- Haskell-Cafe - Haskell.org

Building the community
by dons＠cse.unsw.edu.au 15 Dec '06

15 Dec '06

One of the great aspects of programming Haskell is the community. We should aim to have the strongest, friendliest, most productive community we can. We're doing a good job so far, can we do even better? Reading this: "How to Build a User Community" http://headrush.typepad.com/creating_passionate_users/2006/12/how_to_build_… has inspired me to make some suggestions of what *you* can do to help make Haskell the language and community people want to spend time on. * Always encourage newbies to ask questions + I rate us at 8/10 * Encourage newer users--especially those who've been active askers--to start trying to answer questions + we can do more here. If you know the solutoin to a problem, dive in and help out. Canonical, type correct answers preferred! + if you're at the 'intermediate' stage, you can help *now* by contributing to the wiki, solving new user problems, blogging your ideas and code and so on. * Give tips on how to answer questions + Ok. we can put up an article here. Some suggestions: - No questions are bad questions - Code should come with examples of how to run it - Solutions with unsafePerformIO should be discouraged (moreso ;) - Be polite! (we're good at this) * Adopt a near-zero-tolerance "Be Nice" policy when people answer questions + 8/10, we can do even better I think * Teach and encourage the more advanced users (including moderators) how to correct a wrong answer while maintaining the original answerer's dignity. + Pretty good. I encourage people to point out (privately) and encourage grumpy people to be nicer So dive in! Help out new users, collaborate, contribute to the wiki, release your code, and help make Haskell the language people want to use. -- Don

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Aim Of Haskell
by Kaveh Shahbazian 15 Dec '06

15 Dec '06

What is the aim of Haskell? This question may seems too stupid to answer. But I think it needs a re-clarifying attempt. Why? i.e recently there was a project not that critical, but an internal tool for a group. There were three candidates : Haskell, Clean and Erlang. In this company all projects are in C# and this was the first one for using a new approach in development. After all Erlang was chosen, in second place Clean and in 3rd Haskell. Because those two ones has some standards, and Erlang licensing was the chosen one. But Haskell seems to be buzz-full research platform. Now again to the top : what is the aim of Haskell project? If it is going to be used in real world applications it needs more attention to real world application developers and their needs. And if not; and it is just for research, then there could be a global advise : do not use this for doing your tasks, because there is strange variations in syntax, and strange behaviors in components. (Even clean has a simple GUI. Is it that hard to provide a simple GUI like that to be installed by default?) And real applications are not those that really worked in research! Real applications are those that works in real world (That mean-level day to day developing life!). So please do not talk about Lispiry things - that are totally ananymous and virtual. And still there is ambition in licensing GHC and licensing of programs that are developed in that environment. Thanks to all.

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Re: [Haskell] Haskell alternatives: functional programming in rich IDEs
by Jason Dagit 15 Dec '06

15 Dec '06

Moving this to Haskell-Cafe which seems more appropriate given my question. On 12/15/06, Bulat Ziganshin <bulat.ziganshin(a)gmail.com> wrote: > Hello haskell, > > it was several times mentioned that Haskell doesn't provide rich > environments for productive work, including lack of IDEs, bundled > "real-world" libs and so on. i want to mention alternative environments > that is better in these areas > > 1) F#, is Ocaml dialect integrated in .NET environment > 2) Clean, very Haskell-like language with a commercial IDE, GUI libs and so on > 3) Business Objects, integration of Haskell-like language into Java > environment, http://labs.businessobjects.com/cal Can anyone comment about their experiences with these alternatives? Jason

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Book "Haskell in real world"
by Bulat Ziganshin 15 Dec '06

