- Haskell-Cafe - Haskell.org

Sound library?
by Jason Bailey 14 Dec '04

14 Dec '04

Would anyone know of packages out there for Haskell that support mp3's or ogg files? thanks Jason

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special term describing f :: (Monad m) => (a -> m b)?
by Derek Elkins 14 Dec '04

14 Dec '04

> What is a function of the followning type called: > > f :: (Monad m) => (a -> m b) > > Is there a special term describing such a function (a function into a > monad)? > > For f in > a >>= f > is en example. > > Need it for an article/report. > > Regards/Henning Well, formally, it's called a Kleisli arrow (or morphism). A less formal term commonly used for values of type a -> m b and m b, is 'computation' or'action' (though 'action' is usually used for the specific case of IO). In "Notions of Computation and Monads" Moggi calls them 'commands'.

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Named function fields vs. type classes
by Derek Elkins 14 Dec '04

14 Dec '04

> > On the other hand, it's difficult or impossible to make a list of a > > bunch of different types of things that have nothing in common save > > being members of the class. > > I've recently been playing with making, for each class C, a > "interface" datatype IC (appropriately universally and existentially > qualified so as to include a dictionary for class C), and then making > this IC an instance of class C. Then I can wrap any instance of C up > in an IC, and make a list of those. > > The casts get a bit annoying, though; the compiler can't figure out > that this IC is in some sense the maximum type in class C, and so > can't resolve things like > > f :: MyClass a => [a] -> b > f = ... > > upcast :: MyClass a => a -> IMyClass -- usually defined as an > instance of class Cast upcast x = IMyClass x > > f [upcast a, upcast b] -- yields type error > > Instead, you have to redefine f as follows: > > f' :: [IMyClass] -> b > > which is a bit annoying. > > HTH. > > --KW 8-) Not surprisingly, the wiki (http://www.haskell.org/hawiki/ExistentialTypes) has some discussion about this as well, though not too much to add to what has been said.

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The difference between ($) and application
by oleg＠pobox.com 14 Dec '04

14 Dec '04

The operator ($) is often considered an application operator of a lower precedence. Modulo precedence, there seem to be no difference between ($) and `the white space', and so one can quickly get used to treat these operators as being semantically the same. However, they are not the same in all circumstances. I'd like to observe an important case where replacing the application with ($) in a fully-parenthesized expression can lead to a type error. > {-# OPTIONS -fglasgow-exts #-} > > module Foo where > > data WR = WR (Int -> Int) > data W = W (forall a. a->a) > > t1 = WR id > t2 = W id We can also write > t1' = WR $ id However, if we try > t2' = W $ id we get an error: /tmp/t1.hs:13: Inferred type is less polymorphic than expected Quantified type variable `a' escapes Expected type: (a -> a) -> b Inferred type: (forall a1. a1 -> a1) -> W In the first argument of `($)', namely `W' In the definition of `t2'': t2' = W $ id Incidentally, Hugs -98 gives a quite bizarre error message ERROR "/tmp/t1.hs":13 - Use of W requires at least 1 argument It didn't complain about "WR $ id"... The reasons for that behavior are obvious: the compiler cannot generalize to higher-ranked types when instantiating the type of ($). It makes a difference that the application is a built-in construction, whereas ($) is just a regular function.

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special term describing f :: (Monad m) => (a -> m b) ?
by Henning Sato von Rosen 14 Dec '04

14 Dec '04

What is a function of the followning type called: f :: (Monad m) => (a -> m b) Is there a special term describing such a function (a function into a monad)? For f in a >>= f is en example. Need it for an article/report. Regards/Henning

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local loops
by Per Larsson 14 Dec '04

14 Dec '04

I often use local loops in monadic code, e.g. main = do ... let loop = do ... if cond then loop else return () loop It seems that I can encode this idiom slightly more concise with the 'fix' operator (from Control.Monad.Fix), i.e. main = do ... fix (\loop -> do ... if ...) But is it really semantically equivalent? Is it as efficient? Per

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Flattening tail recursion?
by GoldPython 13 Dec '04

13 Dec '04

I'm missing something, a functional idiom, whatever. I know there's "length" to count the elements in a list and it works fine, but the function below stack overflows on a large list. countLines [] = 0 countLines (_:ls) = 1 + countLines ls I would have thought that this was tail recursive and would be flattened into iteration by the compiler. Can anyone explain why? Is it because the call is embedded in an expression? And additionally, how can I predict when the flattening will occur? Thanks, Will

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FiniteMapFiniteMap
by Dominic Steinitz 13 Dec '04

13 Dec '04

See also http://www.mail-archive.com/haskell-cafe@haskell.org/msg05809.html Dominic.

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FiniteMapFiniteMap
by S. Alexander Jacobson 13 Dec '04

13 Dec '04

I would like to read a large finitemap off of a disk faster than the time it takes to read the entire list of pairs. My solution is to save it as a bunch of smaller lists of pairs covering various key intervals (or recency intervals). I then can readfile all of these lists back into a bunch of finitemaps. Because readfile is lazy my program can start very quickly without waiting to read the contents of all of these files. To make this solution work, I need some datastructure that looks like a finitemap but operates on a bunch of them organized either in parallel (key interval model) or series (time interval model). Is there some pre-existing data structure that does this or do I need to roll my own? Or is there a better way to (de-)serialize FiniteMaps? -Alex- ______________________________________________________________ S. Alexander Jacobson tel:917-770-6565 http://alexjacobson.com

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AbstractDataType question
by Jason Bailey 13 Dec '04

13 Dec '04

So in the wiki on AbstractDataType ( http://haskell.org/hawiki/AbstractDataType ) it gives the following example: data Tree a = Nil | Node { left :: Tree a, value :: a, right :: Tree a } The part where I am confused is with the use of '{' and '}' my reference book is apparently out of date as it states that Haskell doesn't even use those characters :) Could someone point me to some documentation on whats being created here and how its used? thank you Jason

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RE: [Haskell-cafe] Flattening tail recursion?
by Simon Peyton-Jones 13 Dec '04

