September 2001 - Haskell

HOpenGL mailing list (?)
by Andre W B Furtado 27 Sep '01

27 Sep '01

Is there any interest out there in creating a HOpenGL mailing list? Thanks, Andre W B Furtado

1 0

FranTk with ghc 5.00
by Han Tuong Hau 27 Sep '01

27 Sep '01

Hi I'm trying to run the patched version of FranTk for ghc-4.06 with ghc-5.00. I used the fixes provided by Jan Kort for getting FranTk to work with ghc-4.08. This allows 'make boot' to succeed but produces errors at 'make all'. Are there any current fixes for running FranTk with ghc-5.00. Thanks Tuong

1 0

Joy and Concatenative Programming
by S. Alexander Jacobson 26 Sep '01

26 Sep '01

I just found out about a functional programming language called Joy (see http://www.latrobe.edu.au/philosophy/phimvt/joy.html) Joy differs from Haskell in that it has no variables. Instead, all functions are postfix, taking a stack as their argument and returning a stack as a result. Joy advocates contend that the elimination of variables and environments improves on functional languages in much the same way the elimination of state improved on imperative languages. In particular, they claim the result is massively simplified semantics and implementation (all the tree-rewriting rules go away), faster development, easier optimization (search and replace lists of functions) and even simple meta-programming. Here is a quick example program to give a flavor for how it works. [1 2 3 4] [dup *] map == [1 2 3 4] [square] map is the same as Haskell's map (\x->x*x) [1,2,3,4] == map square [1,2,3,4] Recursion is handled via some built in combinator primitives. For example this is qsort: qsort == [small] [] [uncons [>] split] [[swap] dip cons concat] binrec (the explanation of how this works is at http://www.latrobe.edu.au/philosophy/phimvt/joy/j01tut.html) Currently Joy is a interpreted language without a compiler checked type-system, but there is some discussion about adding such a system. (It is also apparently non-lazy, but I'm not sure what that means in a world without variables). The system is very new and primitive, but looks promising. I am curious what the wiser and more experienced people on this list think of Joy's approach. -Alex- ___________________________________________________________________ S. Alexander Jacobson Shop.Com 1-646-638-2300 voice The Easiest Way To Shop (sm)

3 2

More GHC 5.02 binaries available
by Julian Seward (Intl Vendor) 26 Sep '01

26 Sep '01

The web site (http://www.haskell.org/ghc) now has final binary builds for x86-Linux sparc-solaris Windows NT/2K/XP and allegedly 95/98/ME Additionally, the final source tarball is now on the web page. I claim (and earnestly hope) it is suitable for building other binary builds of 5.02. $ md5sum -b ghc-5.02-src-2.tar.bz2 0bf8b670759240032c317fec6b02f59d *ghc-5.02-src-2.tar.bz2 J

2 1

RE: ANNOUNCE: Happy version 1.11
by Simon Marlow 26 Sep '01

26 Sep '01

> ANNOUNCING Happy 1.11 - The LALR(1) Parser Generator for Haskell > ----------------------------------------------------------------- Owing to a rather embarrassing bug related to precedence parsing in the 1.11 release, I've uploaded new versions of the packages with the bug fixed. My apologies to anyone who already downloaded/installed 1.11 - please re-install with the updated packages. Cheers, Simon

1 0

Re: Application letters at the Haskell workshop: suggestion
by Mark Carroll 26 Sep '01

26 Sep '01

Mike - I hope you don't mind passing this to the list - but it's a great, simple explanation of a big problem with my approach. On 14 Sep 2001, Mike Gunter wrote: > The problem is not a loss of referential transparency but the > requirement that evaluation order must be specified. E.g. > what should > > raise "left" + raise "right" > > return? (snip) Ah! Yes, I see what you mean - this explains what Andy Moran was thinking, probably. (-: Moreover, if we have a pseudo-Haskell code snippet like, try f (a 1) (b 2) catch error-1 -> 1 error-2 -> 2 where a _ = raise error-1 b _ = raise error-2 ... then is the return value of this 1 or 2? AFAICS a simple way to get out of this is to only have one exception type that carries no information instead of different ones so we can't distinguish one exception from another, but that's obviously not great. One other thing you could do, which might mean a bit more evaluating than you otherwise would have done, is to evaluate enough to find out what the different possible "first exception"s are, gather them all up, and the handler that operates is the first applicable one if you list the higher-level 'catch' statements before the lower ones (so there's a total order on the handlers for exceptions arising from any particular expression within an evaluation). So, in this case, we detect that error-1 and error-2 were both thrown, but we return '1' because the error-1 handler was listed before the error-2 handler, just as we do with pattern matching IYSWIM. So, maybe we do have a way to resolve this that doesn't reveal evaluation order, with the penalty that we have to evaluate enough to discover which possible exceptions get thrown so that we really do use the 'first' applicable handler. I'm also subscribe to haskell-cafe if people think this discussion should migrate to there. -- Mark

