April 2001 - Haskell - Haskell.org

question of decimal pointed literals
by S.D.Mechveliani 20 Apr '01

20 Apr '01

Can we solve and close the problem of the meaning of decimal pointed leterals? To my | People wrote about toRational (0.9) == 9%10 = False | ... | Probably, the source of a `bug' is a language agreement that the | input is in decimal representation (`0.9') and its meaning is a | floating approximation in _binary_ representation. | For example, 1%5 yields a finite mantissa in decimal representation | and an infinite (periodic) mantissa for the binary representation of | toBinary(1%5) = 1B % 1001B. (a typo: this should be 101B) | Therefore applying toRational to any finite float approximation | (Double, or other) of 1%5 does not return 1%5. Lennart Augustsson <lennart(a)mail.augustsson.net> writes > What are you talking about? Input in decimal representation is > stored as a Rational number. There is absolutely no loss of > precision. and in his next letter citates the Report: > "The floating point literal f is equivalent to > fromRational (n Ratio.% d), where fromRational is a > method in class Fractional and Ratio.% constructs a rational from > two integers, as defined in the Ratio library. The integers n and > d are chosen so that n/d = f." By saying "input is in decimal representation (`0.9')" I meant that a number `0.9' is written by a programmer keeping in mind a decimal representation. Further, according to the citation, 0.9 --> fromRational (9%10), 0.2 --> fromRational (1%5) are stored as the values of type Fractional a => a. (1) What is this `a' for our example of toRational (fromRational (0.9)) == 9%10 ? (2) Why Haskell does not report an ambiguity error? For `a' may be Rational, Double, Float - just anything of Fractional. If we take Lennart's assertion > Input in decimal representation is stored as a Rational number. > There is absolutely no loss of precision. then it should be `a' = Rational. Then, in particular, toRational (0.d) == d%10 = True for any decimal literal d and * any other behavior is a bug. * Is this really so? Now, Hugs-98-Feb-2000, probably, decides that `a' = Double. Because it returns False for 0.9. And in this case these values are _not_ stored as the rational numbers, but convert to Double, with the precision loss caused, as I wrote initially, by truncating of the division result, like 1001B % 1010B. Who could explain, please, whether I understand correct the whole question, and answer to the questions (1), (2) ? And is `False' is a bug? Thanks in advance for the comments. ----------------- Serge Mechveliani mechvel(a)botik.ru

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c2hs on ghc5?
by Jens-Ulrik Petersen 20 Apr '01

20 Apr '01

I checked c2hs-cvs a couple of days ago, and am wondering if anyone has any patches yet for building c2hs under ghc5? I guess it is just a matter of tweaking the config files a bit. So if noone else has had time yet, I will try to do it soon. Cheers, Jens

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Introducing a New Concept on Advanced Garbage Treatment Process
by zwj 19 Apr '01

19 Apr '01

Introducing a new concept on advanced garbage treatment process, and licensing patents For details, please reference the web site: http://zwj5382.3322.net http://zwj5382.163.net The inventor would like to assign exclusive patent license to anyone who is interested in patented advanced garbage treatment process technology. For patent license, please contact the inventor via E-mail: zwj88zww(a)371.net

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haskell in a programming languages course?
by Fred Hosch 19 Apr '01

19 Apr '01

For the time in MANY years, I'm scheduled to teach a junior-senior level programming languages course this fall. Our students are -- uhhh -- shall we say "marginal"? (I mean, this is no Mississippi State after all.) I've looked at a number of possible textbooks and found them to be disappointingly shallow. (Well, THIS one's pretty good, but it assumes a knowledge of Scheme. sigh.) So I thought that maybe I'd do the course as it was done in olden times, as a case study of a few languages using the standards documents. I'm looking for a nice functional language to present, and Haskell seems an obvious choice. (I've dabbled a bit with ML and Miranda years ago, but haven't really done anything with Haskell.) The Haskell report, however, seems a bit daunting, particularly for our troops. (C'mon, one of you guys is really van Wijngaarden, right?) So I'm looking for suggestions: is there anything out there that's a bit more of a technical look at the language than "How to program in Haskell" but more approachable than the report? Or is Haskell not the right thing to try? Thanks for any input. Hope I didn't interrupt any serious threads on the list. Fred Hosch fred(a)cs.uno.edu Computer Science Department (504)-280-6594 University of New Orleans (504)-280-7228 (fax) New Orleans, LA 70148

