March 2001 - Haskell-Cafe

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by biotechstox13＠excite.com 17 Mar '01

17 Mar '01

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Linearity Requirement for Patterns
by Samuel E. Moelius III 17 Mar '01

17 Mar '01

What is the reasoning for the requirement that patterns be linear? Am I correct to say that if non-linear patterns were allowed, it would require equality to be defined for all data types? Is this the reason, or are there others? Sam Moelius

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GHC HQ are looking for a Linux-IA64 box
by Julian Seward (Intl Vendor) 12 Mar '01

12 Mar '01

[Apologies if you get multiple copies of this msg.] Folks, Following a recent discussion about future development directions for GHC, it seems one thing we want to start thinking about is support for the IA64 architecture. Does any kind person have an IA64 box, running Linux, on which we could have an account? The extent of the work would be to make GHC's runtime-support system work again on a 64-bit platform (it used to), and possibly to build an IA64 native code generator. This work would be spread across a couple of months, I imagine. Basic requirements are: * IA64 Linux box, with development tools (gcc, perl, autoconf, gdb, etc -- all the usual Linux/Unix stuff). * As many spare processor cycles as possible. GHC building/debugging tends to CPU intensive. Also, probably at least 256MB of memory would be necessary to keep us out of trouble. * At a bare minimum, 300 MB of free disk space; 1 GB would be preferable, since it would allow more thorough testing of the system. * Decent, permanent, reliable internet connection from so that we can work remotely (obviously) and so that we can talk to our CVS server. I'd say at a bare minimum a 128 kb/sec connection. Preferably as few as possible network hops from Cambridge, UK. This work is likely to be on-and-off (not all the time) over a couple of months, I'd guess. We probably won't be ready to start on it for at least a month, so some time around the start of May would be when we'd really want to start moving on this. Availability of such a machine would be a useful contribution to the GHC development effort, so we'd be grateful if any of you could point us in the right direction. J (speaking for the GHC crew as a whole)

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zips and maps
by Eric Allen Wohlstadter 09 Mar '01

09 Mar '01

I find myself very often needing to use this function and was wondering if there was already a way to do this using zip,maps, and folds. zipMap::[a->b]->[a]->[b] zipMap [] _ = [] zipMap _ [] = [] zipMap (f:fs) (x:xs) = (f x):(zipMap fs xs) Alternatively I can get the same affect like this: fstOnSnd::(a->b,a)->b fstOnSnd (f,x) = f x zipMap::[a->b]->[a]->[b] zipMap fs xs = map fstOnSnd (zip fs xs) Both require me to invent some new function (or use a lambda) which I am trying to avoid. If it is unavoidable then can someone think of a better name then zipMap? Eric Wohlstadter UCDavis Software Engineering

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RE: zips and maps
by Conal Elliott 09 Mar '01

09 Mar '01

Note also that zipMap is the classic S combinatory if you think of lists as functions over the natural numbers, so there's something especially compelling about it. Similarly, repeat is K. From zipMap & repeat, you can easily define map, zip, zipWith, zipWith3, etc. s = zipWith ($) k = repeat mapT f xs = s (k f) xs zipWithT f as bs = s (mapT f as) bs zipT = zipWithT (,) zipWith3T f as bs cs = s (zipWithT f as bs) cs - Conal -----Original Message----- From: Mieszko Lis [mailto:elf@sandburst.com] Sent: Thursday, March 08, 2001 6:30 PM To: Eric Allen Wohlstadter Cc: haskell-cafe(a)haskell.org Subject: Re: zips and maps Eric Allen Wohlstadter wrote: > > I find myself very often needing to use this function and was wondering if > there was already a way to do this using zip,maps, and folds. Do you mind using zipWith? How about zipMap = zipWith ($) ..? -- Mieszko _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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RE: zips and maps
by Conal Elliott 08 Mar '01

