December 2003 - Haskell

GHC: Installation problem on suse 9.0.
by Gustavo Villavicencio 18 Dec '03

18 Dec '03

Dear all i have running ghc on suse 7.3, but i can't install it on suse 9.0. the next error is raising during the HC files compilation: -------------------------------------------- ... CTypes.hc:55265: warning: (near initialization for `CTypes_tpl890_closure.payload') CTypes.hc:55297: warning: excess elements in array initializer CTypes.hc:55297: warning: (near initialization for `CTypes_tpl891_closure.payload') CTypes.hc:55324: warning: excess elements in array initializer CTypes.hc:55324: warning: (near initialization for `CTypes_zdfReadCChar_closure.payload') CTypes.hc:55324: warning: excess elements in array initializer CTypes.hc:55324: warning: (near initialization for `CTypes_zdfReadCChar_closure.payload') CTypes.hc:55324: warning: excess elements in array initializer CTypes.hc:55324: warning: (near initialization for `CTypes_zdfReadCChar_closure.payload') Prologue junk?: czvw_ret: movl $0, 16(%esp) movl $0, 20(%esp) movl $0, 8(%esp) movl $0, 12(%esp) gmake[2]: *** [CTypes.o] Error 255 gmake[1]: *** [all] Error 1 gmake: *** [all] Error 1 -------------------------------------------- any help will be appreciated. gustavo

1 0

RE: haddock (and -- $)
by Simon Marlow 18 Dec '03

18 Dec '03

> hello. a few comments and questions on haddock > (www.haskell.org/haddock/) > > 1. haddock is great Thanks ;) > 2. haddock's interpretation of "-- $" is un-great: > > I have two types of "-- $" occurences in my code > that conflict with haddock's idea of "named doc chunks" > > a. CVS macros: -- $Id: ...$ > > b. pipes like this, with some lines commented out: > > let x = this_function > $ that_function > -- $ but_not_this > $ arg I'm not sure that we can/should do anything about this. The same problem crops up with '-- |' too: you might comment out some guards for example. The solution is to add an extra space after the '--', or use three dashes '---', etc. etc. > 3. how can I refer to external system libraries documentation > (i. e. Data.FiniteMap from the ghc web site)? Download a GHC distribution, which has the .haddock files for the libraries. Then use the --read-interface option, something like this: $ haddock --read-interface=file:///usr/share/ghc-6.2/html/libraries/base,/usr/shar e/ghc-6.2/html/libraries/base/base.haddock or you can point to the online docs, by replacing the first URL with http://www.haskell.org/ghc/docs/6.2/html/libraries/base. You can add further --read-interface options for the other packages that come with GHC. In the future, Haddock will make this easier by asking GHC where it keeps its documentation. > 4. haddock does not seem to understand cpp #ifdefs. > how can I work around this? (I know I shouldn't use cpp > in the first place, but I want to document existing code, > and not rewrite it just to make the doc tool happy :-) You can run cpp over the source file before feeding it to Haddock. This is what we do for GHC's libraries. eg. $ ghc -E -cpp Foo.hs -o Foo.raw-hs $ haddock Foo.raw-hs ... You can use some appropriate Makefile rules to automate this. Cheers, Simon

1 0

haddock (and -- $)
by Johannes Waldmann 18 Dec '03

18 Dec '03

hello. a few comments and questions on haddock (www.haskell.org/haddock/) 1. haddock is great 2. haddock's interpretation of "-- $" is un-great: I have two types of "-- $" occurences in my code that conflict with haddock's idea of "named doc chunks" a. CVS macros: -- $Id: ...$ b. pipes like this, with some lines commented out: let x = this_function $ that_function -- $ but_not_this $ arg 3. how can I refer to external system libraries documentation (i. e. Data.FiniteMap from the ghc web site)? 4. haddock does not seem to understand cpp #ifdefs. how can I work around this? (I know I shouldn't use cpp in the first place, but I want to document existing code, and not rewrite it just to make the doc tool happy :-) again, haddock is great. even running it on the code as-is (without any annotations) gives nice interface documentation, indexing and cross-refs. -- -- Johannes Waldmann, Tel/Fax: (0341) 3076 6479 / 6480 -- ------ http://www.imn.htwk-leipzig.de/~waldmann/ ---------

