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<Re:lexical description problem in language report?>
by To Anthony Widjaja 18 Jul '01

18 Jul '01

<Hi Gary, Sorry I'm not answering your question. But I just want to know what sort of book (or perhaps something else) that contains this problem? Because you said in section 2.2, 2.3 and so on. On Wed, 18 Jul 2001 11:51:40 -0700 "Memovich, Gary" <GARY.MEMOVICH(a)kla-tencor.com> wrote: I believe I've found a problem, or at least a confusion, in the Haskell 98 Language Report. The section on lexical structure seems to use the term "lexeme" in an inconsistent way. "lexeme" is one of the productions in the lexical grammar in section 2.2, but the term is also used in section 2.3 where it is claimed that the string "{-" is a lexeme. However the string "{-" cannot be produced by the given grammar production. Is section 2.3, and the discussion of the maximal-munch rule, using the term lexeme in a different way than the grammar production in section 2.2? If so, maybe a new term should be introduced such as "rawlexeme", with a production like: rawlexeme -> lexeme | opencom | closecom | dashes Then perhaps the maximal-munch rule could be described in terms of "rawlexeme". Any thoughts? -- Gary > Sign up for your FREE E-MAIL @ COMETMAIL: http://www.cometmail.com

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Re: Counting Constructors
by Jay Cox 18 Jul '01

18 Jul '01

> From: Tobias Haeberlein <T.Haeberlein(a)gmx.de> > To: haskell(a)haskell.org > Subject: Counting Constructors > > I want a show - instance for that type: > data Bind a = Zero | Succ a > resp. for the types (Bind ( ... (Bind a)...)) > > showing the following: > > show (Succ ( ... (Succ Zero)..)) = n > (where n is the number of Succ's) > and > > show (Succ ( ... (Succ x)..)) = show x > (when x != Zero) that doesnt make sense. You want n to be some some integral type and show x is a string. > > Does anyone know, how to define those functions in haskell/hugs ?? > (Are they defineable at all?) sounds like you really want something like data Bind a = Zero (Maybe a) | Succ (Bind a) instance (Show a) => Show (Bind a) where show x = z 0 x where z count (Zero Nothing) = show count z _ (Zero (Just x)) = show x z count (Succ x) = z (count+1) x Main> let {x :: Bind String; x = Succ $ Succ $ Succ $ Zero Nothing} in show x "3" Main> show (Succ $ Succ $ Zero (Just "Funky")) "\"Funky\"" However just because you can do it doesnt mean you should. Personally, I would think data Bind a = Something Int (Maybe a) or even using the Either datatype in a similar fashion could be more useful (and has a very trivial show instance which would meet your requirements).Meh, I'm probably doing somebody's homework here anyway. Jay

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Re: Counting Constructors
by Marcin 'Qrczak' Kowalczyk 18 Jul '01

18 Jul '01

Tue, 17 Jul 2001 12:08:51 +0200 (MEST), Tobias Haeberlein <T.Haeberlein(a)gmx.de> pisze: > show (Succ ( ... (Succ Zero)..)) = n > (where n is the number of Succ's) > and > > show (Succ ( ... (Succ x)..)) = show x > (when x != Zero) This is not possible in Haskell 98 - you can't overload an operation on "any type except this one". There are no "negative assertions" or "exceptions". It might be possible in Hugs run with -98 option (define "instance Count a" and "instance Count a => Count (Bind a)" and "instance Count a => Show (Bind a)", where class Count has a function of type a->Int), but I would not be surprised if it didn't work correctly in all cases, e.g. if the answer was too small sometimes. Overlapped instances is not a well behaved concept. -- __("< Marcin Kowalczyk * qrczak(a)knm.org.pl http://qrczak.ids.net.pl/ \__/ ^^ SYGNATURA ZASTÊPCZA QRCZAK

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Dead code detection
by Pertti Kellomäki 18 Jul '01

