[Haskell-cafe] Munich Haskell Meeting
Dear all, we will meet again for our monthly Haskell Meeting in Munich on the 26th of April, at 19h30 at Cafe Puck. If you plan to join, please go to the site an click the button in order to reserve enough tables: http://www.haskell-munich.de/dates Also, consider joining us for our local Hackathon which will be held on Saturday, the 12th of May. See the details on the site. Until then, I wish all of you a good time, Heinrich -- -- hoerde...@funktional.info www.funktional.info -- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Data-Type Serialization
I think both ATerms and the Zephyr project's ASDL could handle recursive types - certainly ASDL was a sum and product representation like ML or Haskell's algebraic types (ATerms were a bit more like Prolog). Both never gained much traction and for better or worse JSON won the game. I implemented generators for both a very long time ago when I was staring out with Haskell. I didn't use TH or a generics library. If I were doing it again now I'd start with a generics library and see how that pans out - basically you want a type representation and generics libraries have that already. Also I'm no fan of TH. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: signed-multiset-0.1
I don't think max would be a good choice, as that would mean that the default
multiplicity would have to be negative infinity (the identity element of max)
instead of 0, and then using Int as the type for multiplicity would not cut it.
greetings,
Sjoerd
On Apr 20, 2012, at 11:02 AM, Stefan Holdermans wrote:
Wren,
For a specific example, I haven't the faintest intuition about
what 'map' should do. Suppose we have
{(k1)x1, (k2)x2}
and f x1 == f x2 = y. Should the value of map f {...} be
{(k1+k2)y} or {(k1`max`k2)y} or what?
Good question. I'd suppose that they should be parametrized by any
(Abelian?) group on the weights/multiplicities, where (+) is the canonical
one since we're talking about negative membership.
Any groupoid on the multiplicities would do, I guess.
As I wrote in my answer to Richard, max seems a better choise, as it nicely
generalises mapping on sets.
Cheers,
Stefan
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--
Sjoerd Visscher
sjo...@w3future.com
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Re: [Haskell-cafe] ANN: signed-multiset-0.1
Sjoerd,
For a specific example, I haven't the faintest intuition about
what 'map' should do. Suppose we have
{(k1)x1, (k2)x2}
and f x1 == f x2 = y. Should the value of map f {...} be
{(k1+k2)y} or {(k1`max`k2)y} or what?
I don't think max would be a good choice, as that would mean that the default
multiplicity would have to be negative infinity (the identity element of max)
instead of 0, and then using Int as the type for multiplicity would not cut
it.
Why would one need such an identity element for map?
Note that the monoidal structure isn't defined over the maximum of
multiplicites but over the maximum of *nonzero* multiplicites. (For ordinary
sets and ordinary multisets these operations happen to coincide.)
Cheers,
Stefan
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Re: [Haskell-cafe] ANN: signed-multiset-0.1
This is not just about map, but it also a problem for the Monoid instance. You
are basically adding an extra identity element, 0, to the max monoid, which
works but is weird. You'll have to call norm everywhere to make it work, f.e.
you would expect this to work:
empty' = insert () $ delete () empty
but:
empty' delete () empty == empty'
while:
empty delete () empty == delete () empty
(I couldn't test it as I don't have base 4.5, so I hope I didn't make a mistake
here.)
greetings,
Sjoerd
On Apr 23, 2012, at 2:07 PM, Stefan Holdermans wrote:
Sjoerd,
For a specific example, I haven't the faintest intuition about
what 'map' should do. Suppose we have
{(k1)x1, (k2)x2}
and f x1 == f x2 = y. Should the value of map f {...} be
{(k1+k2)y} or {(k1`max`k2)y} or what?
I don't think max would be a good choice, as that would mean that the
default multiplicity would have to be negative infinity (the identity
element of max) instead of 0, and then using Int as the type for
multiplicity would not cut it.
Why would one need such an identity element for map?
Note that the monoidal structure isn't defined over the maximum of
multiplicites but over the maximum of *nonzero* multiplicites. (For
ordinary sets and ordinary multisets these operations happen to coincide.)
Cheers,
Stefan
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[Haskell-cafe] Is protocol-buffers package maintainer reachable?
