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RE: [Haskell] Running haskell from within Haskell
by Nick Benton 19 Jan '05

19 Jan '05

I have a forthcoming expository JFP paper on one way to do what I think you're asking for without any extra-language hackery: Embedded Interpreters This is a tutorial on using type-indexed embedding/projection pairs when writing interpreters in statically-typed functional languages. The method allows (higher-order) values in the interpreting language to be embedded in the interpreted language and values from the interpreted language may be projected back into the interpreting one. This is particularly useful when adding command-line interfaces or scripting languages to applications written in functional languages. We first describe the basic idea and show how it may be extended to languages with recursive types and applied to elementary meta-programming. We then show how the method combines with Filinski's continuation-based monadic reflection operations to define an `extensional' version of the call-by-value monadic translation and hence to allow values to be mapped bidirectionally between the levels of an interpreter for a functional language parameterized by an arbitrary monad. Finally, we show how SML functions may be embedded into, and projected from, an interpreter for an asynchronous \picalc\ via an `extensional' variant of a standard translation from $\lambda$ into $\pi$. There's a preprint available on my web page at http://research.microsoft.com/~nick/publications.htm The code is in SML, but the basic idea works just the same in Haskell (in fact, you can use type classes to make it look even slicker). Nick -----Original Message----- From: haskell-bounces(a)haskell.org [mailto:haskell-bounces@haskell.org] On Behalf Of Donald Bruce Stewart Sent: 19 January 2005 02:51 To: Vivian McPhail Cc: haskell(a)haskell.org Subject: Re: [Haskell] Running haskell from within Haskell vivian.mcphail: > > Dear All, > I have a parser which has entries for each word, such as: > > ate = s \ np / np : ^x y.did(eat y x); > > so each word has a type (s \ np / np) and a semantics (the > lambda term ^x y.did(eat y x)). > > Currently I parse the semantics into lambda terms and use my > own lambda-interpreter to do evaluation. > > "I ate a python programmer" would be evaluated as: > > did(eat I (a python programmer)) > > What I would like to be able to do is actually use haskell > functions in the semantic slot for each word. This requires > parsing a fragment of a file into haskell and then making it > available as code within my program. > > Is this possible? > > for example: > > kicked = s \ np / np : \x y -> case x of > > (the bucket) = did(die > y) > > _ = did(k > ick y x); > > Thanks in advance. You may be able to use the eval functions provided by hs-plugins http://www.cse.unsw.edu.au/~dons/hs-plugins/ A number of mini-edsl-interpreters for Haskell have been written this way. Where: eval :: Typeable a => String -> [Import] -> IO (Maybe a) An example of an interpreter for Haskell, using this mechanism, is at: http://www.cse.unsw.edu.au/~dons/hs-plugins/hs-plugins-Z-H-14.html#node_ chap_B -- Don _______________________________________________ Haskell mailing list Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell

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[ANNOUNCE] New version of unicode CWString library with extras
by John Meacham 19 Jan '05

19 Jan '05

A while ago I wrote a glibc specific implementation of the CWString library. I have since made several improvements: * No longer glibc specific, should compile and work on any system with iconv (which is unix standard) (but there are still glibc specific optimizations) * general iconv library for conversion to any other supported character sets * LocaleIO, a plug in replacement for many of the standard prelude and IO calls which transparently handle locale encoding. and best of all, it now has a darcs repository. http://repetae.net/john/recent/out/HsLocale.html It could still using some fleshing out, LocaleIO is still incomplete, I add to it as I need a function, but I figure I should make it available in case the CWString stuff came in handy for implementing the FFI spec for ghc. John PS. is there a way to replace the top level error handler in ghc? (from a haskell library) I'd like to be able to print the error messages with the LocaleIO library as it is the only place where the wrong encoding still can leak out. -- John Meacham - ⑆repetae.net⑆john⑈

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Running haskell from within Haskell
by Vivian McPhail 19 Jan '05

19 Jan '05

Dear All, I have a parser which has entries for each word, such as: ate = s \ np / np : ^x y.did(eat y x); so each word has a type (s \ np / np) and a semantics (the lambda term ^x y.did(eat y x)). Currently I parse the semantics into lambda terms and use my own lambda-interpreter to do evaluation. "I ate a python programmer" would be evaluated as: did(eat I (a python programmer)) What I would like to be able to do is actually use haskell functions in the semantic slot for each word. This requires parsing a fragment of a file into haskell and then making it available as code within my program. Is this possible? for example: kicked = s \ np / np : \x y -> case x of (the bucket) = did(die y) _ = did(kick y x); Thanks in advance. Vivian

