November 2000 - Haskell

First class modules
by Tom Pledger 08 Nov '00

08 Nov '00

Hallo again. Supposing that (some version of) Haskell had first class modules, and type variables could be universally quantified at the module level, would rule 2 of the monomorphism restriction go away? Is this among the aims of the "First-class modules for component-based programming" (proposal document by Simon Peyton Jones and Mark Jones, 1996) research project? Regards, Tom

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Re: Passing an environment around
by José Romildo Malaquias 08 Nov '00

08 Nov '00

On Fri, Oct 27, 2000 at 09:07:24AM -0700, Jeffrey R. Lewis wrote: > José Romildo Malaquias wrote: > > > On Thu, Oct 19, 2000 at 09:08:16AM -0700, Conal Elliott wrote: > > > Indeed Fran behaviors are like your alternative #1 (function passing), and > > > hence sharing loss is a concern. Simon PJ is right that I have a paper > > > discussing this issue and some others. See "Functional Implementations of > > > Continuous Modeled Animation" on my pubs page > > > (http://research.microsoft.com/~conal/papers) > > > > > > About alternative #2 (implicit arguments), would it help? Does it eliminate > > > the non-memoized redundant function applications, or just hide them? For > > > Fran, Erik Meijer suggested implicit functions to me a couple of years ago. > > > I hadn't thought of it, and it did indeed seem to be attractive at first as > > > a way to eliminate the need for overloading in Fran. However, the (Time -> > > > a) representation of Fran behaviors is not really viable, so I wouldn't > > > merely want to hide that representation behind implicit arguments. > > > > It seems that implicit parameters does not eliminate redundant function > > applications, as Conal Elliott has commented. Reading the paper > > > > Implicit Parameters: Dynamic Scoping with Static Types > > Jefrrey Lewis, Mark Shields, Erik Meijer, John Launchbury > > http://www.cse.ogi.edu/~jlewis/ > > > > (especially section 5.1) I got this impression. I would like to hear > > from others as well, as I had some difficulties with the paper. > > I am sorry you had difficulties! The difficulties I had is basicaly due to my lack of solid knowledge on type theory and semantic formalisms. Not that the paper was badly written. > Yes, as implemented using the dictionary > translation, implicit parameterization can lead to loss of sharing, exactly in > the same way that overloading (and HOF in general) can lead to loss of sharing. > > However, I can imagine that a compiler might chose to implement implicit > parameters more like dynamic variables in lisp. Each implicit param essentially > becomes a global variable, implemented as a stack of values - the top of the > stack is the value currently in scope. This would avoid the sharing problem > nicely. > > --Jeff I suppose your implementation of implicit parameterization in GHC and Hugs uses the dictionary translation, right? Would an alternative implementation based on a stack of values be viable and even done? Does it have serious drawbacks when compared with the dictionary translation technique? Thanks. Romildo -- Prof. José Romildo Malaquias <romildo(a)iceb.ufop.br> Departamento de Computação Universidade Federal de Ouro Preto Brasil

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ANNOUNCE: hdirect-0.17
by Sigbjorn Finne 08 Nov '00

08 Nov '00

Hi, a new release of HDirect is now available from the new home of HDirect, http://www.haskell.org/hdirect/ see the web pages for more info as to what HDirect can help you out with. This 0.17 release is a source-only, bugfix release. The main user-level fix is that the sources should now compile out-of-the-box with GHC-4.08 Enjoy; bug reports/feedback to sigbjorn_finne(a)hotmail.com --sigbjorn

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Translations
by M. S. Poole 08 Nov '00

08 Nov '00

Can anyone point me toward some reasearch that implements a translator from Prolog to Haskell? Mark Poole

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07 Nov '00

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1st Call for Papers
by Kristina Striegnitz 06 Nov '00

