Re: [Haskell-cafe] Announce: Leksah 0.13.1 (a bit experimental)
Hi Hamish, Features in process-leksah have been merged into process. For newer versions of GHC leksah-server just depends on process. I trust this applies to the unreleased beta version that you just announced, right? (The latest release versions still seem to depend on process-leksah.) In that case, I'll try again building Leksah once the new version is available from Hackage. Thank you for the quick response! Peter ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Example programs with ample use of deepseq?
On Tue, Jan 8, 2013 at 10:54 PM, Joachim Breitner m...@joachim-breitner.de wrote: Am Dienstag, den 08.01.2013, 13:01 -0800 schrieb Evan Laforge: surprisingly, deepseq is not used as much as I thought. http://packdeps.haskellers.com/reverse/deepseq lists a lot of packages, but (after grepping through some of the code) most just define NFData instances and/or use it in tests, but rarely in the „real“ code. For some reason I expected it to be in more widespread use. I've been using deepseq quite a bit lately, but for the purpose of debugging space leaks. If, when I deepseq a big structure, the space leak goes away, I can then apply it to some subset. After much trial-and-error I can find something which is insufficiently strict. Ideally I can then strictify that one thing and stop using the deepseq. I wish there was a more efficient way to do this. this is also a possible application of my approach, by providing a „I want this data structure to be fully evaluated now, please tell me how it currently looks, i.e. where in the data structure still thunks lie hidden.“ Do you have a nice, striking example where using your approach (using deepseq and comparing efficiency) you could make a difference, and where a tool as described above would make the analysis much easier? We've also used this approach to debug space-leaks, and would have loved such a tool. We used deepseq, and compared the heap profiles. We finally found the leaks this way, and fixed them using strictness annotations. Finally, we verified by running deepseq again at top level and observing that it didn't change anything anymore. Erik ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Example programs with ample use of deepseq?
Hi Erik, Am Mittwoch, den 09.01.2013, 14:23 +0100 schrieb Erik Hesselink: We've also used this approach to debug space-leaks, and would have loved such a tool. We used deepseq, and compared the heap profiles. We finally found the leaks this way, and fixed them using strictness annotations. Finally, we verified by running deepseq again at top level and observing that it didn't change anything anymore. same question to you: Would you have a suitable test case that can be used to test and demonstrate the usefulness of such tools? Greetings, Joachim -- Joachim nomeata Breitner m...@joachim-breitner.de | nome...@debian.org | GPG: 0x4743206C xmpp: nome...@joachim-breitner.de | http://www.joachim-breitner.de/ signature.asc 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] HaskellDB-HDBC-PostgreSQL installation problem
Hello Community, I have a problem installing the HaskellDB-HDBC-PostgreSQL package with cabal. I'm using Haskell Platform in Windows and I tried to install this package, but there was the error could not find pq library. So I tried to install libpq wich includes pq but there was another error: this package needs a unix installation. Is there any way to install pq on Windows or get the HaskellDB-HDBC-PostgreSQL in another way? Thanks for your advice Johannes Reiher ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HaskellDB-HDBC-PostgreSQL installation problem
Tricky. For what it's worth, if you can't figure this out in the end, you could perhaps use my pgsql-simple which is implemented in pure haskell: https://github.com/chrisdone/pgsql-simple It's been in use on hpaste.org for about 2 years. On 9 January 2013 14:44, Johannes.Reiher johannes.rei...@fh-zwickau.de wrote: Hello Community, I have a problem installing the HaskellDB-HDBC-PostgreSQL package with cabal. I'm using Haskell Platform in Windows and I tried to install this package, but there was the error could not find pq library. So I tried to install libpq wich includes pq but there was another error: this package needs a unix installation. Is there any way to install pq on Windows or get the HaskellDB-HDBC-PostgreSQL in another way? Thanks for your advice Johannes Reiher ___ 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] Example programs with ample use of deepseq?