1 0

Annotating Expressions
by John Meacham 17 Dec '03

17 Dec '03

Imagine I have a data structure like so: data E = EAp E E | ELam Int E | ELetRec [(Int,E)] E | EVar Int now, I want to annotate every occurence of E with some pass specific information, such as free variables or levels for lambda lifting. in [PEY91] this technique was used: data EAn a = EaAp (a,EAn a) (a,EAn a) | EaLam Int (a,EAn a) | EaLetRec [(Int,(a,EAn a))] (a,EAn a) | EaVar Int however this suffered from two problems, 1. EAn () is not computationally identical to E, since it has an extra indirection 2. it is anoying to work with EAn () when we don't want to use the extra info, meaning we keep both E and EAn around, despite them being very similar using an idea inspired by [SHEARD01] I came up with the following newtype Id a = Id a type Er f = f (E f) -- E used recursivly data E f = EAp (Er f) (Er f) | ELam Int (Er f) | ELetRec [(Int,Er f)] (Er f) | EVar Int now, this solves problem 1. (E Id) is computationally identical to the original E, however problem 2 persists. If I don't want to be constantly casting to and from Id, I have to use both the seperate annotated and unannotated versions. is this actually the case? is there a better solution I don't see? perhaps something using crazy GHC extensions? if not, are there any proposed extensions which would solve this promlem? if there were some limited way to partially apply a type declaration that would solve the problem, but raise others. perhaps a 'nullary' type constructor, as in type Id = or just type Id so Id is of kind (* -> *) and expands to nothing. then in (E Id) it is fully applied... any other ideas? perhaps some that work :) John [PEY91] http://research.microsoft.com/~simonpj/papers/fully-lazy-lambda-lifter.ps.gz [SHEARD01] http://www.cse.ogi.edu/~sheard/papers/generic.ps -- --------------------------------------------------------------------------- John Meacham - California Institute of Technology, Alum. - john(a)foo.net ---------------------------------------------------------------------------

4 4

FW: [Caml-list] Data structures and algorithms in Caml programs
by Simon Peyton-Jones 15 Dec '03

15 Dec '03

Dear Haskell library folk Here's an interesting survey about data structure libraries. It's Caml oriented, but very relevant to Haskell too. Simon -----Original Message----- From: owner-caml-list(a)pauillac.inria.fr [mailto:owner-caml-list@pauillac.inria.fr] On Behalf Of Diego Olivier Fernandez Pons Sent: 10 December 2003 14:43 To: caml-list(a)inria.fr Subject: [Caml-list] Data structures and algorithms in Caml programs Bonjour, I have reviewed 20 programs I think representative of Caml, trying to investigate the usages and needs in data structures and algorithms. http://www.edite-de-paris.com.fr/~fpons/Caml/Ressources/dsInCaml.html The purpose is to have a more precise idea of what is really giving trouble and help library designers to provide solutions that are closely related to the programmers needs. All comments are welcome including corrections and programmers feedback on code design, etc. Reviewed programs Caml (21) (data) aifad, ibal (bioinformatics) biocaml (compilation) ccured, dml, fftw, flowcaml, mojave (constraint solving) cime, facile, wallace (parsing) cil, cfg, sister-head (text) cduce, galax, hevea, regex, timbuk (theorem proving) coq, harrison, link Standard ML (1) (compilation) mlrisc Haskell (4) (parsing) alex, happy, parsec (text) regexplib

