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Re: declaring a generic type in type synonyms
"Andre W B Furtado" <[EMAIL PROTECTED]> writes: > Is is possible to declare a generic type without using "data" or "newtype"? > For example, I woud like that "pair" is a type synonym for "(t,t)" where t > is a generic type, but just saying: > > > type pair = (t,t) > > won't work: i get a parse error. - types in haskell must be capitalized (maybe a better syntax error message would be nice, i ran into the same pb) - "t" is a free variable, so you can't write this. Either write: type Pair t = (t,t) or type Pair = (Int,Int) or even type Pair t1 t2 = (t1, t2) ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
declaring a generic type in type synonyms
Is is possible to declare a generic type without using "data" or "newtype"? For example, I woud like that "pair" is a type synonym for "(t,t)" where t is a generic type, but just saying: > type pair = (t,t) won't work: i get a parse error. Thanks, -- Andre ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: Graphs
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 I used graphs in haskell, but I don't think you'll get anywhere the kind of efficiency of a language like C++ where you have exact control over operations and structures There is the graph code in "functional algorithms" book Algorithms: a functional programming approach Fethi A. Rabhi, University of Hull, UK Guy Lapalme, Université de Montréal, Canada The code is available online. I recommend you to start with that one. Stay away from finite map stuff in edison if you can. (Although you can get it to implement graphs/hypergraphs after some amount of work) If you're going to prototype an algorithm, you will eventually have to use monads which will be harder to write than the final C++/C implementation. Why is that so? Because if you're writing the graph code in haskell, the really easier/better way is to use things like substitution, infinite graphs, etc. for an elegant and short code, in that it reflects the theoretical construction. But an algorithm designed for a serial machine is so much different. I've written graph algorithms from multilevel graph partitioning to graph clustering, so I think I know what I'm talking about :) If you're using C++, you can prototype an algorithm fairly easily. Here is how you can implement it. use list< vector > to store adjacency lists. use a vector< vector* > to index the adjacency lists. use separate vectors to hold labels. I won't go into the reasons why those are the ones to start with, eventually your super-optimized code will be similar to the above. Don't use a graph library. It will make your job harder! Avoid template libraries if you can (except stdlib...), and resist the temptation to templatize your code. You will find that it's much more easier to write graph algorithms that way. And yes, although it would be in theory be a good idea to be able to prototype your algorithm in an easier-to-use language, such a language does not exist. Unless you can show me graph code side-by-side and prove it to me I will never believe it :) For a start one would have to show me the implementation of non-trivial algorithms such as graph coarsening, all-to-all shortest paths, maximal cliques, etc. in the easier-than-C++ language contrasted with (good) C++ implementation. I'm thinking maybe it would be more-possible in ocaml, but I'm a beginner in ocaml and I don't think I'm enough of a ocaml-hacker to talk about it. Thanks, On Thursday 21 February 2002 18:01, Wojciech Fraczak wrote: > Hi everybody, > > I would like to ask you, if you do not know any graph library for > haskell. I would like to use haskell for prototyping some of > algorithms on graphs and finite state automata/transducers. In fact > what I'm looking for is a good (efficient and easy readable) data type > definition for labeled graphs. > > Thanks, - -- Eray Ozkural (exa) <[EMAIL PROTECTED]> Comp. Sci. Dept., Bilkent University, Ankara www: http://www.cs.bilkent.edu.tr/~erayo GPG public key fingerprint: 360C 852F 88B0 A745 F31B EA0F 7C07 AE16 874D 539C -BEGIN PGP SIGNATURE- Version: GnuPG v1.0.6 (GNU/Linux) Comment: For info see http://www.gnupg.org iD8DBQE8dSjSfAeuFodNU5wRAk8rAJ9CIwZUmEKHpttK2IwTXO0fnk8/egCeOV/A y3yq4cDFx1mZQPC6SbK19JU= =QoPG -END PGP SIGNATURE- ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Graphs
Hi everybody, I would like to ask you, if you do not know any graph library for haskell. I would like to use haskell for prototyping some of algorithms on graphs and finite state automata/transducers. In fact what I'm looking for is a good (efficient and easy readable) data type definition for labeled graphs. Thanks, Wojtek ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
ICFP 2002: write now!
Don't miss your chance to submit a paper to ICFP02. It'll be fun!Simon PJ ICFP 2002 International Conference on Functional Programming October 4-6, 2002, Pittsburgh, USA Final call for papers Submission deadline: 21 March 2002 18:00 UTC Program Chair: Simon Peyton Jones (Microsoft Research) Full call for papers including submission details: http://icfp2002.cs.brown.edu/CfP/ ICFP 2002 seeks original papers on the full spectrum of the art, science, and practice of functional programming. The conference invites submissions on all topics ranging from principles to practice, from foundations to features, and from abstraction to application. The scope covers all languages that encourage programming with functions, including both purely applicative and imperative languages, as well as languages that support objects and concurrency. Topics of interest include, but are not limited to, the following: Foundations: formal semantics, lambda calculus, type theory, monads, continuations, control, state, effects. Design: modules and type systems, concurrency and distribution, components and composition, relations to object-oriented and logic programming, multiparadigm programming. Implementation: abstract machines, compile-time and run-time optimization, just-in-time compilers, memory management, foreign-function and component interfaces. Transformation and analysis: abstract interpretation, partial evaluation, program transformation, theorem proving, specification and verification. Software development techniques for functional programming: design patterns, specification, verification and validation, debugging, test generation, etc. Human productivity of functional programming: visual, graphical (etc) approaches, evaluating language usability, empirical studies of human effectiveness, etc. Applications and domain-specific languages: scientific and numerical computing, symbolic computing and artificial intelligence, systems programming, databases, graphic user interfaces, multimedia programming, Web programming. Practice and experience: functional programming in education and industry, ramifications on other paradigms and computing disciplines. Functional pearls elegant, instructive examples of functional programming. General Chair: Mitchell Wand (Northeastern University) Program Committee Matthias Blume (Lucent) Margaret Burnett (Oregon State University) Manuel Chakravarty (University of New South Wales) Matthew Flatt (University of Utah) Haruo Hosoya (Kyoto University) Uwe Nestmann (EPFL, Lausanne) Chris Okasaki (United States Military Academy) Norman Ramsey (Harvard University) David Sands (Chalmers University) Olin Shivers (Georgia Tech) Stephanie Weirich (Cornell) Joe Wells (Heriot Watt University) ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
