[Haskell-cafe] SYB with Existentials
It is quite straightforward to extend the SYB generic programming
framework to existential data types, including existential data types
with type class constraints. After all, an existential is essentially
a variant data type with the infinite, in general, number of variants.
The only, non-fatal, problem is _not_ with writing the instance of
gunfold. Defining gunfold is easy. The problem is that the existing
SYB -- or, the module Data/Data.hs to be precise -- has
non-extensible constructor and datatype descriptions (Constr and
DataType). The problem is not fatal and can be worked around in
various inelegant ways. Alternatively, one can fix the problem once
and for all by making DataType and Constr extensible -- along the
lines of the new Exceptions. The following file
http://okmij.org/ftp/Haskell/DataEx.hs
demonstrates one such fix. The file DataEx.hs also tries to avoid the
overlap with Data.Typeable. (One doesn't need to carry the name of the
datatype's type constructor in DataType. That name can be obtained
from the result of typeOf). The file DataEx can be used alongside the
original Data.hs. The code below uses DataEx in that way, to
complement Data.hs. The hope is that the maintainers of SYB might
choose to extend Data.hs -- perhaps using some bits or ideas from
DataEx.hs.
The following is a complete literal Haskell code illustrating
gfold/gunfold for existentials.
{-# LANGUAGE ExistentialQuantification, Rank2Types, ScopedTypeVariables #-}
{-# LANGUAGE PatternGuards #-}
{-# LANGUAGE DeriveDataTypeable #-}
module SybExistential where
We import the old Data.Data and complement it with DataEx. We assume
that DataEx.hs present in the -i path.
import Data.Generics (gnodecount)
import Data.Data as Old
import DataEx
-- The following is the sample existential data type suggested by
-- Oscar Finnsson. We use that data type as our running example.
data DataBox = forall d. (Show d, Eq d, DataEx d) = DataBox d
We make the DataBox itself to be a member of Typeable, Eq and Show.
instance Typeable DataBox where
typeOf _ = mkTyConApp (mkTyCon DataBox) []
instance Show DataBox where
show (DataBox x) = DataBox[ ++ show x ++ ]
-- Two databoxes are the same if the types of their enclosed values
-- are the same, and their values are the same too
instance Eq DataBox where
DataBox x == DataBox y | Just y' - cast y = x == y'
DataBox _ == DataBox _ = False
The file DataEx makes constructor representation extensible. We hereby
add a new variant to constructor representation, so to represent _any_
existential data type.
data ExConstr = forall a. Typeable a = ExConstr a
instance Show ExConstr where
show (ExConstr a) = ExConstr ++ show (typeOf a)
instance Typeable ExConstr where
typeOf _ = mkTyConApp (mkTyCon ExConstr) []
instance Eq ExConstr where
ExConstr x == ExConstr y = typeOf x == typeOf y
We are now ready to implement gfold/gunfold for DataBox. First is
gfold; gfold is not affected by our extensions of Constr and is not
re-defined in DataEx.
instance Old.Data DataBox where
gfoldl k z (DataBox d) = z DataBox `k` d
As the instance of DataType for DataBox we use a DataBox object
itself. DataBox is already a member of all needed classes (Eq, Show,
Typeable), except for the following.
The file DataEx.hs defines a Read-like type class to de-serialize
constructor representations. We don't need this feature here.
instance ReadCtor DataBox where
readConstr _ str = error not yet defined
We come to the main instance, of DataEx:
instance DataEx DataBox where
As the `description' of DataBox's datatype we take a sample DataBox
value. We only care about typeOf of that value.
dataTypeOf _ = DataType (DataBox (undefined::Int))
Since an existential data type is a ``variant data type with,
generally, infinite number of data constructors'', we can use the very
value of the existential as the description of that particular
``constructor.''
toConstr = Constr . ExConstr
And finally, the definition of gunfold
gunfold k z (Constr c) | Just (ExConstr ec)- cast c,
Just (DataBox (_::a)) - cast ec =
k (z (DataBox::a - DataBox))
That is it. Here are a few tests.
-- sample DataBoxes
tdb1 = DataBox (42::Int)
tdb2 = DataBox (string, tdb1)
tdb2_show = show tdb2
-- DataBox[(\string\,DataBox[42])]
The following tests use gfold
tdb1_gcount = gnodecount tdb1
-- 2
tdb2_gcount = gnodecount tdb2
-- 17
whereas the following tests use gunfold.
