Re: [Haskell-cafe] Template Haskell a Permanent solution?
On 27 December 2010 07:35, Jonathan Geddes geddes.jonat...@gmail.com wrote: #1 Parse a string at compile-time so that a custom syntax for representing data can be used. At the extreme, this data might even be an EDSL. Hello Jonathan By this are you meaning to add quasiquoting to the language Haskell or the Glasgow Haskell, taking it out of the domain of Template Haskell? How would the first example look like with Template Haskell and is current quasiquoting syntax? I'm suspecting the differences are pretty small. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] global, modifiable variable for debugging
We have some code to do exactly this: https://github.com/snapframework/snap-core/blob/master/src/Snap/Internal/Debug.hs You set a DEBUG environment variable to turn debugging output on. We should probably split this code out into its own package. G On Sun, Dec 26, 2010 at 8:53 PM, bri...@aracnet.com wrote: Hi, I have a program with a debug flag in it (Strangely I've yet to be able to write bug-free code). I'd like to change the state of the debug flag based on command line args. I looked at IOVar but that would cause all the pure procedures to get swallowed by the IO Monad. Is a better way to get this behavior ? Thanks, Brian ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Gregory Collins g...@gregorycollins.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Template Haskell a Permanent solution?
Hi,
But TH gives me the same feeling as other language features that have
been described as bolted on. Also, TH is both library and built-in
syntax (via an extension) which feels strange to me.
I don't understand why the library/extension duality is a problem. I would
say that the best approach is to have language support (through extensions)
for primitive operations like splicing, and to have libraries that combine
these operations into more complex systems (like automatic derivation of
type classes).
Again, TH is very powerful, and fills in a number of holes in
Haskell's feature set. But it leaves me wondering if these holes
should not be filled in by other, more specialized features, leaving
TH to continue to find other holes to fill.
Shouldn't specialized features be defined in terms of general features?
json :: String - JsonObject
json = ...
data = [ json |
{ name : Jonathan
, favorite language: Haskell
}
|]
How does this differ from the current QuasiQuotes extension? From what I can
tell, all you need to achieve this with TH is to automatically derive a
Language.Haskell.TH.Lift instance for JsonObject, i.e. a function lift ::
JsonObject - Q Exp such that the expression will evaluate to the original
JsonObject. A QuasiQuoter like the one you describe can then be created by
QuasiQuoter { parseExp = lift . json }. Should both approaches be supported
directly, or should we sacrifice the generality of the current quoters for
the simplicity of the ones you suggest?
The second part (deriving instances for general type classes) is a lot more
complicated. I would say that the most general way of showing that a class
can be derived is to provide a function that produces a set of declarations
given the name of the datatype. Here's a very simple suggestion for
incorporating this into the Haskell deriving syntax. Suppose we have these
two classes and TH functions for deriving them:
class Class1 ...
class Class2 ...
class1 :: Name - Q [Dec]
class2 :: Name - Q [Dec]
data D = D deriving (Show,class1,class2)
The last declaration could expand to:
data D = D deriving Show
class1 'D
class2 'D
If you don't want to write class1 and class2 by operating directly on
Haskell declarations, but rather use some DSL for specifying instances, then
all you need is a function deriv :: DerivationDSL - (Name - Q [Dec]).
/J
On 27 December 2010 08:35, Jonathan Geddes geddes.jonat...@gmail.com
wrote:
Cafe,
First let me say that Template Haskell is very powerful and a lot of
great work has been done in this area. It fills in a number of holes
in Haskell's feature set.
But TH gives me the same feeling as other language features that have
been described as bolted on. Also, TH is both library and built-in
syntax (via an extension) which feels strange to me. Finally, It's
very complicated to do some simple things.
I see TH used most for the following tasks:
#1 Parse a string at compile-time so that a custom syntax for
representing data can be used. At the extreme, this data might even
be an EDSL.
#2 Provide instances automatically.
I would propose that more specialized features be implemented to
accomplish these tasks. To start, I'll throw out some ideas that
provide these capabilities.
For TH use #1, compile-time parsing of arbitrary strings, I think it
would be nice for quasiquote semantics to be modified so that code
like
json :: String - JsonObject
json = ...
data = [ json |
{ name : Jonathan
, favorite language: Haskell
}
|]
causes the function json to be called at compile time with a string
argument of{\name\ : \Jonathan\\n , \favorite language\:
\Haskell\\n }. The whole expression being then replaced with the
result of the function application. What I like about this is that
defining quasiquoters is trivial. They're just functions of the form
String - a. Many such quasiquoters already exist and would be ready
for use! I imagine certain rules would apply, ie a quasiquoter must be
defined prior to use and in a separate module, etc.