Hello Cafe! I am using protocol-buffers and hprotoc packages but they fail to compile with recent GHC due to trivial errors. Hackage names Christopher Edward Kuklewicz as their maintainer. I've sent him patches more than a month ago but neiter they were applied nor I got any response. It's quite inconvenient to keep patched versions all the time. Does anybody know if he is still interested in maintaining those packages? Is it possible to contact him? And what should I do if he is unreachable? Thanks! Links: http://hackage.haskell.org/package/protocol-buffers http://hackage.haskell.org/package/hprotoc ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: signed-multiset-0.1
Sjoerd, This is not just about map, but it also a problem for the Monoid instance. You are basically adding an extra identity element, 0, to the max monoid, which works but is weird. Still that's how union is typically defined for hybrid sets. It's what happens if want union and empty to behave as generalisations of these concepts for ordinary (multi)sets. empty' = insert () $ delete () empty but: empty' delete () empty == empty' while: empty delete () empty == delete () empty (I couldn't test it as I don't have base 4.5, so I hope I didn't make a mistake here.) *Data.SignedMultiset let empty' = insert () $ delete () empty *Data.SignedMultiset empty' `union` delete () empty == empty' False *Data.SignedMultiset empty `union` delete () empty == delete () empty True Cheers, Stefan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: signed-multiset-0.1
On Apr 23, 2012, at 3:18 PM, Stefan Holdermans wrote: Sjoerd, This is not just about map, but it also a problem for the Monoid instance. You are basically adding an extra identity element, 0, to the max monoid, which works but is weird. Still that's how union is typically defined for hybrid sets. It's what happens if want union and empty to behave as generalisations of these concepts for ordinary (multi)sets. Then why would you want that? *Data.SignedMultiset let empty' = insert () $ delete () empty *Data.SignedMultiset empty' `union` delete () empty == empty' False *Data.SignedMultiset empty `union` delete () empty == delete () empty True Ah, I missed the check in insertMany. What about the same with let empty' = multiply 0 $ delete () empty greetings, Sjoerd ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANNOUNCE: hsx-0.10.1, hjscript-0.6.0, hsp-0.7.0
Hi all, I'm pleased to announce the release of the latest versions of the libraries in the Haskell Server Pages suite. Haskell Server Pages enables literal XML syntax to be used mixed with Haskell code (like e.g. PHP), in a sane way (unlike said PHP). In principle the functionality could be used together with any Haskell web framework, but is (currently) best integrated in and supported by Happstack. For this release I owe much to Jeremy Shaw, both for inspiration and for actual patches. There are some grand plans in the pipeline for some more extensive changes to the suite, to shape it up to be worthy of the current exciting state-of-the-art of Haskell web development. Stay tuned! Cheers, /Niklas Specific changes in this release: * In the XMLGen class, the following associated types have been renamed to avoid frequent name clashes, and to better match the intention of those types: XML = XMLType, Child = ChildType, Attribute = AttributeType. * Literal CDATA strings are now given an explicit type signature in the post-processed code. This to avoid ambiguities when OverloadedStrings is enabled. * class XMLGenerator m now has EmbedAsChild m () as another premise. * HSX.Transform now exports a method transformExp :: Exp - Exp, intended to be used with quasi-quotation. * trhsx no longer performs fixity resolution before transforming, allowing the tool to be used on files using operators with (locally) unknown fixity. * hsp and hjscript updated to work with hsx-0.10. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: signed-multiset-0.1
Sjoerd, This is not just about map, but it also a problem for the Monoid instance. You are basically adding an extra identity element, 0, to the max monoid, which works but is weird. Still that's how union is typically defined for hybrid sets. It's what happens if want union and empty to behave as generalisations of these concepts for ordinary (multi)sets. Then why would you want that? You don't have to. (SignedMultiset a, additiveUnion, empty) gives you the Monoid that you seem to have a preference for. The library supplies it through the Additive wrapper. The point is that you have a choice: different applications may ask for different monoidal structures. *Data.SignedMultiset let empty' = insert () $ delete () empty *Data.SignedMultiset empty' `union` delete () empty == empty' False *Data.SignedMultiset empty `union` delete () empty == delete () empty True Ah, I missed the check in insertMany. What about the same with let empty' = multiply 0 $ delete () empty *Data.SignedMultiset let empty' = multiply 0 $ delete () empty *Data.SignedMultiset empty' `union` delete () empty == empty' True *Data.SignedMultiset empty `union` delete () empty == delete () empty True Cheers, Stefan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] No email verification token from trac.haskell.org
Hi all, I have problems with my trac for haskell-src-exts. When I log in, I am asked to verify my email address, but no verification token is ever sent to my email address. And before I verify my address, I'm not allowed to do anything on the trac. Help? :-) /Niklas ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is protocol-buffers package maintainer reachable?