-- generic ``minimum''
-- (I took a liberty to define 0 as the min Int value, since
-- it prints better)
genMin :: DataEx a = a
genMin = r
where
r = case DataEx.dataTypeOf r of DataType x - build . min_ctor $ x
min_ctor x | Just (AlgDataType (c:_)) - cast x = Constr c
min_ctor x | Just IntDataType - cast x = Constr . DataEx.IntConstr $ 0
min_ctor x | Just CharDataType - cast x = Constr . DataEx.CharConstr $
min_ctor x |
[Haskell-cafe] Work on Video Games in Haskell
iPwn Studios is seeking Haskell developers for its debut title, BloodKnight. * No prior game development experience is required, but you must be very comfortable working in Haskell. * Compensation is negotiable; profit-sharing may be available in some cases. * To apply, or for more information, contact me at r...@ipwnstudios.com. BloodKnight is an action-roleplaying game inspired by games like Diablo and Fallout. It is currently in the final stages of development, and will be released later this year on a variety of smartphone platforms, including iPhone and Android. iPwn Studios is a start-up company located in Boston, MA. We believe in giving back to the Haskell community, so we've open-sourced our ghc-iphone project, which allows GHC to produce binaries for the iPhone. Check it out at http://projects.haskell.org/ghc-iphone/. Ryan Trinkle iPwn Studios ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Work on Video Games in Haskell
This sounds fantastic. Now I wish I had started learning haskell a few years earlier. As a side note, how is this project getting around the language restrictions apple put in the developer license agreement? --- [http://daringfireball.net/2010/04/iphone_agreement_bans_flash_compiler] In the new version of the iPhone Developer Program License Agreement released by Apple today (and which developers must agree to before downloading the 4.0 SDK beta), section 3.3.1 now reads: 3.3.1 — Applications may only use Documented APIs in the manner prescribed by Apple and must not use or call any private APIs. Applications must be originally written in Objective-C, C, C++, or JavaScript as executed by the iPhone OS WebKit engine, and only code written in C, C++, and Objective-C may compile and directly link against the Documented APIs (e.g., Applications that link to Documented APIs through an intermediary translation or compatibility layer or tool are prohibited). --- On Wed, May 26, 2010 at 2:52 PM, Ryan Trinkle ryan.trin...@ipwnstudios.com wrote: iPwn Studios is seeking Haskell developers for its debut title, BloodKnight. * No prior game development experience is required, but you must be very comfortable working in Haskell. * Compensation is negotiable; profit-sharing may be available in some cases. * To apply, or for more information, contact me at r...@ipwnstudios.com. BloodKnight is an action-roleplaying game inspired by games like Diablo and Fallout. It is currently in the final stages of development, and will be released later this year on a variety of smartphone platforms, including iPhone and Android. iPwn Studios is a start-up company located in Boston, MA. We believe in giving back to the Haskell community, so we've open-sourced our ghc-iphone project, which allows GHC to produce binaries for the iPhone. Check it out at http://projects.haskell.org/ghc-iphone/. Ryan Trinkle iPwn Studios ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Work on Video Games in Haskell
On Wed, May 26, 2010 at 9:23 AM, Lyndon Maydwell maydw...@gmail.com wrote: As a side note, how is this project getting around the language restrictions apple put in the developer license agreement? From the project page : This version uses Apple's official iPhone SDK as its back end compiler. David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [reactive] A pong and integrate
The GHC bugs are now fixed, so it might be stable enough for another adventure like that, but I don't think I would bet on it again. GHC bugs are corrected, but Reactive still have some. (See my previous posts) IMO Haskell is great for writing small clean prototypes, doing interesting research, and maybe making some fun little games, but I wouldn't use it for production reactive game coding, not yet at least. Tim Sweeney (from Epic Games) has another perspective about that [1]. Besides, FRP is not mandatory. You can always make games in Haskell by using a more regular style (more imperative, would some say). For now, the main problem is the small number of Haskell libraries for games when compared to the huge numbers of those which exist in C++, which prevents, for now, Haskell to be used as the main language for big commercial games. But for smaller scale games (like indie), which have less needs, I think it's worth it. [1] http://www.scribd.com/doc/5687/The-Next-Mainstream-Programming-Language-A-Game-Developers-Perspective-by-Tim-Sweeney 2010/5/25 Peter Verswyvelen bugf...@gmail.com Well, first of all, I did not make these PS3 visualization, my former colleagues and I just made the editor, language and runtime that allowed video game artists to do the job for us in a couple of weeks time :-) I wouldn't use Yampa, for performance reasons, and difficulty to get it running on alien platforms (it is well known it performs relatively badly, although the work done by Paul Liu and co on Causal Commutative Arrows looks very promising, but does not support dynamic switching yet). After all, Yampa models a synchronous dataflow language, and compilers for these languages are relatively easy to make IMO. My previous - now defunct - company Anygma spent a lot of money on trying to use Haskell and Reactive for game programming, which unfortunately ended in some nasty GHC bugs popping up (see http://www.haskell.org/haskellwiki/Unamb), and not all problems with Reactive got fixed; it is amazing how difficult this all turned out to be. The GHC bugs are now fixed, so it might be stable enough for another adventure like that, but I don't think I would bet on it again. IMO Haskell is great for writing small clean prototypes, doing interesting research, and maybe making some fun little games, but I wouldn't use it for production reactive game coding, not yet at least. On Tue, May 25, 2010 at 10:49 AM, Limestraël limestr...@gmail.com wrote: Wow... impressive... And now, with your experience, if you'd have to do this again, would you use Yampa or stick up with C#/C++ ? 2010/5/24 Peter Verswyvelen bugf...