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RE: [Haskell-cafe] Template Haskell question?
by Simon Peyton-Jones 12 Feb '04

12 Feb '04

There is a lot of TH stuff in the HEAD that is not in the released GHC 6.2. TH is still under active development, including design changes, largely in response to feedback from people using it -- so keep us posted on template-haskell(a)haskell.org Simon | -----Original Message----- | From: haskell-cafe-bounces(a)haskell.org [mailto:haskell-cafe-bounces@haskell.org] On Behalf Of | Jeremy Shaw | Sent: 11 February 2004 16:44 | To: Per Larsson | Cc: haskell-cafe(a)haskell.org | Subject: Re: [Haskell-cafe] Template Haskell question? | | Hello, | | I had very similar problems due to bugs in 6.2 that are fixed in cvs head. If you build ghc out of cvs | head that may fix your problem. If not, you can report the bug on the glasgow-haskell- | bugs(a)haskell.org mailing list. | | Jeremy Shaw. | | | On Feb 11, 2004 01:39 AM, Per Larsson <per(a)L4i.se> wrote: | | > I have written a small TH application (module THRecord) which creates update | > functions for records. It is intended to be used like this: | > | > import THRecord | > | > data Record = R {... | > ... | > $(THRecord.generateRecordModifiers (reifyDecl Record)) | > | > It works great, but only if the splice is placed last in the importing module! | > If I place it in the middle of the module it seems to hide subsequent | > declarations and I get 'Variable not in scope ...' compiler errors. If I | > place it at the top of the module I get: | > | > ghc-6.2: panic! (the `impossible' happened, GHC version 6.2): | > nameModule Record {- tc 01D -} | > | > Has anybody a clue of what is happening here? | > | > -- Per | > | > | > _______________________________________________ | > Haskell-Cafe mailing list | > Haskell-Cafe(a)haskell.org | > http://www.haskell.org/mailman/listinfo/haskell-cafe | | | | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe(a)haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe

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Template Haskell question?
by Per Larsson 11 Feb '04

11 Feb '04

I have written a small TH application (module THRecord) which creates update functions for records. It is intended to be used like this: import THRecord data Record = R {... ... $(THRecord.generateRecordModifiers (reifyDecl Record)) It works great, but only if the splice is placed last in the importing module! If I place it in the middle of the module it seems to hide subsequent declarations and I get 'Variable not in scope ...' compiler errors. If I place it at the top of the module I get: ghc-6.2: panic! (the `impossible' happened, GHC version 6.2): nameModule Record {- tc 01D -} Has anybody a clue of what is happening here? -- Per

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Haskell newbie
by Justin Walsh 08 Feb '04

08 Feb '04

Can anyone recommend a very thin Linux/Haskell setup for DHCP cable? Jus. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com) Version: 6.0.576 / Virus Database: 365 - Release Date: 1/30/04

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Haskell binaries for AIX?
by Bruno Melo 07 Feb '04

07 Feb '04

Maybe, this link can help you: http://www.cin.ufpe.br/~haskell/ghc-AIX/ ## bruno melo ## linux user #334122 www.rootshell.be/~brunoj

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Path names (again?)
by Vincenzo aka Nick Name 06 Feb '04

06 Feb '04

Hi all, I am so often in need for this (I suppose, non-existing) module, that I am going crazy :) I have found discussions in the archives for haskell mailing lists, but is there any, even posix-only, even unix-only, but better portable, implementation of functions to - concatenate file paths - tell if a path is absolute or relative - chase symlinks - find all the files in a directory (yes, that's what I need :)) I am tired of finding bugs in my implementation, is there someone with a better thing to offer? Is there any hope to see such functions in GHC libraries, or are those already there and it's just me who can't find'em? Thanks in advance Vincenzo

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Sat solver
by Ron de Bruijn 05 Feb '04