13 Dec '04

I have not been following the details, but yes, the strictness analyser only runs when you say -O, and without strictness analysis you can get different space behaviour. Sometimes more, sometimes less. In this case, strictness analysis helps. Simon | -----Original Message----- | From: haskell-cafe-bounces(a)haskell.org [mailto:haskell-cafe-bounces@haskell.org] On Behalf Of Jules | Bean | Sent: 10 December 2004 21:38 | To: GoldPython | Cc: Henning Thielemann; haskell-cafe | Subject: Re: [Haskell-cafe] Flattening tail recursion? | | | On 10 Dec 2004, at 20:33, GoldPython wrote: | | > Just compiled this with -O and it ran with no stack overflow. | > Evidently, no `seq` needed for this one. Using ghc 6.2.2. | > | > countLines l = countLines' 0 l | > countLines' n [] = n | > countLines' n (_:ls) = countLines' (n + 1) ls | > | | That's presumably the answer. GHC's strictness analyser *can* cope with | this situation but only under -O... whereas most of us where testing | under ghci... | | Confirmation from one of the Simons? | | Jules | | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe

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ghc install
by Radu Grigore 11 Dec '04

11 Dec '04

Hi, I try to install ghc on 6.2 on a gentoo linux distribution (from sources). It fails with --- /usr/bin/ar: creating libHSbase.a xargs: /usr/bin/ar: terminated by signal 15 --- It looks like it's a lack of resources. The computer is a Celeron 1.3GHz with 160MB RAM & 400MB swap. Isn't that enough to compile ghc? -- regards, radu http://rgrig.idilis.ro/

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Class Synonyms
by Jorge Adriano Aires 11 Dec '04

11 Dec '04

Hello! I got a multi-parameter type class: > class Foo a b | a -> b where > foo_method1 :: ... > foo_method2 :: ... > ... And some particular cases are important on their own, like the one where 'a' and 'b' are the same, I call elements with this property, Bar. So I defined: class Foo a a => Bar a where This is nice, now I can replace (F a a) for (Bar a) in the context of many functions. Less typing and it's more readable. Still, I have to define instances as: > instance Foo A A where > foo_method1 = bla1 > foo_method2 = bla2 > > instance Bar A where I'd like to achieve something better than this. I was looking for something like "class synonyms". So if I declared an instance Foo A A, I automagicaly had Bar A, because they'd be the same. Or even better, I could declare > instance Bar A where > foo_method1 = bla1 > foo_method2 = bla2 Is anything like this possible at all? Thanks, J.A.

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Processing File Dependencies
by chris beddoe 11 Dec '04

11 Dec '04

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Flattening tail recursion?
by Derek Elkins 11 Dec '04

11 Dec '04

> intermediate thunk has already been built. You need a separate "strict > foldl" function, usually called foldl', which was unaccountably > omitted from the prelude. There is one in Data.List.

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Haskell IO and exceptions
by Mark Carroll 11 Dec '04

11 Dec '04

All this talk of IO and exceptions reminds me of a small issue I've been having. I like Control.Monad.Error but often my stuff is threaded through the IO monad so, AFAICT from the functional dependency stuff, that means my errors have to be IOErrors. Is that right? And, then, I want control over what's actually reported to the user, but if I make a userError than the consequent message (where the details are presumably platform-dependent) is wrapped up in extra text that I didn't want appearing. Can I use Control.Monad.Error for IO monad stuff such that I can control what string will appear when my error handler tries to "show" my exception? Admittedly, I'm still learning my way around this bit of the standard libraries, so I may have missed something obvious. -- Mark

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Re: [Haskell-cafe] hGetLine problem
by Keean Schupke 10 Dec '04

10 Dec '04

Hmm, I dont see why the main process would be affected... It should be able to accept multiple connections in parallel. Is it just hGetLine that causes the problem... what if you use hGetContents instead? Does it still not work? (I have a sever implemented - I tested it with "ab -n100 -c10" with no problems...) Keean. Michael Walter wrote: >I did that -- the main process doesn't die, anyway, it just seems to "hang". > >- Michael > > >On Fri, 10 Dec 2004 16:27:05 GMT, MR K P SCHUPKE ><k.schupke(a)imperial.ac.uk> wrote: > > >>>But if the forkIO'ed process terminates because of an exception, that >>>shouldn't influence the main process, right? >>> >>> >>Well, if its unix you might have to set sigPIPE to Ignore... >> >>Otherwise, the main process should not die just because the child has... >> >> Keean. >> >> >>

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RE: [Haskell-cafe] Parse text difficulty
by Simon Marlow 10 Dec '04

10 Dec '04

On 09 December 2004 16:37, Malcolm Wallace wrote: > Robert Dockins <robdockins(a)fastmail.fm> writes: > >>> Prelude> [1..5] `zipWith (+)` [7..] >>> <interactive>:1: parse error on input `(' >> >> is there a technical reason for this or did it just happen? > > If you are asking why general expressions are prohibited between > backticks, yes, there is a reason. The expression could be > arbitrarily large, so you might have to search many lines to find the > closing backtick. But in such a situation, it is surely much more > likely > that the programmer has simply forgotten to close the ticks around > a simple identifier. Just think of the potential for delightfully > baffling type error messages that might result! Forgetting to close a tick would lead to an odd number of ticks, which would probably be flagged as a parse error. Unless you had an even number of missing ticks, of course :-) You can't allow completely general expressions inside backticks, otherwise you run into ambiguity with: 1 `plus` 2 + 3 `plus` 4 so, is that (plus 1 2) + (plus 3 4) or is it ((2+3) plus plus) 1 4 So it would have to be `fexp` only (see the Haskell grammar for fexp). And there's fixities: you can specify the fixity of `x`, but it doesn't make sense to specify the fixity of an expression. There's a historical reason too: `x` and (+) used to be single lexical tokens. I think that changed in Haskell 1.3, but I could be mistaken. Cheers, Simon

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Re: [Haskell-cafe] hGetLine problem
by MR K P SCHUPKE 10 Dec '04

10 Dec '04

>But if the forkIO'ed process terminates because of an exception, that >shouldn't influence the main process, right? Well, if its unix you might have to set sigPIPE to Ignore... Otherwise, the main process should not die just because the child has... Keean.

