- Haskell - Haskell.org

Inspecting reduced/optimized code
by andrew cooke 10 Nov '03

10 Nov '03

Is it possible/easy in any of the compilers/interpreters to see what the results of rewriting/optimisations are? (I'm sure it is *possible*, I'm really asking if any produce simple output in a well documented format that I'm likely to understand). The reason I ask is because I'm curious whether the "well known" fold (foldr) (I don't have it to hand, but it's something like fold (\x g -> \n -> g x n) id) that is equivalent to foldl generates the same code as foldl itself (ie defined recursively). I know I can do timing, or look at the C code from GHC, which would tell me whether they are identical, I guess, but I was hoping for something higher level (I suupose transformed Haskell code is too much to ask for?). Should I be looking at some kind of debugging tool (never used a debugger in Haskell)? Thanks, Andrew PS Despite its sweet naivete, this post comes from a balding middle aged programmer looking for something to relieve the tedium of working shifts away from home, and not some grasping, lazy, evil student that wants to save time on homework to indulge in yet more wild, drunken orgies [sighs wistfully, looks at clock, gets back to work...]. -- http://www.acooke.org/andrew

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Preliminary CFP: GPCE'04 -- Generative Programming and Component Engineering
by Eelco Visser 09 Nov '03

09 Nov '03

PRELIMINARY CALL FOR PAPERS ---------------------------------------------------------------------- Third International Conference on Generative Programming and Component Engineering (GPCE'04) Vancouver, October 24-28, 2004 co-located with OOPSLA 2004 http://gpce04.gpce.org ---------------------------------------------------------------------- ------------------------------------ Scope ------------------------------------ Generative and component approaches have the potential to revolutionize software development in a similar way as automation and components revolutionized manufacturing. Generative Programming (developing programs that synthesize other programs), Component Engineering (raising the level of modularization and analysis in application design), and Domain-Specific Languages (elevating program specifications to compact domain-specific notations that are easier to write and maintain) are key technologies for automating program development. GPCE arose as a joint conference, merging the prior conference on Generative and Component-Based Software Engineering (GCSE) and the Workshop on Semantics, Applications, and Implementation of Program Generation (SAIG). The goal of GPCE is to provide a meeting place for researchers and practitioners interested in cutting edge approaches to software development. We aim to foster further cross-fertilization between the software engineering research community on the one hand, and the programming languages community on the other, in addition to supporting the original research goals of both the GCSE and the SAIG communities. We seek papers both in software engineering and in programming languages, and especially those that bridge the gap and are accessible to both communities at the same time. ------------------------------------ Topics of Interest ------------------------------------ The conference solicits submissions related (but not limited) to: * Generative programming o Reuse, meta-programming, partial evaluation, multi-stage and multi-level languages, step-wise refinement o Semantics, type systems, symbolic computation, linking and explicit substitution, in-lining and macros, templates, program transformation o Runtime code generation, compilation, active libraries, synthesis from specifications, development methods, generation of non-code artifacts, formal methods, reflection * Generative techniques for o Product lines and architectures o Embedded systems o Model-driven architecture * Component-based software engineering o Reuse, distributed platforms, distributed systems, evolution, analysis and design patterns, development methods, formal methods * Integration of generative and component-based approaches * Domain engineering and domain analysis o Domain-specific languages (DSLs) including visual and UML-based DSLs * Separation of concerns o Aspect-oriented programming, feature-oriented programming, o Intentional programming, and multi-dimensional separation of concerns * Industrial applications Reports on applications of these techniques to real-world problems are especially encouraged, as are submissions that relate ideas and concepts from several of these topics, or bridge the gap between theory and practice. The program committee is happy to advise on the appropriateness of a particular subject. ------------------------------------ Important Dates ------------------------------------ * Pre-submission: March 12, 2004 (title + abstract) * Submission: March 19, 2004 * Conference: 24-28 October 2004 ------------------------------------ Organization ------------------------------------ General chair * Tim Sheard (OGI School of Science & Engineering at OHSU) Program committee chairs * Gabor Karsai (Vanderbilt University) * Eelco Visser (Utrecht University) Program committee * Uwe Assmann (Linkopings Universitet) * Don Batory (University of Texas) * Jan Bosch (Universiteit Groningen) * Jean Bezivin (Université de Nantes) * Jim Cordy (Queen's University) * Krzysztof Czarnecki (University of Waterloo) * Mathew Flatt (University of Utah) * Robert Glueck (University of Copenhagen) * George Heineman (Worcester Polytechnic Institute) * Michael Leuschel (University of Southampton) * Karl Lieberherr (Northeastern University) * Simon Peyton Jones (Microsoft Research) * Douglas R. Smith (Kestrel Institute) * Gabriele Taentzer (Technical University of Berlin) * Todd Veldhuizen (Indiana University) * Kris de Volder (University of Britisch Columbia) * Dave Wile (Teknowledge Corp.) * Alexander Wolf (University of Colorado at Boulder) Contact * gpce-chairs(a)cs.uu.nl