05 Feb '04

Hi there, I need a complete 3-CNF-Sat solver that can solve sentences of about length 20 (or shorter). Now I use simple model checking, but that's a bit slow , you understand :) I have seen some algorithms on the web and some code-sniplets in papers. But I presume there is some implementation available, so I thought: Let's ask, and don't reinvent the wheel. Greets Ron P.S. Thanks to those who answered my previous question, although I have found another way of expressing my problem. __________________________________ Do you Yahoo!? Yahoo! Finance: Get your refund fast by filing online. http://taxes.yahoo.com/filing.html

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Syntactic extensions
by Niklas Broberg 05 Feb '04

05 Feb '04

Hello, I am using the haskell-src bundle to implement a preprocessor for some syntactic extensions to haskell. This is all fine and well, but I find myself also wanting the preprocessor to let through some already existing extensions, namely: * implicit parameters * pattern guards * multi-parameter type classes with functional dependencies * possibly template haskell The haskell-src bundle already has support for mptcs (without fundeps), and pattern guards are rather straight-forward, but for the rest; Where can I find formal specifications of these extensions in terms of added/changed syntax? Or even better, is there anyone out there who has already extended the haskell-src bundle with support for any of them? regards, Niklas Broberg (d00nibro[at]dtek.chalmers.se) _________________________________________________________________ Add photos to your e-mail with MSN 8. Get 2 months FREE*. http://join.msn.com/?page=features/featuredemail

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Haskell overview
by Mark Carroll 04 Feb '04

04 Feb '04

A colleague with a mathematics and Lisp background is wanting to learn more about Haskell. The books he's looked at concentrate more on building up from the basics and getting the syntax right, etc., whereas really he's looking more of a top-down view that makes Haskell's features and behavior clear and relates them to category theory, etc. Would anyone be able to suggest some good references? -- Mark

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Type Class Query
by Tim Stitt 03 Feb '04

03 Feb '04

I'm experimenting with type classes in Haskell and tried to implement a new class based on nullifying values of various types e.g. nullify 6 = 0 nullify 7.6 = 0 nullify [1,2,3] = [] nullify Tree = Empty etc. I set up my class as follows: class Null a where nullify :: a -> a instance Null Int where nullify x = 0 but get the following error when I invoke nullify 6 on the Hugs command line: ERROR - Unresolved overloading *** Type : (Num a, Null a) => a *** Expression : nullify 6 I then tried the following: instance Num a => Null a where nullify x = 0 but got the following error in Hugs ERROR "C:\zero.hs":5 - Syntax error in instance head (constructor expected) Can anybody explain what I'm doing wrong ? Thanks in advance, Tim.

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Storing functional values
by nickgrey＠softhome.net 03 Feb '04

03 Feb '04

Hi, I'm writing a game in Haskell. The game state includes a lot of closures. For example, if a game object wants to trigger an event at a particular time, it adds a function (WorldState -> WorldState) to a queue. Similarly there are queues which contain lists of functions which respond to events. (CreatureAttackEvent -> WorldState -> WorldState) I'd like to be able to save the game state to disk so that it can be reloaded. Obviously, these closures are now a problem, as they can't be stored. I could obviously, replace all the functional values with non-functional ones, and have a big case statement specifying the behaviour associated with each constant. However, I don't really like this solution. It means that for each type of function which was in the game state (there are lots) I will need a type which lists all the possible behaviours (again, there are lots) that could occur. First of all, these types are likely to be very large. Secondly, I'd rather the behaviours were defined in different modules. For example, I want to have an "Orc" module which defines functions such as "Response to orc being hit", "Response to orc picking something up", etc. This implementation would force me to have a "Monster reponse to being hit" MODULE, containing an orcs response, a goblins response etc. I.e., the modules would be grouped by type of behaviour, rather than type of monster, meaning that adding a new monster type would require modifications accross many modules. (This example is obviously something of a simplification, but hopefully it shows the point.) Obviously, none of this is fatal. I could make it work. But going through my program and replacing all the functions with values and then doing big pattern matches against the values to find the functions seems like a very non-functional way of doing things. Can anyone suggest a neater design?

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