Re: [Haskell-cafe] Category Theory and Haskell
Le Sun, 25 Nov 2012 21:41:47 +, Gytis Žilinskas gytis.zilins...@gmail.com a écrit : Greetings, I'm only taking my very first steps learning Haskell, but I believe that this mailing list might be appropriate for my question. How difficult would it be to study category theory and simultaneously come up with Haskell examples of various results that it presents? I believe some background is in order. I am a second year maths student (well actually I'm in-between 2nd and 3rd, but let's not delve into details). I have also done some 2nd year CS courses so I have some background in that too. My general interests seem to lie somewhere between maths and compsci (I guess theoretical cs is the word for it), but it doesn't look like there is a good way to study the subject at an undergrad level. Most CompSci undergrad courses seem to concentrate too much on the trade of being a programmer and only present the basics of the theoretical results. While maths departments seem to be reluctant to make room in the undergrad curriculum for a huge subject that, after all, is maths. Recently, whenever I try reading up on something that looks like an exciting topic to me, I hit my head against category theory. That seems to suggest, that I should check it out, as it might be a fun subject to study, or at least provide valuable insights elsewhere. I've tried looking for some resources online. Most of them are outright scary and clearly have prerequisites that I lack. Some a little bit more accessible. Overall, various similar questions on different stackexchanges and even some old discussions on this mailing list, imply that to study category theory one has to know many examples from other advanced fields, in order to see the patterns that category theory describes. Now I obviously lack that. Some basic group theory, linear algebra, real/complex analysis and metric spaces is pretty much all I've got. Moreover, most sources say that without the knowledge of examples - category theory is an extremely dry subject to study. Therefore, my preliminary plan is the following: Read: * Barry Mazur - When is one thing equal to some other thing? * Conceptual mathematics : a first introduction to categories / F. William Lawvere, Stephen H. Schanuel. (People say that it is rather lightweight, but at this point my goal is to see the general idea of category theory and get some taste of it) Then, in the 2nd semester, I have an option of taking a self-study module, and if I don't get bored by cats by that time - it would be great to invest some more time in it (or rather, I'll do anything to avoid applied maths *shudder*). However, I'll need to present my case before the department staff and this, basically, is why I'm here. Right now, it looks like the main argument against me, would be that I can't appreciate the subject since I lack the fundamentals in other areas of maths. So I was hoping, I could convince them that everything I lack example wise - I'll find in Haskell. Okay, everything might be too strong of a statement, but I don't really know what I'm talking about so it's a bit difficult to calibrate. Could you comment whether Haskell would serve me well for this purpose? I've also seen these lecture notes: http://www.haskell.org/haskellwiki/User:Michiexile/MATH198. But I'm not sure if they won't be deemed too comp sci targeted. Therefore, I'm putting more hope into The Joy of Cats which, at least according to the first few pages, doesn't assume any prior knowledge that I don't have. So that's that, I would appreciate any advice you could give. Gytis ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe I would suggest reading Saunders MacLane book (Categories for the working mathematician). I am happy to have bought this one. But do not be impressed by the given exercises, they have no correction, and some are not understandable for a new comer. (The first exercise of the book talks about Lie groups and algebra, that is hard to start with). So for the examples, only read the ones involving the Set, Ab, Rng categories if you are not used to the other ones. The terminology is also annoying, as the formalization was done rather lately, and some concepts merged, so for instance the concept of limit. In the terminology, you have limit=inverse limit and colimit=direct limit which is quite confusing (but MacLane is not at fault for that). Some other resource is the categories channel on IRC (Freenode), the nLab wiki (and Wikipedia of course). You may also be interested in Agda, which would help in using the laws of each category (not ensured by raw Haskell). I learned Coq rather than Agda, so you can also try it too. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org
Re: [Haskell-cafe] lambda case
Andreas Abel andreas.a...@ifi.lmu.de writes:
I had been missing a pattern matching lambda in Haskell for
a long time (SML had fn since ages) and my typical use
will be
monadic_expr = \case
branches
We’ve been through that. I want something similar, but would
have preferred something more algebraic.