08 Mar '01

How about zipMap = zipWith ($) - Conal -----Original Message----- From: Eric Allen Wohlstadter [mailto:wohlstad@cs.ucdavis.edu] Sent: Thursday, March 08, 2001 6:19 PM To: haskell-cafe(a)haskell.org Subject: zips and maps I find myself very often needing to use this function and was wondering if there was already a way to do this using zip,maps, and folds. zipMap::[a->b]->[a]->[b] zipMap [] _ = [] zipMap _ [] = [] zipMap (f:fs) (x:xs) = (f x):(zipMap fs xs) Alternatively I can get the same affect like this: fstOnSnd::(a->b,a)->b fstOnSnd (f,x) = f x zipMap::[a->b]->[a]->[b] zipMap fs xs = map fstOnSnd (zip fs xs) Both require me to invent some new function (or use a lambda) which I am trying to avoid. If it is unavoidable then can someone think of a better name then zipMap? Eric Wohlstadter UCDavis Software Engineering _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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Re: Summer School on Functional Programming?
by Johan Jeuring 08 Mar '01

08 Mar '01

>I was wondering if anyone knew if there was going to be a summer school on >functional programming this year. Also, where would I find information >about it? Thanks. I don't think a summer school on advanced functional programming will be organised this year. Maybe next year, but as far as I know nothing has been decided yet. I will try to start up something (which doesn't mean I will organise it!) soon. -- Johan Jeuring

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Summer School on Functional Programming?
by Eric Allen Wohlstadter 08 Mar '01

08 Mar '01

I was wondering if anyone knew if there was going to be a summer school on functional programming this year. Also, where would I find information about it? Thanks. Eric Wohlstadter UCDavis Software Engineering

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Literate Programming in Haskell?
by Tom Moertel 02 Mar '01

02 Mar '01

In the Haskell community is there a generally accepted best way to approach Literate Programming? The language has support for literate comments, but it seems that many common LP tools don't respect it. For example, in order to convert some .lhs code into LaTeX via the noweb LP tools, I had to write a preprocessor to convert the ">" code blocks into something that noweb would respect. (The preprocessor actually does a bit more and, in conjunection with noweb, gives pretty good results for little effort. For an example, see: http://www.ellium.com/~thor/hangman/cheating-hangman.lhs http://www.ellium.com/~thor/hangman/cheating-hangman.pdf ) Yet somehow, I don't think that my homebrew approach is optimal. Can anybody recommend a particularly elegant LP setup for Haskell programming? Or if you have an approach that works well for you, would you mind sharing it? Cheers, Tom

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RE: Literate Programming in Haskell?
by Conal Elliott 01 Mar '01

01 Mar '01

Has anyone gotten Ralf's lhs2tex to work under Windows? I compiled it up with GHC 4.08.1 and then GHC 4.08.2, on Windows 2k pro, and it appears to fail in all of its file reads. Haven't yet isolated a small bug example to report. - Conal -----Original Message----- From: Ralf Hinze [mailto:ralf@cs.uu.nl] Sent: Thursday, March 01, 2001 5:40 AM To: Patrik Jansson Cc: haskell-cafe(a)haskell.org Subject: Re: Literate Programming in Haskell? Patrik Jansson wrote: > A tool I am using is Ralf Hinze's > > http://www.informatik.uni-bonn.de/~ralf/Literate.tar.gz > > http://www.informatik.uni-bonn.de/~ralf/Guide.ps.gz > > It transforms .lhs files (with some formatting commands in LaTeX-style > comments) to LaTeX. Development based on this idea is something I would be > willing to participate in as I already have a fair amount of Haskell > code/articles (read: my PhD thesis;-) in this format. > > Maybe Ralf can say something about his views on further development of > lhs2tex (copyright etc.) by other people (us?). [Sorry for the delay.] In principle, everyone can use and/or modify the program to adjust it to her needs. However, since I use lhs2text almost daily, I am willing to maintain the program. So if you have suggestions, proposals etc please let me know. Cheers, Ralf _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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