@gmail.com Yeah. Funny that we're still writing games in C++, while mission critical and hard real time systems are written in much nicer languages :) I made something similar to Lucid Synchrone for a game company I used to work, but with the purpose of making reactive programming accessible to computer artists. The integrated development environment provided the typical boxes-and-links user interface, where the boxes were signal functions. Signals itself were not exposed, like Yampa. The system did type inference so artists never really had to deal with types. Special nodes like feedback and delay where provided to allow transferring values to the next frame. This actually was a great success, digital artists could literally create little interactive applications with it, without much help from programmers. This resulted in a Playstation 3 visual experience Mesmerize (http://www.youtube.com/watch?v=rW7qGhBjwhY). This was before I knew Haskell or functional programming, so it was hacked together in C# and C++... I still believe that the reason why computers artists could work with this environment and were not able to learn imperative programming is functional programming itself: the system had all the goodies of FP: type inference, referential transparancy, etc... But is also provided the possibility to edit literals while the simulation was running, providing zero turnaround times, which was equally important for quick adoption of the software. So IMO Haskell and FRP systems have a huge potential for education of a much broader audience than just computer scientists... On Mon, May 24, 2010 at 6:13 PM, Limestraël limestr...@gmail.com wrote: I assumed also that it was a field which was still under research, however, Lustre, again, is used for critical control software in aircraft, helicopters, and nuclear power plants, according to wikipedia. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
On May 26, 2010, at 03:50 , David Virebayre wrote: On Wed, May 26, 2010 at 9:23 AM, Lyndon Maydwell maydw...@gmail.com wrote: As a side note, how is this project getting around the language restrictions apple put in the developer license agreement? From the project page : This version uses Apple's official iPhone SDK as its back end compiler. You might want to reread that license agreement. Specifically: Applications must be originally written in Objective-C, C, C++, or JavaScript as executed by the iPhone OS WebKit engine, and only code written in C, C++, and Objective-C may compile and directly link against the Documented APIs (e.g., Applications that link to Documented APIs through an intermediary translation or compatibility layer or tool are prohibited) -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
On Wed, May 26, 2010 at 9:58 AM, Brandon S. Allbery KF8NH allb...@ece.cmu.edu wrote: You might want to reread that license agreement. Specifically: Applications must be originally written in Objective-C, C, C++, or JavaScript as executed by the iPhone OS WebKit engine, and only code written in C, C++, and Objective-C may compile and directly link against the Documented APIs (e.g., Applications that link to Documented APIs through an intermediary translation or compatibility layer or tool are prohibited) Ah, yes. Ouch, that's abusive. Can they tell the difference though ? David. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
Of course, given that they have no way of determining that short of asking for the source code (and hiring another thousand reviewers to read it) or applying static analysis tools with heuristics to the programs. I really doubt they do the latter, and the former is unrealistic. Most people seem to think the clause is there mostly to discourage large companies like Adobe from making generic tools to translate to the iPhone/iPad. It would be a lot of effort for Apple to actually enforce it strictly. On Wed, May 26, 2010 at 3:58 AM, Brandon S. Allbery KF8NH allb...@ece.cmu.edu wrote: On May 26, 2010, at 03:50 , David Virebayre wrote: On Wed, May 26, 2010 at 9:23 AM, Lyndon Maydwell maydw...@gmail.com wrote: As a side note, how is this project getting around the language restrictions apple put in the developer license agreement? From the project page : This version uses Apple's official iPhone SDK as its back end compiler. You might want to reread that license agreement. Specifically: Applications must be originally written in Objective-C, C, C++, or JavaScript as executed by the iPhone OS WebKit engine, and only code written in C, C++, and Objective-C may compile and directly link against the Documented APIs (e.g., Applications that link to Documented APIs through an intermediary translation or compatibility layer or tool are prohibited) -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
On May 26, 2010, at 04:14 , David Virebayre wrote: On Wed, May 26, 2010 at 9:58 AM, Brandon S. Allbery KF8NH allb...@ece.cmu.edu wrote: You might want to reread that license agreement. Specifically: Ah, yes. Ouch, that's abusive. Can they tell the difference though ? I suspect GHC-generated code is fairly distinctive even as machine code. But they don't have to go to that extent; all they have to do is use Google to find this thread. :( -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] MultiParamClasses question
On Tue, May 25, 2010 at 10:46:47PM +0100, Stephen Tetley wrote: Hi Eugene You can store different things in a Map by collecting them with a simple 'sum' type: Hello, Stephen! The records to be stored into a Map are not related to each other. So wrapping them into another type is not very smart solution in my case :) The problem is really with the fact that records, created from such lines user_1_name=user group_1_name=group do refer to the same key 1. But you gave me idea that I can use single map - but as a key use something like type KeyT k i = (k,i) where k is type of record (Group or User), and i is index, usually Int. This way I will try to redesign my existing code. Thank you for the idea :) -- Eugene Dzhurinsky pgpekoWNsf3na.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
Hi guys, I don't think this licensing issue will be a problem for us. It's not clear to me that our game violates this new term, and we certainly don't violate any of the principles Steve Jobs used to justify it. If Apple wants to reject our app, they already have a variety of excuses at their disposal, as they've demonstrated on many occasions. Frankly, it'd be their loss; Android is now the fastest-growing smartphone market, and we'll be more than happy to focus on it (and other friendlier markets) if Apple's not interested in having our product on their platform. Ryan Trinkle iPwn Studios On Wed, May 26, 2010 at 4:18 AM, Brandon S. Allbery KF8NH allb...@ece.cmu.edu wrote: On May 26, 2010, at 04:14 , David Virebayre wrote: On Wed, May 26, 2010 at 9:58 AM, Brandon S. Allbery KF8NH allb...@ece.cmu.edu wrote: You might want to reread that license agreement. Specifically: Ah, yes. Ouch, that's abusive. Can they tell the difference though ? I suspect GHC-generated code is fairly distinctive even as machine code. But they don't have to go to that extent; all they have to do is use Google to find this thread. :( -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
RE: [Haskell-cafe] [reactive] A pong and integrate