For TH use #2, automatic instances, I would propose a way of declaring
that a class can be automatically derived, and therefore added to the
set [Eq, Ord, Show, Read, ... , etc]. This is the set of classes that
can be put in the deriving clause of a type declaration. I don't
know exactly what the syntax for this would look like, but I imagine
it would look a bit like the various current implementations of
automatic instances in TH.
Again, TH is very powerful, and fills in a number of holes in
Haskell's feature set. But it leaves me wondering if these holes
should not be filled in by other, more specialized features, leaving
TH to continue to find other holes to fill.
I'm wondering if others see TH as a permanent solution, or if you
agree with me that some of TH's most common usages should have more
specialized features dedicated to them. It may very well be that I am
simply not experienced
Re: [Haskell-cafe] Template Haskell a Permanent solution?
Hi Henning, I also think that Template Haskell is used too much. Several things that are done in existing libraries could be done in plain Haskell in a better way. Can you give any examples of this? I'm not saying it's not true, I'm just curious as to why you would venture into the realm of TH without a reason. /J On 27 December 2010 08:44, Henning Thielemann lemm...@henning-thielemann.de wrote: On Mon, 27 Dec 2010, Jonathan Geddes wrote: #1 Parse a string at compile-time so that a custom syntax for representing data can be used. At the extreme, this data might even be an EDSL. I think it would be enough, if the compiler could be told to unfold an expression like parse text in a domain specific language at compile time. #2 Provide instances automatically. http://www.haskell.org/ghc/docs/7.0-latest/html/users_guide/generic-classes.html I also think that Template Haskell is used too much. Several things that are done in existing libraries could be done in plain Haskell in a better way. For the cases where Template Haskell is really needed, I'd prefer a solution that allows to generate the code before compilation, such that packages with automatically generated code can be run also on compilers that do not support Template Haskell. ___ 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] parsec2 vs. parsec3... again
On Thu, Dec 23, 2010 at 12:01 PM, Evan Laforge qdun...@gmail.com wrote: Yeah, I know this has been discussed a number of times, but I have some concrete questions I haven't seen asked before. And the parsec 3 is now as fast as parsec 2 thing I've seen around doesn't seem to be true for me. [ snip responses ] So it sounds like the consensus is to bite the bullet and try converting to ByteString + attoparsec and see if that helps. Or write attoparsec-text myself, or wait for someone else to do it :) I might not get around to this real soon, but I'll post my results when (if) I do. Thanks for the responses! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Template Haskell a Permanent solution?
On Mon, 27 Dec 2010, Jonas Almström Duregård wrote: Hi Henning, I also think that Template Haskell is used too much. Several things that are done in existing libraries could be done in plain Haskell in a better way. Can you give any examples of this? I'm not saying it's not true, I'm just curious as to why you would venture into the realm of TH without a reason. E.g. refer to the recent discussion of storable-endian. http://www.haskell.org/pipermail/haskell-cafe/2010-December/087551.html Or look into package 'encoding'. It uses TemplateHaskell in order to convert Text descriptions of character sets into Haskell tables. I think the character tables could be simply rewritten to Haskell syntax, or they could be parsed by a function, where the parsed content is unfolded at compile time. It could even be computed at runtime, since it is only computed once because of laziness. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Template Haskell a Permanent solution?