1 0

E-CAP2004_ITALY Deadline extension Jan 7
by Lorenzo Magnani 14 Dec '03

14 Dec '03

CALL FOR PAPERS DEADLINE EXTENSION: NEW DEADLINE JAN 7, 2004 (1000 words abstract or PPT file) SEE BELOW! ********************************************************************** COMPUTING AND PHILOSOPHY E-CAP2004_ITALY Pavia, Italy, Collegio Ghislieri, June 3-5, 2004 Chair: Lorenzo Magnani ********************************************************************** Up-to date information on the conference will be found at http://www.unipv.it/webphilos_lab/courses/progra2.html ********************************************************************** ALSO NEW !! Conference MODEL-BASED REASONING IN SCIENCE AND ENGINEERING Pavia, December 2004 http://www.unipv.it/webphilos_lab/courses/progra1.html ********************************************************************** GENERAL INFORMATION From Thursday 3 to Saturday 5 June 2004 (three days) the International European Conference ``COMPUTING AND PHILOSOPHY'' will be held at the University of Pavia (near Milan, Italy). GENERAL INFORMATION The Computational Philosophy Laboratory and the Department of Philosophy of the University of Pavia will be hosting the European Computing and Philosophy (CAP) conference from the 3rd to the 5th of June. PROGRAM The conference will deal with all aspects of the "computational turn" that is occurring within the discipline of Philosophy. We solicit papers that examine topics pertaining to computing and philosophy from the following list. RELEVANT RESEARCH AREAS We call for papers that cover topics pertaining to computing and philosophy from the following list: * Cognitive Science, Epistemology, and Metaphysics * Abductive reasoning, Scientific discovery, Creative processes * Internal and External Representations in Cognitive Science * Simulation, Embodiment, and Distributed Reasoning in Computational Models of Cognitive * Problem of Consciousness in Philosophy * New Models of Logic Software * Computer-based Learning and Teaching Strategies and Resources * Ethics and Computers * The Impact of Distance Learning on the Teaching of Philosophy * The Role of Computers as Tools for Philosophical Research SUBMISSIONS OF PAPERS The deadline for submission is 19th December 2003 - though late submissions will be considered. The deadline for submission is 19th December 2003 - though late submissions will be considered. Authors should submit an electronic version - formatted in Microsoft Word or RTF, but also in PDF or POSTSCRIPT ( in this last case please include source - DOC, TEX, etc., file) - of an extended abstract (total word count aproximately 1000 words). The file should also contain a 300 WORD abstract that will be used for the conference web site/booklet. Contributions expressed in PPT files are also accepted along with or in place of the 1000 words abstract. not later than JANUARY 7, 2004 Please send all submissions to Prof. Magnani at the address lmagnani(a)cc.gatech.edu (if the previous address does not work please use lorenzo.magnani(a)unipv.it) A RIGID LAW ON PRIVACY IN ITALY DOES NOT FAVOR MORE COMFORTABLE COMPUTATIONAL METHODS OF PAYMENTS (CONFERENCE AND ACCOMODATION FEES), SORRY. PLEASE FOLLOW THE INSTRUCTIONS INDICATED BELOW. REGISTRATION AND FURTHER INFORMATION PLEASE REGISTER by email lmagnani(a)cc.gatech.edu (or lorenzo.magnani(a)unipv.it) fax or air mail by sending the PROGRAM CHAIR first and last name, function, institution, full address, phone, fax and email. For information about paper submission and the program that is not available on the web site, please contact the program chair. Registration Fees: Before 15 April 2004: Standard: EURO 150,00 (to participate in all the activities of the Conference Reception Included) Phd Students: EURO 90,00 Students: Free After 15 April 2004: Standard: EURO 180,00 (to participate in all the activities of the Conference Reception Included) Phd Students: EURO 110,00 Students: Free One day only: EURO 80,00 No refunds will be granted after May 12th, 2004 Terms & Conditions: an administration fee of EURO 75,00 will be charged for cancellations confirmed in writing by 12th May. We regret that no refund can be made after that date, for whatever reason, although substitutions will be