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A question about overloading
by Ryoko Nanase 09 Nov '03

09 Nov '03

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Number conversions, like floats to doubles
by Ben Escoto 09 Nov '03

09 Nov '03

Quick and probably stupid question: If I want to convert a Float to a Double, should I use fromRational . toRational ? It seems to work, but isn't this a bit weird? It took a while for me to figure this out. I suppose they are rationals because of the finite precision of Floats and Doubles? And similarly, (fromInteger . toInteger) is the right way to convert the integral types? Why not just have a function like: convertIntegral :: (Integral a, Integral b) => a -> b -- Ben Escoto

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type class problem / GHC bug
by Brandon Michael Moore 08 Nov '03

08 Nov '03

Hi everyone I've built GHC from CVS and I'm getting some odd errors about overlapping instances. This is different from 6.0.1, but it's not obvious it is wrong, so I'm probably missing something here. The example is class A x class (A x) => B x instance A x instance B x The new GHC complains that the second instance overlapps with the first. Maybe because of the context on B x the instance for B x is interpreted as a claim we have A x too, but shouldn't it be the other way, that you need an instance A x from somewhere along with an instance for B x? Also, I tried to update and rebuild, but the makefiles seem to have the dependencies wrong or something. I compiles THSyntax.hs by hand, then ran into some trouble with files that needed some modules from GHCI trying (and dying) to build before the ghci files.Is there a guide to building GHC from CVS anywhere? I had the same problem with alex, but that's small enough to build by hand. Thanks Brandon

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happy Haskell hacking for compiler writers
by nr＠eecs.harvard.edu 07 Nov '03

07 Nov '03

I'm curious about using purely functional data structures to represent a control-flow graph in a compiler. I'm working on a compiler that uses this model: 1. Build a control-flow graph 2. Execute a million optimization steps, each of which makes a small mutation to the control-flow graph 3. Linearize the control-flow graph and emit assembly code Right now we're using mutable data structures, and I'm curious about using functional ones. I figure readers of this list are more likely than most to know how to write things like ``rewrite every basic block as a new subgraph with one entry and one exit.'' Any suggestions about what data structures I should use, what the interface should look like, and especially what the critical higher-order functions are and how they should be implemented? (I should add that I care about efficiency---one of the reasons I'm interested in a functional data structure is that I believe I'm paying a lot for all the mutation I'm doing.) Pointers to papers are code are also very welcome. Norman

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Announce: wxHaskell 0.4
by Daan Leijen 07 Nov '03

07 Nov '03

Announcement: wxHaskell version 0.4 ---------------------------------------------------------------------- <http://wxhaskell.sourceforge.net> The main addition of this new release is extensive support for ODBC database access. This is currently only tested on windows and not yet supported on MacOS X. Further additions: many GUI improvements for MacOS X, resize issues have been fixed, new functionality to manipulate pixel buffers, and support for OpenGL windows (untested yet with HOpenGL... we are looking for volunteers :-). ---------------------------------------------------------------------- wxHaskell is a portable GUI library for Haskell. The goal of the project is to provide an industrial strength portable GUI library, but without the burden of developing (and maintaining) one ourselves. wxHaskell is therefore build on top of wxWindows -- a comprehensive C++ library that is portable across all major GUI platforms; including GTK, Windows, X11, and MacOS X. Furthermore, it is a mature library (in development since 1992) that supports a wide range of widgets with native look-and-feel, and it has a very active community (ranked among the top 25 most active projects on sourceforge). Since most of the interface is automatically generated from the wxEiffel binding, the current release of wxHaskell supports about 85% of the wxWindows functionality -- 2878 methods in 513 classes with 1347 constant definitions. wxHaskell has been build with GHC 6.01 on Windows, MacOS X and Unix systems with GTK. A binary distribution is available for Windows and MacOS X. And even if you don't intend to write GUI's yourself, it will be fun to check out the screenshots at <http://wxhaskell.sourceforge.net>. All the best, dr. :-) Daan Leijen.