2010/12/27 Henning Thielemann lemm...@henning-thielemann.de: Or look into package 'encoding'. It uses TemplateHaskell in order to convert Text descriptions of character sets into Haskell tables. I think the character tables could be simply rewritten to Haskell syntax, or they could be parsed by a function, where the parsed content is unfolded at compile time. It could even be computed at runtime, since it is only computed once because of laziness. http://hackage.haskell.org/package/zeroth ? -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANNOUNCE: greg-client - a scalable distributed logger with a high-precision global time axis
Hi cafe, Let me bring to your attention this package developed by me and Dmitry Astapov: http://hackage.haskell.org/package/greg-client It is a Haskell binding to the greg logger ( http://code.google.com/p/greg , http://github.com/jkff/greg - global registrator ). You can read the project's description and motivation at the homepage http://code.google.com/p/greg , but here are some highlights: * It's designed for debugging lattency bottlenecks or synchronization issues in distributed systems. I've been using it on small and large clusters, Dmitry has been using it for debugging haskell-mpi if I'm correct (Dmitry, can you elaborate a bit?). * It's a client/server logger - you launch a server and clients log messages to it * It provides a high-precision global time axis by computing clock offset between server and each client (this allows to register events with their occurence timestamps, not arrival-to-server timestamps) * It's very fast (I squeezed 400,000 messages/sec = 20Mb/s out of the Java binding) * It can handle a huge number of clients (a much less scalable implementation was tested on a 2000-core cluster) * It's robust to intermittent deaths of clients, server or the link between them * It's very lightweight - no persistence infrastructure, piles of config files or whatever - just send him the messages, it will align them on the global axis and log them to console I found it especially useful in conjunction with the log visualization tools described here http://slideshare.net/jkff/two-visualization-tools . P.S. How to use it (while hackage hasn't yet rebuilt the docs): import System.Log.Greg main = withGregDo defaultConfiguration $ do ...logMessage Something happened... -- Eugene Kirpichov Senior Software Engineer, Grid Dynamics http://www.griddynamics.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsec2 vs. parsec3... again
Hello! On Mon, Dec 27, 2010 at 9:41 AM, Evan Laforge qdun...@gmail.com wrote: So it sounds like the consensus is to bite the bullet and try converting to ByteString + attoparsec and see if that helps. Or write attoparsec-text myself, or wait for someone else to do it :) I might not get around to this real soon, but I'll post my results when (if) I do. I've uploaded attoparsec-text and attoparsec-text-enumerator to Hackage. I've written those packages late last week and asked for comments from attoparsec and attoparsec-enumerator's maintainers. Although both packages weren't stress tested (actually they were very lightly tested), I'm releasing them so that we don't waste efforts duplicating work =). I'll make an announcement later today if no critical bugs are found. Please test it and try to break it =). Bonus points if we give us some numbers about how it compares to your Parsec 2/3 approach. Links: http://hackage.haskell.org/package/attoparsec-text http://hackage.haskell.org/package/attoparsec-text-enumerator Cheers! =D -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsec2 vs. parsec3... again
I've uploaded attoparsec-text and attoparsec-text-enumerator to Hackage. I've written those packages late last week and asked for Very nice! I'll download this and try it out. Attoparsec has a bit different combinators than parsec so it'll take some rewriting, but it's work I'd have to do anyway to try the bytestring+attoparsec approach. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANNOUNCE: yackage 0.0.0
Hi all, I was speaking with my coworker Yitz[1] about a project he's working on. Basically, he's going to end up with about 16 cabal packages that are not going to be deployed to Hackage, and wanted us to set up a Hackage server for our company to deploy these kinds of things. However, getting all the pieces of Hackage aligned properly for such a simple use case seemed a bit overkill. I then realized that I had the exact same problem during Yesod development: before I make a major release, I usually end up with about 10-15 packages that are not yet live on Hackage. It gets to be a real pain when suddenly wai-extra is depending on network 2.3 and authenticate requires network 2.2, and suddenly I need to manually recompile 10 packages. So I decided to write up a simple web service to act as a local Hackage server. It has no security (anyone with access can upload a package), doesn't build haddocks, doesn't show package descriptions, etc. All it does is: Show a list of uploaded packages/versions Links to the tarballs Allows you to upload new versions, which will automatically overwrite existing packages Provides the 00-index.tar.gz file needed by cabal-install, as well as the tarballs for all the packages In order to use this, just do the following: cabal install yackage run yackage Upload your packages Add remote-repo: yackage:http://localhost:3500/ to your ~/.cabal/config file cabal update Install your packages are usual You'll need to leave yackage running whenever you want to run an update or download new packages. A few other usage notes: If you overwrite a package, your cache folder will still have the old version. You might want to just wipe our your cache folder on each usage. Running cabal update will download the update for both yackage and the main hackage server; the latter can be a long process depending on your internet connection. Here's a little shell script that will disable the Hackage repo, wipe our the Yackage cache, update and re-enable the Hackage repo: #!