06 Nov '00

!!! Concerns all students in Logic, Linguistics and Computer Science !!! !!! Please circulate and post among students !!! We apologize, if you receive this message more than once. ESSLLI 2001 STUDENT SESSION FIRST CALL FOR PAPERS August 13-24 2001, Helsinki, Finland Deadline: February 18, 2001 http://www.coli.uni-sb.de/~kris/esslli We are pleased to announce the Student Session of the 13th European Summer School in Logic, Language and Information (ESSLLI 2001) organized by the University of Helsinki under the auspices of the European Association for Logic, Language and Information (FoLLI). ESSLLI 2001 will be held at the University of Helsinki in August 2001. We invite submission of papers for presentation at the ESSLLI 2001 Student Session and for appearance in the proceedings. PURPOSE: This sixth ESSLLI Student Session will provide, like the other editions, an opportunity for ESSLLI participants who are students to present their own work in progress and get feedback from senior researchers and fellow-students. The ESSLLI Student Session encourages submissions from students at any level, from undergraduates (before completion of the Master Thesis) as well as postgraduates (before completion of the PhD degree). Papers co-authored by non-students will not be accepted. Papers may be accepted for full presentation (30 minutes including 10 minutes of discussion) or for a poster presentation. The accepted papers will be published in the ESSLLI 2001 Student Session proceedings, which will be made available during the summer school. KLUWER BEST PAPER AWARD: As in previous years, the best paper will be selected by the program committee and will be offered a prize by Kluwer Academic Publishers consisting in 1000 Dfl worth of books. REQUIREMENTS: The Student Session papers should describe original, unpublished work, completed or in progress that demonstrates insight, creativity, and promise. No previously published papers should be submitted. All topics within the six ESSLLI subject areas (Logic, Language, Computation, Logic & Language, Logic & Computation, Language & Computation) are of interest. FORMAT OF SUBMISSION: Student authors should submit an anonymous extended abstract headed by the paper title, not to exceed 5 pages in length exclusive of references and send a separate identification page (see below). Note that the length of the full papers will not be allowed to exceed 10 pages. Since reviewing will be blind, the body of the abstract should omit author names and addresses. Furthermore, self-references that reveal the author's identity (e.g., "We previously showed (Smith, 1991)... ") should be avoided. It is possible to use instead references like "Smith (1991) previously showed...". For any submission, a plain ASCII text version of the identification page should be sent separately, using the following format: Title: title of the submission First author: firstname lastname Address: address of the first author ...... Last author: firstname lastname Address: address of the last author Short summary: abstract (5 lines) Subject area (one of): Logic | Language | Computation | Logic and Language | Logic and Computation | Language and Computation If necessary, the program committee may reassign papers to a more appropriate subject area. The submission of the extended abstract should be in one of the following formats: PostScript, PDF, RTF, or plain text. But note that, in case of acceptance, the final version of the paper has to be submitted in LaTeX format. Please, use A4 size pages, 11pt or 12pt fonts, and standard margins. Submissions outside the specified length and formatting requirements may be subject to rejection without review. The extended abstract and separate identification page must be sent by e-mail to: kris(a)coli.uni-sb.de by FEBRUARY 18, 2001 ESSLLI 2001 INFORMATION: In order to present a paper at ESSLLI 2001 Student Session, at least one student author of each accepted paper has to register as a participant at ESSLLI 2001. The authors of accepted papers will be eligible for reduced registration fees. For all information concerning ESSLLI 2001, please consult the ESSLLI 2001 web site at http://www.helsinki.fi/esslli. IMPORTANT DATES: Deadline for submission of abstracts: February 18, 2001. Authors Notifications: April 17, 2001. Final version due: May 18, 2001. ESSLLI-2001 Student Session: August 13-24, 2001. PROGRAM COMMITTEE: Raffaella Bernardi, University of Utrecht (Logic & Language) Patrick Blackburn, University of the Saarland (Logic & Language) Gilles Dowek, INRIA (Computation) Ruth Kempson, King`s College London (Language) Carsten Lutz, University of Aachen (Logic & Computation) Ani Nenkova, Columbia University (Logic) Ilkka Niemel�, Helsinki University of Technology (Logic & Computation) Malvina Nissim, University of Pavia (Language) Susanne Salmon-Alt, Loria, Nancy (Language & Computation) Jan Schwinghammer, University of the Saarland (Computation) Kristina Striegnitz, University of the Saarland (Chair) Yde Venema, University of Amsterdam (Logic) Shuly Wintner, University of Haifa (Language & Computation) For any question concerning the ESSLLI 2001 Student Session, please, do not hesitate to contact me: Kristina Striegnitz Computational Linguistics, University of the Saarland, Germany phone: +49 - 681 - 302 4503 email: kris(a)coli.uni-sb.de

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Error compiling gtk+hs in Red Hat Linux 7.0
by José Romildo Malaquias 05 Nov '00

