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Tutorial for literate Haskell
by Daniel Luna 03 Mar '03

03 Mar '03

I am planning to write a small project in Haskell and stumbled upon some text that mentioned literate Haskell. Is there any good tutorial on how to write literate Haskell? I know that I could take any tutorial on latex and use that, but that's not what I am after. What I want is more like a base document with header and footer done, and perhaps a couple of example files. With that as a base I could get a hint on what the correct idioms for literate Haskell are. If there is no such tutorial a few hints on how other persons write would be very welcome. (with that I mean: how to comment (what info is relevant), how much/little one should describe a function/module, and such stuff) #Luna -- Daniel Luna | Top reasons that I have a beard: luna(a)update.uu.se | a) Laziness. http://www.update.uu.se/~luna/ | b) I can. Don't look at my homepage (it stinks).| c) I can get away with it.

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int to float problem
by Mike T. Machenry 03 Mar '03

03 Mar '03

Hello, I am having a problem. I recently desided I wanted a bunch function to return float instead of Int. I changed their type and wrote a new function that returned a float. I figured it'd be okay if all the others still returned Int since it's trivial to convert Int to Float. Sadly Haskell won't let me do this. What should I do? I attempted to cast all of the values in the functions that returned Int to Float, but I found no way to do this. I found fromInteger but it didn't seem to work on the return value of the cardinality function for instance. I guess cardinality much return Int. This is one of my functions. smallestSet :: GameState -> Float smallestSet s = (-1 * cardinality (fLocations s)) This function is an error because it infer's an Int. Thanks, -mike

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GUI for Windows
by Markus.Schnell＠infineon.com 03 Mar '03

03 Mar '03

What User Interface Library would you recommend for use under Windows? I tried FranTk but it crashes as soon as I run the display function (under hugs) and with ghc it won't even compile (I already tinkered with the makefiles, so finally I could make the package, but then the demos won't compile). Any ideas, suggestions? Markus

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The Revised Haskell 98 Report
by Simon Peyton-Jones 03 Mar '03

03 Mar '03

Folks I am holding in my hands the first copy of the Haskell 98 Report to roll off the presses at Cambridge University Press. It looks great. And it has a copyright notice that says "It is intended that this Report belong to the entire Haskell community...", just as the online version does. It's in CUP's catalogue here: http://titles.cambridge.org/catalogue.asp?isbn=0521826144 Order your copy now (£35)! Not only is a physical copy useful, but CUP's agreement to the rather unique copyright terms deserves our support. Simon

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How to make Parser explicitly "fail"?
by L BB 03 Mar '03

03 Mar '03

Hi, there. I am glad to join Haskell community. :) Here I have a question about Parser: how to make a parser explicitly "fail"? My question arises from the syntax below: <statement>::=<keyword><seperator><variable> <keyword>::="define" <seperator>::=':' <variable>::=identifier other than <keyword> <identifier>::=(<letter>)+ <letter>::=a..z|A..Z Now I am thinking of writing a Parser for variable. My thought is: variable::Parser String variable = do s<-identifier if not (s=="define") then return s else --let parser fail I will be very happy if there is some mechanism to implement the "else" branch, for I have thought of it for long. :) __________________________________________________ Do you Yahoo!? Yahoo! Tax Center - forms, calculators, tips, more http://taxes.yahoo.com/

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How to catch and error message and how to make it create unix files instead of dos files??
by Alexandre Weffort Thenorio 02 Mar '03

02 Mar '03

I am trying to write a small software to take info from one file and write it into another file. The problem is that when I don't give any input I get the normal haskell nosuchfile error message but I want to give my own error message. I am a newbie, how can I do that? Also I need the file that is gonna be created (A text file), to be created in UNIX type and not as a DOS file type, how can I do that? I am using ghc to compile on Windows. Here is the main code main :: IO() main = do args <- getArgs codes <- codes args conax <- readconax "conax.txt" makeIrdFile (lines codes) (lines conax) --Read input file------------------------------------ codes :: [String] -> IO[Char] codes [] = return "" codes (x:xs) = do first <- readFile x return first --Read Inbuilt file--------------------------------- readconax file = do list <- readFile file return list

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How to force UNIX text files as output instead of DOS text files??
by Alexandre Weffort Thenorio 02 Mar '03

02 Mar '03

I am working on a small program which writes a text file but I need this file to be in UNIX format and as it is a Windows program I am compiling it, the output file tends to be in DSO format. Is there anyway that I can force it to create the file in UNIX format??? Best Regards NooK

