January 2001 - Haskell

ANNOUNCE: GHood -- a Graphical Hood (pre-release)
by C.Reinke 04 Jan '01

04 Jan '01

Ever wanted to see what your Haskell program is doing? Andy Gill's Hood library (http://www.haskell.org/hood/) represents a big improvement over previous uses of trace & co. It doesn't affect strictness properties, and instead of displaying debug information in the nearly incomprehensible order in which it is generated, it collects, post-processes and pretty-prints the information and displays the results after program evaluation, in a more readable form. However, as Andy already noted in the Hood documentation, there is a lot of useful information to be gathered from the order in which (parts of) data structures are observed. Now that Hood associates individual observation events with the data structures to which they belong, thus facilitating comprehension of observations, it would be nice to find a way to visualise the observation order as well. Andy's plan was to incorporate such a feature into a textual browser add-on for Hood (in CVS, not released yet?). But for tasks for which structural context and relationships between parts dominate over details, my personal preference would be a graphical form of visualisation. GHood is my current attempt to add a such a graphical viewer to Hood. It hasn't yet reached its final form, but it is quite useful and usable already. We have played with it locally, and I can't spent too much time on this, but I would like to get some external feedback before I finalise the development. Hence this pre-release. Currently, GHood comes in two files: a drop-in replacement for the Hugs98 variant of Hood (only minimal changes, same interface) and a Java class file archive for the graphical viewer itself. To find the two files, please visit my Haskell corner at: http://www.cs.ukc.ac.uk/people/staff/cr3/toolbox/haskell/ Enjoy (and let me know what you think about it), Claus -- Claus Reinke, http://www.cs.ukc.ac.uk/people/staff/cr3/ Computing Lab, University of Kent at Canterbury

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Happy InstallShield update
by Reuben Thomas 04 Jan '01

04 Jan '01

I just noticed that the Happy 1.9 InstallShield contained a dynamically linked executable for Happy. This was a Bad Idea, so I've replaced it with a statically linked executable. This should work for more people. -- http://sc3d.org/rrt/ | maxim, n. wisdom for fools

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Learning Haskell and FP
by Doug Ransom 04 Jan '01

04 Jan '01

I have read "The Craft of Functional Programming" by Simon Thompson and a few paper on the web. "The Craft" is a good book, but it is an introduction to FP. It seems to me it there are a lot of books on OO design I can pick up at the bookstore, but in the FP world, one must worm their way through all sorts of papers. I have seen papers on Catamorphisms, Monads, Programming with Barbed Wire, folds, etc. I think these papers are hard to understand if you don't have the acadademic/mathematical background -- being papers and not textbooks these papers assume a fair bit of base knowledge. I know I can design a fold function to use in place of primitive recursion for most data structures -- I just don't know if I should. It is pretty easy to get through "The Craft of Functional Programming" without understanding what Category Theory , a Catamorphism , or a Kleisli Composition is. I can see lots of real Software Engineering oppurtunities for these various techniques if I could just put them together. Is there a good textbook on Functional Programming which starts from a base point similar to "The craft of Functional Programming" but more advanced in terms of introducing necessary topics like Category theory, catamorphisms, monads, etc? I would find such a book very useful, especially if it concentrated on lazy functional programming. Doug Ransom Systems Engineer Power Measurement Ltd. http://www.pml.com 250-652-7100 office 250-652-0411 fax mailto:doug_ransom@pml.com

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RE: Learning Haskell and FP
by Simon Peyton-Jones 04 Jan '01

04 Jan '01

| > 1. How the #$!? do I read some data from a file. Good, I've | > got the data, now I can work on it. Nope, now I have an "IO | > thingie" whatever that is, but all of the standard functions want | > a regular "thingie" now what? Perhaps this would be a good moment to advertise the revised version of Tackling the Tackling the Awkward Squad: monadic input/output, concurrency, exceptions, and foreign-language calls in Haskell http://research.microsoft.com/~simonpj/#marktoberdorf (Concerning the thread I'm responding to, it gives an introduction to monadic input/output.) I've revised and extended this tutorial quite a bit since I announced it last year, with a lot of help from people on the Haskell mailing list: thank you! Further suggestions are most welcome. Simon Abstract Functional programming may be beautiful, but to write real applications we must grapple with awkward real-world issues: input/output, robustness, concurrency, and interfacing to programs written in other languages. These lecture notes give an overview of the techniques that have been developed by the Haskell community to address these problems. I introduce various proposed extensions to Haskell along the way, and I offer an operational semantics that explains what these extensions mean.