/bin/sh CABAL_DIR=~/.cabal cp $CABAL_DIR/config $CABAL_DIR/config.sav sed 's/^remote-repo: hackage/--remote-repo: hackage/' $CABAL_DIR/config.sav $CABAL_DIR/config rm -rf $CABAL_DIR/packages/yackage cabal update cp $CABAL_DIR/config.sav $CABAL_DIR/config I hope others find this tool useful. Michael [1] http://www.haskellers.com/user/Yitz_Gale/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANNOUNCE: yackage 0.0.0
This is very interesting. I was thinking if this could work like an overlayed namespace on top of Hackage, rather than a complete override, that it would be a very interesting way to fork Hackage so it does what you want, transparently, and as a proxy. Is that actually how it works though? (It might be that I've not had my coffee yet, but I'm a little fuzzy on that point). While the Haskell-platform is a great stabilizing technology for the Haskell community and gives a nice warm fuzzy feeling to those who want to try it in commercial settings, it's not always true that it provides enough functionality for everyone's needs, and being able to somewhat modify what's available on Hackage could be very valuable. Dave On Mon, Dec 27, 2010 at 8:41 AM, Michael Snoyman mich...@snoyman.comwrote: Hi all, I was speaking with my coworker Yitz[1] about a project he's working on. Basically, he's going to end up with about 16 cabal packages that are not going to be deployed to Hackage, and wanted us to set up a Hackage server for our company to deploy these kinds of things. However, getting all the pieces of Hackage aligned properly for such a simple use case seemed a bit overkill. I then realized that I had the exact same problem during Yesod development: before I make a major release, I usually end up with about 10-15 packages that are not yet live on Hackage. It gets to be a real pain when suddenly wai-extra is depending on network 2.3 and authenticate requires network 2.2, and suddenly I need to manually recompile 10 packages. So I decided to write up a simple web service to act as a local Hackage server. It has no security (anyone with access can upload a package), doesn't build haddocks, doesn't show package descriptions, etc. All it does is: Show a list of uploaded packages/versions Links to the tarballs Allows you to upload new versions, which will automatically overwrite existing packages Provides the 00-index.tar.gz file needed by cabal-install, as well as the tarballs for all the packages In order to use this, just do the following: cabal install yackage run yackage Upload your packages Add remote-repo: yackage:http://localhost:3500/ to your ~/.cabal/config file cabal update Install your packages are usual You'll need to leave yackage running whenever you want to run an update or download new packages. A few other usage notes: If you overwrite a package, your cache folder will still have the old version. You might want to just wipe our your cache folder on each usage. Running cabal update will download the update for both yackage and the main hackage server; the latter can be a long process depending on your internet connection. Here's a little shell script that will disable the Hackage repo, wipe our the Yackage cache, update and re-enable the Hackage repo: #!/bin/sh CABAL_DIR=~/.cabal cp $CABAL_DIR/config $CABAL_DIR/config.sav sed 's/^remote-repo: hackage/--remote-repo: hackage/' $CABAL_DIR/config.sav $CABAL_DIR/config rm -rf $CABAL_DIR/packages/yackage cabal update cp $CABAL_DIR/config.sav $CABAL_DIR/config I hope others find this tool useful. Michael [1] http://www.haskellers.com/user/Yitz_Gale/ ___ 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] Template Haskell a Permanent solution?
On Mon, Dec 27, 2010 at 12:44 AM, Henning Thielemann lemm...@henning-thielemann.de wrote: I think it would be enough, if the compiler could be told to unfold an expression like parse text in a domain specific language at compile time. I'm afraid I have to disagree with you here. Being able to specify that the string should be parsed at compile time is only half of the equation in my mind. The other half is the clean syntax for multi-line strings. Haskell already has great syntax for specifying data in a declarative manner. Especially in contrast with ie Java/C++. Even as good as the dynamic languages ie JavaScript/Python/Ruby. When you add the ability to specify data in ANY syntax you can parse, Haskell is clearly the best. But the complexity of TH detracts from the elegance of this greatly in my opinion. And wrapping your data in string syntax, multi-line or otherwise, detracts from the elegance as well. A syntax has to be less painful or more convenient or more readable/maintainable than literal list/record syntax before it is useful. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Template Haskell a Permanent solution?