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hGetLine problem
by Michael Walter 10 Dec '04

10 Dec '04

Herro, thanks for your feedback on my last question, it helped quite a bit. I continued toying with my toy web server, and I'm "sometimes" getting "Invalid argument" errors in hGetLine for a handle I retrieved from Network.listenOn. "Sometimes", because it works fine in the browser, except when I reload very frequently -- maybe it's related to some concurrency issues (I'm using forkIO to spawn off the handler process from the main server loop). When I wanted to benchmark the server using "ab" (Apache Benchmark), it didn't even "survive" one request but Fail'ed using that error message - "<handle: n>: hGetLine: Invalid argument". I tried adjusting the buffering mode. Do you have any ideas? Cheers, Michael

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RE: [Haskell-cafe] Flattening tail recursion?
by Bayley, Alistair 10 Dec '04

10 Dec '04

http://haskell.org/hawiki/TailRecursive A common technique to make a function tail-recursive is to introduce an accumulating parameter, although in the 5 minutes I've spent looking on the wiki, there's no specific page for this. Perhaps add a link from the Efficiency section on http://haskell.org/hawiki/CommonHaskellIdioms ? > -----Original Message----- > From: GoldPython [mailto:goldpython@gmail.com] > Sent: 10 December 2004 15:07 > To: haskell-cafe(a)haskell.org > Subject: [Haskell-cafe] Flattening tail recursion? > > I'm missing something, a functional idiom, whatever. I know there's > "length" to count the elements in a list and it works fine, but the > function below stack overflows on a large list. > > countLines [] = 0 > countLines (_:ls) = 1 + countLines ls > > I would have thought that this was tail recursive and would be > flattened into iteration by the compiler. Can anyone explain why? Is > it because the call is embedded in an expression? > > And additionally, how can I predict when the flattening will occur? > > Thanks, > Will > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > ----------------------------------------- ***************************************************************** Confidentiality Note: The information contained in this message, and any attachments, may contain confidential and/or privileged material. It is intended solely for the person(s) or entity to which it is addressed. Any review, retransmission, dissemination, or taking of any action in reliance upon this information by persons or entities other than the intended recipient(s) is prohibited. If you received this in error, please contact the sender and delete the material from any computer. *****************************************************************

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Re: [Haskell-cafe] Parse text difficulty
by MR K P SCHUPKE 10 Dec '04

10 Dec '04

Oops, please ignore, I just replied to the wrong emaiL! Keean.

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Re: [Haskell-cafe] Parse text difficulty
by MR K P SCHUPKE 10 Dec '04

10 Dec '04

At the moment the unix encrypted passwords are downloaded using sov_slave (an application written by ICT that talks directly to the SOV database)... As far as I am aware all unix cluster in college that are part of ICTs single sign-on us this method unless you have recently changed them... I am suggesting that if there are currently no restrictions on which machines can download using sov_slave, then such restrictions should be put in place. We use scp to update the shadow password files directly on each machine, so the unix crypted password is not exposed (except on a legacy YP domain which is not used by us anymore for password authentication)... I should be able to disable this YP domain, in which case there would be no exposure of the unix passwords, except the possiblility of snooping the sov_slave transfer. This in turn could be done over an encryted SSH tunnel, removing _all_ exposure of the passwords. (we would still download using sov_slave - but as we would authenticate using an ssh key, and only the shadow files would be updates there would be no exposure)... Anyway that is all temporary, we intend to move to Kerberos, once I have sorted out a couple of issues (like ACLs for restricted access machines). Keean.

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Non-technical Haskell question
by GoldPython 10 Dec '04

10 Dec '04

Hi, all, I'm new to the Cafe, but not to Haskell (experimented with it on and off on a small scale over the last 5 or 6 years and enjoy the language quite a lot) and had more of a political question and wanted to see what people thought: Has anyone tried presenting the language to the average rank and file programming community? If so, was it successful? If not, is there interest in doing so? By "rank and file" I mean, outside of the acedemic world where a large number of the programmers I see have very little math background. This would be the typical commercial Visual Basic crowd and the like. Thanks, Will Collum

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Re: [Haskell-cafe] Parse text difficulty
by David Menendez 10 Dec '04

10 Dec '04

Conor McBride writes: > Jan-Willem Maessen - Sun Labs East wrote: > > Tomasz Zielonka wrote: > > > >>I found it useful recently, when I needed zip functions for Trees - > >>this way I didn't have to define functions for 3 trees, 4 trees, > >>and so on. > > > > > > Note also that: > > > > repeat f `zwApply` xs = map f xs > > > > When cooking up my own collection-y things (including splittable > > supplies, for example), I generally provide fmap and an equivalent > > of zwApply (a generic repeat is not quite so simple or useful). > > It's a nice little idiom, and a recommend it highly. > ^^^^^ > > Funny you should choose that word: > > http://www.mail-archive.com/haskell@haskell.org/msg15073.html > > saves me banging the same old drum. Now that I think about it, you can generalize the trick I mentioned elsewhere to work over any Idiom/Sequence/more-than-a-functor-not-yet-a-monad thingy. > class Sequence f where > unit :: a -> f a > (<*>) :: f (a -> b) -> f a -> f b > > liftN :: Sequence f => (f a -> b) -> a -> b > liftN d f = d (unit f) > > suc :: Sequence f => (f b -> c) -> f (a -> b) -> f a -> c > suc d f x = d (f <*> x) > > zero = id > > one :: Sequence f => f (a -> b) -> f a -> f b > one = suc zero > > two :: Sequence f => f (a -> b -> c) -> f a -> f b -> f c > two = suc one > > > newtype L1 a = L1 { unL1 :: [a] } > newtype L2 a = L2 { unL2 :: [a] } > > > instance Idiom L1 where > unit x = L1 [x] > L1 fs <*> L1 xs = L1 [ f x | f <- fs, x <- xs ] > > instance Idiom L2 where > unit x = L2 (repeat x) > L2 fs <*> L2 xs = L2 (zipWith ($) fs xs) *Main> unL1 $ liftN two (,) (L1 [1,2,3]) (L1 "abc") [(1,'a'),(1,'b'),(1,'c'),(2,'a'),(2,'b'),(2,'c'),(3,'a'),(3,'b'),(3,'c') ] *Main> unL2 $ liftN two (,) (L2 [1,2,3]) (L2 "abc") [(1,'a'),(2,'b'),(3,'c')] -- David Menendez <zednenem(a)psualum.com> | "In this house, we obey the laws <http://www.eyrie.org/~zednenem> | of thermodynamics!"