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ANNOUNCE: Happy 1.15
by Simon Marlow 18 Jan '05

18 Jan '05

ANNOUNCING Happy 1.15 - The LALR(1) Parser Generator for Haskell I'm pleased to announce version 1.15 of Happy, the parser generator system for Haskell. Changes from version 1.14 to 1.15 * New %expect directive * the list of tokens passed to happyError now includes the current token (not %lexer). * added support for ambiguous grammars via Generalized LR parsing * added %partial to indicate a parser that can return a result before EOF is reached. NOTE: Happy version 1.15 will be *required* for building newer versions of GHC, due to use of %partial in GHC's parser. If you build GHC from source, get this release, or build it from CVS. Happy is available in source form, which can be compiled with GHC version 5.04+, and we also provide binaries for some architectures. The Happy homepage with links to the various distributions lives at: http://www.haskell.org/happy/ Please send any bug reports and comments to simonmar(a)microsoft.com.

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Functional and Declarative Programming in Education 2005
by S.J.Thompson 18 Jan '05

18 Jan '05

Functional and Declarative Programming in Education (FDPE05) A one day workshop at ICFP05 Sunday, 25 September 2005, Tallin, Estonia http://www.cs.kent.ac.uk/~sjt/fdpe05/ FIRST CALL FOR SUBMISSIONS Overview Functional and declarative programming plays an important role in computing education at all levels. The aim of this workshop is to bring together educators and others who are interested in exchanging ideas on how to use a functional or declarative programming style in the classroom. Scope The workshop will cover a wide spectrum of functional and declarative programming techniques: - programming courses using traditional functional and declarative programming languages (Haskell, Mathematica, ML, Prolog, Scheme, ...); - programming courses teaching functional programming in commercial languages (e.g. C, C++, or Common LISP); - programming courses teaching functional program design in modern OO languages like Java, C#, or Eiffel; - pedagogic programming environments to support functional and declarative programming; - teaching tools implemented with functional and declarative languages; - declarative programming language extensions and implementations with pedagogical relevance; - application courses that benefit heavily from functional and declarative programming (e.g. theorem proving or hardware design). Furthermore, the workshop will also cover all levels of education: secondary school; college and university; post-college and continuing professional education. Submissions Submissions will be sought in two forms: - 30 minute papers, to be reviewed by the workshop organisers and to be published in the proceedings. - 10 minute slots for `tips and tricks': these will be made available through the workshop web site. Submissions will be refereed by the workshop organisers who will call upon other members of the functional/declarative programming community for expert advice. Participants who choose to deliver a standard presentation are asked to submit a draft PDF paper of five pages; presenters of short talks are asked to submit an abstract of 250 words. These should be submitted by June 4, 2005. Comments from the organizers and notice of acceptance will be sent to authors by July 15, 2005. Proceedings will be published by SIGPLAN. Details of the publication procedure will be given on the workshop web site in due course. Organisers Robby Findler, University of Chicago, USA Michael Hanus, University of Kiel, Germany Simon Thompson, University of Kent, UK FDPE05: http://www.cs.kent.ac.uk/~sjt/fdpe05/ ICFP05: http://www.brics.dk/~danvy/icfp05/

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Why is getArgs in the IO monad?
by Jim Apple 18 Jan '05

18 Jan '05

See subject. It seems that it would be constant through execution, and so could be just [String]. Jim

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RE: [Haskell] Typeable and Data instances for Double, FiniteMap, ...
by Simon Peyton-Jones 18 Jan '05

18 Jan '05

| Yes, once you start to use the SYB library you end up wanting it to | cover almost all your types. | I will make an effort *now* hoping that all the instance can still make | it into GHC 6,4. | (There are indeed a few more unsupported types that make obviously sense.) Yes, anything in the HEAD will get into 6.4 Simon

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Typeable and Data instances for Double, FiniteMap, ...
by Georg Martius 18 Jan '05