On Mon, Dec 27, 2010 at 1:14 AM, Stephen Tetley stephen.tet...@gmail.com wrote: By this are you meaning to add quasiquoting to the language Haskell or the Glasgow Haskell, taking it out of the domain of Template Haskell? I believe that all new features should start as extensions and as an extension, these things could coexist with TH. I just can't see TH becoming standard. I think something much simpler that accomplishes the common uses of TH is more likely to make it into Haskell' 20[1-2]x. --Jonathan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANNOUNCE: yackage 0.0.0
There is also the hackage 2.0 code [1]. This can be easily cabal-installed, and added as an extra remote-repo to your .cabal/config file. We've set this up at typLAB [2], and it's working great. Cabal upload doesn't support multiple remote repo's, but we've created a small deployment utility to quickly deploy to our own hackage. By careful version number management, you can also create local forks of hackage packages. Erik [1] http://hackage.haskell.org/trac/hackage/wiki/HackageDB [2] http://www.typlab.com On Mon, Dec 27, 2010 at 17:53, David Leimbach leim...@gmail.com wrote: This is very interesting. I was thinking if this could work like an overlayed namespace on top of Hackage, rather than a complete override, that it would be a very interesting way to fork Hackage so it does what you want, transparently, and as a proxy. Is that actually how it works though? (It might be that I've not had my coffee yet, but I'm a little fuzzy on that point). While the Haskell-platform is a great stabilizing technology for the Haskell community and gives a nice warm fuzzy feeling to those who want to try it in commercial settings, it's not always true that it provides enough functionality for everyone's needs, and being able to somewhat modify what's available on Hackage could be very valuable. Dave On Mon, Dec 27, 2010 at 8:41 AM, Michael Snoyman mich...@snoyman.com wrote: Hi all, I was speaking with my coworker Yitz[1] about a project he's working on. Basically, he's going to end up with about 16 cabal packages that are not going to be deployed to Hackage, and wanted us to set up a Hackage server for our company to deploy these kinds of things. However, getting all the pieces of Hackage aligned properly for such a simple use case seemed a bit overkill. I then realized that I had the exact same problem during Yesod development: before I make a major release, I usually end up with about 10-15 packages that are not yet live on Hackage. It gets to be a real pain when suddenly wai-extra is depending on network 2.3 and authenticate requires network 2.2, and suddenly I need to manually recompile 10 packages. So I decided to write up a simple web service to act as a local Hackage server. It has no security (anyone with access can upload a package), doesn't build haddocks, doesn't show package descriptions, etc. All it does is: Show a list of uploaded packages/versions Links to the tarballs Allows you to upload new versions, which will automatically overwrite existing packages Provides the 00-index.tar.gz file needed by cabal-install, as well as the tarballs for all the packages In order to use this, just do the following: cabal install yackage run yackage Upload your packages Add remote-repo: yackage:http://localhost:3500/ to your ~/.cabal/config file cabal update Install your packages are usual You'll need to leave yackage running whenever you want to run an update or download new packages. A few other usage notes: If you overwrite a package, your cache folder will still have the old version. You might want to just wipe our your cache folder on each usage. Running cabal update will download the update for both yackage and the main hackage server; the latter can be a long process depending on your internet connection. Here's a little shell script that will disable the Hackage repo, wipe our the Yackage cache, update and re-enable the Hackage repo: #!/bin/sh CABAL_DIR=~/.cabal cp $CABAL_DIR/config $CABAL_DIR/config.sav sed 's/^remote-repo: hackage/--remote-repo: hackage/' $CABAL_DIR/config.sav $CABAL_DIR/config rm -rf $CABAL_DIR/packages/yackage cabal update cp $CABAL_DIR/config.sav $CABAL_DIR/config I hope others find this tool useful. Michael [1] http://www.haskellers.com/user/Yitz_Gale/ ___ 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] ANNOUNCE: yackage 0.0.0
This was brought up on reddit[1]. Anyone who is interested in the differences should feel free to look there. Michael [1] http://www.reddit.com/r/haskell/comments/es3of/announcing_yackage_your_personal_hackage_server/c1ah7gi On Mon, Dec 27, 2010 at 9:24 PM, Erik Hesselink hessel...@gmail.com wrote: There is also the hackage 2.0 code [1]. This can be easily cabal-installed, and added as an extra remote-repo to your .cabal/config file. We've set this up at typLAB [2], and it's working great. Cabal upload doesn't support multiple remote repo's, but we've created a small deployment utility to quickly deploy to our own hackage. By careful version number management, you can also create local forks of hackage packages. Erik [1] http://hackage.haskell.org/trac/hackage/wiki/HackageDB [2] http://www.typlab.com On Mon, Dec 27, 2010 at 17:53, David Leimbach leim...@gmail.com wrote: This is very interesting. I was thinking if this could work like an overlayed namespace on top of Hackage, rather than a complete override, that it would be a very interesting way to fork Hackage so it does what you want, transparently, and as a proxy. Is that actually how it works though? (It might be that I've not had my coffee yet, but I'm a little fuzzy on that point). While the Haskell-platform is a great stabilizing technology for the Haskell community and gives a nice warm fuzzy feeling to those who want to try it in commercial settings, it's not always true that it provides enough functionality for everyone's needs, and being able to somewhat modify what's available on Hackage could be very valuable. Dave On Mon, Dec 27, 2010 at 8:41 AM, Michael Snoyman mich...