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RE: "Lambda Dance", Haskell polemic, etc. on O'Reilly site
by Julian Seward (Intl Vendor) 03 Apr '01

03 Apr '01

S. Alexander Jacobsen wrote: | Although I think Haskell is a beautiful language, Jelovic is right on his | core points, Haskell implementations don't meet the needs of | the working programmer. [...] I also largely agree with Jelovic, and I take what he says as constructive criticism. One observation at least as regards Perl and Python is that Haskell has a very much more academically-intense heritage, whereas Perl and (guessing here) Python were motivated more by end-user need. GHC and Hugs suffer from tensions between being research vehicles and being practical implementations suitable for end-users. I'd guess that Perl and Python don't suffer from such tensions, so their implementors can concentrate more directly on providing excellent implementations suitable for widespread use. I say nothing about Ruby because I know nothing about it. A second observation is that Perl and Python are both single -implementation languages, which makes it easier to have a coherent set of libraries. Haskell, by contrast, isn't -- there are at least 4 available implementations (hbc, hugs, nhc, ghc). The core language (Haskell98) is supported by all of these, but there isn't a coherent story on the libraries. We are working on that. This plurality of implementations has worked well for the diverse research interests centered around Haskell. I think there is now a growing feeling that we need to standardise the libraries more and put more emphasis on end-user issues -- the kind of things Jelovic mentions -- if Haskell is to have a long-term future. Here at GHC HQ we are trying hard to make GHC into a suitable vehicle for widespread use. The upcoming GHC version 5 should go some way to addressing issues of installability, library coverage and speed of compilation. As Simon Marlow pointed out, if you feel motivated to help us work on the libraries, that would be excellent. I think it's worth clarifying a couple of potential misunderstandings with the original posting: -- The current version of Hugs is called hugs98 not because the implementation was last revised in 1998 but because it implements the language as standardised in 1998. Hugs is actively maintained. -- Hugs is not the only Haskell implementation. Ours, GHC, strives hard to provide a coherent, complete set of libraries in the standard distribution. NHC is also moving in that direction. We are not yet there, but are, at least, proceeding. J

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Re: "Lambda Dance", Haskell polemic, etc. on O'Reilly site
by Bill Halchin 02 Apr '01

02 Apr '01

Hello, I think Dejan has written in a good spirit and has many cogent points, especially for example with regard to Python. I guess the bottom line is don't be too think-skinned about what seems to me to be constructive criticism. In the FPL community, it is easy to maintain a siege mentality. Before I worked at Microsoft Hotmail. I asked one person (well known) who does research at Microsoft Research on Haskell. I asked him if any projects inside Microsoft were implemented using Haskell and he said no. Of course, this is not his fault. Management has to see that they are not going "out on a limb" to use FPLs. I know that Sun wrote at least one tool in Scheme (albeit it doesn't have ref. transparency). Regards, Bill Halchin >From: "Dejan Jelovic" <djelovic(a)sezampro.yu> >To: <haskell-cafe(a)haskell.org> >CC: <karczma(a)info.unicaen.fr> >Subject: Re: "Lambda Dance", Haskell polemic, etc. on O'Reilly site >Date: Sun, 1 Apr 2001 22:02:29 +0200 > >Jerzy Karczmarczuk wrote: > > > Over and over again the same silly song, by a person who - visibly - > > had never anything to do with functional languages, who thinks now > > about hiring some C and java programmers living in Belgrade > >I don't understand how you deduced I "never had anything to do with >functional languages"? Any how is it relevant to the subject at hand that >I'm hiring Java and C++ (not C) programmers in Belgrade? > > > but who > > writes such silly, incompetent things as: > > > > > And there is an air of staleness: where new versions of these other > > > languages appear frequently, the Haskell community is offering you > > > Hugs98. > >I don't see why what I said is silly or incompetent? The Haskell Compiler >and Interpreters page at haskell.org suggests Hugs98 for newcomers. While >you and I know that the latest version of Hugs has been released two weeks >ago, a curious visitor will wonder why there isn't Hugs 2001. > >And the Haskell website is updated rarely in contrast with, say, the Python >website. > > > Delovic points out that some languages became "immensely" popular, > > as e.g. Ruby, and that Haskell is marginal. Hm. this extremely > > orthodox Japanese essence of O-O programming may have some practical > > merits, especially those which come from shameless borrowing from > > Eiffel, Sather, Clu and Common Lisp, but calling Haskell "marginal" > > or "obscure" informs us not what is Haskell, but who is Jelovic. > >Compared to the usage of C++, Java or Python, the usage of Haskell is >_marginal_. Visit the computer section of your local bookstore if you need >to be reminded of that. > >BTW, you seem to be well-informed about who this Jelovic is. Why don't you >share that knowledge with us? :) > > > He accuses the Haskell community of not providing libraries... > >Two errors here: > >1. I didn't accuse anybody of anything. I was just curious about why people >aren't using Haskell and started to think about it. There's a saying among >Program Managers at Microsoft that "thinking is writing". I subscribe to >that. I often write about things I think about in order to explore the >issues. If I think other people might be interested in the end result, I >post it. > >2. I didn't say that the Haskell community has not provided the libraries. >I >said the Haskell community hasn't provided the libraries together with the >compiler in one standard distribution. I think that's needed in order to >lower the barrier to entry. > > > Perhaps there is *one* point worth mentioning: the necessity to > > publish papers about Haskell far from such journals as JFP or HOSC, > > but to try to reach DrDobbs etc. > >Funny. You said at the beginning of your message that there is "NOTHING" >serious there. :) > >Dejan >http://www.jelovic.com > > > >_______________________________________________ >Haskell-Cafe mailing list >Haskell-Cafe(a)haskell.org >http://www.haskell.org/mailman/listinfo/haskell-cafe _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com