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RE: Learning Haskell and FP
by Simon Peyton-Jones 04 Jan '01

04 Jan '01

| There is a definite lack of "Getting Started" material in the ghc | distribution. I'm sure that's right. Trouble is, we're the last people qualified to write one! Here's a suggestion: would someone like to write such a guide, from the point of view of a beginner, leaving blanks that we can fill in, when you come across a task or issue you don't know the answer to? That is, you provide the skeleton, and we fill in the blanks. Simon

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GHC/Happy on MacOS X/Darwin
by Atze Dijkstra 03 Jan '01

03 Jan '01

On http://www.cs.uu.nl/~atze/Programming/index.html a version of ghc (4.08.1) and happy (still 1.8) for MacOS X/Darwin can be downloaded. However, a few remarks do apply: this version of ghc is not a completely ported version but built with generic settings and meant as a bootstrapping compiler. It also is distributed as binaries for a specific location (/usr/local/{ghc,happy}) in the UNIX directory structure. The main reasons for distributing it in this unfinished form are: - The MacOS X cc (c compiler) has some (blocking) bugs (for example, problems with asm statements) which hinder progress. - I consider 'unfinished' availability now of greater importance than 'perfect' availability later, so people can play with it. - The compiler seems to run ok, that is, after minimal testing (compiling ghc libraries and a local AG + parsercombinator system). -- - Atze - Atze Dijkstra, Dept. of Computer Science, Utrecht University /|\ Tel.: +31-30-2534093/1454 | WWW : http://www.cs.uu.nl/~atze / | \ Fax : +31-30-2513971 | Email: atze(a)cs.uu.nl /--| \ atze.dijkstra(a)hetnet.nl / |___|

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RE: Learning Haskell and FP
by Simon Peyton-Jones 03 Jan '01

03 Jan '01

| PS: are the members of the list expecting to get replies by | private mail? The thing to do is to switch the thread to haskell-cafe(a)haskell.org haskell@haskell-org is meant for openers; longer threads should move to haskell-cafe. That way people can control how inundated they get. You can "move" by simply adding "-cafe" into the address when you reply. Simon

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Re: Learning Haskell and FP
by Ketil Malde 03 Jan '01

03 Jan '01

"Karl M. Syring" <syring(a)web.de> writes: >> Mind if I "me too" a bit? I had just read the SICP, and I too found >> that the Gentle Introduction served well as an introduction to the >> Haskell syntax. > If you start out with zero knowledge in functional programming, as I do, the > GITH is really not very helpful. Exactly. It's "gentle" if you know functional programming, but probably not otherwise. > PS: are the members of the list expecting to get replies by private mail? Expecting? I'd have no qualms about replying to people privately, but then perhaps I am the obnoxious kind of person. :-) Negative feedback is scarce (although this thread might favorably diverge to -cafe? Followup-To: set). -kzm -- If I haven't seen further, it is by standing in the footprints of giants

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(no subject)
by kh0ndor＠aeiou.pt 03 Jan '01

03 Jan '01

somebody can tell me where I can find some ideas that help me in the construction of a minesweeper programmed in haskell I thank any type of help because I am a little confused __________________________________________________________ Mensagem enviada pelo Xekmail: webmail grátis do AEIOU http://xekmail.aeiou.pt

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Re: Learning Haskell and FP
by Ketil Malde 03 Jan '01

03 Jan '01

George Russell <ger(a)tzi.de> writes: > I think Paul is being unduly modest. I found it very useful when I first learnt > Haskell. But I did already know ML, so maybe the "Gentle Introduction" would be > harder going for someone who didn't know anything about functional programming. Mind if I "me too" a bit? I had just read the SICP, and I too found that the Gentle Introduction served well as an introduction to the Haskell syntax. I think it'd be fine if the title were a bit less ambitious - it isn't really aimed at the novice, I think. It's been a while since I read it tho' -kzm -- If I haven't seen further, it is by standing in the footprints of giants

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