18 Jul '01

I am working with a fairly rapidly changing code base, with another person besides me making changes. Can any of the Haskell compilers warn about unused function definitions, or does a similar standalone tool exist? I am fairly sure the code base includes redundant definitions that just clutter up the source, and I would like to be able to detect them easily. Thanks, -- pertti

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RE: Dead code detection
by Simon Peyton-Jones 18 Jul '01

18 Jul '01

GHC will report unused bindings (-fwarn-unused-binds) but only within a module. If it's exported, GHC doesn't help you. I'm sure GHC itself has plenty of dead code that only a global analysis can spot! GHC's interface file for a module reports all the imported things that the module depends on. So the raw material for a global analyser is in place. Simon | -----Original Message----- | From: Pertti Kellomäki [mailto:pk@cs.tut.fi] | Sent: 18 July 2001 11:43 | To: haskell(a)haskell.org | Subject: Dead code detection | | | I am working with a fairly rapidly changing code base, | with another person besides me making changes. Can any of | the Haskell compilers warn about unused function definitions, | or does a similar standalone tool exist? I am fairly sure the | code base includes redundant definitions that just clutter up | the source, and I would like to be able to detect them easily. | | Thanks, | -- | pertti | | _______________________________________________ | Haskell mailing list | Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell |

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BABEL'01: Preliminary programme and Call for Participation
by Andrew Kennedy 17 Jul '01

17 Jul '01

Call for Participation BABEL 2001 First workshop on multi-language infrastructure and interoperability. Part of PLI 2001 Firenze, Italy. 8th September 2001. http://research.microsoft.com/~nick/babel01.htm Preliminary programme now available at http://research.microsoft.com/~nick/babel01prog.htm AIMS AND SCOPE Recent years have seen a resurgence of interest in multi-language tools and intermediate languages, and in interoperability between programs and components written in different programming languages. Shared infrastructure such as code generators, analysis tools and garbage collectors can greatly ease the task of producing a high-quality implementation of a new programming language, whilst being able to interoperate easily with code written in existing languages is essential for such an implementation to be useful in practice. This workshop aims to bring together researchers and developers working on multi-language integration. REGISTRATION http://www.regmaster.com/pli2001.html Note that the deadline for the early registration rate is JULY 25. PROGRAMME COMMITTEE Nick Benton (chair) Microsoft Research Fergus Henderson University of Melbourne Andrew Kennedy (organiser) Microsoft Research Greg Morrisett Cornell University Martin Odersky Ecole Polytechnique Fédérale de Lausanne John Reppy Bell Labs Andrew Tolmach Portland State University David Wakeling University of Exeter PRELIMINARY PROGRAMME http://research.microsoft.com/~nick/babel01prog.htm 9:00-10:00. Invited talk Towards a Principled Multi-Language Infrastructure Zhong Shao (Yale University) 10:30-12:30. Session 1 A framework for interoperability Kathleen Fisher (AT&T Labs, Research), Riccardo Pucella (Cornell University) and John Reppy (Lucent Technologies, Bell Labs) Alice in the Land of Oz - An Interoperability-based Implementation of a Functional Language on Top of a Relational Language Leif Kornstaedt (Universität des Saarlandes) No-Longer-Foreign: Teaching an ML compiler to speak C "natively" Matthias Blume (Lucent Technologies, Bell Labs) ILX: Extending the .NET Common IL for Functional Language Interoperability Don Syme (Microsoft Research, Cambridge) 14:00-15:30. Session 2 Compiling Mercury to the .NET Common Language Runtime Tyson Dowd, Fergus Henderson (University of Melbourne) and Peter Ross (Mission Critical, Belgium) Object-Oriented Style Overloading for Haskell Mark Shields and Simon Peyton Jones (Microsoft Research, Cambridge) Annotations for Portable Intermediate Languages Fermin Reig (University of Glasgow) 16:00-17:30. Session 3 Active Oberon for .NET: An Exercise in Object Model Mapping Jurg Gutknecht (ETH Zurich) Language-Agnostic Approaches to Mobile Code Peter Housel, Christian Stork, Vivek Haldar, Niall Dalton and Michael Franz (University of California, Irvine) Tail call elimination on the Java Virtual Machine Michel Schinz and Martin Odersky (Ecole Polytechnique Fédérale de Lausanne)