@snoyman.com wrote: Hi all, I was speaking with my coworker Yitz[1] about a project he's working on. Basically, he's going to end up with about 16 cabal packages that are not going to be deployed to Hackage, and wanted us to set up a Hackage server for our company to deploy these kinds of things. However, getting all the pieces of Hackage aligned properly for such a simple use case seemed a bit overkill. I then realized that I had the exact same problem during Yesod development: before I make a major release, I usually end up with about 10-15 packages that are not yet live on Hackage. It gets to be a real pain when suddenly wai-extra is depending on network 2.3 and authenticate requires network 2.2, and suddenly I need to manually recompile 10 packages. So I decided to write up a simple web service to act as a local Hackage server. It has no security (anyone with access can upload a package), doesn't build haddocks, doesn't show package descriptions, etc. All it does is: Show a list of uploaded packages/versions Links to the tarballs Allows you to upload new versions, which will automatically overwrite existing packages Provides the 00-index.tar.gz file needed by cabal-install, as well as the tarballs for all the packages In order to use this, just do the following: cabal install yackage run yackage Upload your packages Add remote-repo: yackage:http://localhost:3500/ to your ~/.cabal/config file cabal update Install your packages are usual You'll need to leave yackage running whenever you want to run an update or download new packages. A few other usage notes: If you overwrite a package, your cache folder will still have the old version. You might want to just wipe our your cache folder on each usage. Running cabal update will download the update for both yackage and the main hackage server; the latter can be a long process depending on your internet connection. Here's a little shell script that will disable the Hackage repo, wipe our the Yackage cache, update and re-enable the Hackage repo: #!/bin/sh CABAL_DIR=~/.cabal cp $CABAL_DIR/config $CABAL_DIR/config.sav sed 's/^remote-repo: hackage/--remote-repo: hackage/' $CABAL_DIR/config.sav $CABAL_DIR/config rm -rf $CABAL_DIR/packages/yackage cabal update cp $CABAL_DIR/config.sav $CABAL_DIR/config I hope others find this tool useful. Michael [1] http://www.haskellers.com/user/Yitz_Gale/ ___ 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] Unknown symbol `__dso_handle' with Template Haskell and wxHaskell
We had this problem with a binding to a C++ library (through a C
wrapper). GHCi and cabal didn't work, but ghc --make did. How are you
compiling exactly when you get this error? This is somehow related to
TH, without it, at least cabal also works. I'm not sure about GHCi.
There's also a relevant bug in the GHC trac, but I can't seem to find
it now.
Erik
On Sat, Dec 25, 2010 at 18:41, Alexander Bau a...@imn.htwk-leipzig.de wrote:
Hi,
I am using Template Haskell and wxHaskell [1]. When Graphics.UI.WX is
loaded during THs code generation, I get the following error:
...
Loading package wxdirect-0.12.1.3 ... linking ... done.
ghc: /usr/local/lib/wxcore-0.12.1.6/ghc-6.12.3/HSwxcore-0.12.1.6.o:
unknown symbol `__dso_handle'
Loading package wxcore-0.12.1.6 ...
linking ... ghc: unable to load package `wxcore-0.12.1.6'
System stats:
ghc-6.12.3
template-haskell-2.4.0.1
wx-0.12.1.6
Regards,
Alex
[1] Example:
-- Test.hs --
{-# LANGUAGE TemplateHaskell #-}
module Test2 where
import Language.Haskell.TH
import qualified Graphics.UI.WX as WX
foo :: Q [Dec]
foo = do
info - reify ''WX.Color
runIO $ print info
return []
-- Main.hs --
{-# LANGUAGE TemplateHaskell #-}
module Main where
import Test
$(foo)
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Re: [Haskell-cafe] instance for (Show ([(String, Int)] - Int))
On 24 December 2010 23:58, Daniel Fischer daniel.is.fisc...@googlemail.comwrote: On Saturday 25 December 2010 00:32:38, Aaron Gray wrote: Okay great, works this end too, but what does the 'flip' do ??? It flips the order of arguments to calc. You could also write main = getContents = print . (`calc` []) . lexer Generally, flip f = \x y - f y x or flip f x = \y - f y x flip f x y = f y x Thanks Daniel, Aaron ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] instance for (Show ([(String, Int)] - Int))
On 24 December 2010 23:58, Daniel Fischer daniel.is.fisc...@googlemail.comwrote: On Saturday 25 December 2010 00:32:38, Aaron Gray wrote: Okay great, works this end too, but what does the 'flip' do ??? It flips the order of arguments to calc. You could also write main = getContents = print . (`calc` []) . lexer Generally, flip f = \x y - f y x or flip f x = \y - f y x flip f x y = f y x Or :- calcExpr :: [Token] - Int calcExpr tokens = calc tokens [] process = print . calcExpr . lexer makes things clearer. Aaron ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unknown symbol `__dso_handle' with Template Haskell and wxHaskell
GHCi and cabal didn't work, but ghc --make did. Neither GHCi, cabal nor ghc --make works. I refactored my code, so that all TH related stuff does not depend on wxHaskell, i.e. wxHaskell doesn't need to be loaded during THs code generation. Then ghc --make works fine. But when using cabal, the same error occurs. It seems to me that TH (when used with cabal) loads all packages specified at Build-Depends in your cabal file (whether they are needed or not). ghc --make instead just loads all packages, that are really needed for THs code generation. But this is just a workaround and does not explain why TH does not work with wxHaskell. I think this is somehow related to the inability to use wxHaskell inside of GHCi [1], because then the same error occurs. [1] http://comments.gmane.org/ gmane.comp.lang.haskell.wxhaskell.general/923 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] How to instance MonadIO Identity?