I work in the games industry and I'm also not convinced of the Haskell+FRP path for games, but for different reasons. I am very fond of Haskell for games however, and think it is achievable. Regarding FRP, I don't think it is the right framework to base a game on. It's great for some stuff, particularly the kind of problem Peter demonstrated, but games are a lot more varied than that and efficiency concerns aside, it's just not the right approach for everything. I see it more as a useful tool for some elements than a framework that should form the backbone of a game. Functional programming on the other hand is a big thing. Games look a lot more functional now days than they ever did before, and C++ doesn't have the right vocabulary to allow you to scratch this itch properly. EDSLs, parallelism, composability, higher order functions, and static typing are really where it's at, and Haskell excels at this. There's a lot of missed opportunities for more elegant and powerful architectures going by at the moment simple because it's not realistic to attempt them in C/C++. One area where Haskell is not so hot and needs a bit of TLC is it's 'embedability'. A large cross-platform 100% Haskell game is not on the cards at the moment, but Haskell could start getting its hands dirty, if only it could be sensibly embedded within an otherwise C++ app. This would allow people to start to take advantage of it, without some wholesale switch over. However, to do this, Haskell implementations at least need to be more compiler and platform agnostic, and we would probably need a lot more control over the Haskell runtime itself, particularly wrt memory handling. Lua (which is very popular in the games industry) and ATS (which isn't used to my knowledge, but has excellent interaction with C) are good examples of languages where this kind of thing is considerably easier. Haskell would have to fit in differently to this, but that's the kind of idea. Interesting things to note are that in this scenario, you could probably ditch IO altogether and just embed 'pure' Haskell. Games have very limited IO which would likely be best handed in C++ anyway. Laziness/space leaks, garbage collection and general performance concerns are obviously also issues, but that's for another day J Cheers, Sam From: haskell-cafe-boun...@haskell.org [mailto:haskell-cafe-boun...@haskell.org] On Behalf Of Limestraël Sent: 26 May 2010 08:52 To: Peter Verswyvelen Cc: haskell-cafe@haskell.org; Patai Gergely Subject: Re: [Haskell-cafe] [reactive] A pong and integrate The GHC bugs are now fixed, so it might be stable enough for another adventure like that, but I don't think I would bet on it again. GHC bugs are corrected, but Reactive still have some. (See my previous posts) IMO Haskell is great for writing small clean prototypes, doing interesting research, and maybe making some fun little games, but I wouldn't use it for production reactive game coding, not yet at least. Tim Sweeney (from Epic Games) has another perspective about that [1]. Besides, FRP is not mandatory. You can always make games in Haskell by using a more regular style (more imperative, would some say). For now, the main problem is the small number of Haskell libraries for games when compared to the huge numbers of those which exist in C++, which prevents, for now, Haskell to be used as the main language for big commercial games. But for smaller scale games (like indie), which have less needs, I think it's worth it. [1] http://www.scribd.com/doc/5687/The-Next-Mainstream-Programming-Language-A-Game-Developers-Perspective-by-Tim-Sweeney 2010/5/25 Peter Verswyvelen bugf...@gmail.com Well, first of all, I did not make these PS3 visualization, my former colleagues and I just made the editor, language and runtime that allowed video game artists to do the job for us in a couple of weeks time :-) I wouldn't use Yampa, for performance reasons, and difficulty to get it running on alien platforms (it is well known it performs relatively badly, although the work done by Paul Liu and co on Causal Commutative Arrows looks very promising, but does not support dynamic switching yet). After all, Yampa models a synchronous dataflow language, and compilers for these languages are relatively easy to make IMO. My previous - now defunct - company Anygma spent a lot of money on trying to use Haskell and Reactive for game programming, which unfortunately ended in some nasty GHC bugs popping up (see http://www.haskell.org/haskellwiki/Unamb), and not all problems with Reactive got fixed; it is amazing how difficult this all turned out to be. The GHC bugs are now fixed, so it might be stable enough for another adventure like that, but I don't think I would bet on it again. IMO Haskell is great for writing small clean prototypes, doing interesting research, and maybe making some fun little games, but I wouldn't use it for production reactive
Re: [Haskell-cafe] Re: currying combinators
I wrote: keep :: ((t - b) - u - b) - ((t1 - t) - b) - (t1 - u) - b so then nameZip = keep (drop' . drop') names Günther Schmidt wrote: don't be tease man, show me what you got :) Ivan Miljenovic wrote: Methinks Yitzchak made a typo Yes, sorry about that. Tested in ghci this time :). keep :: (forall c . (t - c) - u - c) - ((t1 - t) - b) - (t1 - u) - b keep transform rec = \fn - rec $ transform id . fn Regards, Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Unicode vs. System.Directory
After upgrading to haskell-platform-2010.1.0.0, with the improved unicode support for IO in ghc-6.12, I hoped to be able to deal with filenames containing non-ascii characters. This still seems problematic, though: $ ls m×n♯α $ ghci GHCi, version 6.12.1: http://www.haskell.org/ghc/ :? for help Prelude :m +System.Directory Prelude System.Directory getDirectoryContents . = mapM_ putStrLn .. mÃnâ¯Î± . I hope this passes through the various email systems unharmed; on my terminal, the output of 'ls' contains shiny unicode characters, while 'ghci' garbles up the filename. (My locale is en_GB.utf8.) Similar problems arise with functions such as 'copyFile', which refuses to handle filenames with non-ascii characters (unless wrapping it with encoding functions). Is this a known problem? I searched ghc's trac, but there are no relevant bugs for the component 'libraries/directory'. I have parts of a unicode-aware layer on top of System.Directory laying around somewhere. I was rather hoping to ditch it, but I can polish it and put it on hackage, if people are interested. Kind regards, Arie ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: currying combinators
I wrote: keep :: (forall c . (t - c) - u - c) - ((t1 - t) - b) - (t1 - u) - b keep transform rec = \fn - rec $ transform id . fn Just to clarify - you don't really need the RankNTypes here, I just wrote it that way so you could see what I had been thinking, and to make it clear how the first parameter of keep takes transformers like drop'. But you could write it as keep :: ((t - t) - u - t) - ... and it would work just fine, because transformers like drop' would specialize nicely to what you need for keep. If you let GHC deduce the type of keep from its definition, GHC comes up with something else: keep :: ((a - a) - u - t) - ((t1 - t) - b) - (t1 - u) - b That also works, but it's weird. It generalizes in a direction that we don't really need here, and thus obscures the meaning of what we're doing. Regards, Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unicode vs. System.Directory