On Wed, Jan 9, 2013 at 2:40 PM, Joachim Breitner m...@joachim-breitner.de wrote: Hi Erik, Am Mittwoch, den 09.01.2013, 14:23 +0100 schrieb Erik Hesselink: We've also used this approach to debug space-leaks, and would have loved such a tool. We used deepseq, and compared the heap profiles. We finally found the leaks this way, and fixed them using strictness annotations. Finally, we verified by running deepseq again at top level and observing that it didn't change anything anymore. same question to you: Would you have a suitable test case that can be used to test and demonstrate the usefulness of such tools? Sadly, no. This is a private, core part of our application that I cannot share. I can describe what we did, and also the structure of the data in broad terms: we have several Maps, where the keys are usually Text, and the values are custom data types. These contain keys into these maps again. The whole thing defines a graph with several indexes into it. We finally solved the problems by completely moving to strict map operations, strict MVar/TVar operations, and strict data types. If you have more questions, or tools you want to test, I'd be happy to help, though. Regards, Erik ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HaskellDB-HDBC-PostgreSQL installation problem
Try Persistent package. It doesn't depends on libpq and has many useful features (see http://www.yesodweb.com/book/persistent for details) On 01/09/2013 05:50 PM, Christopher Done wrote: Tricky. For what it's worth, if you can't figure this out in the end, you could perhaps use my pgsql-simple which is implemented in pure haskell: https://github.com/chrisdone/pgsql-simple It's been in use on hpaste.org for about 2 years. On 9 January 2013 14:44, Johannes.Reiher johannes.rei...@fh-zwickau.de wrote: Hello Community, I have a problem installing the HaskellDB-HDBC-PostgreSQL package with cabal. I'm using Haskell Platform in Windows and I tried to install this package, but there was the error could not find pq library. So I tried to install libpq wich includes pq but there was another error: this package needs a unix installation. Is there any way to install pq on Windows or get the HaskellDB-HDBC-PostgreSQL in another way? Thanks for your advice Johannes Reiher ___ 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 -- Best regards, Alexander Alexeev http://eax.me/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Seeking feedback for a tutorial paper draft about GADTs
On Tue, Jan 08, 2013 at 11:22:39PM +0400, Anton Dergunov wrote: I have written a draft of an introductory-level tutorial paper about GADTs in Haskell (for submittion to proceedings of the recent LASER summer school) and I would like to seek initial feedback about its content: what information is probably missing? are there any subtle mistakes? Not exactly the feedback you asked for, but I hope it still can be of some use. As a person with no prior knowledge about GADTs, I found your paper a good introduction. Following proof of correctness of red-black tree insertions turned out to be a little bit of a challenge as type annotations quickly become tangled (made me wondering how one should prove correctness of the proof). I particularly liked how you handle things that are not central to tutorial, like phantom and existential types: you give single-sentence explanation that provides good enough intuition to follow you further. Talking of quick explanations, I would love to see kinds and singleton types explained in the same manner. You tried to explain singleton types at page 13, but I find explanation provided by GHC documentation[1] to be much more clear. As for kinds, it just puzzles me why you use the term but don't explain it. 1. http://hackage.haskell.org/trac/ghc/wiki/TypeNats/Basics The same goes for type families - while I was able to quickly look up definition of singleton types, I failed to comprehend basics of type families by reading Haskell Wiki. I ended up pretending that type families are just type-level functions. I would love to see Yampa optimizations section expanded with more interesting examples. Are there any? Last but not least, a few minor typos and errors I spotted: * at page 8, Than we need to declare type instances... should be Then we need...; * probably due to excessive editing, parameters to repeatElem at page 13 are in the different order than before; * at page 14, you state: As in all binary search trees, for a particular node N c l x r values greater than x are stored in left sub-tree (in l) and values less than x are stored in right sub-tree (in r). But later on, your code contradict that statement by recursing to left sub-tree when x we look for is less than value in the node, and to right sub-tree when x is greater than value in the node. Thank you once again for a nice introduction to GADTs! -- Regards, Alexander Batischev PGP key 356961A20C8BFD03 Fingerprint: CE6C 4307 9348 58E3 FD94 A00F 3569 61A2 0C8B FD03 signature.asc Description: Digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HaskellDB-HDBC-PostgreSQL installation problem