I think \case is not the worst choice, certainly better than
of ...
What’s your argument? You’ll have to do better than blatant
assertion to convince me. Making “case exp” optional builds on
an existing expression syntax, giving an explicit meaning to a
part of it, so a reader only has to know that “of {alts}” is a
function and case does something specific with it. This “\case”
takes the keyword from that expression syntax and makes it a
special case of lambda, so a reader seeing a lambda now has to
check for a keyword instead of knowing straight off that the
next thing is going to be a variable.
Back when we originally designed Haskell there were lots of
things that people wanted to put in, and eventually we reached a
point where we said that we would only put something new in if
it allowed us to remove (or simplify) something else. “\case”
complicates lambda, using “of” simply breaks “case … of …” into
two easily understood parts.
--
Jón Fairbairn jon.fairba...@cl.cam.ac.uk
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[Haskell-cafe] ANN: base-compat
Hi, I just released the first version of a package that provide new additions to base for older versions of base [2]. So far the following is covered: readMaybe readEither lookupEnv getExecutablePath Source is on GitHub [2]; patches welcome ;) Cheers, Simon [1] http://hackage.haskell.org/package/base-compat [2] https://github.com/sol/base-compat ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] lambda case
Jon Fairbairn jon.fairba...@cl.cam.ac.uk writes:
[...]
“\case” complicates lambda, using “of” simply breaks “case … of …”
into two easily understood parts.
Just some observation (I'm rather late to the lambda-case discussion, so
this might have been already pointed out previously):
if the reserved keyword 'of' was to take the place of '\case', shouldn't
then
'case' exp
w/o the 'of' { alts }-part become a separately valid expression (with
'case' essentially meaning 'flip ($)') to really break it up into two
independent parts? Then 'case exp of { alts }' wouldn't be a special
form anymore, but would just result from combining 'case' and 'of';
'case' wouldn't even need to be a reserved keyword (and thus the grammar
could be simplified), if it wasn't for the current grammar which
requires to isolate a \case-expression by using () or $, consider e.g.:
{-# LANGUAGE LambdaCase #-}
import System.Environment
case' :: b - (b - c) - c
case' = flip ($)
main = do
s - getArgs
case' s $ \case -- image '\case' was actually '\of' or 'of'
[x] - putStrLn (Hello ++ x)
_ - putStrLn wrong number of arguments given
just my 2¢
cheers,
hvr
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Re: [Haskell-cafe] ANN: base-compat
Adding could be useful. On Fri, Nov 30, 2012 at 12:23 PM, Simon Hengel s...@typeful.net wrote: Hi, I just released the first version of a package that provide new additions to base for older versions of base [2]. So far the following is covered: readMaybe readEither lookupEnv getExecutablePath Source is on GitHub [2]; patches welcome ;) Cheers, Simon [1] http://hackage.haskell.org/package/base-compat [2] https://github.com/sol/base-compat ___ 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: base-compat
On Fri, Nov 30, 2012 at 02:32:12PM +0100, dag.odenh...@gmail.com wrote: Adding could be useful. Yes, patch is welcome ;) Cheers, Simon ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why Kleisli composition is not in the Monad signature?