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Re: constants and functions without arguments
by Tom Pledger 31 Mar '01

31 Mar '01

Andreas Leitner writes: : | The classic examlple for this is class POINT, which has an interface | like that: | -- | POINT | -- group 1 | x: DOUBLE | y: DOUBLE | -- group 2 | rho: DOUBLE | abs: DOUBLE | -- | Now, you can choose to either implement group 1 as attributes, or | group 2 and calculate the other one. With the uniform access | principle, which says that accessing attributes and functions with no | arguments happen in the same syntactic way, you can change the | implementaion without notice. No user of this class needs to know. | | I am to new to FP to say whether this is equaly important in | FP-languages, since the semantics are different (constants vs. | attributes and immutable values vs. objects), but for now I am just | currious wether it is possible theoretically. That uniformity of access can certainly be achieved in Haskell. Here's the Point example. I've done it with two constructors so as to get fewer floating point imprecisions, but some other possible representations (e.g. one with only the Polar constructor) would look identical outside the module. module Point(Point, cartesian, polar, x, y, r, theta) where -- data type with hidden constructors data Point = Cartesian Double Double -- corresponds to group 1 | Polar Double Double -- corresponds to group 2 -- proxy constructor functions cartesian x y = Cartesian x y polar r theta = Polar r theta -- attribute extraction functions x (Cartesian x y) = x x (Polar r theta) = r * cos theta y (Cartesian x y) = y y (Polar r theta) = r * sin theta r (Cartesian x y) = sqrt (x*x + y*y) r (Polar r theta) = r theta (Cartesian x y) = atan2 y x theta (Polar r theta) = theta

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Instances of Read and Show
by Ingo Sander 30 Mar '01

30 Mar '01

I have a question concerning the Read and Show classes. I have read the Haskell 98 report (section 6.3.3 The Read and Show Classes), but I still do not figure out how to make instances. I have a simple data type: data TVal a = Abst | Prst a I managed to define the function show, so that I can use it with the data type TVal instance (Show a) => Show (TVal a) where show Abst = "_" show (Prst x) = show x Signals> [Prst 1, Abst, Prst 2] [1,_,2] :: [TVal Integer] which is what I want to have. But how do I make a Read instance? I still do not understand the meaning of 'readsPrec' and 'readList' (and not of 'showPrec' and 'showList') either. Can somebody explain to me or give me a good reference so that I can make TVal an instance of the classes Read and Show. Thanks in advance for your help! Ingo Sander