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ghc has problems with 'zipWith' ?
by Derek Elkins 10 Dec '04

10 Dec '04

> Is it possible and senseful for a compiler to extract common > sub-expressions? Naively I think that for a given tree of an > expression it is efficiently possible to find all common sub-trees. > Referential transparency would assure that equal expressions have the > same value, so they can be replaced by the same object. E.g. the > example above could be automatically transformed to: > > ms as = > let tmp0 = zipWith (+) (zipWith (*) as tmp1) (0:tmp1) > tmp1 = 1:tmp0 > in tmp0 It's possible and will preserve semantics, but isn't always an optimization. http://www.haskell.org/pipermail/haskell-cafe/2003-December/005574.html

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Parse text difficulty
by Derek Elkins 09 Dec '04

09 Dec '04

> Robert Dockins <robdockins at fastmail.fm> writes: > > > > And I thought that most programmers used "zipWith", which has to > > > be prefix. > > > [1..5] `zipWith (+)` [7..] > > You don't have a computer at your end of the internet? :-) > > Prelude> [1..5] `zipWith (+)` [7..] > <interactive>:1: parse error on input `(' > Prelude> let zwp = zipWith (+) in [1..5] `zwp` [7..] > [8,10,12,14,16] A way to accomplish the above is given on http://www.haskell.org/hawiki/InfixExpression Also for those who haven't looked too hard at the wiki (or at all), http://www.haskell.org/hawiki/CommonHaskellIdioms is probably the most densely packed page of information on it and makes a great starting point for finding answers on the wiki. The above link is on it, and also the perennial questions about making functions strict is on it under section "Efficiency" "ForcingEagerEvaluation" (where you'll find things like DeepSeq), and some documentation on Control.Monad.* modules under MonadTemplateLibrary. So, just in general, it's a useful and interesting page, and many posts to haskell(-cafe) can be avoided just by perusing it.

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RE: [Haskell-cafe] Non-technical Haskell question
by azrael＠demonlords.net 09 Dec '04

09 Dec '04

> -------- Original Message -------- > Subject: Re: [Haskell-cafe] Non-technical Haskell question > From: "Keith Wansbrough" <Keith.Wansbrough(a)cl.cam.ac.uk> > Date: Mon, December 06, 2004 9:00 am > To: "Georg Martius" <mai99dgf(a)studserv.uni-leipzig.de> > Cc: "Jason Bailey" <azrael(a)demonlords.net>, "Jules Bean" > <jules(a)jellybean.co.uk>, Haskell-Cafe(a)haskell.org > > > > When I compile it I get three files, an actual runnable binary (at only > > > 5M in size), a .o file and a .hi file. I'm sure these additional files > > > are usefull in someway and as soon as I come across the right piece of > > > documentation everything should make sense. But as a person new to the > > > language I'm just left wondering why. > > gcc of course leaves .o files lying around, so this is no different than C. > > javac often creates tens or hundreds of .class files, some with > strange names like MyClass$1.class, MyClass$2.class, and so on (yes, I > know what they are for), and doesn't even generate a native binary. The original observation was that the compiler seems archaic. When asked, I gave some general comments. What I should have just said was that it was to much like a C compiler. Which, no matter how neat you think it is, is archaic. When I use javac every file that is created is necessary for the application to run. This can't be said of the ghc compiler. Having an excuse that this is way the C compiler does it or that this is the way its always been done is to poor of a reason to even argue against. If a file isn't needed then it shouldn't be left there. > I don't think the output of ghc is any more surprising than these; I'm > surprised it bothers you. > Does this bother me? Not in particular, its just an indication that this is an old design. > The static vs dynamic linking question has been discussed many times. > The summary is: GHC is a highly-optimising compiler, and the binary > interface _necessarily_ changes with every minor revision (even > patchlevel revision) of the compiler and each library. So you can't > sensibly share libraries between apps. Anyway, disc is cheap. > I design and build business applications. I'm very good at this. Part of being very good at something like that is acknowledging that that there are some areas where I can't be as good.. such as compilers. The reason I say this is that if your telling me that no one here can figure out how to make it work then I will take your word for it. I'm certainly not in a position to argue :) The whole disc is cheap argument is a cop out. Certainly for a single application this is true. But your inherently limiting yourself. This means no one would consider haskell for embedded devices, or an OS, and it would even impact to a certain degree the decision to use it for a commericial product. You can see how this is reflected today in the fact that you can find almost no binary programs available for download. Programs and applications are out there but almost exclusivly as source code and yes a few of the website even mention that the binary size is the reason why they aren't making it available. (bandwith costs time and money) However this is just a view of a rank and file programmer who's new to haskell. Some of my concerns and issues are probably not valid just because I am not familiar with the language as a whole. However if there is a desire to make Haskell more accessible to the majority of programmers then the first impressions that I, and those like me have is important. Jason > HTH. > > --KW 8-)

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Re: Haskell and qualified identifiers
by Duncan Coutts 08 Dec '04

08 Dec '04

On Wed, 2004-12-08 at 17:04 +0100, Henning Thielemann wrote: > On Wed, 8 Dec 2004, Duncan Coutts wrote: > > > There are actually several options here, you can import modules only > > qualified, then every value from that module needs to be qualified. Some > > modules are designed to be used this way, see for example Data.HashTable > > http://www.haskell.org/ghc/docs/latest/html/libraries/base/Data.HashTable.h… > > (and people are encouraged to write new modules in this style). > > Good to know that there others who conform to this style. But ... why is > the name of HashTable still HashTable.HashTable? Wouldn't be HashTable.T, > HashTable.Type or something like that the better choice? I see your point. I use HashTable like so: import Data.HashTable (HashTable) import qualified Data.HashTable as HashTable That way you can use HashTable unqualified as the name of the type, and then all the other operations are qualified like HashTable.new, HashTable.lookup etc This is like the C++/Java OOP naming convention. The class name is the type and it also qualifies all of the operations. This style is quite readable I find without requiring java.system.io.very.long.qualified.names.all.over.the.place. :-) Duncan

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RE: [Haskell-cafe] namespacing?
by Jason Bailey 08 Dec '04

08 Dec '04

I'm appreciating the feedback. I discovered where I was going wrong. The library I was using allowed me to import a module, which in turn allowed me to use functions from other modules. So even though I could use func directly I couldn't use B.func because I hadn't explicitly imported B. I find that interesting. I would have thought that if I hadn't explicitly imported a module I would either be forced to use the qualified name, not use the function at all, or at the very least be allowed to qualify the name. thanks Jason > -------- Original Message -------- > Subject: Re: [Haskell-cafe] namespacing? > From: "Duncan Coutts" <duncan.coutts(a)worc.ox.ac.uk> > Date: Wed, December 08, 2004 10:12 am > To: azrael(a)demonlords.net > Cc: haskell-cafe(a)haskell.org > > On Wed, 2004-12-08 at 07:58 -0700, azrael(a)demonlords.net wrote: > > I've got a general new person type question. > > > > I understand that I can hide a function in a module that I am importing > > if it conflicts with another identical function name. > > > > But if the situation arises that I would like to use two identically > > named functions from two different modules is there anyway for me to > > specify that I want to use the function from module A rather then the > > function from module B. > > module C where > > import A > import qualified A (foo) > > import B > import qualified B (foo) > > > ... A.foo ... > > ... B.foo ... > > > There are actually several options here, you can import modules only > qualified, then every value from that module needs to be qualified. Some > modules are designed to be used this way, see for example Data.HashTable > http://www.haskell.org/ghc/docs/latest/html/libraries/base/Data.HashTable.h… > (and people are encouraged to write new modules in this style). > > If it's just one or two values that clash then the example above is > good, ie import the whole thing unqualified and just qualify the one or > two names that clash. > > You can even give short names to modules you import, eg: > > import qualified System.Gnome.GConf as Config > > now I can say Config.get rather than System.Gnome.GConf.get > > Hope this helps. > > Duncan