05 Nov '00

Hello. When trying to build gtk+hs from CVS I am getting the following error message: ==================== + make Entering preparation phase... make[1]: Entering directory `/home/romildo/rpms/BUILD/gtk+hs-0.10.1/glib' /usr/bin/c2hs --cppopts="-I/usr/lib/glib/include -I/usr/X11R6/include" glib.h GL ist.chs c2hs: Generic fatal error. /usr/lib/gcc-lib/i386-redhat-linux/2.96/include/stdarg.h:43: (column 26) [FATAL] >>> Syntax error! The symbol `__gnuc_va_list' does not fit here. make[1]: *** [GList.hs] Error 1 make[1]: Leaving directory `/home/romildo/rpms/BUILD/gtk+hs-0.10.1/glib' make: *** [prep] Error 2 ==================== I am using c2hs from CVS. The system is Red Hat Linux 7.0. Any clues? Romildo -- Prof. José Romildo Malaquias <romildo(a)iceb.ufop.br> Departamento de Computação Universidade Federal de Ouro Preto Brasil

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Research Associateship in Metaprogramming Languages
by Andrew Pitts 01 Nov '00

01 Nov '00

POSTDOCTORAL RESEARCH ASSOCIATE IN METAPROGRAMMMING LANGUAGES at the UNIVERSITY OF CAMBRIDGE COMPUTER LABORATORY Cambridge, UK We are seeking a postdoctoral Research Associate to work on implementing an exciting new approach to representing, computing and reasoning about syntactical structures that involve variable-binding. START DATE: 1 January 2001, or as soon as possible thereafter. SALARY: 16,775--25,213 GBP per year, depending on age and qualifications. DURATION: 3 years. THE PROJECT: People who create software systems that manipulate syntactical structures (interpreters, compilers, proof checkers, proof assistants, etc) agree that dealing with variable-binding constructs, renaming of bound variables, capture-free substitution, etc, is very often a nightmare. Despite the efforts of many smart people, no clear winner has emerged from the different approaches to this problem that have been proposed so far---name-carrying terms, de Bruijn nameless terms, higher order abstract syntax. We have a new approach to this long-standing problem based on some simple mathematics to do with permuting variables. We think it is very exciting because our way of representing abstract syntax modulo renaming of bound names seems to integrate very well with the inductive data types and pattern-matching facilities of existing functional programming languages commonly used for metaprogramming activities, such as ML or Haskell. Roughly speaking, we are aiming to extend those languages so that the user can write syntax-manipulating code using explicitly named bound variables and be notified by the language's static type system if their code descends below the level of abstraction that identifies pieces of syntax up to renaming bound variables. Can our new approach be implemented efficiently? Does it result in a programming style that's useful for metaprogramming and that aids refining and reasoning about such programs? That's what we aim to find out. The project is called "FreshML: A Fresh Approach to Name Binding in Metaprogramming Languages" and is funded by the UK EPSRC and Microsoft Research. It is led by Andrew Pitts in collaboration with Mike Gordon at the Cambridge University Computer Laboratory and Simon Peyton Jones at the Cambridge Laboratory of Microsoft Research. See the FreshML web page at <www.cl.cam.ac.uk/users/amp12/freshml/> for more details. THE JOB: We are looking for an experienced hacker (in the best sense of the word) to design and implement a new language, FreshML, embodying our new approach to binding. You need to have enough brain-power to understand the FreshML type system and dynamic semantics, and you will have an opportunity to contribute to them---but the main areas where we need your help are in the design of a programming language to embody the type system, an implementation to demonstrate its practicality, and significant examples of its use. You should hold a PhD or equivalent qualification and have experience with the implementation of typed functional programming languages such as ML or Haskell. Experience with systems for machine-assisted reasoning or with programming language theory will be advantageous. THE ENVIRONMENT: You will be based in the Cambridge University Computer Laboratory (currently located in central Cambridge, but which will move to purpose-built accommodation on the west side of the city during late summer 2001). Further details of the Computer Laboratory can be found at <www.cl.cam.ac.uk>. The FreshML project involves the Laboratory's Theory and Semantics research group <www.cl.cam.ac.uk/Research/TSG/> and the Automated Reasoning research group <www.cl.cam.ac.uk/Research/HVG/>. It also involves collaboration with the Programming Principles & Tools group at Microsoft Research Cambridge <research.microsoft.com/ppt/>. HOW TO APPLY: Send a full CV, names of at least two referees, and a brief statement saying how you think you fit the post, what you expect to contribute, and what you hope to get out of the job, to: Ms Caroline Bean Cambridge University Computer Laboratory Pembroke Street Cambridge CB2 3QG, UK email: Caroline.Bean(a)cl.cam.ac.uk tel: +44 1223 334607 fax: +44 1223 334611 ENQUIRIES about this job should be directed to: Andrew Pitts, Cambridge University Computer Laboratory, Pembroke Street, Cambridge CB2 3QG, UK (email: Andrew.Pitts(a)cl.cam.ac.uk, tel: +44 1223 334629). CLOSING DATE FOR APPLICATIONS: 1 December 2000

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