On Wed, May 26, 2010 at 1:25 PM, Arie Peterson ar...@xs4all.nl wrote: Is this a known problem? I searched ghc's trac, but there are no relevant bugs for the component 'libraries/directory'. This bug might be relevant: http://hackage.haskell.org/trac/ghc/ticket/3307 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unicode vs. System.Directory
Arie Peterson wrote: After upgrading to haskell-platform-2010.1.0.0, with the improved unicode support for IO in ghc-6.12, I hoped to be able to deal with filenames containing non-ascii characters. This still seems problematic, though Yes, unfortunately. This is not simple to fix, for several reasons: o The impedance mismatch between various operating systems and file systems about how filenames are represented internally w.r.t. Unicode o Haskell 98, which specifies that a FilePath is a String, i.e., Unicode o Backwards compatibility with existing Haskell implementations, which abuse the String type and represent bytes in a file path as if they were Unicode characters Johan Tibell wrote: This bug might be relevant: http://hackage.haskell.org/trac/ghc/ticket/3307 #3307 System.IO and System.Directory functions not Unicode-aware under Unix Related bugs: #3308 getArgs should return Unicode on Windows #3309 getArgs should return Unicode on Unix #4006 System.Process doesn't encode its arguments. See the linked discussions in those bugs for a lot more details, and various ideas about how to proceed. I hope your pinging this issue will bring it closer to being resolved. It's important. Thanks, Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
Anyway, does the license imply that one can't compile GHC's core language and RTS into objective-c, then compile it with their so great software ? El 26/05/2010, a las 05:51, Ryan Trinkle escribió: Hi guys, I don't think this licensing issue will be a problem for us. It's not clear to me that our game violates this new term, and we certainly don't violate any of the principles Steve Jobs used to justify it. If Apple wants to reject our app, they already have a variety of excuses at their disposal, as they've demonstrated on many occasions. Frankly, it'd be their loss; Android is now the fastest-growing smartphone market, and we'll be more than happy to focus on it (and other friendlier markets) if Apple's not interested in having our product on their platform. Ryan Trinkle iPwn Studios On Wed, May 26, 2010 at 4:18 AM, Brandon S. Allbery KF8NH allb...@ece.cmu.edu wrote: On May 26, 2010, at 04:14 , David Virebayre wrote: On Wed, May 26, 2010 at 9:58 AM, Brandon S. Allbery KF8NH allb...@ece.cmu.edu wrote: You might want to reread that license agreement. Specifically: Ah, yes. Ouch, that's abusive. Can they tell the difference though ? I suspect GHC-generated code is fairly distinctive even as machine code. But they don't have to go to that extent; all they have to do is use Google to find this thread. :( -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
If you guys get a nice library layer going between the Java APIs and Android NDK Haskell, I would very much like it if you could post it up somewhere. I think the entire community could benefit. Cheers. ~Liam On 26 May 2010 19:51, Ryan Trinkle ryan.trin...@ipwnstudios.com wrote: Hi guys, I don't think this licensing issue will be a problem for us. It's not clear to me that our game violates this new term, and we certainly don't violate any of the principles Steve Jobs used to justify it. If Apple wants to reject our app, they already have a variety of excuses at their disposal, as they've demonstrated on many occasions. Frankly, it'd be their loss; Android is now the fastest-growing smartphone market, and we'll be more than happy to focus on it (and other friendlier markets) if Apple's not interested in having our product on their platform. Ryan Trinkle iPwn Studios On Wed, May 26, 2010 at 4:18 AM, Brandon S. Allbery KF8NH allb...@ece.cmu.edu wrote: On May 26, 2010, at 04:14 , David Virebayre wrote: On Wed, May 26, 2010 at 9:58 AM, Brandon S. Allbery KF8NH allb...@ece.cmu.edu wrote: You might want to reread that license agreement. Specifically: Ah, yes. Ouch, that's abusive. Can they tell the difference though ? I suspect GHC-generated code is fairly distinctive even as machine code. But they don't have to go to that extent; all they have to do is use Google to find this thread. :( -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [reactive] A pong and integrate
On Wed, May 26, 2010 at 6:19 AM, Sam Martin sam.mar...@geomerics.comwrote: There’s a lot of missed opportunities for more elegant and powerful architectures going by at the moment simple because it’s not realistic to attempt them in C/C++. I beg to differ on that point. See my presentation[1]/paper[2] I gave at boostcon a couple weeks ago. I have successfully used C++ as a functional language in multiple production software applications, including FRP designs. [1] http://www.filetolink.com/c109d02b [2] http://www.filetolink.com/ff94ea7e David -- David Sankel Sankel Software www.sankelsoftware.com 585 617 4748 (Office) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] currying combinators
There are no interesting (i.e. total) functions of that type. 2010/5/25 Yitzchak Gale g...@sefer.org: Günther Schmidt wrote: http://www.hpaste.org/fastcgi/hpaste.fcgi/view?id=25694 in which I attempt to develop a currying combinator library. I'm stuck at some point and would appreciate any help. How about this: keep :: ((t - b) - u - b) - ((t1 - t) - b) - (t1 - u) - b so then nameZip = keep (drop' . drop') names Regards, Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
On Wed, May 26, 2010 at 5:51 AM, Ryan Trinkle ryan.trin...@ipwnstudios.comwrote: Hi guys, I don't think this licensing issue will be a problem for us. It's not clear to me that our game violates this new term, and we certainly don't violate any of the principles Steve Jobs used to justify it. If Apple wants to reject our app, they already have a variety of excuses at their disposal, as they've demonstrated on many occasions. Frankly, it'd be their loss; Android is now the fastest-growing smartphone market, and we'll be more than happy to focus on it (and other friendlier markets) if Apple's not interested in having our product on their platform. Steve Jobs has been quite clear that apps written in other languages, even ones that are interpreted in, compiles down to or otherwise generate objective c source code, don't comply with the changes in section 3.3.1 of their license, so I'm not sure that you have much of a case. “We’ve been there before, and intermediate layers between the platform and the developer ultimately produces sub-standard apps and hinders the progress of the platform.” Read more: http://techcrunch.com/2010/04/10/steve-jobs-responds-to-iphone-sdk-complaints-intermediate-layers-produce-sub-standard-apps/#ixzz0p3gfoNZI Haskell definitely qualifies as an 'intermediate layer', just like MonoTouch, and just like the Flash-to-Objective-C compiler that provoked the original response from Apple. http://www.taoeffect.com/blog/2010/04/steve-jobs-response-a-brief-followup/ Heck, even libraries that may contain scripting and modeling utilities like Unity3d are in jeopardy, due to this cockamamie restriction, which threatens to send the art of level design and game programming for the iphone technologically clear back into the early 90s, though at least there they appear to be treading lightly, since Unity has been useful in providing the iphone with a lot of high end content. http://answers.unity3d.com/questions/7408/is-unity3d-banned-by-new-apple-sdk-licence But, there are other numerous discussions floating around in the blogosphere involving previously approved applications written in scheme (even compiled via objective c), c#, or other middleware languages having their applications removed from the app store. So, sadly, I think your chances of shipping your a title written in Haskell on the iPhone are shot to hell. -Edward Kmett ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [reactive] A pong and integrate