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Re: int to float problem
by Zdenek Dvorak 01 Mar '03

01 Mar '03

Hello, [snip] >Try > >intToFloat :: Int -> Float >intToFloat n = fromInteger (toInteger n) [snip] >Use the Prelude function realToFrac. it sometimes happens to me that I must spend some time browsing prelude to devise somethink like this; it might be useful to have a library for this, that would define class Coerce a b where coerce :: a->b of course this cannot work without multiparametric type classes. Zdenek _________________________________________________________________ Help STOP SPAM with the new MSN 8 and get 2 months FREE* http://join.msn.com/?page=features/junkmail

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RE: fundeps for extended Monad definition
by oleg＠pobox.com 28 Feb '03

28 Feb '03

Hello! Simon Peyton-Jones wrote: > class C a b | a -> b where {} > instance C Int Int where {} > f1 :: (forall b. (C Int b) => Int -> b) > f1 x = undefined Indeed, this gives an error message Cannot unify the type-signature variable `b' with the type `Int' Expected type: Int Inferred type: b The reason, which is thoroughly explained in Simon Peyton-Jones' message, is that the given type signature is wrong: it should read f1 :: (exists b. (C Int b) => Int -> b) Alas, 'exists' is not an allowed type quantifier. Not explicitly that is. We can get 'exists' if we use the permitted 'forall' in a negative position (aka in an existential type). The following code > class C a b | a -> b where {} > instance C Int Int where {} > newtype M a = M (forall b.(C a b) => b) > f :: Int -> M Int > f x = M undefined typechecks in both Haskell compilers. Hal Daume's original example works as well: > newtype MM2 m a = MM2 (forall mb.(Monad2 m a mb) => mb) > class Monad2 m a ma | m a -> ma, ma -> m a where > return2 :: a -> ma > bind2 :: ma -> (a -> (MM2 m a)) -> (MM2 m a) > unused :: m a -> () > unused = \_ -> () > instance Monad2 [] a [a] where > bind2 = error "urk" Again, it typechecks both in Hugs and GHC.

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One-month alert to ICFP submission deadline
by Olin Shivers 28 Feb '03