acceptable if notified in writing before the event. METHOD OF PAYMENT: SWIFT TRANSFER Bank (Swift) Transfer to BANCA REGIONALE EUROPEA S.p.A BRANCH PAVIA - Sede SWIFT BREUITM2 301 Bank Code 06906.11301 Acc. n. 42113 COMITATO CONVEGNI E. W. I. C. IBAN: IT32O0690611301000000042113 (attention: the fifth symbol is the letter O and not zero). Please indicate CONVEGNO INTERNAZIONALE E-CAP2004_ITALY Please ask your BANK to clearly indicate in the order of payment your first and last NAME. In case of problems please contact Elena Gandini Local Organizer elena(a)acrossevents.com) If you prefer, you can mail an international check to CONVEGNO INTERNAZIONALE E-CAP2004_ITALY, Dipartimento di Filosofia, Piazza Botta 6, 27100 Pavia, Italy . ACCOMMODATION To book a reservation please fill and fax to +39-0382-23215 the ACCOMMODATION FORM you will find in the Conference Web Site http://www.unipv.it/webphilos_lab/courses/progra1.html (to dr. Elena Gandini Local Organizer). POSSIBLY BEFORE APRIL 15, 2003. For information please email Elena Gandini, Local Organizer elena(a)acrossevents.com. Please do not send email messages containing your credit card data. All accommodation is hotel-based with en-suite facilities (the prices are per room per day). Hotel Moderno ****Euro 103,00 (single b&b) Euro138,00 (double b&b) Hotel Ariston *** Euro 80,00(single) Euro 110,00 (double), Breakfast Euro 10,00 Hotel Excelsior *** Euro 50,00(single) Euro 73,00(double) Euro 62,00(D/S) breakfast Euro 6,00 Hotel Ritz*** Euro 65,00 (single b&b) Euro 87,00 (double b&b) Hotel Excelsior (from the station walk east) Hotel Moderno (from the station walk north) Hotel Ritz (San Genesio-PV); an Hotel bus service is available. To reach Hotel Ariston take the bus n. 3 or taxi. If the Hotels above will be completely booked other Hotels are available, in this last case please email dr. Elena Gandini Local Organizer e-mail: elena(a)acrossevents.com PENALTY In case of no show the Hotels will charged you their own penalty. For further information, please contact our local organiser Elena Gandini elena(a)acrossevents.com. IMPORTANT DATES Submission deadline...........................7 Janaury 2004 Notification of acceptance................... 19 March 2004 Conference................................... 3-5 June 2004 Final papers............................due.. 15 July 2004 PROGRAM CHAIR Lorenzo MAGNANI Professor of Logic and Epistemology Department of Philosophy and Computational Philosophy Laboratory University of Pavia, Piazza Botta 6, 27100 Pavia, Italy Office: +39-0382-506283, Home: +39-0383-371067 Fax: +39-0382-23215 & Weissman Distinguished Visiting Professor Department of Philosophy, Baruch College, 1 Bernard Baruch Way, New York , NY 10010 Office: +646-312-4367, Fax: +646- 312-4361, Home: 646-432-9309 Email: lmagnani(a)unipv.it, lmagnani(a)cc.gatech.edu PROGRAM COMMITTEE - Atocha Aliseda, Instituto de Investigaciones Filosoficas Universidad Nacional Autonoma de Mexico (UNAM), Mexico City, MEXICO - Diderik Batens, Centre for Logic and Philosophy of Science, Universiteit Gent, Ghent, Belgium - Robert Cavalier, Department of Philosophy, Carnegie Mellon, Pittsburgh, PA, USA - Simon Colton, Department of Computing, Imperial College London, London, UK - Roberto Cordeschi, Department of Communication Sciences, University of Salerno, Salerno , ITALY - Chris Dobbyn, Faculty of Maths and Computing,The Open University,Walton Hall, Milton Keynes MK7 6AA - Roy Dyckhoff, School of Computer Science,University of St Andrews,North Haugh, St Andrews,Fife, KY16 9SS, Scotland - Luciano Floridi, Wolfson College, University of Oxford, Oxford, UK and University of Bari,Bari, ITALY - Theo Kuypers, Dept. of Philosophy, University of Groningen, Groningen, The Netherlands - Lorenzo Magnani, Department of Philosophy, University of Pavia, Pavia, ITALY and Baruch College, The City University of New York, New York, USA - Nancy J. Nersessian, College of Computing, Georgia Institute of Technology, Atlanta, GA, USA - Claudio Pizzi, Department of Philosophy and Social Sciences, University of Siena, Siena, ITALY - Susan Stuart, Humanities Advanced Technology and Information Institute, University of Glasgow, Glasgow, UK - Guglielmo Tamburrini, Department of