On Fri, Nov 30, 2012 at 02:33:54AM +0100, Ben Franksen wrote: Brent Yorgey wrote: On Thu, Nov 29, 2012 at 03:52:58AM +0100, Ben Franksen wrote: Tony Morris wrote: As a side note, I think a direct superclass of Functor for Monad is not a good idea, just sayin' class Functor f where fmap :: (a - b) - f a - f b class Functor f = Apply f where (*) :: f (a - b) - f a - f b class Apply f = Bind f where (=) :: (a - f b) - f a - f b class Apply f = Applicative f where unit :: a - f a class (Applicative f, Bind f) = Monad f where Same goes for Comonad (e.g. [] has (=) but not counit) ... and again for Monoid, Category, I could go on... Hi Tony even though I dismissed your mentioning this on the Haskell' list, I do have to admit that the proposal has a certain elegance. However, before I buy into this scheme, I'd like to see some striking examples for types with natural (or at least useful) Apply and Bind instances that cannot be made Applicative resp. Monad. Try writing an Applicative instances for (Data.Map.Map k). It can't be done, but the Apply instance is (I would argue) both natural and useful. I see. So there is one example. Are there more? I'd like to get a feeling for the abstraction and this is hard if there is only a single example. Any data type which admits structures of arbitrary but *only finite* size has a natural zippy Apply instance but no Applicative (since pure would have to be an infinite structure). The Map instance I mentioned above falls in this category. Though I guess I'm having trouble coming up with other examples, but I'm sure some exist. Maybe Edward knows of other examples. -Brent ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] lambda case
Oh, PLEASE people. Let's not have another round of bikeshedding about
this AFTER the feature is already implemented!
-Brent
On Fri, Nov 30, 2012 at 01:25:27PM +0100, Herbert Valerio Riedel wrote:
Jon Fairbairn jon.fairba...@cl.cam.ac.uk writes:
[...]
“\case” complicates lambda, using “of” simply breaks “case … of …”
into two easily understood parts.
Just some observation (I'm rather late to the lambda-case discussion, so
this might have been already pointed out previously):
if the reserved keyword 'of' was to take the place of '\case', shouldn't
then
'case' exp
w/o the 'of' { alts }-part become a separately valid expression (with
'case' essentially meaning 'flip ($)') to really break it up into two
independent parts? Then 'case exp of { alts }' wouldn't be a special
form anymore, but would just result from combining 'case' and 'of';
'case' wouldn't even need to be a reserved keyword (and thus the grammar
could be simplified), if it wasn't for the current grammar which
requires to isolate a \case-expression by using () or $, consider e.g.:
{-# LANGUAGE LambdaCase #-}
import System.Environment
case' :: b - (b - c) - c
case' = flip ($)
main = do
s - getArgs
case' s $ \case -- image '\case' was actually '\of' or 'of'
[x] - putStrLn (Hello ++ x)
_ - putStrLn wrong number of arguments given
just my 2¢
cheers,
hvr
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Re: [Haskell-cafe] lambda case
Right, case..of is superfluous,
case e of
branches
can now be written as
e | \case
branches
with backwards application | (or some prefer --- sadly, the proposal
to add backwards appliation to base did not make it to a consensus).
This is in accordance to the monadic
me = \case
branches
If there was an opportunity to make drastic language changes, case..of
could be disposed of altogether. \case could become 'cases' or 'match'
or 'fun' (rather not 'of', for my taste).
The current compromise it not too bad, I think.
Unfortunately, I have to wait for 7.6 to become the standard before
using \case in Agda source...
Cheers,
Andreas
On 30.11.12 7:25 AM, Herbert Valerio Riedel wrote:
Jon Fairbairn jon.fairba...@cl.cam.ac.uk writes:
[...]
“\case” complicates lambda, using “of” simply breaks “case … of …”
into two easily understood parts.
Just some observation (I'm rather late to the lambda-case discussion, so
this might have been already pointed out previously):
if the reserved keyword 'of' was to take the place of '\case', shouldn't
then
'case' exp
w/o the 'of' { alts }-part become a separately valid expression (with
'case' essentially meaning 'flip ($)') to really break it up into two
independent parts? Then 'case exp of { alts }' wouldn't be a special
form anymore, but would just result from combining 'case' and 'of';
'case' wouldn't even need to be a reserved keyword (and thus the grammar
could be simplified), if it wasn't for the current grammar which
requires to isolate a \case-expression by using () or $, consider e.g.:
{-# LANGUAGE LambdaCase #-}
import System.Environment
case' :: b - (b - c) - c
case' = flip ($)
main = do
s - getArgs
case' s $ \case -- image '\case' was actually '\of' or 'of'
[x] - putStrLn (Hello ++ x)
_ - putStrLn wrong number of arguments given
just my 2¢
cheers,
hvr
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--
Andreas AbelDu bist der geliebte Mensch.