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namespacing?
by azrael＠demonlords.net 08 Dec '04

08 Dec '04

I've got a general new person type question. I understand that I can hide a function in a module that I am importing if it conflicts with another identical function name. But if the situation arises that I would like to use two identically named functions from two different modules is there anyway for me to specify that I want to use the function from module A rather then the function from module B. thanks Jason

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RE: [Haskell-cafe] More on dynlinking
by Simon Marlow 08 Dec '04

08 Dec '04

Your suggestion amounts to giving the programmer more control over the ABI compared to the current extreme options: (a) -O0, ABI == API (b) -O[12], ABI == entire implementation + ABI of dependencies in addition, the ABI includes the version of GHC that compiled the code. Providing an option somewhere between (a) and (b) seems reaonsable. Making the details work out is pretty tricky: for example, you can't inline the definition of an unexposed function into an exposed function. Indeed, the inlining of an exposed function can't depend even on the type of a hidden function. Cheers, Simon On 07 December 2004 14:24, Robert Dockins wrote: > What if (go with me here) we invent a new aggregate unit of haskell > code, and we call it a library, and we design libraries with the > express intent of allowing dynamic linking. We would desire: > > 1) True dynamic linking for reduced memory (and disk) footprint and > drop-in replacement > > 2) ABI versioning (because its a mess otherwise) > > 3) Acceptable performance penalties, by still allowing inlining of > some code > > I propose something along these lines. Libraries are composed of some > number of modules. A module is either an "interior" or "boundry" > module; the library author somehow distinguishes the boundry modules. > The library is compiled as normal and the object files are packeged > together. The .hi files of _boundry_ modules are combined into a > single library-wide interface file, which is then packaged together > with the library code. The interface file would contain a) the > definition of any functions _declared_ in a boundry modules b) > datatypes and classes _exported_ from boundry modules c) the types > (but not definitions) of > any functions re-exported through a boundry module d) instances for > classes which are either imported from elsewhere or exported from a > boundry module e) a version number (eg, with major, minor and build > numbers). The library-wide interface file, and the sybmol names of > closures for the exported functions then constitute the ABI. > > Future changes to or deletions of elements in the interface represent > an incompatable change, whereas additions would be compatable. > Libraries > can then have their version numbers incremented when incompatable > changes are made. > > > This method then allows the library author to decide where to trade > off possible optimizations for implementation hiding (by deciding > what to > put in boundry modules). Things ripe for inlining and unlikley to > change, like monad definitions, could go in the boundry modules, > whereas more volitle heavyweight code could stay in the interior. To > get > behavior similar to the current package behavior, just declare all > modules boundry modules, but still reap some of the reduced footprint > advantages. > > OK, those are my thoughts, flame away, :) > > Robert Dockins > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe

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ghc has problems with 'zipWith' ?
by Daniel Fischer 08 Dec '04

08 Dec '04

Hi, I have recently come across the curious phenomenon that ghci is sometimes much slower than hugs. The occasion that gave rise to it was in connection with continued fractions, where, having a continued fraction with quotients a(n), n >= 0, you get the numerators of the convergents by the recursion formula p(n) = a(n)*p(n-1) + p(n-2) starting with p(-2) = 0 and p(-1) = 1 (same recursion formula for the denominators, starting with q(-2) = 1 and q(-1) = 0). Now I implemented this algorithm first using 'zipWith': ms :: [Integer] -> [Integer] ms as = zipWith (+) (zipWith (*) as (1:ms as)) (0:1:ms as) only to find it awfully slow, ms (replicate 27 2) for example took over 10 seconds, feeding a large list to 'ms' is inadvisable. Then I wrote a fast version of that algorithm, namely ps :: [Integer] -> [Integer] ps as = pStep 0 1 as where pStep :: Integer -> Integer -> [Integer] -> [Integer] pStep _ _ [] = [] pStep x y (a:as) = z:pStep y z as where z = a*y+x This works fine, so I wanted to find out what went wrong in the first version. In hugs, the 'zipWith'-version takes fewer reductions and both versions take more or less the same time, much less than 'ms' in ghci, more than 'ps' in ghci. The performance of 'ms' in ghci is significantly improved by a 'let' (or 'where') expression: pms :: [Integer] -> [Integer] pms as = let mas = pms as in zipWith (+) (zipWith (*) as (1:mas)) (0:1:mas) (no difference in hugs), however this is still much slower than 'ps', last (pms (replicate 1000 1)) takes about 2.75 secs, last (ps (replicate 1000 1)) about 0.01, even last (ps (replicate 10000 1)) took only 0.34 secs. Since usually ghci is MUCH faster than hugs, I am baffled by this behaviour. Does anybody know why this is so? And, apart from avoiding 'zipWith', what can be done to remedy the situation? Greetings, Daniel Fischer P.S.: ghci doesn't take 'zipWith' too well in other circumstances either, referring to the example of Fibonacci numbers in the book of Simon Thompson, the 'fastFib' function on page 76 runs faster in ghci than 'fibs' on page 431, in hugs, 'fibs!!n' takes fewer reductions (no big difference though).

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numerical subtyping
by Derek Elkins 08 Dec '04

08 Dec '04

> Is there a standard Haskell trick for checking run-time assignment to > data types? I'd like a data type of Probability that ensures its > Double argument is between 0 and 1. > > Jim A fairly common technique to achieve this is smart constructors (apparently also called factory functions). http://www.haskell.org/hawiki/FactoryFunction You simply enforce the invariant on construction. For your example, it would look like, newtype Probability = Probability Double probability p | 0.0 <= p && p <= 1.0 = Probability p unProbability (Probability p) = p Simply don't export Probability's constructor and it will be impossible to create a Probability with a value outside of [0,1]. However, you may want to export the constructor, or alternatively, export a function with a name like unsafeProbability (= Probability) for situations where you can statically decide that the invariant will hold if the superfluous checking costs too much, which doesn't seem particularly likely in this case. Providing a function of type Double -> Maybe Probability is also likely a good idea.