On 23.04.2012 17:01, Paul Graphov wrote: Hello Cafe! I am using protocol-buffers and hprotoc packages but they fail to compile with recent GHC due to trivial errors. Hackage names Christopher Edward Kuklewicz as their maintainer. I've sent him patches more than a month ago but neiter they were applied nor I got any response. It's quite inconvenient to keep patched versions all the time. Does anybody know if he is still interested in maintaining those packages? Is it possible to contact him? And what should I do if he is unreachable? I've too tried to contact him almost year ago about same issue. Never got an answer. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: signed-multiset-0.1
On Apr 23, 2012, at 4:34 PM, Stefan Holdermans wrote: Sjoerd, This is not just about map, but it also a problem for the Monoid instance. You are basically adding an extra identity element, 0, to the max monoid, which works but is weird. Still that's how union is typically defined for hybrid sets. It's what happens if want union and empty to behave as generalisations of these concepts for ordinary (multi)sets. Then why would you want that? You don't have to. (SignedMultiset a, additiveUnion, empty) gives you the Monoid that you seem to have a preference for. The library supplies it through the Additive wrapper. The point is that you have a choice: different applications may ask for different monoidal structures. Agreed. But I just can't imagine that the other instance is in any way useful. You basically define a function max': max' :: Int - Int - Int max' 0 b = b max' a 0 = a max' a b = max a b i.e. max' -2 -1 = -1 max' -2 0 = -2 max' -2 1 = 1 Wouldn't you agree that if you saw this defined in some code, you'd think something is wrong? *Data.SignedMultiset let empty' = multiply 0 $ delete () empty *Data.SignedMultiset empty' `union` delete () empty == empty' True *Data.SignedMultiset empty `union` delete () empty == delete () empty True And this doesn't bother you? greetings, Sjoerd ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is protocol-buffers package maintainer reachable?
On Mon, Apr 23, 2012 at 15:01, Paul Graphov grap...@gmail.com wrote: And what should I do if he is unreachable? My feeling is that if you are willing to take it on, you should ask this list if anybody objects to your taking over the maintainership, and if they do not, take it over (on Hackage, this just means uploading a new version of the package). --Max ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is protocol-buffers package maintainer reachable?
On Mon, Apr 23, 2012 at 7:53 AM, Max Rabkin max.rab...@gmail.com wrote: On Mon, Apr 23, 2012 at 15:01, Paul Graphov grap...@gmail.com wrote: And what should I do if he is unreachable? My feeling is that if you are willing to take it on, you should ask this list if anybody objects to your taking over the maintainership, and if they do not, take it over (on Hackage, this just means uploading a new version of the package). If Chris is indeed out of the loop we should find a new maintainer. Mark and I are also interested in the future of protocol buffers in Haskell. -- Johan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] No email verification token from trac.haskell.org
On Mon, Apr 23, 2012 at 7:42 AM, Niklas Broberg niklas.brob...@gmail.com wrote: Hi all, I have problems with my trac for haskell-src-exts. When I log in, I am asked to verify my email address, but no verification token is ever sent to my email address. And before I verify my address, I'm not allowed to do anything on the trac. Help? :-) /Niklas I've had the same problem for a long time. I assume the Trac instance is broken. -- Johan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is protocol-buffers package maintainer reachable?
