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List.partition a bit too eager
by George Russell 22 Dec '00

22 Dec '00

I think the following program import List main = putStr . show . fst . (partition id) . cycle $ [True,False] should display [True,True,True,...]. But instead, for both GHC and Hugs, you get a stack overflow. Is this a bug, or could someone explain it to me?

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ANNOUNCE: Happy version 1.9
by Simon Marlow 21 Dec '00

21 Dec '00

ANNOUNCING Happy 1.9 - The LALR(1) Parser Generator for Haskell ----------------------------------------------------------------- I'm pleased to announce version 1.9 of Happy, the parser generator system for Haskell. Changes in this version, relative to version 1.8 (the previous full release): * A grammar may now contain several entry points, allowing several parsers to share parts of the grammar. * Some bugfixes. Happy is available in source form, which can be compiled with GHC version 4.xx (4.08.1 recommended), and we also provide binaries for some architectures. The Happy homepage with links to the various distributions lives at: http://www.haskell.org/happy/ Please send any bug reports and comments to simonmar(a)microsoft.com.

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GHC for Darwin?
by Ashley Yakeley 21 Dec '00

21 Dec '00

Are there any plans to port GHC to Darwin? Darwin is a FreeBSD-variant that runs on the PowerPC processor. <http://www.opensource.apple.com/projects/darwin/>. I was going to compile it myself before I remembered that compilers do platform-specific code-generation. Duh. -- Ashley Yakeley, Seattle WA

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RE: Haskell Productivity
by Peter Douglass 20 Dec '00

20 Dec '00

Hello all, You will need to manually reconnect the link I sent into a single line for it to work. > There is a thread on comp.lang.functional which may be of interest. > Here is a link that might work for you. > > http://www.deja.com/dnquery.xp?search=thread&svcclass=dnserver&recnum=%3c8lh 8ss$6le$1@bird.wu-wien.ac.at%3e%231/1

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RE: Haskell Productivity
by Peter Douglass 20 Dec '00

20 Dec '00

There is a thread on comp.lang.functional which may be of interest. Here is a link that might work for you. http://www.deja.com/dnquery.xp?search=thread&svcclass=dnserver&recnum=%3c8lh 8ss$6le$1@bird.wu-wien.ac.at%3e%231/1 > -----Original Message----- > From: Steinitz, Dominic J > [mailto:Dominic.J.Steinitz@BritishAirways.com] > Sent: Wednesday, December 20, 2000 11:12 AM > To: haskell > Subject: Haskell Productivity > > > The Haskell website claims that > > "Ericsson measured an improvement factor of between 9 and 25 > in one set of experiments on telephony software". > > Presumably this is with Erlang not with Haskell. I have > searched for the reference that substantiates this claim but > I've only been able to find: > > http://set.gmd.de/~ap/femsys/wiger.html > > which talks about a productivity factor of 4 > > and > > http://www.md.chalmers.se/Cs/Research/Functional/Fudgets/haske ll-vs-ada-abstract.html which suggests that Haskell is about 2-3 times as productive as imperative languages. Can someone point me at some more references? Especially the one that talks about a productivity improvement of 9-25? Thanks, Dominic. ---------------------------------------------------------------------------- --------------------- 21st century air travel http://www.britishairways.com _______________________________________________ Haskell mailing list Haskell(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell

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Re: Haskell Productivity
by Paul Hudak 20 Dec '00

20 Dec '00

> Can someone point me at some more references? See http://haskell.org/papers/NSWC/jfp.ps. -Paul

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Haskell Productivity
by Steinitz, Dominic J 20 Dec '00

20 Dec '00

The Haskell website claims that "Ericsson measured an improvement factor of between 9 and 25 in one set of experiments on telephony software". Presumably this is with Erlang not with Haskell. I have searched for the reference that substantiates this claim but I've only been able to find: http://set.gmd.de/~ap/femsys/wiger.html which talks about a productivity factor of 4 and http://www.md.chalmers.se/Cs/Research/Functional/Fudgets/haskell-vs-ada-abs… which suggests that Haskell is about 2-3 times as productive as imperative languages. Can someone point me at some more references? Especially the one that talks about a productivity improvement of 9-25? Thanks, Dominic. ------------------------------------------------------------------------------------------------- 21st century air travel http://www.britishairways.com

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Re: Finding primes using a primes map with Haskell and Hugs98
by Colin.Runciman＠cs.york.ac.uk 20 Dec '00

20 Dec '00

> There are numerous ways of optimising sieving for primes, none of which > have much to do with this list. For example, two suggestions: > (1) for each k modulo 2*3*5*7, if k is divisible by 2/3/5 or 7, ignore, otherwise > sieve separately for this k on higher primes. (Or you might use products of > more or less primes, depending on memory and how high you were going.) > ... > I don't really see why any of this has anything to do with Haskell though. > When it comes to seriously icky bit-twiddling algorithms I don't think Haskell > has much to offer over C, especially as you'd have to make everything unboxed if > you want comparable speed. Forgive the self-reference, but the following short article is all about this very topic: C. Runciman, Lazy wheel sieves and spirals of primes, Journal of Functional Programming, v7, n2, pp219--226, March 1997.

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Excessive restriction in ghc ?
by Sebastien Carlier 19 Dec '00

19 Dec '00

Hello. I am getting an error message from ghc 4.08.1 with the following code: > class Collection e ce | ce -> e where > empty :: ce > insert :: e -> ce -> ce > > class (Eq e, Collection e ce) => Set e ce where > member :: e -> ce -> Bool > union :: ce -> ce -> ce Main.lhs:7: Class type variable `e' does not appear in method signature union :: {- implicit forall -} ce -> ce -> ce Since `ce' uniquely determines `e', I would expect the compiler to assume that `e' appears in the method signature. Either I am misunderstanding something, or something may be missing in the compiler around rename/RnSource.lhs:249. Regards, Sebastien Carlier

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RE: Excessive restriction in ghc ?
by Simon Peyton-Jones 19 Dec '00

19 Dec '00

Functional dependencies aren't fully implemented in 4.08 I'm afraid, and won't ever be. It'll be significantly better in 5.0, but we won't release that for a while yet. (Unless you care to build from the CVS tree.) Simon | -----Original Message----- | From: Sebastien Carlier [mailto:sebastien@posse42.net] | Sent: 19 December 2000 14:15 | To: haskell(a)haskell.org | Subject: Excessive restriction in ghc ? | | | Hello. | | I am getting an error message from ghc 4.08.1 with | the following code: | | > class Collection e ce | ce -> e where | > empty :: ce | > insert :: e -> ce -> ce | > | > class (Eq e, Collection e ce) => Set e ce where | > member :: e -> ce -> Bool | > union :: ce -> ce -> ce | | Main.lhs:7: | Class type variable `e' does not appear in method signature | union :: {- implicit forall -} ce -> ce -> ce | | Since `ce' uniquely determines `e', I would expect the | compiler to assume that `e' appears in the method signature. | Either I am misunderstanding something, or something may be | missing in the compiler around rename/RnSource.lhs:249. | | Regards, | Sebastien Carlier | | | | _______________________________________________ | Haskell mailing list | Haskell(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell |

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