18 Jan '05

Hi, I was playing around with "Scap you Boilerplate" and realised some missing instances of Typeable and Data. Is there a particular reason why there is no Data Double instance? Furthermore I was wondering why no instance for the collection types such as FiniteMap, Set and HashTable is provided. At the end of the mail [1] there is my implementation of instances for at least Double and FiniteMap. Apart from that I looked at the library source-code (GHC) and reallised that there is really much documenting comments in, but which are not Haddock comments. Again I don't understand that. Is the programmer supposed to look at the source-code rather the API documentation? Regards, Georg [1] instances: Data Double, Typeable FiniteMap, Data FiniteMap > -- > -- Data instance for Double. > -- IMHO It should be added as a basic type to Data.Constr with DoubleConstr like Float > doubleConstr :: Double -> Constr > doubleConstr x = mkConstr 1 (show x) Prefix > doubleDataType :: DataType > doubleDataType = mkDataType [doubleConstr 0.0] > > instance Data Double where > toConstr x = doubleConstr x > fromConstr c = read $ conString c > dataTypeOf _ = doubleDataType > > > > -- > -- Typeable instance for FiniteMap > fmTc :: TyCon > fmTc = mkTyCon "FM" > > instance (Typeable a, Typeable b) => Typeable (FiniteMap a b) where > typeOf fm = mkAppTy fmTc [typeOf ((undefined :: FiniteMap a b -> a) fm)] > > -- > -- Data instance for FiniteMap > -- treats the FiniteMap as a list. > -- More performant solutions might be possible, > -- if internal of FM can be exploited > fmConstr :: Constr > fmConstr = mkConstr 1 "FM" Prefix > fmDataType :: DataType > fmDataType = mkDataType [fmConstr] > > instance (Data a, Data b, Ord a) => Data (FiniteMap a b) where > gfoldl f z fm = z listToFM `f` (fmToList fm) > toConstr _ = fmConstr > fromConstr c = case conIndex c > of 1 -> emptyFM > dataTypeOf _ = fmDataType > -- ---- Georg Martius, Tel: (+49 34297) 89434 ---- ------- http://www.flexman.homeip.net ---------

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PhD Position in Technical University of Valencia (Spain)
by Santiago Escobar 18 Jan '05

18 Jan '05

Please, pass on to interested students. Apologies for multiple copies. ---------------------------------------------------------------------- PhD Position (DEADLINE 4 February 2004! See "How to apply" below.) Departamento de Sistemas Informaticos y Computacion Technical University of Valencia Spain http://www.dsic.upv.es/users/elp The group ELP "Automated Software Engineering, Logic Programming and Programming Languages" of the Technical University of Valencia (UPV) has an open position for a PhD student for 2 years (which can be extended to 4 years) funded by the Spanish Ministry of Education and Scientific Research, to work in the project: "SELF: Software Engineering and Lightweight Formalisms" Project coordinator: Maria Alpuente http://www.dsic.upv.es/~alpuente The goal of the project is to investigate on analysis, specification, verification, debugging, testing, learning, certification, transformation & optimization techniques for (multiparadigm) programs. The candidate must have an adequate theoretical background in computer science with some knowledge of mathematical logic. Knowledge of logic programming or functional/equational programming is not required but will be an asset. Salary for a first year PhD student is around 1100 Euros/month with an incremental raise for each subsequent year. Besides the salary, health insurance is provided. How to apply ------------ First, register your intention to apply immediately using the electronic application form on the WWW via http://213.229.161.10/becasfpi The full application should contain: 1 A signed, printed copy of the Web application form, where the project SELF must be explicitly choosed (from the projects list) 2 A passport photocopy 3 Attested copies of degrees and other certificates, including the complete list of courses, grades, and dates. An explanation of the corresponding evaluation system (min and max. qualification to pass) is also required 4 A certification, granted by an spanish university, that the undergraduate degree is valid for admission in its PhD programme. This can be obtained from UPV if document 3 above is timely provided. 5. Curriculum Vitae For further information on how to apply please consult our website: http://www.dsic.upv.es/users/elp Send your application (paper mail), to arrive BEFORE ***** February 4th, 2004 **** to: Salvador Lucas (slucas(a)dsic.upv.es) Departamento de Sistemas Informaticos y Computacion Universidad Politecnica de Valencia Camino de Vera s/n E-46022 Valencia (Spain) Phone +34 96 387 7007 (ext. 73531) http://www.dsic.upv.es/~slucas ----------------------------------------------------------------------

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RE: [Haskell] Typeable and Data instances for Double, FiniteMap, ...
by Simon Peyton-Jones 18 Jan '05

18 Jan '05

| I was playing around with "Scap you Boilerplate" and realised some missing instances of Typeable and | Data. Is there a particular reason why there is no Data Double instance? | Furthermore I was wondering why no instance for the collection types such as FiniteMap, Set and | HashTable is provided. At the end of the mail [1] there is my implementation of instances for at least | Double and FiniteMap. I've asked Ralf if he'll add them. | Apart from that I looked at the library source-code (GHC) and reallised that there is really much | documenting comments in, but which are not Haddock comments. Again I don't understand that. Is | the programmer supposed to look at the source-code rather the API documentation? It should be Haddock'd. We'd be delighted if anyone was willing to transfer code in comments to Haddock comments, where that is appropriate, and probably add new Haddock comments where necessary. Any volunteers? We'd give CVS access... Simon

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