28 Feb '03

The submission deadline for ICFP -- the International Conference on Functional Programming -- is coming up soon: Saturday, March 29, which is four weeks away. The 2003 ICFP will be in Uppsala, Sweden on August 25-29, in conjunction with PPDP (Principles and Practice of Declarative Programming). Please take a moment to read the "call for papers" I've appended below, and see if you have a topic or result you would like to submit to the program committee. Please forward this notice to any relevant internal mailing lists, as well. See you in Sweden. -Olin Shivers program chairman =============================================================================== Eighth Annual ACM SIGPLAN International Conference on Functional Programming ICFP 2003 Call for Papers (Revised 2003/2/5) Affiliated with PLI 2003 August 25-29, 2003 Uppsala, Sweden http://www-users.cs.york.ac.uk/~colin/icfp2003.html http://www.cc.gatech.edu/icfp03/cfp.html ------------------------------------------------------------------------------- * Important dates ----------------- Submission deadline 18:00 EST 29 March, 2003 (Saturday) Notification of acceptance rejection 19 May, 2003 Final paper due 16 June, 2003 Conference 25-29 August, 2003 * Scope ------- ICFP 2003 seeks original papers on the full spectrum of the art, science, and practice of functional programming. The conference invites submissions on all topics ranging from principles to practice, from foundations to features, and from abstraction to application. The scope covers all languages that encourage programming with functions, including both purely applicative and imperative languages, as well as languages that support objects and concurrency. Topics of interest include, but are not limited to, the following: Foundations formal semantics, lambda calculus, type theory, monads, continuations, control, state, effects. Design Algorithms and data structures, modules and type systems, concurrency and distribution, components and composition, relations to object-oriented and logic programming, multiparadigm programming. Implementation abstract machines, compile-time and run-time optimization, just-in-time compilers, memory management. Interfaces to foreign functions, services, components and low-level machine resources. Transformation and analysis abstract interpretation, partial evaluation, program transformation, theorem proving, specification and verification. Software development techniques for functional programming design patterns, specification, verification and validation, debugging, test generation, tracing and profiling. Applications and domain-specific languages systems programming, scientific and numerical computing, symbolic computing and artificial intelligence, systems programming, databases, graphical user interfaces, multimedia programming, application scripting, system administration, distributed-systems construction, web programming. Practice and experience functional programming in education and industry, ramifications on other paradigms and computing disciplines. Functional pearls elegant, instructive examples of functional programming. Papers in the latter three categories need not necessarily report original research results; they may instead, for example, report practical experience that will be useful to others, re-usable programming idioms, or elegant new ways of approaching a problem. The key criterion for such a paper is that it makes a contribution from which other practitioners can benefit. It is not enough simply to describe a program! * Submission guidelines ----------------------- Due date & time: Submissions must be filed at the web site by 18:00 EST on Saturday 29 March. Some convenient equivalents to 18:00 EST are New York: 6:00 PM = 18h00 San Francisco: 3:00 PM = 15h00 Chicago: 5:00 PM = 17h00 Paris: Midnight Hong Kong: 7:00 AM (30 March) UTC: 2300 For other time-zones/locations, see http://www.timeanddate.com/worldclock/fixedtime.html Submission URL: http://www.cc.gatech.edu/icfp03/submit Authors should submit a 100-200 word abstract and a full paper by 23:00 Universal Coordinated Time on Saturday, 29 March, 2003. Submissions should be no more than 12 pages (including bibliography and appendices) in standard ACM conference format: two columns, nine-point font on a ten-point baseline, with pages 20pc (3.33in) wide and 54pc (9in) tall, with a column gutter of 2pc (0.33in). Detailed formatting guidelines are available at http://www.acm.org/sigs/pubs/proceed/template.html, along with formatting templates or style files for LaTeX, Word Perfect, and Word. You don't need to include categories, keywords, etc., though you are welcome to do so. Also, note that the ACM copyright notice is not required of submissions, only of accepted papers. Authors wishing to supply additional material to the reviewers beyond the 12-page limit can do so in clearly marked appendices, on the understanding that reviewers are not required to read the appendices. Submissions that do not meet these guidelines will not be considered. The submission deadline and length above are firm. Submissions will be carried out electronically via the Web, at the URL given above. Papers must be submitted in either PDF format, or as PostScript documents that are interpretable by Ghostscript, and they must be printable on US Letter sized paper. Individuals for which this requirement is a hardship should contact the program chair at least one week before the deadline. Submitted papers must have content that has not previously been published in other conferences or refereed venues; simultaneous submission to other conferences or refereed venues is unacceptable. Each paper should explain its contributions in both general and technical terms, clearly identifying what has been accomplished, saying why it is significant, and comparing it with previous work. Authors should strive to make the technical content of their papers understandable to a broad audience. Authors of accepted papers will be required to sign the ACM copyright form. Proceedings will be published by ACM Press. * Student Attendees ------------------- Students who have a paper accepted for the conference are offered student membership of SIGPLAN free for one year. As members of SIGPLAN they may apply for travel fellowships from the PAC fund. * Conference Chair ------------------ Colin Runciman University of York, UK * Program Chair --------------- Olin Shivers College of Computing Georgia Institute of Technology Atlanta, Ga. 30332-0280, USA shivers at cc.gatech.edu Phone: +1 404 385.00.91 Fax: +1 404 383.12.53 * Program Committee ------------------- Andrzej Filinski (DIKU, University of Copenhagen) Robby Findler (University of Chicago) Fritz Henglein (IT University of Copenhagen) Hugo Herbelin (INRIA) Ralf Hinze (Universität Bonn) Annie Liu (Stony Brook University) Benjamin Pierce (University of Pennsylvania) Todd Proebsting (Microsoft Corp.) Amr Sabry (University of Indiana) Zhong Shao (Yale University) Tim Sheard (OGI School of Science and Engineering) Eijiro Sumii (University of Tokyo) Andrew Wright (Cisco, Critical Infrastructure Assurance Group) * Accessing this document ------------------------- This document can be obtained in the following formats: HTML http://www.cc.gatech.edu/icfp03/cfp.html PostScript http://www.cc.gatech.edu/icfp03/cfp.ps PDF http://www.cc.gatech.edu/icfp03/cfp.pdf Plain text http://www.cc.gatech.edu/icfp03/cfp.txt * Change log ------------ 2003/2/5 Added program committee; revised submission deadline from 3/20 to 3/29; updated student travel-fellowship information. 2003/2/5 March 29 is Saturday, not Thursday. (March 20 is a Thursday.) 2003/2/7 Added Andrew Wright to PC list. 2003/2/9 Added URLs for accessing the CFP in various formats.

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