Well, this does not contradict Sam's point, which was that you may have written nicer, faster and more elegant code in way less time, had you used a true programming language ;-) El 26/05/2010, a las 12:28, David Sankel escribió: On Wed, May 26, 2010 at 6:19 AM, Sam Martin sam.mar...@geomerics.com wrote: There’s a lot of missed opportunities for more elegant and powerful architectures going by at the moment simple because it’s not realistic to attempt them in C/C++. I beg to differ on that point. See my presentation[1]/paper[2] I gave at boostcon a couple weeks ago. I have successfully used C++ as a functional language in multiple production software applications, including FRP designs. [1] http://www.filetolink.com/c109d02b [2] http://www.filetolink.com/ff94ea7e David -- David Sankel Sankel Software www.sankelsoftware.com 585 617 4748 (Office) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
On May 26, 2010, at 10:17 , Pierre-Etienne Meunier wrote: Anyway, does the license imply that one can't compile GHC's core language and RTS into objective-c, then compile it with their so great software ? As I read it, yes; it says that the calls to their APIs must *originate* from permitted languages, and specifically prohibits using those languages via translation layers. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] currying combinators
keep :: ((t - b) - u - b) - ((t1 - t) - b) - (t1 - u) - b On Wed, May 26, 2010 at 12:49 PM, Lennart Augustsson lenn...@augustsson.net wrote: There are no interesting (i.e. total) functions of that type. I wonder how one would prove that to be the case. I tried and didn't come up with anything. David -- David Sankel Sankel Software www.sankelsoftware.com 585 617 4748 (Office) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
So, sadly, I think your chances of shipping your a title written in Haskell on the iPhone are shot to hell. +1 for the android version. Disclaimer: biased google employee :P Unfortunately then you get another cockamamie restriction in the whole JVM vs. tail calls thing... but if you can get around that then lots of people will like you a lot. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
Well in this case I'd be really interested in seeing how the can tell the difference, be it only from a simple complexity theoretic point of view ! I understand they may look for common patterns in their compiler code to tell the difference between GHC's generated code and theirs, but pretending they can do it in this case only shows that Apple lawyers never communicate with the engineers. El 26/05/2010, a las 15:32, Brandon S. Allbery KF8NH escribió: On May 26, 2010, at 10:17 , Pierre-Etienne Meunier wrote: Anyway, does the license imply that one can't compile GHC's core language and RTS into objective-c, then compile it with their so great software ? As I read it, yes; it says that the calls to their APIs must *originate* from permitted languages, and specifically prohibits using those languages via translation layers. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
wouldn't they just want to have TCO happen during the compilation into java? why would you want to output java that has recursion? -Dan On Wed, May 26, 2010 at 4:17 PM, Evan Laforge qdun...@gmail.com wrote: So, sadly, I think your chances of shipping your a title written in Haskell on the iPhone are shot to hell. +1 for the android version. Disclaimer: biased google employee :P Unfortunately then you get another cockamamie restriction in the whole JVM vs. tail calls thing... but if you can get around that then lots of people will like you a lot. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
On May 26, 2010, at 17:22 , Pierre-Etienne Meunier wrote: Well in this case I'd be really interested in seeing how the can tell the difference, be it only from a simple complexity theoretic point of view ! I understand they may look for common patterns in their compiler code to tell the difference between GHC's generated code and theirs, but pretending they can do it in this case only shows that Apple lawyers never communicate with the engineers. No clue how they might be planning to enforce it, but it's not like the lawyers care; it's up to Apple to decide if they want to pursue any individual possible case of infringement, and Jobs to figure out what kind of hole he's dug himself into. :) -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Math questions
Mujtaba Boori wrote: Define a higher order function that tests whether two functions , both defined on integers , coincide for all integers between 1 and 100 If this really is a homework question, I dare you to submit this solution. Try it for yourself, it works fine. :-) module Main where import Control.Monad import Data.IORef import System.IO.Unsafe forLoop :: Int - Int - (Int - IO ()) - IO () forLoop start stop body = mapM_ body [start..stop] test :: (Eq a) = (Int - a) - (Int - a) - Bool test f1 f2 = unsafePerformIO $ do goodSoFar - newIORef True forLoop 1 100 $ \i - when (f1 i /= f2 i) $ writeIORef goodSoFar False readIORef goodSoFar testFunc1 27 = numpty testFunc1 i = show i testFunc2 270 = numpty testFunc2 i = show i main = do print $ test show testFunc1 print $ test show testFunc2 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
On Wed, May 26, 2010 at 01:17:00PM -0700, Evan Laforge wrote: Unfortunately then you get another cockamamie restriction in the whole JVM vs. tail calls thing... but if you can get around that then lots of people will like you a lot. Working on it... :) John -- John Meacham - ⑆repetae.net⑆john⑈ - http://notanumber.net/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Proposal to solve Haskell's MPTC dilemma
Hi Carlos,
Apologies for the lateness of my reply.
On 23 May 2010 02:24, Carlos Camarao carlos.cama...@gmail.com wrote:
I think that a notion of orphan instances based on whether an
instance is defined or not in the module where the class of the
instance is defined is not very nice
I broadly agree, but pragmatically the notion of orphans is useful for
designing robust libraries, even if the notion is a bit horrible.