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RE: "Lambda Dance", Haskell polemic, etc. on O'Reilly site
by Simon Marlow 30 Mar '01

30 Mar '01

> There are, perhaps good reasons for all these failures, but please > recognize them for what they are: failures to meet the needs of the > working programmer who just wants to get something done > (whether he/she > lives in YU, FR, JP, or US) > > I would love to be using Haskell for day to day programming work but I > can't at this time. Unless the community recognizes what is > required and > gets it done, I never will. There is one good reason that Haskell fails in these areas, and that's shortage of effort. We in the GHC team are actively trying to encourage our users to contribute: with an open CVS source tree, open development mailing lists, etc. We've had some good results (thanks to our developers!), but we need more. GHC is a large and complex system, and with trying to be all things to all people - a research vehicle / experimentation platform / production compiler, our developer resources are stretched a bit thin. I'm sure this goes for the other Haskell systems too. I see libraries as the biggest missing piece in the Haskell language. Let's face it, Joe Programmer isn't going to pass Haskell by just because it doesn't support a particular flavour of overlapping instance declarations. But he might if it doesn't have a networking library, or unicode support, or an XML parser. Please, join libraries(a)haskell.org. </rant> Cheers, Simon

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"Lambda Dance", Haskell polemic, etc. on O'Reilly site
by Fritz K Ruehr 30 Mar '01

30 Mar '01

Forgive me if the following links were announced here and I just missed them. I found them through the O'Reilley Meerkat "Open Wire Service", in the "Lambda" channel of the "Lang" category (see: <http://www.oreillynet.com/meerkat/index.php?&c=4623&t=ALL> ). The first link is the "Lambda Dance" page, presumably inspired by the infamous "Hamster Dance" (if you don't know the latter, you are better off for it, so don't ask): <http://lambdadance.spacebar.org/> "Beta-reduce the night away", as the site says! The second link is a little polemic entitled "Why People Aren't Using Haskell", which I presume would be of interest to readers of this list (the author is Dejan Jelovic, whom I don't recognize as a regular contributor here): <http://www.jelovic.com/articles/why_people_arent_using_haskell.htm> There are several other interesting looking links on the Meerkat site ("Moving FP from Academia", "Object Functional Patterns", etc.), but I will let you investigate on your own. Enjoy ... -- Fritz Ruehr, still humming to the lambda dance

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Printed Haskell 98 Report
by Mark Carroll 29 Mar '01

29 Mar '01

I don't suppose it's possible to get a reasonable printed copy of the Haskell 98 Report and Haskell 98 Library Report at a sensible price, is it? Just wondering, before I go pricing printing and binding. Thanks. -- Mark

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(no subject)
by Atenea Azcue 28 Mar '01

28 Mar '01

Hello My name is Atenea . I just want to ask you that how can i Creat a program that just say "hello word" and another that can add a "matrix" if you can help me I would really going to apreciate please. Thank you for your listening --------------------------------- Do You Yahoo!? Yahoo! Mail Personal Address - Get email at your own domain with Yahoo! Mail.

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(no subject)
by Atenea Azcue 28 Mar '01

28 Mar '01

Hello My name is Atenea : I�m what to ask you who can I make a program in haskell like une program that say hello word --------------------------------- Do You Yahoo!? Yahoo! Mail Personal Address - Get email at your own domain with Yahoo! Mail.

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Re: the constant functor
by Tom Pledger 28 Mar '01

28 Mar '01

Tobias Haeberlein writes: | | > What is wrong with: | > | > class Functor ConstInt where | > map f (Const n) = Const n | | Ups - absolutely nothing. | I actually tried it with | | data ConstInt a = Int This version doesn't refer to the type Int. Instead, it introduces a new nullary data constructor called Int, which you could use like this: instance Functor ConstInt where fmap f Int = Int ...but I don't think that's what you were after. If you use a type alias (type ConstInt a = Int) instead of declaring a data type, it will refer to the type Int. However, then you'd need to use ConstInt partially applied in the instance declaration, which Haskell doesn't allow. I think Gofer has a more liberal type system which does allow it. | and didnt manage to make this an instance of | class Functor. Sorry for giving the wrong | example.

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