler > Project problems for fun. I have mostly been using Basic, but have read up > about Haskell and think it looks like a sensible way to solve many of the > problems. > > I see others have already answered your immediate question; however, I thought I'd throw in some general comments. Project Euler is indeed a great way to learn some Haskell, but you will certainly run into problems with the numeric types (as you already have). Haskell is very picky about numeric types (for good reason!), and until you get used to it, it can be a big pain and a source of some confusion. I highly recommend that you read about type classes, and you may also want to read something like http://haskell.org/haskellwiki/Converting_numbers. As someone else already mentioned, asking questions in the #haskell IRC channel on irc.freenode.netis also an excellent way to learn things and get past error messages and things like this which are probably simple, but you just can't figure out. Hope this helps, -Brent

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Re: [Haskell] (no subject)
by Chaddaï Fouché 05 Sep '07

05 Sep '07

2007/9/5, Tomi Owens <t.owens(a)hautlieu.sch.je>: > So now I try to apply the function to the list: > > Prelude> map (f) [(a2+b2,a)| a <- [1..4] , b<- [1..4], a2+b2<20, b<=a] > > and I get this result: > > <interactive>:1:5: > Ambiguous type variable `t' in the constraints: > `Integral t' arising from use of `f' at <interactive>:1:5 > `RealFrac t' arising from use of `f' at <interactive>:1:5 > Probable fix: add a type signature that fixes these type variable(s) > > > I'm sorry, but I don't quite get how to set the type signature and how it > will apply to my function... > It's because f need a real, not an integer as the second element of its parameter (since it use (/) in (10000/b)), and as it also needs an integer as it's first, the type checker don't know what the type of a should be (it can't be both an integer and a floating value at the same time). The easiest IMO is to keep a as an integer, but use "fromIntegral" to convert it to a real in the second part of the tuple : map f [( a^2+b^2, fromIntegral a) | a <- [1..4] , b<- [1..4], a^2+b^2<20, b<=a] You would get more help and faster from an IRC channel like %23haskell(a)irc.freenode.net though. -- Jedaï

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