- Haskell-Cafe - Haskell.org

Membership
by Pradeep Arora 22 Mar '02

22 Mar '02

Dear Madam/sir, I want to become a member of your newsgroup. I want to know more about Haskell. My name is 'Pradeep' and I am working with Aptech Computers. Kindly send me the details asap. rgds, Pradeep __________________________________________________ Do You Yahoo!? Yahoo! Movies - coverage of the 74th Academy Awards� http://movies.yahoo.com/

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literate haskell
by Jorge Adriano 21 Mar '02

21 Mar '02

Why is it necessary to leave a blank line between comments and code? I'm using LaTeX in my lhs files, with the code inside a verbatim environment, and I'd rather start writing my code right after the \begin{verbatim}. I'd also like to know if anyone as changed is xemacs configuration file in such a way that is easy to change from haskell to LaTeX mode from within lhs files, and compile (latex compile) them. I always have to change to latex mode, the change the syntax highlight, and even then I can't compile the from the included lhs files - it always calls view instead of compile, even if I specify the correct Master file. Thanks in advance J.A.

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Re: Haskell slicing tool?
by Richard Uhtenwoldt 20 Mar '02

20 Mar '02

Olaf Chitil writes: >Sengan.Baring-Gould(a)nsc.com wrote: >> >> > > Are there any tools to perform program slicing on Haskell? >> > > I often find myself wanting to find all "fromJusts" invoked >> > > from the current function, or all functions that use a >> > > particular member of my monad's ADT. > >> Actually I was hoping for a static tool. > >I'd be interested to learn for what purpose you want this kind of >information and also more precisely what you would like such a static >tool to do for you. I do not know Sengan but, from reading that one paragraph I will venture that he is one of those programmers who refactors his code a lot and wants the information to to facilitate refactoring. (by refactoring I mean changing interface boundaries, eg, introducing and eliminating functions.) -- Richard Uhtenwoldt

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Re: finding ....
by Pixel 20 Mar '02

20 Mar '02

Lennart Augustsson <lennart(a)augustsson.net> writes: > Thank you for making my point. All these are indeed examples of broken code. > (Not because it's Perl. :) ok, sorry for trying. I won't change my code and you won't change your mind.

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Re: finding ....
by D. Tweed 20 Mar '02

20 Mar '02

[Moved to haskell-cafe] On Tue, 19 Mar 2002, David Sankel wrote: > > *everytime* about race conditions. (of course using > > this existFile before > > creating a temporary file is wrong, but existFile > > has *many* other > > applications) > > Could someone post an example of the creation of a > temporary file where race conditions are important? IIRC one of the classic issues is --------- myscript wants to create a temporary file called /tmp/storedStuff being half-careful, checks file doesn't exist (*) miniscule delay occurs creates a new file called /tmp/storedStuff --------- creating a new file generally deletes a file of the same without causing any errors since this is often the desired semantics All this is ok until a malicious person manages to get ln -s /home/sankel/reallyImportantUnbackedupData /tmp/storedStuff in the interval denoted by (*) ___cheers,_dave_________________________________________________________ www.cs.bris.ac.uk/~tweed/|`...heat generated by its microprocessors will email:tweed@cs.bris.ac.uk|slope upward exponentially, reaching the power work tel:(0117) 954-5250 |density of a nuclear reactor before 2010'-Intel

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RE: finding ....
by Konst Sushenko 19 Mar '02

19 Mar '02

Moved to haskell café I do not have a code example, but how about a system that compiles different (and say independent) software projects in parallel, and which uses the same code to create temporary files needed for compilation? konst > -----Original Message----- > From: David Sankel [mailto:camio@yahoo.com] > Sent: Tuesday, March 19, 2002 6:38 PM > To: Pixel; Lennart Augustsson > Cc: haskell(a)haskell.org > Subject: Re: finding .... > > > --- Pixel <pixel(a)mandrakesoft.com> wrote: > > Lennart Augustsson <lennart(a)augustsson.net> writes: > > > > > > Diego Yanivello wrote: > > > > > > > > > hi, is there (in Haskell) a function like > > existFile :: FilePath -> > > > > > IO (Bool) ? Thanks! > > > > > > Using such a function is generally a bad idea > > because of race conditions. > > > > however, real world programs use those tests since > > you don't need to care > > *everytime* about race conditions. (of course using > > this existFile before > > creating a temporary file is wrong, but existFile > > has *many* other > > applications) > > Could someone post an example of the creation of a > temporary file where race conditions are important? > > Thanks, > > David J. Sankel > > __________________________________________________ > Do You Yahoo!? > Yahoo! Sports - live college hoops coverage > http://sports.yahoo.com/ > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell >

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Re: Gaussian Integers
by Ashley Yakeley 19 Mar '02

19 Mar '02

(moved to Cafe) At 2002-03-19 03:33, dominic.j.steinitz(a)britishairways.com wrote: >I've already declared Gaussian a as being of class Eq so why does it need >to be told again? No you haven't. You've declared 'Eq a => Eq (Gaussian a)' -- 'Gaussian a' is Eq if 'a' is, not 'Eq (Gaussian a)'. Try this instance Eq a => Num (Gaussian a) where ... ...and actually looking at your code, I think you want this: instance Num a => Num (Gaussian a) where ... -- Ashley Yakeley, Seattle WA

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partial application
by Cagdas Ozgenc 19 Mar '02

19 Mar '02

Greetings. Is there a reason why partial application cannot be applied in arbitrary order? Was it a technical difficulty in the design of Haskell? Or is it just following beta reduction rigorously? Thanks

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Reading and processing data file
by Ramachandran M 18 Mar '02

18 Mar '02

I'm working on an assignment at my uni that requires me to prompt the user for an input and to locate that item in a data file. For example, if the user enters a flight no. of IC009, the program should locate that particular record in the file and output the flight's origin and destination. How should I go about writing this in Haskell? Any pointers would be greatly appreciated. Thanks. _________________________________________________________________ Chat with friends online, try MSN Messenger: http://messenger.msn.com

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Partial application on any argument(s) regardless of argument order (Was: Re: partial application)
by Dimitre Novatchev 18 Mar '02

18 Mar '02

Koen Claessen koen(a)cs.chalmers.se wrote: > Cagdas Ozgenc wondered: > > | Is there a reason why partial application cannot be > | applied in arbitrary order? Was it a technical > | difficulty in the design of Haskell? Or is it just > | following beta reduction rigorously? > > Alastair David Reid answered: > > | Haskell doesn't dictate any particular evaluation > | order. If you look at the name of the Haskell report, > | it calls Haskell a "non-strict" language not a "lazy" > | language. > > Somehow I do not think that Cagdas was talking about > evaluation order at all. I think he referred to the > following: Suppose I have a function f which is defined to > have 3 arguments: Partial application on any subset of arguments regardless of their order has been implemented in the FXSL functional programming library and is described here: http://www.topxml.com/xsl/articles/df/ Cheers, Dimitre Novatchev. __________________________________________________ Do You Yahoo!? Yahoo! Sports - live college hoops coverage http://sports.yahoo.com/

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