For what it's worth, I think he is active on stackoverflow. Thu Le 23 avril 2012 17:13, Johan Tibell johan.tib...@gmail.com a écrit : On Mon, Apr 23, 2012 at 7:53 AM, Max Rabkin max.rab...@gmail.com wrote: On Mon, Apr 23, 2012 at 15:01, Paul Graphov grap...@gmail.com wrote: And what should I do if he is unreachable? My feeling is that if you are willing to take it on, you should ask this list if anybody objects to your taking over the maintainership, and if they do not, take it over (on Hackage, this just means uploading a new version of the package). If Chris is indeed out of the loop we should find a new maintainer. Mark and I are also interested in the future of protocol buffers in Haskell. -- Johan ___ 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] No email verification token from trac.haskell.org
On Mon, Apr 23, 2012 at 5:13 PM, Johan Tibell johan.tib...@gmail.comwrote: On Mon, Apr 23, 2012 at 7:42 AM, Niklas Broberg niklas.brob...@gmail.com wrote: I have problems with my trac for haskell-src-exts. When I log in, I am asked to verify my email address, but no verification token is ever sent to my email address. And before I verify my address, I'm not allowed to do anything on the trac. I've had the same problem for a long time. I assume the Trac instance is broken Certainly sounds plausible - but how to fix it? There are some possible fixes listed on the Trac homepage, but I don't seem to have enough permissions to do anything at all. /Niklas ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Correspondence between libraries and modules
On 04/23/2012 12:03 AM, wren ng thornton wrote: However, until better technical support is implemented (not just for GHC, but also jhc, UHC,...) it's best to follow social practice. Wren, I am new to Haskell and not aware of all of the conventions. Is there a place where I can find information on these social practices? Are they documented some place? However, centralization is prone to bottlenecks and systemic failure. As such, while it would be nice to ensure that a given module is provided by only one package, there is no mechanism in place to enforce this (except at compile time for the code that links the conflicting modules together). From someone new to the community, it seems that yes centralization has its issues, but it also seems that practices could be put in place that minimize the bottlenecks and systemic failures. Unless I greatly misunderstand the challenges, there seem to be lot of ways to approach this problem and none of them are new. We all use systems that are composed of many modules neatly combined into complete systems. Linux distributions do this well. So does Java. Maybe should borough from their experiences and think about how we put packages together and what mechanisms we need to resolve inter-package dependencies. Am I missing something that makes this problem harder than other systems and languages? Is anyone currently working on the packaging and distribution issues? If not, does anyone else want to work on it? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] desactivate my Show instance implementations temporarily
I use a custom Pretty class along with HughesPJ, ala ghc's Outputable. It means I can omit data or print it out in a more readable form (even just rounding floats to %.03f can help a lot), and also get nice layout and wrapping. The downside is a certain amount of boilerplate to write output routines for records. Actually, types with multiple constructors are the most annoying. At some point I should investigate the new generic deriving feature to see if some of that can be automated. As a user of libraries, I get annoyed when they implement Show to something nonstandard. It makes it harder to figure out how the library works. On Sun, Apr 22, 2012 at 4:20 AM, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com wrote: On 22 April 2012 19:55, TP paratribulati...@free.fr wrote: On Sunday 22 April 2012 19:37:19 Ivan Lazar Miljenovic wrote: Is there any particular reason you're *not* using the defaults? This is a good question which I have asked myself. I have searched about the topic, and found that: http://blog.romanandreg.com/post/13545420287/haskells-show-and-pretty- printing-bad-practice So, according to this address, Show implementation should be used with Read so as to have show.read equal to identity: this is the only good practice requirement. In my case, I use Show to print mathematical expressions, but it is not strictly pretty printing (not over several lines as in classical Computer Algebra Sytems). Why not using my own Show implementation to do that? For exactly the same reason you're discovering: Show/Read exist for debugging. Show and Read are meant to produce/read valid Haskell code (modulo [qualified] imports) so that you can work out what code is going wrong (and coincidentally used as a quick`n`dirty serialisation method). The term pretty-printing is meant in regards to producing _human-readable_ versions of your data (though the pretty-printing libraries can also be used to produce code formatted for some other tool to parse, etc.). Show/Read happen to be auto-derivable classes that implement one such form of pretty-printing (i.e. printing values that look like the actual source code that represents them). Let me provide you with a personal anecdote: when I took over maintaining the graphviz library, it was still using the Show class for printing (but a proper parser library for parsing), and it was working with the limited functionality it had. However, whenever I tried to do something new, I found problems: * Existing Show instances meant that it was very difficult to extend what the library could represent and then print properly. * As you've found, it can then be a PITA to debug because you have no idea what the internal values actually are. In the end, I eventually wrote a custom pretty-printing class (the existing pretty-printing classes had instances that didn't suit, just like Show) and it's worked a lot better since. The only time it's valid to override the default Show/Read instances is when the constructors aren't exported (e.g. Data.Map), but even then it should be valid Haskell (if you ignore imports, etc.). So leave Show/Read as they are, and write a custom function[s] that does the actual pretty-printing you want. -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com ___ 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] ANN: signed-multiset-0.1
Sjoerd, Then why would you want that? You don't have to. (SignedMultiset a, additiveUnion, empty) gives you the Monoid that you seem to have a preference for. The library supplies it through the Additive wrapper. The point is that you have a choice: different applications may ask for different monoidal structures. Agreed. But I just can't imagine that the other instance is in any way useful. You basically define a function max': max' :: Int - Int - Int max' 0 b = b max' a 0 = a max' a b = max a b i.e. max' -2 -1 = -1 max' -2 0 = -2 max' -2 1 = 1 Wouldn't you agree that if you saw this defined in some code, you'd think something is wrong? If max' is supposed to implement the maximum of two nonzero values, I wouldn't be the slightest bit concerned. Seriously: if this is what people have agreed on to be a sensible semantics for hybrid sets, I am fine implementing it like this. *Data.SignedMultiset let empty' = multiply 0 $ delete () empty *Data.SignedMultiset empty' `union` delete () empty == empty' True *Data.SignedMultiset empty `union` delete () empty == delete () empty True And this doesn't bother you? Of course it does; it pinpoints a bug in multiply. It's fixed now: *Data.SignedMultiset let empty' = multiply 0 $ delete () empty *Data.SignedMultiset empty' `union` delete () empty == empty' False *Data.SignedMultiset empty `union` delete () empty == delete () empty True Cheers, Stefan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Need feedback on my EDSL attempt for writing test scripts
Dear cafe,
Recently, I decided to use Haskell to drive the testing of a C++ DLL that
we develop. After getting the FFI etc working, I thought it might be a good
idea to expose an EDSL for the testers to alter the flow of invocations of
the functions in the DLL. I've tried to demonstrate the approach I am
contemplating here - http://hpaste.org/67495
The outcome is that I'll have a set of Instructions for the testers can
arrange to create a sequence of calls.
