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FW: Literate scripts not handled correctly
by Simon Peyton-Jones 24 Sep '01

24 Sep '01

Folks, Back to the H98 grindstone: > > Then I think hugs and nhc98 are wrong. The report states that the > > unliterate version of the file is recovered by "taking only > those lines > > beginning with '>', and removing the first character of > those lines", > > which would leave the lines indented by a single space, not two. > > This would appear to be an un-remarked change to the Report since > version 1.2. That version states that "program lines have the leading > '>' replaced by a leading space, to preserve tab alignments". Version > 1.3 removed this specification, and the changed specification only > appeared in Haskell'98. This does indeed seem peculiar. I propose to revert to the Haskell 1.2 story, in which '>' is replaced by ' ' (not simply deleted) Not a big issue. Any objections? Simon

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RE: Prelude and (:) and []((:), []) bugs?
by Simon Peyton-Jones 24 Sep '01

24 Sep '01

The Report quite deliberately does not allow you to write the type constructors for built-in syntax in import or export lists. The idea is that the types [Int] and [] Int always mean "list of Int" regardless of what module fiddling you have done. So [] is not an ordinary type constructor, to be imported or hidden at will. It always means "list as defined in the Prelude". I'll add a paragraph to 4.1.2 to make this explicit. Simon | -----Original Message----- | From: Ian Lynagh [mailto:igloo@earth.li] | Sent: 19 September 2001 13:14 | To: haskell(a)haskell.org | Subject: Prelude and (:) and []((:), []) bugs? | | | | As far as I can tell, the report doesn't allow (:) or []((:), | []) in the export list, yet the hugs prelude has the first | and the GHC prelude has the second. Have I missed something | that allows them or is this a bug in the preludes or the report? | | | Thanks | Ian | | | _______________________________________________ | Haskell mailing list | Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell |

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Your Bid 4 Placement Account
by AccountInfo＠bid4placement.com 23 Sep '01

23 Sep '01

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Your Bid 4 Placement Account
by AccountInfo＠bid4placement.com 23 Sep '01

23 Sep '01

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Re: Student Programming Projects
by Johannes Waldmann 21 Sep '01

21 Sep '01

> Next Semester, I am supposed to teach a short course in Haskell. > Can anyone recommend interesting programming projects which can > be completed in about a month? Thank you very much. apart from "pure" programming exercise (see Haskell textbooks http://haskell.org/bookshelf/) here are a few suggestions in the area of experimental mathematics. also, check with your introductory discrete mathematics course (or equivalent). a lot of combinatorial problems on finite structures can be illustrated by finding (counter-)examples by computer. say Ramsey colorings, Monochromatic arithmetic subsequences (van der Waerden's theorem), words avoiding patterns, and so on. http://www-igm.univ-mlv.fr/~berstel/Lothaire/ChapitresACW/C3.ps next, perhaps some game theory? nim (and variants), other take-and-break games (octal games). you can safely ignore all of the Sprague-Grundy theory, and just define the game, and ask for some method to determine quickly who wins. or graph theory: finding hamiltonian paths (knights tours on a x b chessboards, for instance) if the students alreay took some computability theory, then a nice topic is Posts Correspondence Problem, see http://www.cs.ualberta.ca/~zhao/PCP/intro.htm http://www.informatik.uni-leipzig.de/~pcp/pcpcontest_en.html also string rewriting: finding/avoiding loops. this (open!) problem is easily stated: http://www.lri.fr/~rtaloop/95.html hope this helps. I'm happy to provide more detail. -- -- Johannes Waldmann ---- http://www.informatik.uni-leipzig.de/~joe/ -- -- joe(a)informatik.uni-leipzig.de -- phone/fax (+49) 341 9732 204/252 --

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Haskell Communities Survey - Call for Contacts (update)
by C.Reinke 21 Sep '01