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Re: [Haskell-cafe] ghc has problems with 'zipWith' ?
by Tom Pledger 08 Dec '04

08 Dec '04

Daniel Fischer wrote: >Hi, >I have recently come across the curious phenomenon that ghci is sometimes much >slower than hugs. > [...] >ms as = zipWith (+) (zipWith (*) as (1:ms as)) (0:1:ms as) > Hugs has(**) a specific optimisation for the case where the left hand side of the declaration occurs as a subexpression in the right hand side. You can get a similar benefit under ghci if you share the common subexpression by hand: ms' as = let bs = ms' as in zipWith (+) (zipWith (*) as (1:bs)) (0:1:bs) (**) I haven't actually seen the code in question, and am repeating something which was on one of the mailing lists a few years ago. So please don't treat this as authoritative! Regards, Tom

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Is this a useful higher-order function, or should I RTFM?
by Steven Huwig 08 Dec '04

08 Dec '04

I am basically a newbie at Haskell, and have been experimenting with it where typically I would use Python. One source of frustration I had with the standard library is that "words . unwords" is not an identity function. I would like to perform per-word transformations and predicates while preserving whitespace. So I implemented wordsAndSpaces and unwordsAndSpaces, which I believe to be a decent way to get that kind of behavior. In working on this problem, I realized that I was looking for a pair of higher-order functions. My code and an example of usage is below: -- unravel :: (a -> Bool) -> [a] -> ([[a]], [[a]], Int) unravel _ [] = ([], [], 0) unravel p xs = unravel' ([],[], if p (head xs) then 0 else 1) p xs unravel' :: ([[a]], [[a]], Int) -> (a-> Bool) -> [a] -> ([[a]], [[a]], Int) unravel' (sheep, goats, pos) _ [] = (reverse sheep, reverse goats, pos) unravel' acc@(sheep, goats, pos) p rest@(x:xs) | p x = unravel' addSheep p (dropWhile p xs) | otherwise = unravel' addGoat p (dropWhile (not . p) xs) where addSheep = ((takeWhile p rest):sheep, goats, pos) addGoat = (sheep, (takeWhile (not . p) rest):goats, pos) ravel :: [a] -> ([[a]], [[a]], Int) -> [a] ravel zero (sheep, goats, pos) | length sheep > length goats = concat (zipWith (++) sheep (goats ++ repeat zero)) | length sheep < length goats = concat (zipWith (++) goats (sheep ++ repeat zero)) | pos == 0 = concat (zipWith (++) sheep goats) | otherwise = concat (zipWith (++) goats sheep) initcap :: String -> String initcap (c:cs) = toUpper c:[toLower c' | c' <- cs] wordsAndSpaces = unravel (not . isSpace) unwordsAndSpaces = ravel "" teststr = "This is a test\n A very\t\t good\ntest" main = (putStrLn . unwordsAndSpaces) (map initcap words, spaces, pos) where (words, spaces, pos) = wordsAndSpaces teststr -- So unravel takes a predicate and a list, and returns a tuple of two lists -- the first is a list of lists of consecutive elements where predicate is true, and the second where they are false. Its opposite ravel takes a zero element -- to pad out fenceposts -- and the output of unravel, and returns the lists all concatenated together. I have several questions about this: 1) Did I miss something in the Prelude or standard library that gives me this functionality, or something close to it? 2) Do unravel and ravel have any other practical uses on their own? Looking at it, I think they could be used in a single function of type f :: (a->Bool) -> ([a] -> [a]) -> [a] -> [a] that would encapsulate both. E.g. mapWords = f (not . isSpace) main = putStrLn (mapWords initcap "lots \tof\nwhitespace") (syntax not checked for sanity) Can one get that function out of the Prelude in an easier manner than above? Is there a simpler way to get that functionality besides composing ravel and unravel with a map in between? 3) The 3-tuple output of unravel looks ugly to me, but I can't think of an alternative. For the case where there is an equal number of p-groups and not-p-groups, we need to know which side to start the zipWith. Does anyone have a better way? Any comments and criticism are welcome. -- Steven Huwig

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Haskell as data manipulation language?
by Dimitry Golubovsky 08 Dec '04

08 Dec '04

Hi, I am probably not the first to think about this, yet I was unable to find any signs of activities in this direction, so maybe I will be able to know something from this list. First of all, reading multiple messages about global and mutable variables desired in Haskell, I was thinking: isn't the root of the problem in the fact that there are no variables in Haskell at all? Indeed (and my experience of digging in Hugs sources confirms) Haskell program (function) is just a description of some memory structure which being completed by the bindings of its arguments, is further transformed by the evaluator into some other data structure, etc. Now imagine a data storage with structure similar to one of a Haskell program. I. e. a storage having metadata-objects like data constructor functions, data types which are parents to data constructors (like in data X = Foo Int | Bar Float), classes, instances, modules, etc. Also data objects themselves, i. e. precompiled and serialized functions along with their type information. Data objects do not differ from functions i. e. they are stored the same way. Now quoting Graham Klyne Subject was: [HAskell-Cafe] Mutable and persistent values (was: Top Level TWI's again) posted 2004-11-23 05:11:25 PST: (I tried to post reply via Google Groups, but it did not make it back to the list): > It is my view that use a functional language effectively, it is necessary > to think differently about its structure than one would for a conventional > imperative program. Global values become parameters and return > values; mutable values become input values and new (separate) return > values. If you're used to writing imperative programs that do not use > global state, but rather use parameters to pass values, the difference > isn't always quite as great as might be imagined. > > For complex values, this sounds horribly inefficient, but because values > are pure (not mutable), very high levels of sharing can (sometimes, with > good design!) be extensively shared. Thus, a return value may well consist > mostly of a copy of the input value, with differences, rather than actually > being a complete new copy. (Chris Okasaki's book shows well how to design > to obtain these benefits.) > > Also, because Haskell is lazy, complex structures passed between functions > don't necessarily ever exist in their entirety. Sometimes, I think of a > data structure as describing a computational traversal through some data, > rathert than something that actually exists. (This leads to very elegant > expression of things like Prolog search-and-backtrack algorithms.) So, if there is a data object (say, a list) stored with version number N, and another value is cons'ed to the list, then version N+1 will be stored as an application of cons to the value added, and the version N. Thus, via versioning, some kind of mutability may be achieved (and of course these check-in and check-out must belong to IO monad). These stored functions must be visible to the compiler, and when compiling some function f which calls g (compiled earlier and stored as version N), the code of this version of f (say, M) is built to call version N of g further on. So, all the type checks are done during compilation, and are not necessary during runtime, and yet the functions are compiled and stored separately (trying to address the issue with too large monolithic programs). Newer version of f (say M+1) may be compiled against newer (at that time) version of g (N+1). So different versions of the same function may demonstrate different behaviors, but the "history of development" is preserved. Put together, this gives some conceptual image of a "programmable data storage" with queries being calls to stored functions (with externally supplied agruments). All good things of Haskell like static type safety are preserved. I am thinking of implementation of something like this using Hugs runtime as the basis. I realize, this may be very time consuming, so I am wondering, maybe someone already is developing something like this? Or someone already tried, and found this inefficient or in some other way not feasible to implement? Dimitry Golubovsky Middletown, CT