data Command = Void | Init | Get3Numbers Int Int Int| GetName String |
PrintName | PrintSum | Close | PrintMessage String
deriving (Show)
mainloop :: StateT (ScriptState Command) IO ()
mainloop = do
liftIO $ putStrLn Hello World
executeCommand Init
executeCommand Init
executeCommand $ PrintMessage Enter name
executeCommand $ GetName abcd
return ()
I'd like to ensure that some level of validation done. For example, if Init
is called twice, the tester should get to know about it. Similarly, GeName
should not be called unless PrintMessage has been called.
executeCommand :: Command - StateT (ScriptState Command) IO ()
executeCommand Init = do
(ScriptState c) - get
case c of
Void - liftIO $ putStrLn (show c)
_- liftIO $ putStrLn Init already called
put (ScriptState Init)
return ()
executeCommand (GetName x) = do
(ScriptState c) - get
case c of
PrintMessage _ - do { str - liftIO $ getLine; put
(ScriptState (GetName str)); return ()}
_ - liftIO $ putStrLn PrintMessage not
called
executeCommand (PrintMessage m) = do
liftIO $ putStrLn m
put (ScriptState (PrintMessage m))
I'd appreciate it very much if you could give me some feedback on my
approach. I get this feeling that I am wrapping up the whole program inside
a State monad - does this mean that I am giving up the functional goodies.
Regards,
Kashyap
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[Haskell-cafe] Is it only one data structure per ST monad?
Is it only one data structure per ST monad? -- -- Regards, KC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is it only one data structure per ST monad?
I would argue that there is just one ST monad, which makes the question even more strange. On 23 Apr 2012, at 22:32, KC wrote: Is it only one data structure per ST monad? -- -- Regards, KC ___ 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] Correspondence between libraries and modules
Thanks for the write-up -- it's been very helpful! On Mon, Apr 23, 2012 at 12:03 AM, wren ng thornton w...@freegeek.orgwrote: Consider one of my own libraries (chosen randomly via Safari's url autocompletion): http://hackage.haskell.org/**package/bytestring-lexinghttp://hackage.haskell.org/package/bytestring-lexing When I inherited this package there were the Data.ByteString.Lex.Double and Data.ByteString.Lex.Lazy.**Double modules, which were separated because they provide the same API but for strict vs lazy ByteStrings. Both of those modules are concerned with lexing floating point numbers. I inherited the package because I wanted to publicize some code I had for lexing integers in various formats. Since that's quite a different task than lexing floating point numbers, I put it in its own module: Data.ByteString.Lex.Integral. I see. The first thing that comes to mind is the notion of module granularity, which of course is subjective, so whether a single module or multiple ones should handle e.g. doubles and integrals is a good question; are there guidelines as to how those choices are made? At any rate, why do these modules, with sufficiently-different functionality, live in the same library -- is it that they share some common bits of implementation, or to ease the management of source code? When dealing with FFI code, because of the impedance mismatch between Haskell and imperative languages like C, it's clear that there's going to be some massaging of the API beyond simply declaring FFI calls. As such, clearly we'd like to have separate modules for doing the low-level binding vs presenting a high-level API. Moreover, depending on what you're interfacing with, you may be forced to have multiple low-level modules. Ah, that's a good use case. Is the lower-level module usually made public as well, or is it only an implementation detail? On the other hand, the main purpose of packages or libraries is as unit of distribution, code reuse, and separate compilation. Even with the Haskell culture of making small libraries, most worthwhile units of distribution/reuse/compilation tend to be larger than a single namespace/concern. Thus, it makes sense to have more than one module per package, because otherwise we'd need some higher level mechanism in order to manage the collections of package-modules which should be considered a single unit (i.e., clients will almost always want the whole bunch of them). This is the part that I'm trying to get