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RE: automaticly create the ana, cata, hylomorphisms
by Marta Isabel Oliveira 07 Nov '03

07 Nov '03

Thanks and sorry. Beside new in Haskell i'm also new in this archive lists. So, i was not aware i had sent with sucess the mail to the first list. lesina > -----Original Message----- > From: Keith Wansbrough [SMTP:Keith.Wansbrough@cl.cam.ac.uk] > Sent: Friday, November 07, 2003 3:00 PM > To: Marta Isabel Oliveira > Cc: haskell(a)haskell.org; haskell-cafe(a)haskell.org > Subject: Re: automaticly create the ana, cata, hylomorphisms > > > Hello programmers, > > > > I have a problem to solve and don't have a clue where to start. > > This is a homework question. Please read > > http://www.haskell.org/hawiki/HomeworkHelp > > for some helpful hints. > > By the way, you shouldn't post the same message to multiple lists - you should choose the right one (haskell-cafe in this case), or if you must, cross-post one message to both. This means people who subscribe to both won't see your message twice. > > --KW 8-) > -- > Keith Wansbrough <kw217(a)cl.cam.ac.uk> > http://www.cl.cam.ac.uk/users/kw217/ > University of Cambridge Computer Laboratory. >

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automaticly create the ana, cata, hylomorphisms
by Marta Isabel Oliveira 07 Nov '03

07 Nov '03

Hello programmers, I have a problem to solve and don't have a clue where to start. I need to do a program in haskell that creates automaticly the ana, cata and hylomorphisms to arbitraty types. It's sort of a pre-processer. How can i start? I have the HaPar.hs that has uses Haskell parser to extract the type declarations from a file containing a Haskell module. I also have the TDec1.hs that has some dataTypes defined(TDec1, CDec1, Type) and some Show instances. Can anyone help me? I'm totally new to Haskell :(

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Doing weird things with types.
by David Sankel 07 Nov '03

07 Nov '03

Hello All, I'm trying to create a generic function (*) using classes. I've been playing with ghc extensions but haven't found what I need yet. class HasTimes a b c where (*) :: a -> b -> c This doesn't work because it can't figure out what the return types are for a general expression a*(b*c). This kinda makes sense since someone could overload HasTimes Float Float Int and HasTimes Float Float Float. What about: class HasTimes a b where (*) :: a -> b -> c This would sort of imply that c is the only possible result of a (*) for types a and b. But I'm pretty sure this functionality hasn't been implemented. Why is this important? I'm trying to reduce ugliness of code using the following library: data Matrix = Matrix ((Float,Float),(Float,Float)) data HVec = HVec Float Float data VVec = VVec Float Float idMatrix = Matrix ((1.0,0.0),(0.0,1.0)) vhVecMult (VVec a b) (HVec c d) = Matrix ((a*c,a*d),(b*c,b*d)) matMult (Matrix ((a,b),(c,d))) (Matrix ((e,f),(g,h))) = Matrix (((a*e+b*g),(a*f+b*h)),((c*e+d*g),(c*f+d*h))) matVVecMult (Matrix ((c,d),(e,f))) (VVec a b) = VVec (a*c + b*d) (a*e + b*f) hVecMatMult (HVec a b) (Matrix ((c,d),(e,f))) = HVec (c*c+b*e) (a*d+b*f) vVecMinus (VVec a b) (VVec c d) = VVec (a-c) (b-d) vVecPlus (VVec a b) (VVec c d) = VVec (a+c) (b+d) matMinus (Matrix ((a,b),(c,d))) (Matrix ((e,f),(g,h))) = Matrix ((a-e,b-f),(c-g,d-h)) hvVecMult (HVec a b) (VVec c d) = a*c + b*d scalHVecMult :: Float -> HVec -> HVec scalHVecMult i (HVec a b ) = HVec (i*a) (i*b) Thanks, David J. Sankel

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