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numerical subtyping
by Jim Apple 08 Dec '04

08 Dec '04

Is there a standard Haskell trick for checking run-time assignment to data types? I'd like a data type of Probability that ensures its Double argument is between 0 and 1. Jim

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Re: [Haskell-cafe] Non-technical Haskell question
by Henning Thielemann 07 Dec '04

07 Dec '04

On Tue, 7 Dec 2004, Brian Smith wrote: > FWIW, I use a directory structure like: > src/ source code > build// intermediate files (.hi, .o) > dist/ deliverables > I execute GHC using: > ghc --make Main -isrc -hidir build -odir build -o dist/program > As a result, I never have any non-source files mixed in with the > source files. So, I think what you want is possible today. The difference is that for Modula-3 the same effect is achieved by e.g. m3build or cm3 that is, I never called the compiler but always used the M3 build system. Would be nice to have this with Haskell, too. Maybe 'hmake' and Cabal can help here?

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RE: [Haskell-cafe] Re: Non-technical Haskell question
by Simon Marlow 07 Dec '04

07 Dec '04

On 06 December 2004 14:39, John Goerzen wrote: > On 2004-12-06, Keith Wansbrough <Keith.Wansbrough(a)cl.cam.ac.uk> wrote: >> The static vs dynamic linking question has been discussed many times. >> The summary is: GHC is a highly-optimising compiler, and the binary >> interface _necessarily_ changes with every minor revision (even >> patchlevel revision) of the compiler and each library. So you can't > > We already have a way to deal with that using sonames. It's not that > hard, and is routinely used. > > BTW, is this a problem even if no -O options are given when building a > library? Certainly it's possible to get a more stable library ABI by not compiling with -O. The question is, do you want to? You certainly don't want to do this for the Prelude and other essential libraries. For example, GHC wouldn't be able to see the definition of 'instance Num Int', and hence (x + 1 :: Int) would be compiled as (+) dNumInt x (I# 1) instead of (after inlining (+) and dNumInt): case x of I# x# -> I# (x# +# 1#) which can then be further optimised: the compiler can see that it is strict in x, so might be able to unbox x, and so on. This is pretty essential to get any kind of reasonable performance, but it might be less important for higher-level libraries, as long as you don't have any important monads that need to be inlined, for example. Dynamic linking is (almost) a separate issue. GHC 6.4 will have some support for dynamic linking in the native code generator thanks to Wolfgang Thaller, but it needs someone to push it the final mile on x86/Linux and Windows. Dynamically linked libraries will work (albeit slightly slower than statically linked ones), but you still have the versioning issue. Since libraries are getting really big nowadays (eg. wxHaskell) making dynamic linking work even without worrying about versioning seems like it would be worthwhile. Cheers, Simon

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RE: [Haskell-cafe] Re: Non-technical Haskell question
by Simon Marlow 07 Dec '04

07 Dec '04

On 06 December 2004 21:54, Sven Panne wrote: > And just a remark: We don't need a new technique for a "no inline > barrier": Just compile the library optimized and use a facade which > re-exports your public API compiled without optimizations. That probably won't work. GHC goes to the .hi file for the module which originally defined a function to get its definition. Cheers, Simon

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RE: [Haskell-cafe] Classes in type declarations in Hugs
by Simon Peyton-Jones 07 Dec '04

07 Dec '04

http://www.haskell.org/ghc/docs/latest/html/users_guide/type-extensions. html#NEWTYPE-DERIVING | -----Original Message----- | From: Graham Klyne [mailto:GK@ninebynine.org] | Sent: 07 December 2004 10:46 | To: Simon Peyton-Jones; haskell-cafe(a)haskell.org | Subject: RE: [Haskell-cafe] Classes in type declarations in Hugs | | At 10:15 06/12/04 +0000, Simon Peyton-Jones wrote: | >| This is where I find ghc's newtype deriving to be incredibly useful. | >| | >| newtype CPError a = CPError (Either Error a) | >| deriving(Monad,MonadError) | >| | >| now CPError is a monad and an instance of MonadError and you are free | >to | >| override or inherit more interesting instances at will without | >| conflicting with the basic types for Either :) | > | >Aha! I've always wondered whether anyone uses this feature, which I | >implemented at John Hughes's suggestion. I'd be interested to know if | >you are alone, or whether others do so too. | | Not a user, but sounds maybe interesting. Can you point to documentation? | | #g | | | ------------ | Graham Klyne | For email: | http://www.ninebynine.org/#Contact

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RE: [Haskell-cafe] Classes in type declarations in Hugs
by Graham Klyne 07 Dec '04

07 Dec '04

At 10:15 06/12/04 +0000, Simon Peyton-Jones wrote: >| This is where I find ghc's newtype deriving to be incredibly useful. >| >| newtype CPError a = CPError (Either Error a) >| deriving(Monad,MonadError) >| >| now CPError is a monad and an instance of MonadError and you are free >to >| override or inherit more interesting instances at will without >| conflicting with the basic types for Either :) > >Aha! I've always wondered whether anyone uses this feature, which I >implemented at John Hughes's suggestion. I'd be interested to know if >you are alone, or whether others do so too. Not a user, but sounds maybe interesting. Can you point to documentation? #g ------------ Graham Klyne For email: http://www.ninebynine.org/#Contact

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RE: [Haskell-cafe] Classes in type declarations in Hugs
by Simon Peyton-Jones 07 Dec '04

07 Dec '04

| This is where I find ghc's newtype deriving to be incredibly useful. | | newtype CPError a = CPError (Either Error a) | deriving(Monad,MonadError) | | now CPError is a monad and an instance of MonadError and you are free to | override or inherit more interesting instances at will without | conflicting with the basic types for Either :) Aha! I've always wondered whether anyone uses this feature, which I implemented at John Hughes's suggestion. I'd be interested to know if you are alone, or whether others do so too. Simon

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RE: [Haskell-cafe] Classes in type declarations in Hugs
by David Menendez 07 Dec '04

07 Dec '04

Simon Peyton-Jones writes: > | This is where I find ghc's newtype deriving to be incredibly useful. ... > Aha! I've always wondered whether anyone uses this feature, which I > implemented at John Hughes's suggestion. I'd be interested to know if > you are alone, or whether others do so too. I think there were a few times where I would have used it, had I known about it. -- David Menendez <zednenem(a)psualum.com> | "In this house, we obey the laws <http://www.eyrie.org/~zednenem> | of thermodynamics!"