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(fromRational (1%5)) :: Double
by S.D.Mechveliani 19 Apr '01

19 Apr '01

Lennart Augustsson <lennart(a)mail.augustsson.net> writes > "S.D.Mechveliani" wrote: >> the matter is in what the _language standard_ says. >> If it puts that `0.9' in the user program means precizely 9%10, >> then Lennart is right. > I quote the report: > > "The floating point literal f is equivalent to > fromRational (n Ratio.% d), where fromRational is a > method in class Fractional and Ratio.% constructs a rational from > two integers, as defined in the Ratio library. The integers n and > d are chosen so that n/d = f." > > I think the way Haskell handles numeric literals is pretty nice and > it's important to understand what happens if you use them. :) I confess, I do not understand from the previous letters, in what way, for example, Hugs finds Prelude> (fromRational (1%5)) :: Double 0.2 I never dealt with Floats in Haskell. And thought that a value of Double has mantissa in a binary representation. So, the interpreter has to convert a decimal 5 to a binary 101B, evaluate 1B / 101B obtaining an infinite sequence of binary digits and take the first m of them required for Double. Printing the result should yield something like 0.1999... Thank you in advance for the explanation. ----------------- Serge Mechveliani mechvel(a)botik.ru

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Re: Dimensional analysis with fundeps
by Ashley Yakeley 19 Apr '01

19 Apr '01

At 2001-04-19 01:19, Ashley Yakeley wrote: >Herewith my attempt. Sorry, that should have gone to the Haskell Cafe list. -- Ashley Yakeley, Seattle WA

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Re: Dimensional analysis with fundeps
by Ashley Yakeley 19 Apr '01

19 Apr '01

At 2001-04-09 10:29, Dylan Thurston wrote: >I hadn't thought about doing rational arithmetic with GCDs. Might be >nice. Herewith my attempt. I can't test it though, it runs afoul of one of the many bugs in Hugs' type-extension handling, and I haven't been able to run GHC on my MacOS X box. -- Ashley Yakeley, Seattle WA

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Concurrent Haskell (Ops...)
by Andre W B Furtado 19 Apr '01

19 Apr '01

[I mean "CONCURRENT Haskell" rather than "Haskell DIRECT" in the last email. Sorry.] ------- I am trying to create a program that prints interleaved sequences of 'a's and 'z's, using Haskell Direct (under GHC). I've tryied the following: import Concurrent main :: IO() main = let loop ch = putStr(ch) >> loop ch in forkIO (loop "a") >> loop "z" But this program prints only 'z's, and no 'a's. I was surprised by this, since GHC uses preemptive multitasking, not cooperative multitasking. Does anyone knows what's going wrong? Thanks, Andre W B Furtado

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SAS'01 Call For Participation
by radhia＠lix.polytechnique.fr 18 Apr '01