2 1

RE: GUI Library Task Force
by Ashley Yakeley 26 Sep '01

26 Sep '01

At 2001-09-25 01:53, Manuel M. T. Chakravarty wrote: >* I am not a big fan of introducing an extra monad (`GUI' in > this case). It can easily become a pain in programs that > do a lot of "normal" IO as you have to lift all IO > functions to GUI. Heh. I had to do this for JVM-Bridge because all the JNI functions need the JavaVM. A bit like this: data JVM a = MkJVM (JavaVM -> IO a) instance Monad JVM where etc. ...actually there's more to the 'context' than that, but you get the idea. Of course there's a 'callIO' function to make lifting as painless as possible. On the other hand with the full Java API hopefully there's less necessity to use "normal" IO at all anymore so perhaps it will be less of an issue. -- Ashley Yakeley, Seattle WA

1 0

IEEE Conf.on Software Maintenance, Italy,Florence, ICSM2001
by icsm2001 26 Sep '01

26 Sep '01

Dear Colleague I would like to invite you to attend the IEEE International Conference on Software Maintenance, 2001, and associated workshops: IEEE SCAM, IEEE WESS, IEEE WSE, TABOO. FLORENCE, ITALY, 6-10 November 2001 http://www.dsi.unifi.it/icsm2001 ICSM is the major international conference in the field of software and systems maintenance, evolution, and management. Theme: Systems and Software Evolution in the era of the Internet kEYWORDS: software evolution, embedded suystems, program analysis, reengineering, managment, maintenance, lyfe cycle, Internet and distributed systems, Multimedia systems, User interface evolution, Commercial off-the-shelf (COTS), Program comprehension, Formal methods, Empirical studies, Testing and regression testing, Measurement of software, METRICS,etc. Please forward the following to anybody you think may be interested. The discount for the advanced registration fee will be active for few days. Apologies for multiple receptions. If you would like to be removed from our list please send an email to icsm2001(a)dsi.unifi.it with REMOVE in the subject. Paolo Nesi (ICSM2001 General Chair)

1 0

Satisfiability and ambiguity
by Carlos Camar�o 25 Sep '01

25 Sep '01

Folks, I have recently been referred to a paper by Duggan and Ophel, about "Type-checking Multi-parameter type classes" [1]. I think it will be useful to consider the following. ---------------------------------------------------------------------- 1. "Domain-driven unifying overload resolution" (DDUOR, so-called in definition 4.1 in [1]) should not fail to terminate; i.e. satisfiability is not undecidable (see system CT [2]). DDUOR should consider the *set* of constraints (in C, in def. 4.1), instead of one after another, for finding unifying substitions (\theta'' in def. 4.1). For the example (page 17 of [1]): class F a b where f:: a -> b -> Int instance F Int Float where f x y = 0 instance F a b => F [a] [b] where f [x] [y] = f x y g x y = (f [x] y) + (f y [x]) the definition of g will be detected as erroneous (not well-typed) if the *set* of constraints is considered for finding the unifying substitution, instead of one constraint after another. In this way, DDUOR terminates. I think full details will not be needed, but this can be (easily) understood by reading/following the definition of sats in system CT. -------------------------------------------------------------------- 2. The usefulness of multi-parameter type classes has been hindered by the restrictiveness of the rule for detecting ambiguity. Instead of tv(P) \subseteq tv(t), where P is the set of constraints and t is the simple type, the rule for nonambiguity should be P = P |* tv (t,G) where |* denotes "constraint projection" and G the typing context. For the definition of |* see [3]; the idea is to include constraints that have type variables in t and G and constraints that have type variables previously included. In the example: For: P = F a b and t = a We have that: P => t is not ambiguous Since: P |* {a} = P This rule would allow multi-parameter type classes to be used in (well-known) compelling examples, without giving rise to ambiguities. Carlos [1] Type-checking multi-parameter type classes, Dominic Duggan and John Ophel, to appear in JFP. [2] Type Inference for Overloading, Carlos Camarão and Lucília Figueiredo, Technical report UFMG, available at http://www.dcc.ufmg.br/~camarao/jfp-ct.ps.gz. [3] Overloading and Coherence, Carlos Camarão and Lucília Figueiredo, Technical report UFMG, available at http://www.dcc.ufmg.br/~camarao/overloading-and-coherence.ps.gz .

1 0

Final CALL: WICS'2002
by Dr. Muhammad Sarfraz 25 Sep '01

25 Sep '01

Apologies if you receive multiple copies FINAL CALL FOR PAPERS WICS'2002 ---The Fourth Workshop on Information & Computer Science March 17-18, 2002 King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia Information & Computer Science Department (KFUPM) in collaboration with IEEE Computer Society Saudi Arabia Chapter Theme: Internet Computing Best papers will be published in A Special Issue Of Information Sciences Journal Important Dates September 30, 2001 Papers due (about 15 pages). November 25, 2001 Notification of acceptance. December 23, 2001 Camera-ready papers. March 17 - 18, 2002 Workshop. For detailed information, please visit: http://www.ccse.kfupm.edu.sa/wics/ Contact Address : Chairman, Organizing Committee, WICS'2002 Department of Information & Computer Science KFUPM # 5066 King Fahd University of Petroleum and Minerals Dhahran 31261, Saudi Arabia Tel.: +966-3-860-2175 Fax: +966-3-860-2174 Email: wics(a)ccse.kfupm.edu.sa WWW: www.ccse.kfupm.edu.sa/wics/

1 0