1 0

Select.hs in GHC 6.2.1+ Windows 2000
by Henning Sato von Rosen 06 Dec '04

06 Dec '04

Hi! My friend wants to do a haskell lab assignment on windows 2000, but the code depends on Select.hs , is there a workaround in windows one can use instead? Is Cygwin (a / the only) solution Thankful for any info on where to look! /Regards Henning

2 1

Force evaluation
by Michael Walter 06 Dec '04

06 Dec '04

Hi, is there a way to force the "full" evaluation of a value (unless seq, which only brings the term to WHNF)? In my case, I have an algebraic data type Foo, and I would like to catch the exceptions that will occur during the evaluation of a value of Foo, for something like: foo <- force makeFoo `catch` \e -> defaultFoo Thanks, Michael PS: Ooops, posted this to haskell-ml first.

2 1

Practical Question: Large memory items
by GoldPython 06 Dec '04

06 Dec '04

In another thread's discussion, we touched on the implementation of a text editor. It invariably comes up, in building a text editor, as to whether to allow editing of things larger than will fit in memory, etc. And so, practical concerns enter in that, in my mind at least, take us away from solving the conceptual problem at hand, and now the focus shifts to implementation details that we'd rather not be bothered with. One approach is to let the OS's virtual memory take care of it. Sometimes this is fine, sometimes not, often times around issues of performance, where a completely general purpose swapping device can't perform as well as a more specifically targeted design. Question: Should the Haskell runtime enviroment provide swapping services for large objects?

2 1

Mutable data design question
by GoldPython 06 Dec '04

06 Dec '04

In the case of writing something like a text editor where the data involved is by its very nature mutable, what sort of design paradigm would you use in a functional language?

10 13

OT: A little AI fun
by John Goerzen 06 Dec '04

06 Dec '04

For kicks, I set up a MegaHal AI bot named MegaMonad on irc.freenode.net#haskell today, trained with the logs from this year's conversations on that channel. Here are a few quotes, thought you might enjoy them. (A few made more sense with context, so "User" is what was said to MegaMonad, and "MegaHAL" is the response.) To me java is a monomorphic type. i just have to capture their scope to me. User: Java is evil MegaHAL: How experienced he is evil evil evil. "phd student" means you are talking at the moment. If you insult and anger your teammates, they're not first class functions? MegaHAL: And interfaces can only put it another way, but you can sequence a bunch of noobs. User: I haven't seen any prefixes, and NO, you can't just sequence all of us noobs!! MegaHAL: Yes from the ground while wrapped around the right sequence of strings in the sequence too. User: a noob monad ? MegaHAL: (Lots of monad if you throw me a noob. User: what is haskell? MegaHAL: Well, i'd ask john hughes about using haskell actually. User: Good advice. User: what is scheme? MegaHAL: Man i love scheme.. So i'll do freelance coding of this is a neat solution. User: but what _is_ Haskell? MegaHAL: It's is always stupid peoples to do this in haskell. User: You traitor! Many people *don't* have a conscious will to build a box with the existing instances of the language haskell programming is kind of stimulant drug or something? User: shapr likes unicycles. MegaHAL: This is very generic nowadays, and include mixed languages like haskell after a variable x which i have two unicycles, and mountain unicycles. User: Isn't coding refraction easy once you have done reflection? MegaHAL: It reminds me of the reflection of the functional world, the same as refraction. Vegai starts a summerjob as a directed graph. if you want ml you know type info, but also sort of weenie. User: have you ever met Simon? MegaHAL: Simon^2 expands to simon simon. Boegel why is that haskell is devishly mind bending. Ok, rebooting to install several of the life of the universe. User: do you ever shut up ? MegaHAL: Shapr: don't know. I just need to find something you import a module th at lets me easily use the debs to build a linux/x86, so 10.1 is a kind of german music is stuff i like it might contain serious mistakes, and i'm stuck on (cont ag (tupletag n), ...), because cont expects a directory or what-have-you. The s hort answer and wouldn't shut up and at the farthest end leasable compute time. The reason i ask igloo to do icfp in a system where the case, on a category theory can improve your code, then it's too late to unicycle. User: linux MegaHAL: Metasteganographic obfuscation is a go too, its got the "cloud of objects" syle rather than linux that would be it. User: are you evil? MegaHAL: I seem to get into it if using jakarta collections User: I suspect that really, you are part of the Microsoft Cabal that's plotting to take over Haskell!!! MegaHAL: So cabal would be even easier, with generic haskell back to plotting. User: cabal and jakarta User: I knew it! User: haskell is a warm gun MegaHAL: Er. Depends what you want in the warm part of a gun. User: I think you should soothe the frustrated blackdog. MegaHAL: Blackdog: you might be a bit frustrated. Ah. C# is not that safe. User: is ssh turing complete? MegaHAL: Shapr: you have little choice if that is complete enough to be turing complete. MegaHAL: Me going to use java for a lisp weenie. User: are you comparing Lisp weenies to Java weenies? MegaHAL: To me java is a confusing network of stream data, write out the weenies. I mumble to those late-night commercials like the darcs repo from the end of the lexical language User: Bush or Kerry? MegaHAL: I'll re-port it and mention them on the grounds that emacs and xemacs are, but kerry has to get a vote for kerry. User: the summer is a long time to wait to push those changes. MegaHAL: I was just wondering how much time to wait for it to push. User: they usually push in a couple of minutes MegaHAL: 6 Minutes if you couple it with mud and other permission fields. beginning perl is possible, but untested. User: ttyl good night MegaHAL: Ok night....thanks for the night. User: \msg MegaMonad you weren't supposed to talk about that in public! User: how many roads must a man walk down? MegaHAL: But man is not a walk in the type system much like java.

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