a better sense of. I can see how in some cases, it makes sense for more than one module to form a unit, because they are tightly coupled semantically or implementation-wise -- so clients will indeed want the whole bunch. On the other hand, several libraries provide modules that are all over the place, in a way that doesn't form a unit of any kind (e.g. MissingH), and it's not clear that you would want any Network stuff when all you need is String utilities. However, centralization is prone to bottlenecks and systemic failure. As such, while it would be nice to ensure that a given module is provided by only one package, there is no mechanism in place to enforce this (except at compile time for the code that links the conflicting modules together). With few exceptions, it's considered bad form to knowingly use the same module name as is being used by another package. In part, it's bad form because egos are involved; but it's also bad form because there's poor technical support for resolving namespace collisions for module names. In GHC you can use -XPackageImports, which is workable but conflates issues of code with issues of provenance, which the Haskell Report intentionally keeps separate. However, until better technical support is implemented (not just for GHC, but also jhc, UHC,...) it's best to follow social practice. But the way you describe it, it seems that despite centralization having those disadvantages, it is more or less the way the system works, socially (egos, bad form, etc.) and technically (because of the lack of compiler support) -- except that it is ad-hoc instead of mechanically enforced. In other words, I don't see what the advantages of allowing ambiguity currently are. Some people figured to solve the new issue by implementing it both ways in separate packages, but reusing the same module names. (Witness for example mtl-2 aka monads-fd, vs monads-tf.) In practice, that didn't work out so well. Part of the reason for failure is that although fundeps and TF/ATs are formally equivalent in theory, in practice the implementation of TF/ATs has(had?) been missing some necessary machinery, and consequentially the TF/AT versions were not as powerful as the original fundep versions. Though the butterfly dependency issues certainly didn't help. Ah, interesting. So, perhaps I misunderstand, but this seems like an argument in favor of having uniquely-named modules (e.g. Foo.FD and Foo.TF) instead of
[Haskell-cafe] Announce: Hackager - new version of hackage-test
Hi all, I've updated the old hackage-test tool and renamed to hackager. http://hackage.haskell.org/package/hackager Hackager is a tool to automate the compiling of all packages on Hackage. It builds each package on hackage in isolation and records the results. The purpose being to catch regressions caused by changes to GHC (and Cabal although this was not the motivation). Two runs of Hackager can be compared, so the first run is done with a known version of GHC and the next run with a new, experimental version of GHC... ect. The improvements to Hackager over hackage-test are: * Parallelized the build process. Can now specify how many packages to build in parallel, which cuts total run time down greatly (e.g 2 days - 5 hours) * hackage-test and hackage-report are now one tool, 'hackager' that works as a mutli-command tool. * Proper option handling * Fixed some stability issues The new homepage for development can be found here: https://github.com/dterei/Hackager Cheers, David ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Correspondence between libraries and modules
On Mon, Apr 23, 2012 at 11:39, Gregg Lebovitz glebov...@gmail.com wrote: Am I missing something that makes this problem harder than other systems and languages? Is anyone currently working on the packaging and distribution issues? If not, does anyone else want to work on it? The other dirty little secret that is carefully being avoided here is the battle between the folks for whom Haskell is a language research platform and those who use it to get work done. It's not entirely inaccurate to say the former group would regard a fragmented module namespace as a good thing, specifically because it discourages people from considering it to be stable -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is protocol-buffers package maintainer reachable?