Hi, From another thread in this list, I got code as: instance MonadIO Identity where liftIO = id Well, it does not work for me as: Message.hs:22:12: Couldn't match expected type `Identity a' with actual type `IO a' Expected type: IO a - Identity a Actual type: IO a - IO a In the expression: id In an equation for `liftIO': liftIO = id -- 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
Re: [Haskell-cafe] How to instance MonadIO Identity?
The only way to create such an instance would be with unsafePerformIO, which in this case would be a Very Bad Idea (tm). Michael On Tue, Dec 28, 2010 at 7:29 AM, Magicloud Magiclouds magicloud.magiclo...@gmail.com wrote: Hi, From another thread in this list, I got code as: instance MonadIO Identity where liftIO = id Well, it does not work for me as: Message.hs:22:12: Couldn't match expected type `Identity a' with actual type `IO a' Expected type: IO a - Identity a Actual type: IO a - IO a In the expression: id In an equation for `liftIO': liftIO = id -- 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to instance MonadIO Identity?
Ah, that is a bad news. I am using Control.Monad.Writer and Data.Encoding. Code like (not compilable) 43|instance WithMessage String where 44| append s = (liftIO $ getSystemEncoding) = (\e - tell $ encodeLazyByteString e s) May I know how to make this work? 2010/12/28 Michael Snoyman mich...@snoyman.com: The only way to create such an instance would be with unsafePerformIO, which in this case would be a Very Bad Idea (tm). Michael On Tue, Dec 28, 2010 at 7:29 AM, Magicloud Magiclouds magicloud.magiclo...@gmail.com wrote: Hi, From another thread in this list, I got code as: instance MonadIO Identity where liftIO = id Well, it does not work for me as: Message.hs:22:12: Couldn't match expected type `Identity a' with actual type `IO a' Expected type: IO a - Identity a Actual type: IO a - IO a In the expression: id In an equation for `liftIO': liftIO = id -- 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 -- 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
Re: [Haskell-cafe] How to instance MonadIO Identity?
Well, you *could* use unsafePerformIO on getSystemEncoding, though I'm not familiar with getSystemEncoding, so I can't tell you whether this is an acceptable usage of unsafePerformIO. On Tue, Dec 28, 2010 at 7:47 AM, Magicloud Magiclouds magicloud.magiclo...@gmail.com wrote: Ah, that is a bad news. I am using Control.Monad.Writer and Data.Encoding. Code like (not compilable) 43|instance WithMessage String where 44| append s = (liftIO $ getSystemEncoding) = (\e - tell $ encodeLazyByteString e s) May I know how to make this work? 2010/12/28 Michael Snoyman mich...@snoyman.com: The only way to create such an instance would be with unsafePerformIO, which in this case would be a Very Bad Idea (tm). Michael On Tue, Dec 28, 2010 at 7:29 AM, Magicloud Magiclouds magicloud.magiclo...@gmail.com wrote: Hi, From another thread in this list, I got code as: instance MonadIO Identity where liftIO = id Well, it does not work for me as: Message.hs:22:12: Couldn't match expected type `Identity a' with actual type `IO a' Expected type: IO a - Identity a Actual type: IO a - IO a In the expression: id In an equation for `liftIO': liftIO = id -- 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 -- 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
Re: [Haskell-cafe] How to instance MonadIO Identity?
