- Haskell-Cafe - Haskell.org

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!"

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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

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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.

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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?

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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?

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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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Re: [Haskell-cafe] Non-technical Haskell question
by Keean Schupke 06 Dec '04

06 Dec '04

Looks like your right, I thought cabal was just a library packaging standard, but it appears to have an on-line archive... I guess the real question is, can i do: cabal install <package> (or equivalent) and have all dependancies and the package I want downloaded, configured, compiled, and installed on my system, such that I only have to type the one command and then I can start using the library straight away? (like with install <blah> in CPAN....) Keean. Arthur van Leeuwen wrote: > >Aren't the Hackage and Cabal projects supposed to lead to something >like that? http://www.haskell.org/cabal > >Doei, Arthur. > > >

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Propagating Parsec errors
by Mark Carroll 05 Dec '04

05 Dec '04

Is there a way in Parsec to, within a parser, throw an error generated by another parser? For instance, something of type ParseError -> GenParser tok st a or whatever. -- Mark

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(no subject)
by balarcon＠dsic.upv.es 05 Dec '04

05 Dec '04

Hi, I have to install HDirect on a windows plataform but I have a lot of problems. When I try to install the version 0.21,"make boot" has problems with Happy and I've commented this line(the path is correct),latter "make lib" give 2 errors: ../src/ihc :command not found [hugs/PointerPrim.hs] Error I don't know if this version is for windows too,the 0.16 isn't available in the page.I do the installation with "cygwin" I don't know if it's the best opcion.Please I need use HDirect,help me. Thanks for all, Bea ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.

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