AFAIK, persistent's PostgreSQL support does depend on libpq via postgresql-libpq. On Wed, Jan 9, 2013 at 12:39 PM, Alexander Alexeev m...@eax.me wrote: Try Persistent package. It doesn't depends on libpq and has many useful features (see http://www.yesodweb.com/book/persistent for details) On 01/09/2013 05:50 PM, Christopher Done wrote: Tricky. For what it's worth, if you can't figure this out in the end, you could perhaps use my pgsql-simple which is implemented in pure haskell: https://github.com/chrisdone/pgsql-simple It's been in use on hpaste.org for about 2 years. On 9 January 2013 14:44, Johannes.Reiher johannes.rei...@fh-zwickau.de wrote: Hello Community, I have a problem installing the HaskellDB-HDBC-PostgreSQL package with cabal. I'm using Haskell Platform in Windows and I tried to install this package, but there was the error could not find pq library. So I tried to install libpq wich includes pq but there was another error: this package needs a unix installation. Is there any way to install pq on Windows or get the HaskellDB-HDBC-PostgreSQL in another way? Thanks for your advice Johannes Reiher ___ 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 -- Best regards, Alexander Alexeev http://eax.me/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Is http://hackage.haskell.org/packages/hackage.html having a challenging serving up archive.tar?
:) -- -- Regards, KC ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Undo records
I think acid-state (http://hackage.haskell.org/package/acid-state) might do what you want, at least in broad strokes. It uses a durable transaction log to store query and update events. As far as I know, the interface to the library doesn't expose an undo/rollback function, so you'd have a bit of work to do to extend it to your use case. But the core functionality to make it possible should be there. Can you use ghc extensions aside from Template Haskell? Template Haskell you can do without with acid-state, but without GADTs and so on you'll have problems. On Sun, Jan 6, 2013 at 12:01 PM, Casey Basichis caseybasic...@gmail.comwrote: Hi, I am still getting a hang of Haskell. Sorry if the answer is obvious. What sorts of packages and approaches should I be looking at if I was looking to store something like an Undo stack into a database. Each table would refer to a function. Each records input and outputs would specify both a table ID and record ID. The records would also have a data and a Process ID to associate all functions to a specific process and give them an order. No records are ever deleted. Rolling something back is instead a process of recreating a new, modified graph by taking the old graph from the database. I should note that while I can generate some of the boiler parts from template haskell in advance I'm ultimately using a stage 1 compiler with no GHCI o template haskell. Thanks, Casey -- Casey James Basichis Composer - Cartoon Network http://www.caseyjamesbasichis.com caseybasic...@gmail.com 310.387.7540 ___ 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] Undo records
Hi Ben, Thanks for the reply. I am planning on using Persistent which can work without template haskell, though I am planning on using the TH on my workstation to create the boiler code parts of the database setup. The part that I'm having trouble with is collecting the composed functions. It may be a very typical problem but I'm just lost. Let me just describe a simple example; A message comes through the FFI to: Haskell chooses criteria to select a sequence of data from the database --- many functions exist to do this, some may take a random number as a parameter, the seed needs to be stored Haskell similarly chooses a process to apply to the data --- A random number or other deterministic chain of functions The results from the processing are loaded into memory - (these are not the focus here) The minimal chain of functions, parameters and seeds is stored to allow for a deterministic recall/modification --- The input parameters and output parameters are Table and Row ID's So Haskell isn't reacting to many input events, just a trigger that may come with a few initialization parameters. If a function is composed of other functions which do not depend on external state they should not need to be stored in the database as they are implicit. I imagine this is a monad problem, but kind and what other things spring to mind that might help in approaching this kind of problem? Thanks, Casey On Wed, Jan 9, 2013 at 11:40 AM, Ben Doyle benjamin.peter.do...