A benefit of adopting our approach would be that defaulting would
become unnecessary (defaulting always occurring in favor of visible
definitions).
This is something I don't understand (and is not elaborated in your
paper that I can see). Defaulting seems like an orthogonal mechanism.
It turns a constraint that really does have multiple solutions (e.g.
(Num a) = ...) into one where a particular preferred choice is taken
(e.g. Num Int), in situations where abstracting over the choice is
disallowed.
However, you mechanism only turns constraints into instances when
there is no ambiguity.
Can you perhaps explain what you mean a bit further?
I looked at your definition for orphan-hood, which I think might be OK
if you don't have FlexibleInstances. However, if you do then consider
this series of modules:
{-# LANGUAGE MultiParamTypeClasses #-}
module Common where
class C a b where
foo :: a - b - String
{-# LANGUAGE MultiParamTypeClasses, FlexibleInstances #-}
{-# OPTIONS_GHC -fwarn-orphans #-}
module Mod2 where
import Common
data E = E
instance C a E where
foo _ _ = Mod2
{-# LANGUAGE MultiParamTypeClasses, FlexibleInstances #-}
{-# OPTIONS_GHC -fwarn-orphans #-}
module Mod1 where
import Common
data D = D
instance C D b where
foo _ _ = Mod1
{-# OPTIONS_GHC -fwarn-orphans #-}
import Common
import Mod1
import Mod2
main = putStrLn (foo D E)
None of the instances are reported as orphans but IMHO they should be,
because we get a conflict in the Main module. I guess that a MPTC
instance (C t1 .. tn) for class C in module M1 is NOT an orphan if:
1) C is defined in the same module as the instance
2) OR ALL the t1..tn are instantiated to some concrete type (i.e. not
a type variable) defined in the same module as the instance
Imagine that we had an instance defined in a different module than the
class and violating 2). Then:
\exists i. t_i is a type variable or a datatype defined in another module
Case 1: If t_i is a type variable, we can have a parallel module M2:
data F = F
instance C a_1 ... a_{i-1} F a_{i+1} ... a_n where
Adding the instance to M2 may break client code because it is
potentially ambiguous with the one from M1. Furthermore, the instance
is considered non-orphan by GHC because it has at least one type which
is defined in the same module. However, at least one of this instance
and the one in M1 should have been flagged as orphans :(
Case 2: if t_i is a datatype G defined in another module, we can
similarly consider adding a new instance to that module:
instance C a_1 ... a_{i-1} G a_{i+1} ... a_n where
Same argument as for case 1.
Does this seem right?
==
Basically, you want an orphanhood criteria P you can test locally on a
per-module basis such that:
* For any composition of modules where P holds on every module individually...
* Changing any module by *adding* instances such that P still holds..
* Is guaranteed not to break any other module due to ambiguity
It is not clear to me exactly what this should look like, especially
in the presence of more complicated instance definitions (like the
instance C [Bool] style of thing allowed by FlexibleInstances. It
would probably be interesting to find out though.
Cheers,
Max
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[Haskell-cafe] yet another functional reactive programming tutorial :)
Dear list, As I'm learning frp and reading the wonderful tutorial at http://www.formicite.com/dopage.php?frp/frp.html , I'm putting up some more basic cheatsheet style tutorial for myself. http://github.com/nfjinjing/frp-guide Feel free to take advantage of it. -- jinjing ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
On Wed, May 26, 2010 at 5:22 PM, Pierre-Etienne Meunier pierreetienne.meun...@gmail.com wrote: Well in this case I'd be really interested in seeing how the can tell the difference, be it only from a simple complexity theoretic point of view ! I understand they may look for common patterns in their compiler code to tell the difference between GHC's generated code and theirs, but pretending they can do it in this case only shows that Apple lawyers never communicate with the engineers. I think it is more a matter of Jobs trying to find any way he could to quickly block Adobe's attempted end-run around his blockade against Flash apps. While we can all acknowledge the technical impossibility of identifying the original source language of a piece of code, all they need is to raise the spectre of doubt, and they have practically gutted all concern of a cross platform development environment emerging, because no sound business plan can be built on I hope my major and only possible distributor doesn't figure out what I'm doing! -Edward Kmett ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Math questions
On Wednesday 26 May 2010 5:38:57 pm Pete Chown wrote: test :: (Eq a) = (Int - a) - (Int - a) - Bool test f1 f2 = unsafePerformIO $ do goodSoFar - newIORef True forLoop 1 100 $ \i - when (f1 i /= f2 i) $ writeIORef goodSoFar False readIORef goodSoFar The problem with this algorithm is that it needlessly tests f1 against f2 for all i, even when a non-matching value has has already been found. Using the power of call-with-current-continuation, I have constructed an algorithm that lacks this deficiency: import Control.Monad.Cont test f g = flip runCont id . callCC $ \escape - do forM_ [1..100] $ \n - when (f n /= g n) $ escape False return True This should perform almost 75% less work in the testFunc1 case! It certainly feels much snappier. -- Dan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Problem when installing gtk2hs.
Hi, I have met similar problem before, and I do not know what to do. # cabal install --reinstall gtk2hs-buildtools Resolving dependencies... Configuring gtk2hs-buildtools-0.9... cabal: alex is required but it could not be found. cabal: Error: some packages failed to install: gtk2hs-buildtools-0.9 failed during the configure step. The exception was: ExitFailure 1 # alex -v Alex version 2.3.3, (c) 2003 Chris Dornan and Simon Marlow -- 竹密岂妨流水过 山高哪阻野云飞 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Proposal to solve Haskell's MPTC dilemma
On 05/26/10 15:42, Carlos Camarao wrote:
What do you think?