Philosophy, University of Pisa, Pisa, ITALY - Riccardo Viale, Fondazione Rosselli,Via San Quintino, 18/c, 10121 Torino, Italy LOCAL ORGANIZER dr. Elena Gandini Across Events s.r.l. Via A. Moro, 12 27021 Bereguardo (PV) Italy mobile +39 349 55 41 915 e-mail: elena(a)acrossevents.com www.acrossevents.com LOCAL ORGANIZING COMMITTEE Elena Gandini (elena(a)acrossevents.com) Riccardo Dossena (riki.dox(a)libero.it) Lorenzo Magnani (lmagnani(a)cc.gatech.edu) (Department of Philosophy, University of Pavia, Pavia, Italy) Stefanelli Mario (mstefa(a)aim.unipv.it) Matteo Piazza (pimat(a)yahoo.com) (Dipartimento di Informatica e Sistemistica, Università di Pavia, Pavia, Italy) IMPORTANT ADDRESSES PROGRAM CHAIR Lorenzo MAGNANI Department of Philosophy and Computational Philosophy Laboratory University of Pavia, Piazza Botta 6, 27100 Pavia, Italy Office: +39-0382-506283, Home: +39-0383-371067 Fax: +39-0382-23215 Email: lmagnani(a)unipv.it also Department of Philosophy, Baruch College, The City University of New York 1 Bernard Baruch Way, New York , NY 10010 Office: +646-312-4364 Fax: +646- 312-4361 CONFERENCE SITE: Collegio Ghislieri, Piazza Ghislieri, 27100 PAVIA, Italy, phone +39 0382 37861. http://www.ghislieri.it/ The Conference is sponsored by UNIVERSITY OF PAVIA, ITALY UNIVERSITY OF SIENA, ITALY MIUR (Ministero dell'Università e della Ricerca Scientifica e Tecnologica), ITALY HOW TO REACH PAVIA LINATE Airport: www.sea-aeroportimilano.it/linate People arriving by plane at LINATE should take the bus to the CENTRAL STATION of Milan (cf. below from this Station to Pavia). In LINATE it could be convenient to take a Taxi because the airport is close to the center of Milan. Moreover,the bus company SILA ( www.sila.it ) offers six runs from LINATE to Pavia at 9.00, 10.00, 12.00 AM and 2.00, 5.00, 8.30 PM. The last stop is Pavia, near the station (see again our updated web page for possible alterations of this time-table) (from Pavia to LINATE six runs at 5.00, 7.30, 10.00 AM, 1.00, 4.00, 6.00 PM) (one hour trip; _13,00 return ticket, _8,00 one way ticket). In Pavia there is only one station. The easiest way to reach the center of the town is to get off at the station and than take the bus n. 3. MALPENSA 2000 and OLD MALPENSA Airports: www.sea-aeroportimilano.it/malpensa (usually people arrive to Malpensa 2000 and not to OLD MALPENSA): People arriving by plane at MALPENSA 2000 (also called MALPENSA 2000 Terminal 1) or at "old" MALPENSA (now called MALPENSA NORTH but also called Malpensa 2000 Terminal 2) should take the bus to the CENTRAL STATION of Milan. There is also a bus AND A shuttle TRAIN (Malpensa Express) from Malpensa 2000 to the NORTH STATION (Piazzale Cadorna) of Milan, in this case from NORTH Station you will have to take the underground MM2 (green line) to the Central Raylway Station: trains to Pavia leave from Central station. Moreover, the bus company SILA offers various runs from MALPENSA 2000 to Pavia at 9.00, 11:00 AM, 1:30 3:00, 5:00, 7:00, 9:30, PM (from Pavia to MALPENSA 2000 and to OLD MALPENSA various runs at 7.00, 9:00, 11:00 AM, 1:00, 3:15, 5:00, 7:00 PM) (one hour and half trip; _18,00 retourn ticket, _12,00 one way ticket). The last stop is Pavia, near the rail station In Pavia there is only one rail station. The easiest way to reach the center of the town is to get off at the station and than take the bus n. 3. There are trains from MILAN (Central Raylway Station) to PAVIA and vice versa about every an hour www.trenitalia.it (routes: MILAN-GENOVA; MILAN-VENTIMIGLIA; MILAN-LA SPEZIA; MILAN-SAVONA; MILAN-SESTRI LEVANTE; MILAN-IMPERIA; MILAN-ALBENGA; Pavia is the first stop only if the train is not slow, that is, if it is not, in ITALIAN, "L", locale). (see again our updated web page for possible alterations of this time-table) For any further information do not hesitate to contact our local organizer, Elena Gandini at elena(a)acrossevents.com -- Lorenzo Magnani Department of Philosophy & Computational Philosophy Laboratory University of Pavia, Piazza Botta 6, 27100 Pavia, Italy Department of Philosophy, Baruch College, The City University of New York 1 Bernard Baruch Way, New York , NY 10010 Computational Philosophy Laboratory, Italy <http://www.unipv.it/webphilos_lab/>