@gmail.comwrote: I think acid-state (http://hackage.haskell.org/package/acid-state) might do what you want, at least in broad strokes. It uses a durable transaction log to store query and update events. As far as I know, the interface to the library doesn't expose an undo/rollback function, so you'd have a bit of work to do to extend it to your use case. But the core functionality to make it possible should be there. Can you use ghc extensions aside from Template Haskell? Template Haskell you can do without with acid-state, but without GADTs and so on you'll have problems. On Sun, Jan 6, 2013 at 12:01 PM, Casey Basichis caseybasic...@gmail.comwrote: Hi, I am still getting a hang of Haskell. Sorry if the answer is obvious. What sorts of packages and approaches should I be looking at if I was looking to store something like an Undo stack into a database. Each table would refer to a function. Each records input and outputs would specify both a table ID and record ID. The records would also have a data and a Process ID to associate all functions to a specific process and give them an order. No records are ever deleted. Rolling something back is instead a process of recreating a new, modified graph by taking the old graph from the database. I should note that while I can generate some of the boiler parts from template haskell in advance I'm ultimately using a stage 1 compiler with no GHCI o template haskell. Thanks, Casey -- Casey James Basichis Composer - Cartoon Network http://www.caseyjamesbasichis.com caseybasic...@gmail.com 310.387.7540 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Casey James Basichis Composer - Cartoon Network http://www.caseyjamesbasichis.com caseybasic...@gmail.com 310.387.7540 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Example programs with ample use of deepseq?
Hi, Am Mittwoch, den 09.01.2013, 15:11 +0100 schrieb Erik Hesselink: We finally solved the problems by completely moving to strict map operations, strict MVar/TVar operations, and strict data types. do you mean strict by policy (i.e. before storing something in a [MT]Var, you ensure it is evaluated) or by construction (by `seq` or `deepseq`’ing everything before it is stored)? In the latter case: Seq or deeqseq? Again in the latter case: Do you worry about the performance of repeatedly deepseq’ing an already deepseq’ed and possibly large value? You are not the first user of Haskell who ends up with that approach to lazy evaluation. I’m not sure what that means for Haskell, though. Greetings, Joachim -- Joachim nomeata Breitner m...@joachim-breitner.de | nome...@debian.org | GPG: 0x4743206C xmpp: nome...@joachim-breitner.de | http://www.joachim-breitner.de/ signature.asc 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] HaskellDB-HDBC-PostgreSQL installation problem
there was another error: this package needs a unix installation. you need to use MinGW, but it still fails because of a GHC bug http://hackage.haskell.org/trac/ghc/ticket/7103 https://github.com/lpsmith/postgresql-libpq/issues/7 -e ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] haskell.cs.yale.edu error
I was hoping to check on the status of Yampa, but: http://haskell.cs.yale.edu/ [an error occurred while processing this directive] You don't have permission to access the requested directory. There is either no index document or the directory is read-protected. [an error occurred while processing this directive] Do you know who maintains this website? Thanks, Greg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell Weekly News: Issue 254
Welcome to issue 254 of the HWN, an issue covering crowd-sourced bits
of information about Haskell from around the web. This issue covers the
week of December 02, 2012 to January 05, 2013.
As some of you might have noticed, there has been an interruption in
the scheduled transmission of the newsletter. I have, over the past few
weeks, completed a move to NYC! It has been wonderful to meet many in
the community at the Haskell NYC meetups. Here is to a great year for
our cherised community.
Let's get things started out the right way, with a litte Lambda
Style :-)
[1] http://goo.gl/nQYdp
Quotes of the Week
* GuySteele: Some people prefer not to commingle the functional,
lambda-calculus part of a language with the parts that do side
effects. It seems they believe in the separation of Church and
state.