I think you are proposing using the current set of instances in scope in
order to remove ambiguity. Am I right? ..I read the haskell-cafe
thread so far, and it looks like I'm right. This is what I'll add to
what's been said so far:
Your proposal appears to allow /incoherent/ instance selection. This
means that an expression can be well-typed in one module, and well-typed
in another module, but have different semantics in the two modules. For
example (drawing from above discussion) :
module C where
class F a b where f :: a - b
class O a where o :: a
module P where
import C
instance F Bool Bool where f = not
instance O Bool where o = True
k :: Bool
k = f o
module Q where
import C
instance F Int Bool where f = even
instance O Int where o = 0
k :: Bool
k = f o
module Main where
import P
import Q
-- (here, all four instances are in scope)
main = do { print P.k ; print Q.k }
-- should result, according to your proposal, in
-- False
-- True
-- , am I correct?
Also, in your paper, example 2 includes
m = (m1 * m2) * m3
and you state
In Example 2, there is no means of specializing type variable c0 occurring in
the
type of m to Matrix.
I suggest that there is an appropriate such means, namely, to write
m = (m1 * m2 :: Matrix) * m3
. (Could the paper address how that solution falls short? Are there
other cases in which there is more than just a little syntactical
convenience at stake?, or is even that much added code too much for some
use-case?)
-Isaac
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Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
On 27/05/2010, at 9:01 AM, Edward Kmett wrote: While we can all acknowledge the technical impossibility of identifying the original source language of a piece of code... Uh, desire:tmp benl$ cat Hello.hs main = putStr Hello desire:tmp benl$ ghc --make Hello.hs desire:tmp benl$ strings Hello | head Hello base:GHC.Arr.STArray base:GHC.Arr.STArray base:GHC.Classes.D:Eq base:GHC.Classes.D:Eq failed to read siginfo_t failed: Warning: select buildFdSets: file descriptor out of range ... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
Next up, binary obfuscation! Apple already uses these extensively in their Fairplay code. Surely it isn't against the rules (yet?) to apply them to your program before submitting it to the store? :P On Wed, May 26, 2010 at 11:01 PM, Ben Lippmeier b...@ouroborus.net wrote: On 27/05/2010, at 9:01 AM, Edward Kmett wrote: While we can all acknowledge the technical impossibility of identifying the original source language of a piece of code... Uh, desire:tmp benl$ cat Hello.hs main = putStr Hello desire:tmp benl$ ghc --make Hello.hs desire:tmp benl$ strings Hello | head Hello base:GHC.Arr.STArray base:GHC.Arr.STArray base:GHC.Classes.D:Eq base:GHC.Classes.D:Eq failed to read siginfo_t failed: Warning: select buildFdSets: file descriptor out of range ... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
Objects in the heap also have a very regular structure. They all have code pointers as their first word, which point to info tables that also have a regular structure [1]. GHC produced code is probably one of the easiest to identify out of all compiled languages... http://hackage.haskell.org/trac/ghc/wiki/Commentary/Rts/Storage/HeapObjects Ben. On 27/05/2010, at 1:15 PM, Daniel Peebles wrote: Next up, binary obfuscation! Apple already uses these extensively in their Fairplay code. Surely it isn't against the rules (yet?) to apply them to your program before submitting it to the store? :P On Wed, May 26, 2010 at 11:01 PM, Ben Lippmeier b...@ouroborus.net wrote: On 27/05/2010, at 9:01 AM, Edward Kmett wrote: While we can all acknowledge the technical impossibility of identifying the original source language of a piece of code... Uh, desire:tmp benl$ cat Hello.hs main = putStr Hello desire:tmp benl$ ghc --make Hello.hs desire:tmp benl$ strings Hello | head Hello base:GHC.Arr.STArray base:GHC.Arr.STArray base:GHC.Classes.D:Eq base:GHC.Classes.D:Eq failed to read siginfo_t failed: Warning: select buildFdSets: file descriptor out of range ... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
On Wed, May 26, 2010 at 11:01 PM, Ben Lippmeier b...@ouroborus.net wrote: While we can all acknowledge the technical impossibility of identifying the original source language of a piece of code... Uh, ∀p (PieceOfCode(p) - CanIdentifySourceLanguage(p)) is clearly false, while ∃p (PieceOfCode(p) - CanIdentifySourceLanguage(p)) is clearly true. Natural language does a rather poor job of making quantification unambiguous. - C. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
On May 26, 2010, at 23:23 , C. McCann wrote: On Wed, May 26, 2010 at 11:01 PM, Ben Lippmeier b...@ouroborus.net wrote: While we can all acknowledge the technical impossibility of identifying the original source language of a piece of code... Uh, ∀p (PieceOfCode(p) - CanIdentifySourceLanguage(p)) is clearly false, while ∃p (PieceOfCode(p) - CanIdentifySourceLanguage(p)) is clearly true. Natural language does a rather poor job of making quantification unambiguous. If you really want to get jiggy with the corner cases, ask what counts as a transformation. /bin/cat? sed 's/a/b/g'? sed 'y/abcdefghijklmnopqrstuvwxyz/zyxwvutsrqponmlkjihgfedcba/'? unlit? cpp? -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell] Re: [Haskell-cafe] Work on Video Games in Haskell
On May 27, 2010, at 00:20 , Brandon S. Allbery KF8NH wrote: On May 26, 2010, at 23:23 , C. McCann wrote: On Wed, May 26, 2010 at 11:01 PM, Ben Lippmeier b...@ouroborus.net wrote: While we can all acknowledge the technical impossibility of identifying the original source language of a piece of code... Uh, ∀p (PieceOfCode(p) - CanIdentifySourceLanguage(p)) is clearly false, while ∃p (PieceOfCode(p) - CanIdentifySourceLanguage(p)) is clearly true. Natural language does a rather poor job of making quantification unambiguous. If you really want to get jiggy with the corner cases, ask what counts as a transformation. And the best, if obsolescent, example of all: cfront. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