15 Dec '06

Hello haskell-cafe, first, i should say that i'm real-world programmer with 15 years experience. and my experience taught me that programming language in first place should allow to express complex algorithms easily, factor out any code patterns, and facilitate development of error-proof programs. from several tens of languages that i know, Haskell is best in these areas and therefore i think that it is the best language for professional program development i've written several medium-sized apps and libs in Haskell so i somewhat know how to write real-world programs here, and have written a few pages that may help other haskellers to grok tricky parts of Haskell the note on lambdadot mentioned here don't contain anything new for us - the problems are the same as for any other not-so-popular language. there is even Wadler's paper "Why Haskell will NOT become popular" which said exactly the same: while language itself is great, we lack in areas of libraries, tools/IDEs, and information support (teaching, books, training...); i call all these things "infrastructure". Moreover, for any other language not in "top 5" list, you will found just the same problems Is this means that developers of C# and Java are only smart guys and all other are suckers? No, it's just chicken-and-egg problem - development of rich infrastructure needs large number of developers and gathering large number of interesting developers needs rich infrastructure. the only thing we cam do now is to find "critical points", where small improvements may give significant overall changes and address these problems one of such points may be the book for commercial programmers that will show them how their real programs can be written Haskell and convince them that Haskell really cuts off development cycle and increase software reliability a few pages that i already wrote may be considered as precursors of such book and i will be glad to take part in this work but only if this book will be online-available. not everyone prefers (or even can) order the paper book. it should be allowed to translate book to other languages too next question - how this book should be organized. i think that it should contain two parts: first, we should look which concepts are already described in YAHT and other introductory books, and cover all remaining concepts that will be required for professional programming. second part will describe process of development real program(s) which use all above-mentioned concepts. we can even start with second part just to find which concepts will be required in first part. of course, first part should also contain small examples for each described detail, because it's better one time to look rather than 100 times to hear my a few pages: http://haskell.org/haskellwiki/Modern_array_libraries http://haskell.org/haskellwiki/OOP_vs_type_classes http://haskell.org/haskellwiki/IO_inside http://www.haskell.org/bz/th3.htm -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

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Draft MissingH Reorg Plan
by John Goerzen 15 Dec '06

15 Dec '06

Please tell me if I should just go away or go to another list here. Thanks again for all the feedback you've sent. I've got the new MissingH website getting started, and I've posted there the draft reorganization, module rename, and package split plan here: http://software.complete.org/missingh/wiki/TransitionPlanning Your comments (and edits! -- must register/login first) are welcome. I have not yet audited the plan for dependency sanity. This could complicate things a few places, but hopefully not too many. -- John

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Re: what are the points in pointsfree?
by Chad Scherrer 15 Dec '06

15 Dec '06

> so pointsfree is a step beyond leaving the domain unspecified. Actually, the domain is specified - a function written as f = g . h has the same domain as h has. > my reading knowledge of haskell at this point far exceeds my ability > to write haskell. but so far, it has seemed to me that functions > written in the pf style are the most reuseable. > > from what you just told me, it's not an artifact of the pf style, but > that maximally reusable functions will be expressible in a pointsfree > style. that those functions embody a pattern of computation, without > concern for the details. > I don't see where reusability is affected either way. Many (all?) functions can be written in either style, and the definitions are equivalent. There are a few advantages I've seen to pf style: 1. Function definitions are shorter, and sometimes clearer. 2. It saves you from having to give points in the domain a name. 3. It can make reasoning about programs simpler. For example, if we know that reverse . reverse == id then anywhere we see reverse . reverse, we can replace it with id, without having to track any other variables. In particular, Richard Bird's book and articles use this to great effect for program transformation and derivation from specification ("Bird-Meertens formalism") The only disadvantage I know of is that it can lead to obfuscation, especially if Haskell hasn't twisted your brain yet (in a good way). -- Chad Scherrer "Time flies like an arrow; fruit flies like a banana" -- Groucho Marx

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On improving libraries: wanted list
by dons＠cse.unsw.edu.au 15 Dec '06