* edwardk: type level ieee floats are a crime against nature. i had
to implement them in c++ for template meta programming once. never
ever again
* acowley: (regarding Proxy) Haven't you ever wanted to put something
in a box and never think about it?
elliott: children
* merijn: xenocons: I spend the entire week grading FP homework, I
think it's impossible for you to surprise me :p
merijn: That's confusing :
* andr00: Today's software engineering word is farpotshket. This is
a Yiddish word meaning, broken, because someone tried to fix it.
* dmwit: I know, I know. 0, 1, many. But then I also write most of
my programs in a language whose type system has 4 levels. Four! Is
that even a number??
* aristid: a dubious motivation IMHO
edwardk: i've had worse =P
* ziarkaen: I'm thinking I can kill two birds with one stone by
learning Haskell while producing a website, but all the birds are
still alive at the moment.
* ion:
monad.bind = function (func, args) {
return func.apply(undefined,
[value].concat(Array.prototype.slice.apply(args || [])));
};
is idiomatic JavaScript?
* beaky: if stacks are recursion, what are queues?
Hafydd: Procrastination.
* elliott: I think lens is the first library I've seen that promises
letting you write abstract totally-inefficient-looking
compositional code and getting reliably good compilation which has
actually delivered on that promise.
* elliott: I didn't say half the things I said.
* shachaf: The two-letter and three-letter identifiers are for
edwardk's libraries. The one-letter identifiers are for his actual
code.
elliott: edwardk has non-library code?
* neutrino: in many ways, Haskell is like this primodial soup out of
which other languages end up springing
* mm_freak: bruce schneier is an endofunctor that turns all
automorphisms into identities
* roconnor: where are all the category theoriest? why don't they
already have all the answers for us?
edwardk: roconnor: this is the point in your career where you look
around for the cavalry and realize that you're it ;)
* cmccann: multi-letter type variables is an experimental new
extension
* elliott: I can't remember the last time I wrote any Haskell without
an evil grin.
* neutrino: when you're told you have to use javascript, the viable
alternative always remains in seppuku. and it's much more
honorable.
* shachaf: chrisdone: Please make Author not mandatory. [on hpaste]
donri: shachaf: just write not shachaf and no one will ever know
it's you
* tac: If you're not part of the solution, you're part of the
precipitate
* cmccann: some people blame themselves, some people blame the
language, but the people who really know what they're doing blame
shachaf.
Top Reddit Stories
* The end of an era, and the dawn of a new one
Domain: haskell.org, Score: 148, Comments: 32
On Reddit: [2] http://goo.gl/fiyVt
Original: [3] http://goo.gl/dlxsF
* Simon Peyton-Jones invests in FP Complete
Domain: fpcomplete.com, Score: 92, Comments: 15
On Reddit: [4] http://goo.gl/nPTk1
Original: [5] http://goo.gl/wzfpP
* 24 Days of Hackage - Thank YOU!
Domain: ocharles.org.uk, Score: 88, Comments: 12
On Reddit: [6] http://goo.gl/2yodj
Original: [7] http://goo.gl/hSsH6
* Heist 0.10...now with a 3000x performance improvement
Domain: snapframework.com, Score: 81, Comments: 38
On Reddit: [8] http://goo.gl/p7R7u
Original: [9] http://goo.gl/znugn
* 24 Days of Hackage: EKG
Domain: ocharles.org.uk, Score: 68, Comments: 15
On Reddit: [10] http://goo.gl/ltPb1
Original: [11] http://goo.gl/UeYOA
* pipes-3.0: Simpler, unified API
Domain: haskellforall.com, Score: 64, Comments: 71
On Reddit: [12] http://goo.gl/ZSVtT
Original: [13] http://goo.gl/6Yt01
* Hoodle : Pen note-taking program written in haskell
Domain: youtube.com, Score: 64, Comments: 21
On