Theoretical Computer Science, University of Munich
Oettingenstr. 67, D-80538 Munich, GERMANY
andreas.a...@ifi.lmu.de
http://www2.tcs.ifi.lmu.de/~abel/
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Re: [Haskell-cafe] Why Kleisli composition is not in the Monad signature?
Lists! The finite kind. This could mean Seq for instance. On Nov 30, 2012 9:53 AM, Brent Yorgey byor...@seas.upenn.edu wrote: On Fri, Nov 30, 2012 at 02:33:54AM +0100, Ben Franksen wrote: Brent Yorgey wrote: On Thu, Nov 29, 2012 at 03:52:58AM +0100, Ben Franksen wrote: Tony Morris wrote: As a side note, I think a direct superclass of Functor for Monad is not a good idea, just sayin' class Functor f where fmap :: (a - b) - f a - f b class Functor f = Apply f where (*) :: f (a - b) - f a - f b class Apply f = Bind f where (=) :: (a - f b) - f a - f b class Apply f = Applicative f where unit :: a - f a class (Applicative f, Bind f) = Monad f where Same goes for Comonad (e.g. [] has (=) but not counit) ... and again for Monoid, Category, I could go on... Hi Tony even though I dismissed your mentioning this on the Haskell' list, I do have to admit that the proposal has a certain elegance. However, before I buy into this scheme, I'd like to see some striking examples for types with natural (or at least useful) Apply and Bind instances that cannot be made Applicative resp. Monad. Try writing an Applicative instances for (Data.Map.Map k). It can't be done, but the Apply instance is (I would argue) both natural and useful. I see. So there is one example. Are there more? I'd like to get a feeling for the abstraction and this is hard if there is only a single example. Any data type which admits structures of arbitrary but *only finite* size has a natural zippy Apply instance but no Applicative (since pure would have to be an infinite structure). The Map instance I mentioned above falls in this category. Though I guess I'm having trouble coming up with other examples, but I'm sure some exist. Maybe Edward knows of other examples. -Brent ___ 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] Why Kleisli composition is not in the Monad signature?
On 11/30/12 10:44 AM, Dan Doel wrote: Lists! The finite kind. This could mean Seq for instance. On Nov 30, 2012 9:53 AM, Brent Yorgey byor...@seas.upenn.edu mailto:byor...@seas.upenn.edu wrote: Any data type which admits structures of arbitrary but *only finite* size has a natural zippy Apply instance but no Applicative (since pure would have to be an infinite structure). The Map instance I mentioned above falls in this category. Though I guess I'm having trouble coming up with other examples, but I'm sure some exist. Maybe Edward knows of other examples. Another common case would be an embedded DSL representing code in a different language, targeting a different platform (or even an FPGA or the like), etc. You can apply `OtherLang (a - b)` to an `OtherLang a` and get an `OtherLang b`, but you clearly can't promote (or lower, I guess) an arbitrary Haskell function into a function in your target language. This is the same reason that GArrows remove the `arr` function (http://www.cs.berkeley.edu/~megacz/garrows/). --Gershom ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is anyone working on a sparse matrix library in Haskell?