15 Dec '06

With the upcoming hackathon[1], and its timely focus on real world libraries, infrastructure and tools support, I've started a list of truly missing libraries, for particular problem domains. If you have a problem, for which you think there *should* be a Haskell library, please add it to this page: http://haskell.org/haskellwiki/Wanted_libraries Or, if you see a 'missing' entry there, but happen to know of a real library that solves the problem, add it to the list. If you feel an existing library isn't suitable for a task, note this in the 'could be improved section'. A good constructive list here will help focus developer efforts, and someone may just step up with the code! -- Don The future only happens if we write the code. 1. http://haskell.org/haskellwiki/Hac_2007

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Dynamic types through unsafeCoerce
by Alfonso Acosta 14 Dec '06

14 Dec '06

Hi, I've been using Data.Dynamic but the Typeable requirement doesn't go well with FFI declarations (which don't accept type contexts). This is a little example of what I would like to do: data MyDyn = MyDyn myToDyn :: a -> MyDyn myToDyn = unsafeCoerce myFromDyn :: MyDyn -> a myFromDyn = unsafeCoerce -- this is a type I want to transform back and forth from dynamic -- and store into lists etc etc ... data MyType a b = MyType a b -- This it's "abstract" Generic type (it's contructor should be hidden) data MyGenType = MyGenType MyDyn mt2mgt :: MyType a b -> MyGenType mt2mgt = MyGenType.myToDyn mgt2mt :: MyGentype -> MyType a b mgt2mt (MyGenType dyn) = myfromDyn dyn The question is, ¿if only mt2mgt and mgt2mt are used by the user, would the use of unsafeCoerce be dangerous? Thanks in advance, Alfonso Acosta

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Reversing a string of words: C# v Perl V Ruby v Haskell
by Andrew Savige 14 Dec '06

14 Dec '06

Recently, the C# programmers at work have been asking job applicants to write a function to reverse a string of words. For example, given an input string of: " one two three four " the function should produce: "four three two one" That is, the input string reversed word by word, with a single space between each word and with no leading or trailing space. (You may assume that the input string consists only of alphabetic characters, spaces and tabs). A popular C# approach goes something like: private static string reverseWords(string str) { string[] words = Array.FindAll<string>(str.Split( new char[] {' ','\t'}), delegate(string s) { return !String.IsNullOrEmpty(s); }); int i = words.Length - 1; if (i < 0) return String.Empty; StringBuilder sb = new StringBuilder(words[i]); while (--i >= 0) sb.Append(' ').Append(words[i]); return sb.ToString(); } Though the C# programmers seem happy enough with this solution, it's a bit too verbose for my personal taste. For cheap thrills, I'd like to show them some solutions to their little problem in other, er, less verbose languages. In Perl, I have: sub reverseWords { join ' ', reverse split(' ', shift) } In Ruby: def reverseWords(str) str.split(' ').reverse.join(' ') end Finally, and please don't laugh, in Haskell (GHC): reverseWords :: String -> String reverseWords xs = (concat (intersperse " " (reverse (words xs)))) which does appear to work correctly. However, I would like to do justice to Haskell as a language -- and given that my clumsy Haskell is not written in expert style -- I'm hoping that someone on this list might offer a better, faster, or more idiomatic Haskell solution to this little problem. Thanks, /-\ Send instant messages to your online friends http://au.messenger.yahoo.com

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Interoperating with Java
by mark＠ixod.org 14 Dec '06

14 Dec '06

I was wondering, what's the status of the various means of two-way interoperation with Java? Are things actively maintained? According to the WWW, HaskellDirect's (I have Lambada in mind) current version was released Jan 2004 and compiles with 'recent' versions of GHC, such as ghc-6.2, and the latest released JVM Bridge isn't much newer. We were looking at using the Standard Widget Toolkit (SWT) but don't want to rely on driving it from Haskell if the connectors are going to rot away. (We could still use FP, after all - e.g. Scheme's Kawa and Bigloo have good Java interoperation.) -- Mark

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