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Dealing with implementation differences
by Pertti Kellomäki 17 Jul '01

17 Jul '01

Hello all, How does one deal cleanly with implementation differences, e.g. things like isAscii being defined in Hugs but not in GHC? I'd hate to resort to Makefile trickery and preprocessing. Btw, the reason I want to run the same sources with Hugs and GHC is that I have a compiler whose parser is generated with Happy. Compiling the parser on a smallish computer takes ages and I don't need the efficiency at this stage anyway. On the other hand, I find the error messages given by GHC very good. If someone can suggest another compiler to try out or a way to reduce the time needed for compiling the parser, I'd be grateful. The parser is about 3500 lines of Haskell. -- Pertti

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Counting Constructors
by Tobias Haeberlein 17 Jul '01

17 Jul '01

I want a show - instance for that type: data Bind a = Zero | Succ a resp. for the types (Bind ( ... (Bind a)...)) showing the following: show (Succ ( ... (Succ Zero)..)) = n (where n is the number of Succ's) and show (Succ ( ... (Succ x)..)) = show x (when x != Zero) ------------------------------------------------ And - a very similar problem - i'd like to have a function 'count' which get something of type 'Bind' and returns a value of type (Either Int a): count ((Succ ( ... (Succ Zero)..)) = Left n (n = #succ's) and count (Succ ( ... (Succ x)..)) = Right x (x != Zero) ------------------------------------------------- Does anyone know, how to define those functions in haskell/hugs ?? (Are they defineable at all?) Thanks, -Tobi -- GMX - Die Kommunikationsplattform im Internet. http://www.gmx.net GMX Tipp: Machen Sie Ihr Hobby zu Geld bei unserem Partner 1&1! http://profiseller.de/info/index.php3?ac=OM.PS.PS003K00596T0409a

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Re: Dealing with implementation differences
by Wolfgang Lux 17 Jul '01

17 Jul '01

Hello, > How does one deal cleanly with implementation differences, e.g. things > like > isAscii being defined in Hugs but not in GHC? I'd hate to resort to > Makefile > trickery and preprocessing. You can try to use some special compatibility module where you collect all the workarounds for the implmentation differences. But in this particular you should better read the (library) report and simply import the Char module (from where isAscii should be exported -- Hugs still exports it from the Prelude though it shouldn't). Wolfgang -- Wolfgang Lux Phone: +49-251-83-38263 Institut fuer Wirtschaftinformatik FAX: +49-251-83-38259 Universitaet Muenster Email: wlux(a)uni-muenster.de

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RE: Dealing with implementation differences
by Simon Peyton-Jones 17 Jul '01

17 Jul '01

| How does one deal cleanly with implementation differences, | e.g. things like isAscii being defined in Hugs but not in | GHC? I'd hate to resort to Makefile trickery and preprocessing. isAscii is certainly defined in GHC. It's in module Char, like the language definition says. | Btw, the reason I want to run the same sources with Hugs and | GHC is that I have a compiler whose parser is generated with | Happy. Provided you stick to Haskell98, the same sources should run on both. | Compiling the parser on a smallish computer takes ages | and I don't need the efficiency at this stage anyway. On the | other hand, I find the error messages given by GHC very good. | If someone can suggest another compiler to try out or a way | to reduce the time needed for compiling the parser, I'd be | grateful. The parser is about 3500 lines of Haskell. Hugs compiles really fast. The interactive version of GHC compiles much slower, but much faster than the batch version. ghc --interactive. [GHC 5.02 at least.] Simon

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