21 Sep '01

First, a big thanks to those of you who immediately volunteered to act as contact persons to their communities. That means that five of the areas are already covered. ******************************************* *** keep those contact offers coming!-) *** ******************************************* *** if you can't cover a whole area, status reports for any of *** *** the sub-areas listed can still be a good starting point *** To avoid duplication of work, and to remind everyone which areas are still looking for contact persons, here is my current list (note that there are more topics covered than contacts;-): Generic Programming/Generic Haskell [contact: Johan Jeuring] Hierarchical library proposal [contact: Simon Marlow] Happy [contact: Simon Marlow] Concurrent Haskell [contact: Simon Marlow] GHC [contact: Simon Peyton-Jones] Thanks also for the positive feedback - it seems that many of you have waited for something in this direction. There have been a few alternative suggestions as well, all of which could be pursued, if someone is willing to make a start. So I would like to pass on those suggestions to the list, with a few comments. - Tom Pledger points out the inevitable problems of a hierarchical structure, and suggests a keyword/phrase glossary instead, with definitions and links to project summaries, tending towards Wiki. I think Jan Sibinsky had started a nice glossary - unfortunately, he still seems to be offline? Has someone saved his work? As for Wikis, I've never been impressed with their apparent inability to self-organise, but we do have a Haskell Wiki, so everyone is welcome to prove me wrong there! Other structures for presenting the information might work (we'll see), but from my experience, it takes some active prodding and definite goals to get others to contribute. Hence the present structure for a start. - Ketil Malde suggests a web zine, with a group of people monitoring and summarising mailing list traffic. I'm not so sure about that specific mode (any volunteers out there?), but I do think that functional programming as a whole would profit from some kind of magazine-style publication, to bridge between the academic forums and the increasing number of (would-be) Haskell practitioners out there who have no need to conform to academic quality guidelines but would still want a quality forum more permanent and organised than mailing lists. Such a magazine would collect, edit and archive contributions about Haskell (or other FPLs) in practice, how to design, how to solve all those problems that are not really scientific in nature, but still need to be solved. I think many academics would be happy to contribute as well, focussing on their own role as practitioners. Many of those nice explanations on the mailing lists would no longer be lost to mailing list archives, and volunteer (that word again) reporters could write about interesting projects, events, etc.. That would still need some good and active editors in place (and twice a year there could be a special issue on Haskell, including the Haskell communities report;-). So a Haskell or FP web zine is a good idea, and complementary to the report we are trying to get together now. - Last, but certainly not least, Andrei Serjantov supports the idea of a separate mailing list for applications of Haskell discussions, pointing out that some potential posters to the current lists are unsure whether their own questions and contributions have any place amongst those highly technical discussions about advanced language extensions or recent implementation details. AFAIC, those "other" contributions are welcome as well on the current lists, but a separate applications list would still make a lot of sense (I would subscribe). Just remember that anything good needs volunteers to get things started (without them, we wouldn't have the language&library reports, not to speak of implementations). And that means you, dear reader!-) I'll be at IFL next week, but keep those contact offers coming! Claus

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Re: Prelude and (:) and []((:), []) bugs?
by Marcin 'Qrczak' Kowalczyk 21 Sep '01

21 Sep '01

20 Sep 2001 12:37:36 -0600, Alastair David Reid <reid(a)cs.utah.edu> pisze: >> Ah, I forgot that you can't export a constructor on its own. > > You can't? > > I probably knew this once but looking at it now, it seems kinda > surprising. Haskell's module system is supposed to be just namespace > control --nothing more-- so why is it preventing me from doing > something which is perfectly safe and well-defined? It's ambiguous whether you mention a value constructor or a type constructor / class. They are in separate namespaces and distinguished by context in normal source, but the export list doesn't provide the context. There is a strange exception that you can *hide* value constructors directly. Hiding a name beginning with uppercase applies to all relevant namespaces. -- __("< Marcin Kowalczyk * qrczak(a)knm.org.pl http://qrczak.ids.net.pl/ \__/ ^^ SYGNATURA ZASTÊPCZA QRCZAK

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Re: Prelude and (:) and []((:), []) bugs?
by Marcin 'Qrczak' Kowalczyk 21 Sep '01

21 Sep '01

Thu, 20 Sep 2001 13:32:54 +0100, Simon Marlow <simonmar(a)microsoft.com> pisze: > (:) is allowed in an export list; it is just a normal operator. Not quite, it's a reservedop. "Notice that a colon by itself, ":", is reserved solely for use as the Haskell list constructor; this makes its treatment uniform with other parts of the list syntax, such as "[]" and "[a,b]"." (Haskell 98) -- __("< Marcin Kowalczyk * qrczak(a)knm.org.pl http://qrczak.ids.net.pl/ \__/ ^^ SYGNATURA ZASTÊPCZA QRCZAK

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RE: Prelude and (:) and []((:), []) bugs?
by Simon Peyton-Jones 21 Sep '01

21 Sep '01

It's hard to distinguish a constructor from a class in an export list. S | -----Original Message----- | From: Alastair David Reid [mailto:reid@cs.utah.edu] | Sent: 20 September 2001 19:38 | To: Simon Marlow | Cc: Ian Lynagh; haskell(a)haskell.org; hugs-bugs(a)haskell.org | Subject: Re: Prelude and (:) and []((:), []) bugs? | | | | > Ah, I forgot that you can't export a constructor on its own. | | You can't? | | I probably knew this once but looking at it now, it seems | kinda surprising. Haskell's module system is supposed to be | just namespace control --nothing more-- so why is it | preventing me from doing something which is perfectly safe | and well-defined? | | I'll readily agree that there's no strong motivation for | exporting a constructor on its own (I think the only reason | Hugs allows it is just so we can export (:) from the Prelude) | but what is the motivation for disallowing it? | | -- | Alastair Reid reid(a)cs.utah.edu | http://www.cs.utah.edu/~reid/ | | | _______________________________________________ | Hugs-Bugs mailing list | Hugs-Bugs(a)haskell.org | http://www.haskell.org/mailman/listinfo/hugs-bugs |

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Problem: "invalid argument" emitted by sendTo
by mgross＠dorsai.org 21 Sep '01

21 Sep '01

Found the error. No need to follow up. Apologies to anyone who objects to mail that turns out not to need answering. Murray Gross mgross(a)dorsai.org

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