I'm not sure about being a maintainer - I don't even know how those packages work and have no experience in preparing package for hackage. But fixes are really trivial - maybe I'll just upload patched versions if it is possible? Is it possible to contact StackOverflow user? On Mon, Apr 23, 2012 at 7:26 PM, Vo Minh Thu not...@gmail.com wrote: For what it's worth, I think he is active on stackoverflow. Thu Le 23 avril 2012 17:13, Johan Tibell johan.tib...@gmail.com a écrit : On Mon, Apr 23, 2012 at 7:53 AM, Max Rabkin max.rab...@gmail.com wrote: On Mon, Apr 23, 2012 at 15:01, Paul Graphov grap...@gmail.com wrote: And what should I do if he is unreachable? My feeling is that if you are willing to take it on, you should ask this list if anybody objects to your taking over the maintainership, and if they do not, take it over (on Hackage, this just means uploading a new version of the package). If Chris is indeed out of the loop we should find a new maintainer. Mark and I are also interested in the future of protocol buffers in Haskell. -- Johan ___ 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] [Haskell-beginners] Is it only one data structure per ST monad?
If you mean, per 'ST s a', no: you can generate as many STRefs as you want. Edward Excerpts from KC's message of Mon Apr 23 14:32:57 -0400 2012: Is it only one data structure per ST monad? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] (no subject)
buildPair = do arr - newArray ((1,1),(1,10)) 37 :: ST s (STArray s (Int,Int) Int) a - readArray arr (1,1) writeArray arr (1,1) 64 b - readArray arr (1,1) return (a,b) main = print $ runST buildPair -- -- Regards, KC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] The last statement in a 'do' construct must be an expression: a - readArray arr (1, 1)
I'm getting the above error message and I cannot figure out why? buildPair = do arr - newArray ((1,1),(1,10)) 37 :: ST s (STArray s (Int,Int) Int) a - readArray arr (1,1) writeArray arr (1,1) 64 b - readArray arr (1,1) return (a,b) main = print $ runST buildPair -- -- Regards, KC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] The last statement in a 'do' construct must be an expression: a - readArray arr (1, 1)
Perhaps you are mixing tabs and spaces? On Mon, Apr 23, 2012 at 4:52 PM, KC kc1...@gmail.com wrote: I'm getting the above error message and I cannot figure out why? buildPair = do arr - newArray ((1,1),(1,10)) 37 :: ST s (STArray s (Int,Int) Int) a - readArray arr (1,1) writeArray arr (1,1) 64 b - readArray arr (1,1) return (a,b) main = print $ runST buildPair -- -- Regards, KC ___ 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] HaL-7, 2012-07-13, Call for submissions
Call for submissions and Save the date for our local Haskell Workshop in Halle/Saale, Germany. Tutorials, talks, demonstrations ... everything welcome. Workshop language is German (mainly), and English (by request). Submission deadline: May, 21, Workshop date: July, 13 Workshop homepage: http://iba-cg.de/hal7.html The complete call in German: - Aufruf zum Einreichen von Beiträgen und Hinweis zum Vormerken des Termins Was: Haskell-Treffen HaL-7 Wann: Freitag, 13.07.2012 Wo: Institut für Informatik an der Martin-Luther-Universität in Halle an der Saale Wir suchen Vorträge zu Haskell im Besonderen und der funktionalen Programmierung im Allgemeinen, zum Beispiel zu den Themen * Neues von Sprache, Bibliotheken, Werkzeugen, * Anwendungen von Kunst bis Industrie, * Lehre an Schulen und Hochschulen, gerne aber auch zu anderen Themen. Die Beiträge können präsentiert werden als * Tutorium (60 .. 90 min) * Vortrag (30 min) * Demonstration, künstlerische Aufführung Die Veranstaltungssprache ist Deutsch, in begründeten Ausnahmen Englisch. Presentations will be given in German but we can switch to English if requested. Bitte reichen Sie Kurzfassungen der Beiträge ein (2 bis 4 Seiten), die dem Programmkomitee eine Einschätzung ermöglichen. Die Kurzfassung soll mit einer Zusammenfassung (10 Zeilen) beginnen und einem Literaturverzeichnis enden. Teilnehmer des Workshops sind Interessenten (keine Erfahrung mit Haskell/FP), Anfänger (wenig Erfahrung) und Experten. Wir bitten die Vortragenden, die Zielgruppe des Beitrags anzugeben und die nötigen Vorkenntnisse zu beschreiben. Bei Tutorien sollen Teilnehmer auf eigenen Rechnern arbeiten. Bitte beschreiben Sie dazu die vorher zu installierende Software. Schicken Sie Beitragsvorschläge als PDF-Dokument bis zum 21.05.2012 per Mail an hal-committee at iba-cg punkt de oder an ein Mitglied des Programmkomitees. Programmkomitee * Henning Thielemann - Univ. Halle (Vorsitzender), * Petra Hofstedt - BTU Cottbus, * Alf Richter - iba CG Leipzig, * Uwe Schmidt - FH Wedel, * Janis Voigtländer - Univ. Bonn, * Johannes Waldmann - HTWK Leipzig. Mit besten Grüßen Henning Thielemann ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] The last statement in a 'do' construct must be an expression: a - readArray arr (1, 1)