There are a couple of ways to handle this - either call getSystemEncoding on the outside, before calling 'runWriter', and then pass it in to your writer computation, or use 'WriterT IO' instead of 'Writer'. That would be something like: main = do result - runWriterT ( computation involving 'tell' and 'liftIO') ( computation using result) The error message in your case can be difficult to understand - the 'Writer' type is a synonym for the type 'WriterT Identity'. Since none of these types involve IO, then liftIO can't be used. Antoine On Tue, Dec 28, 2010 at 12:47 AM, Magicloud Magiclouds magicloud.magiclo...@gmail.com wrote: Ah, that is a bad news. I am using Control.Monad.Writer and Data.Encoding. Code like (not compilable) 43|instance WithMessage String where 44| append s = (liftIO $ getSystemEncoding) = (\e - tell $ encodeLazyByteString e s) May I know how to make this work? 2010/12/28 Michael Snoyman mich...@snoyman.com: The only way to create such an instance would be with unsafePerformIO, which in this case would be a Very Bad Idea (tm). Michael On Tue, Dec 28, 2010 at 7:29 AM, Magicloud Magiclouds magicloud.magiclo...@gmail.com wrote: Hi, From another thread in this list, I got code as: instance MonadIO Identity where liftIO = id Well, it does not work for me as: Message.hs:22:12: Couldn't match expected type `Identity a' with actual type `IO a' Expected type: IO a - Identity a Actual type: IO a - IO a In the expression: id In an equation for `liftIO': liftIO = id -- 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 -- 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to instance MonadIO Identity?
Wow, this explains a lot. Thanks. On Tue, Dec 28, 2010 at 2:05 PM, Antoine Latter aslat...@gmail.com wrote: There are a couple of ways to handle this - either call getSystemEncoding on the outside, before calling 'runWriter', and then pass it in to your writer computation, or use 'WriterT IO' instead of 'Writer'. That would be something like: main = do result - runWriterT ( computation involving 'tell' and 'liftIO') ( computation using result) The error message in your case can be difficult to understand - the 'Writer' type is a synonym for the type 'WriterT Identity'. Since none of these types involve IO, then liftIO can't be used. Antoine On Tue, Dec 28, 2010 at 12:47 AM, Magicloud Magiclouds magicloud.magiclo...@gmail.com wrote: Ah, that is a bad news. I am using Control.Monad.Writer and Data.Encoding. Code like (not compilable) 43|instance WithMessage String where 44| append s = (liftIO $ getSystemEncoding) = (\e - tell $ encodeLazyByteString e s) May I know how to make this work? 2010/12/28 Michael Snoyman mich...@snoyman.com: The only way to create such an instance would be with unsafePerformIO, which in this case would be a Very Bad Idea (tm). Michael On Tue, Dec 28, 2010 at 7:29 AM, Magicloud Magiclouds magicloud.magiclo...@gmail.com wrote: Hi, From another thread in this list, I got code as: instance MonadIO Identity where liftIO = id Well, it does not work for me as: Message.hs:22:12: Couldn't match expected type `Identity a' with actual type `IO a' Expected type: IO a - Identity a Actual type: IO a - IO a In the expression: id In an equation for `liftIO': liftIO = id -- 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 -- 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 -- 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
Re: [Haskell-cafe] Template Haskell a Permanent solution?
Thanks, everyone, for the responses.
I don't understand why the library/extension duality is a problem.
I don't think it is a _problem_ it just feels strange to me. Maybe I'm
misunderstanding, is it possible to use TH without using the library
components?
Shouldn't specialized features be defined in terms of general features?
Absolutely, but usually don't you use the specialized features over
general ones where you can? For example, I don't often (if ever) use
the general feature of the goto statement in C. Instead I use
conditionals, loops, and functions. I don't often write explicitly
recursive functions in Haskell, rather I use map, filter, fold, etc.
whenever the structure of the recursion allows.
How does this differ from the current QuasiQuotes extension? From what I can
tell, all you need to achieve this with TH is to automatically derive a
Language.Haskell.TH.Lift instance for JsonObject, i.e. a function lift ::
JsonObject - Q Exp such that the expression will evaluate to the original
JsonObject. A QuasiQuoter like the one you describe can then be created by
QuasiQuoter { parseExp = lift . json }.
Right, it's not a lot of extra work. But it's enough that in most
cases, I stick with constructing records or using other built-in
syntax.
Should both approaches be supported
directly, or should we sacrifice the generality of the current quoters for
the simplicity of the ones you suggest?
No, I don't think TH should be sacrificed. I just think more specific
(and more simple) features might be nice in place of some of TH's
specific uses.
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