18 Apr '01

PROGRAMME AND CALL FOR PARTICIPATION SAS'01 Eigth International Static Analysis Symposium La Sorbonne, Paris, 16-18 July, 2001 http://www.ens.fr/sas01/ Registration information is available at the bottom of this announcement. Electronic registration is also available on the SAS'01 website. The hotels reservations are to be done by --22 April 2001--. PROGRAMME MONDAY JULY 16 8:00-9:00 Registration 9:00-10:00 Invited Talk Program Analysis for Multi-threaded Programs Martin C. Rinard (Massachusetts Institute of Technology) 10:00-10:30 Break 10:30-12:00 Program transformation Communication and Parallelism Introduction and Elimination by Static Formal Transformations Miquel Bertran, Francesco Babot and August Climent Miquel Nicolau Using Slicing to Identify Duplication in Source Code Raghavan Komondoor and Susan Horwitz Soft Scheduling for Hardware Richard Sharp and Alan Mycroft 12:00-13:30 Lunch 13:30-15:00 Strictness and termination Effective Strictness Analysis with HORN Constraints Kevin Glynn, Peter J. Stuckey, and Martin Sulzmann Applying Static Analysis Techniques for Inferring Termination Conditions of Logic Programs Fred Mesnard and Ulrich Neumerkel An Abstract Analysis of the Probabilistic Termination of Programs David Monniaux 15:00-15:30 Break 15:30-17:00 Semantics abstraction Watchpoint Semantics: A Tool for Compositional and Focussed Static Analyses Fausto Spoto Logic and constraint programming Parameterizing a Groundness Analysis of Logic Programs Lunjin Lu Finite-Tree Analysis for Constraint Logic-Based Languages Roberto Bagnara, Roberta Gori, Patricia M. Hill and Enea Zaffanella 20:00 Reception TUESDAY, JULY 17 9:00-10:00 Invited Talk Applications of Extended Static Checking K. Rustan M. Leino (Compaq SRC) 10:00-10:30 Break 10:30-12:00 Data structures Cleanness Checking of String Manipulations in C Programs via Integer Analysis Nurit Dor, Michael Rodeh and Mooly Sagiv Solving Regular Tree Grammar Based Constraints Yanhong A. Liu, Ning Li and Scott D. Stoller Static analyses of floating-point operations Éric Goubault 12:00-13:30 Lunch 13:30-15:30 Pointer analysis Estimating the Impact of Scalable Pointer Analysis on Optimization Manuvir Das, Ben Liblit, Manuel Fahndrich and Jakob Rehof Efficient Computation of Parameterized Pointer Information for Interprocedural Analyses Donglin Liang and Mary Jean Harrold Model Checking Parametric Optimization of Open Real-Time Systems Farn Wang and Hsu-Chun Yen Embedding Chaos Natalia Sidorova and Martin Steffen 15:30-16:00 Break 16:00-17:00 Abstract Model Checking Analyzing Fair Parametric Extended Automata A. Annichini, A. Bouajjani, Y. Lakhnech, and M. Sighireanu Incompleteness, Counterexamples and Refinements in Abstract Model-Checking Roberto Giacobazzi and Elisa Quintarelli 20:00 Reception WEDNESDAY, JULY 18 9:00-10:00 Invited Talk Language-based Security: What's needed and Why Fred Schneider (Cornell University) 10:00-10:30 Break 10:30-12:00 Mobility A Behavioral Module System for the Pi-Calculus Sriram K. Rajamani and Jakob Rehof An Abstract Interpretation Framework for Analysing Mobile Ambients Francesca Levi and Sergio Maffeis Abstract Interpretation-Based Static Analysis of Mobile Ambients Jérôme Feret 12:00-13:30 Lunch 13:30-15:00 Invited Session on Security ... David Wagner (University of california, Berkeley) A type and Effect Analysis of Security Protocols (joint work with Alan jeffrey) Andrew Gordon (Microsoft Research, Cambridge) 15:00-15:30 Break 15:30-17:00 Invited Session on Security (Cont'd) Abstracting Cryptographic Protocols by Prolog Rules Bruno Blanchet (Inria Rocquencourt) Security-Typed languages Andrew Myers (Cornell University) ------------------------- REGISTRATION FORM --------------------- Send your registration form with payment to: SAS'01 c/o Evelyne Rayssac LIX Ecole Polytechnique 91128 Palaiseau cedex France Phone: +33 1 69 33 45 95 Fax: +33 1 69 33 30 14 email: sas01(a)lix.polytechnique.fr Electronic registration is also available at URL: http://www.ens.fr/sas01/ Name:............................................................ Affiliation:..................................................... Address:......................................................... ......................................................... ......................................................... Phone:........................................................... Fax:............................................................. E-mail:.......................................................... Dietary requirements:............................................ Do you need an Internet connection for a laptop from your hotel?: ......................................................... Payment: enclosed check ___ enclosed order form (for french institutions only) ___ bank tranfer (enclose a copy of the transfer order) ___ Registration fees: (in Euros or French Francs) by June, 15 2001: 500 ¤ ___ or 3,300 FF___ 365 ¤ ___ or 2,400 FF___ (Full-time Student) after June, 15 2001: 550 ¤ ___ or 3,600 FF___ 415 ¤ ___ or 2,700 FF___ (Full-time Student) Registration includes the proceedings, reception, lunches and coffee breaks. ---------------------------- PAYMENT ----------------------------- Choose one of the three following options for the payment of the registration fees. Make sure that the bank and change costs are at your charge. - Bank transfer to: Bank: Tresorerie Generale des Hauts-de-Seine 167, avenue Joliot Curie 92013 Nanterre Cedex, France (State your name and the reference: SAS'01) Domiciliation: RGFIN PARIS NANTERRE Account Number: 40071-9200-00003000310-90 Account Name: CNRS IDF OUEST-NORD (A copy of the transfer order is to be sent with the registration form) - Make checks payable to: Agent comptable secondaire CNRS IDF Ouest & Nord (to be sent with the registration form) - Purchase Order Form (for french institutions only) to: LIX-CNRS (to be sent with the registration form) ------------------------ HOTEL RESERVATION ---------------------- Hotel and travel information, including detailed information on room reservations at any of a number of hotels near the Ecole Normale Supe'rieure, is available at the URL http://www.ens.fr/sas01/ We have arranged rooms for conference attendees at the hotels listed below. To make a reservation, send a fax to the hotel mentioning your credit card number and the reference "SAS'01, La Sorbonne". Please note that all of the reservations are to be done by ---22 April 2001---. (**) Hotel Pierre Nicole 39 rue Pierre Nicole Paris 75005 Phone: +33 (0)1 43 54 76 86 Fax: +33 (0)1 43 54 22 45 Single: 390F, Double: 440F, Breakfast: 40F hotelpierre-nicole(a)voila.fr (***) Observatoire du Luxembourg 107, Boulevard Saint-Michel Paris 75005 Phone: +33 (0)1 46 34 10 12 Fax: +33 (0)1 46 33 73 86 Single: 600F, Double: 700F, Breakfast: included http://Paris.HotelGuide.net/data/h100051.htm (***) Hotel des Jardins de Luxembourg 5 Impasse Royal-Collard Paris 75005 Phone: +33 (0)1 40 46 08 88 Fax: +33 (0)1 40 46 02 28 Single or Double: 825F, Breakfast: 55F http://Paris.HotelGuide.net/data/h100049.htm (***) Hotel Luxembourg luxhotel(a)luxembourg.mgn.fr 4, rue de Vaugirard 75006 Paris Phone: +33 (0)1 43 25 35 90 Fax: +33 (0)1 43 25 17 18 Single: 800F / Double: 910F, Breakfast: included http://www.hotel-luxembourg.com/index.html (***) Hotel du Pantheon Place du Pantheon 75005 Paris Phone: +33 (0)1 43 54 32 95 Fax: +33 (0)1 43 26 64 65 Single or Double: 1100F, Triple: 1300F, Breakfast: 55F http://www.france-hotel-guide.com/h75005pantheon.htm Students rooms at the ENS-Cachan Campus (For students registrating at SAS'01 & CAV'01) 61 av. du Pdt Wilson 94235 Cachan RER-B: Bagneux (45min) Single: 120F (contact person: duflot(a)lsv.ens-cachan.fr) http://www.lsv.ens-cachan.fr/cav01/ -----------------------------------------------------------------

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toRational (0.9)
by S.D.Mechveliani 18 Apr '01

18 Apr '01

Jerzy Karczmarczuk <karczma(a)info.unicaen.fr> writes | Lennart Augustsson wrote: >> "S.D.Mechveliani" wrote: ... ... >> > Probably, the source of a `bug' is a language agreement that the >> > input is in decimal representation (`0.9') and its meaning is a >> > floating approximation in _binary_ representation. >> >> What are you talking about? Input in decimal representation is >> stored as a Rational number. There is absolutely no loss of >> precision. | No need for whatareyoutalkingabout preamble. | Input in decimal representation *in general* is stored as the | implementors wish. | [..] The matter is in what the _language standard_ says. If it puts that `0.9' in the user program means precizely 9%10, then Lennart is right. As I never used such things like `0.9', I would take, so far, what the language experts say. ----------------- Serge Mechveliani mechvel(a)botik.ru

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