1 0

error in the hdirect installation
by Mauro La Salete Costa Lima de Araujo 13 Dec '03

13 Dec '03

Hi people, I have just downloaded the fptools with the purpose of use the hdirect. But when I execute a "make boot; make" in the hdirect directory in the middle of the compile process I get the following error: ... ------------------------------------------------------------------------ ==fptools== make all - --unix -r; in /cygdrive/c/haskell/fptools/hdirect/comlib ------------------------------------------------------------------------ /cygdrive/c/ghc/ghc-6.0.1/bin/ghc -H16m -O -fvia-C -package-name com -package lang -I../lib -DCOM -fglasgow-exts -fvia-C -static -c TypeLib.hs -o TypeLib.o - ohi TypeLib.hi TypeLib.hs:2291: Couldn't match `IUnknown i0' against `()' Expected type: Ptr (IID (IUnknown i0)) Inferred type: Ptr (IID ()) In the fourth argument of `prim_TypeLib_createInstance', namely `riid' In a lambda abstraction: \ riid -> prim_TypeLib_createInstance methPtr iptr pUnkOuter riid ppvObj make[1]: *** [TypeLib.o] Error 1 make: *** [all] Error 1 The steps that I used were: -> "autoreconf" in the fptools directory -> "./configure" in the fptools directory -> "make boot; make" in the alex directory -> "make boot; make" in the happy directory -> "make boot; make" in the hdirect directoty Can anyone help me? I'm just following a tutorial in: http://www.cin.ufpe.br/~haskell/vhs/howto-tarball.html cheers, ------------------------------------------------- | Mauro La-Salette C. L. de Araújo | | Graduando em Ciências da Computação CIn-UFPE | | Bolsista do grupo PET CIn - UFPE | | mscla(a)cin.ufpe.br | | www.cin.ufpe.br/~mscla | ------------------------------------------------- "If this is true, building software will always be hard. There is inherently no silver bullet." (F.P.Brooks)

2 4

GreenCard (How to Marshell Int64)
by Liwen Huang 13 Dec '03

13 Dec '03

Hello: I am using GreenCard to import some C code into Haskell. The code I want to import uses "long" in a lot of places. I tried to write my own DIS for it and I also write a very simple test program. However, the DIS does not work properly. My program and test result are as following: -------------------------------------------------------------------------- module TLong where import Foreign.GreenCard type Long = Int64 %dis long x = int64 x %dis int64 x = %%Int64 ({HsInt64} x) %fun tslong :: Long -> Long %call (long a1) %code long a2; % a2 = a1; % printf("the long integer is %d the original is %d \n", a2, a1); %result (long (a2)) ------------------------------------------------------------------------------ ..... TLong>tslong 1 the long integer is -1073752653 the original is -10173752653 -4611732526480752641 ------------------------------------------------------------------------------ I know it is caused by my DIS, but I have no idea what is the right way to do it. Does anyone know the right way to do it? Best Regards Liwen

3 3

Use of Haskell logos
by Graham Klyne 12 Dec '03

12 Dec '03

Given the open nature of the Haskell community, I am assuming that I don't need permission to use one of the Haskell logos on a web page I'm creating to describe my software project. A work-in-progress -- i.e. incomplete -- copy of the page concerned can be seen here: http://www.ninebynine.org/RDFNotes/Swish/Intro.html If I'm wrong, can someone please let me know, and I'll pull the logo. #g ------------ Graham Klyne For email: http://www.ninebynine.org/#Contact

2 1

type classes, superclass of different kind
by Robert Will 12 Dec '03

12 Dec '03

Hello, As you will have noticed, I'm designing a little library of Abstract Data Structuresm here is a small excerpt to get an idea: class Collection coll a where ... (<+>) :: coll a -> coll a -> coll a reduce :: (a -> b) -> b -> coll a -> b ... class Map map a b where ... (<+) :: map a b -> map a b -> map a b at :: map a b -> a -> b ... Note that the classes don't only share similar types, they also have similar algebraic laws: both <+> and <+ are associative, and neither is commutative. Now I would like to have Collection to be a superclass of Map yielding the following typing reduce :: (Map map a b) => ((a, b) -> c) -> c -> map a b -> c Note that in an OO programming language with generic classes (which is in general much less expressive than real polymorphism), I can write class MAP[A, B] inherit COLLECTION[TUPLE[A, B]] which has exactly the desired effect (and that's what I do in the imperative version of my little library). There seems to be no direct way to achieve the same thing with Haskell type classes (or any extension I'm aware of). Here is a quesion for the most creative of thinkers: which is the design (in proper Haskell or a wide-spread extension) possibly include much intermediate type classes and other stuff, that comes nearest to my desire? I believe this question to be important and profound. (We shouldn't make our functional designs more different from the OO ones, than they need to be.) If I err, someone will tell me :-> Robert

4 3