Thank you, that was it. I was mixing up and tabs and spaces. I expected new versions of NotePad++ to keep my old settings. On Mon, Apr 23, 2012 at 1:54 PM, Ryan Yates fryguy...@gmail.com wrote: Perhaps you are mixing tabs and spaces? On Mon, Apr 23, 2012 at 4:52 PM, KC kc1...@gmail.com wrote: I'm getting the above error message and I cannot figure out why? buildPair = do arr - newArray ((1,1),(1,10)) 37 :: ST s (STArray s (Int,Int) Int) a - readArray arr (1,1) writeArray arr (1,1) 64 b - readArray arr (1,1) return (a,b) main = print $ runST buildPair -- -- Regards, KC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- -- Regards, KC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Correspondence between libraries and modules
On 4/23/2012 3:39 PM, Brandon Allbery wrote: On Mon, Apr 23, 2012 at 11:39, Gregg Lebovitz glebov...@gmail.com wrote: Am I missing something that makes this problem harder than other systems and languages? Is anyone currently working on the packaging and distribution issues? If not, does anyone else want to work on it? The other dirty little secret that is carefully being avoided here is the battle between the folks for whom Haskell is a language research platform and those who use it to get work done. It's not entirely inaccurate to say the former group would regard a fragmented module namespace as a good thing, specifically because it discourages people from considering it to be stable Brandon, I find that a little hard to believe. If the issues are similar to other systems and languages, then I think it is more likely that no one has volunteered to work on it. You volunteering to help? -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Announce: Hackager - new version of hackage-test
Good work David. I used to do something like this for Cabal regression testing but the method I used didn't scale well as hackage grew. I'll look into using your tool next time for testing a major Cabal / cabal-install release. Duncan On 23 April 2012 21:37, David Terei dave.te...@gmail.com wrote: Hi all, I've updated the old hackage-test tool and renamed to hackager. http://hackage.haskell.org/package/hackager Hackager is a tool to automate the compiling of all packages on Hackage. It builds each package on hackage in isolation and records the results. The purpose being to catch regressions caused by changes to GHC (and Cabal although this was not the motivation). Two runs of Hackager can be compared, so the first run is done with a known version of GHC and the next run with a new, experimental version of GHC... ect. The improvements to Hackager over hackage-test are: * Parallelized the build process. Can now specify how many packages to build in parallel, which cuts total run time down greatly (e.g 2 days - 5 hours) * hackage-test and hackage-report are now one tool, 'hackager' that works as a mutli-command tool. * Proper option handling * Fixed some stability issues The new homepage for development can be found here: https://github.com/dterei/Hackager Cheers, David ___ 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] ANN: signed-multiset-0.1
On Apr 23, 2012, at 7:04 PM, Stefan Holdermans wrote: if this is what people have agreed on to be a sensible semantics for hybrid sets, I am fine implementing it like this. I have a hard time believing you have implemented the semantics that people have agreed on to be a sensible semantics for hybrid sets. I would expect that multiplicity k (m `union` n) == multiplicity k m `max` multiplicity k n. Which means that an element of m with negative multiplicity is not a member of m `union` n if it is not a member of n. So that would mean that union would have to be implemented something like this: SMS m `union` SMS n = SMS $ Map.intersectionWith max m n `Map.union` Map.filter (= 0) ((m Map.\\ n) `Map.union` (n Map.\\ m)) greetings, Sjoerd ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Correspondence between libraries and modules
On Mon, Apr 23, 2012 at 17:16, Gregg Lebovitz glebov...@gmail.com wrote: On 4/23/2012 3:39 PM, Brandon Allbery wrote: The other dirty little secret that is carefully being avoided here is the battle between the folks for whom Haskell is a language research platform and those who use it to get work done. It's not entirely inaccurate to say the former group would regard a fragmented module namespace as a good thing, specifically because it discourages people from considering it to be stable Brandon, I find that a little hard to believe. If the issues are similar to other systems and languages, then I think it is more likely that no one has volunteered to work on it. You volunteering to help? Yes, you do find it hard to believe; so hard that you went straight past it and tried to point to the easy technical solution to the problem you decided to see in place of the real one, which doesn't have a technical solution. -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