Hi Mark, For my bachelor thesis I am doing something somewhat in that direction. I am developing a Echo State Neural Networks (ESNs) ( http://minds.jacobs-university.de/esn_research) library in Haskell. I haven't worked on it for a while, since I was reading related literature in the last months. It will be used to classify motion capture data. Feel free to check it out: https://github.com/netogallo/LambdaNN. Sparse matrixes are used to build the ESNs, I have basic functions to produce sparse matrixes but nothing fancy at the moment. Cheers, Ernesto Rodriguez On Thu, Nov 29, 2012 at 11:03 PM, Mark Flamer m...@flamerassoc.com wrote: I am looking to continue to learn Haskell while working on something that might eventually be useful to others and get posted on Hackage. I have written quite a bit of Haskell code now, some useful and a lot just throw away for learning. In the past others have expressed interest in having a native Haskell sparse matrix and linear algebra library available(not just bindings to a C lib). This in combination with FEM is one of my interests. So my questions, is anyone currently working on a project like this? Does it seem like a good project/addition to the community? I'm also interested if anyone has any other project idea's, maybe even to collaborate on. Thanks -- View this message in context: http://haskell.1045720.n5.nabble.com/Is-anyone-working-on-a-sparse-matrix-library-in-Haskell-tp5721452.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ernesto Rodriguez Bachelor of Computer Science - Class of 2013 Jacobs University Bremen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to incrementally update list
Haskell's laziness is tricky to understand coming from imperative languages, but once you figure out its evaluation rules, you'll begin to see the elegance. Is there a paper or other single resource that will help me thoroughly understand non-strictness in Haskell? Once my programs hit a certain level of complexity, their behaviour becomes much harder for me to predict. I've been using the wiki pages up to this point, but apparently they haven't pushed my understanding of laziness nearly far enough. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Can a GC delay TCP connection formation?
On Tue, Nov 27, 2012 at 11:02 AM, Jeff Shaw shawj...@gmail.com wrote: Once each minute, a thread of my program updates a global state, stored in an IORef, and updated with atomicModifyIORef', based on query results via HDBC-obdc. Incidentally, what kind of database are you talking to? Issues of FFI correctness aside, HDBC is in general terribly slow compared to some of the more DB-specific bindings. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] tplot (out of memory)
For the record, it turned out that the key difference between the linux machines was the fonts packages installed via RPM. The strace utility told me that the crash happened shortly after cairo/pango attempted (and failed) to open some font configuration files. After installing some of the X11 font packages (and some others too), the crash went away. On 18 Oct 2012, at 09:55, malcolm.wallace wrote: Did you ever solve this? I have a similar message ( user error (out of memory) ) arising from a different app (not tplot) that uses the Haskell Chart library (and cairo underneath). On some linux machines, it crashes, on others it works fine. I can find no environment differences between the machines. The app does not use a lot of memory, and the machine is not running out of physical or swap. Regards, Malcolm On 04 Sep, 2012,at 04:01 PM, Eugene Kirpichov ekirpic...@gmail.com wrote: Hi Manish, Please provide the input file, I'll debug this. On Mon, Sep 3, 2012 at 1:06 PM, Manish Trivedi trivman...@gmail.com wrote: Hi, I am running into a weird out of memory issue. While running timeplot over an input file having ~800 rows. From below provided info, seems like machine has enough ram (1849MB). Please let me know if anyone has pointers. # free -m total used free shared buffers cached Mem: 3825 1975 1849 0 13 71 -/+ buffers/cache: 1891 1934 Swap: 4031 111 3920 #time tplot -o out.png -or 1024x768 -k 'CurrentPerHour' 'lines' -k 'RequiredPerHour' 'lines' -if adgroup_delivery_chart.input -tf 'date %Y-%m-%d %H:%M:%OS' tplot: user error (out of memory) real 0m0.026s user 0m0.018s sys 0m0.008s -Manish ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Eugene Kirpichov http://www.linkedin.com/in/eugenekirpichov ___ 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] tplot (out of memory)
Hi, Wow, that's weird. I wonder what kinds of fonts were missing? I was just using the default cairo font everywhere. On Fri, Nov 30, 2012 at 11:27 PM, Malcolm Wallace malcolm.wall...@me.comwrote: For the record, it turned out that the key difference between the linux machines was the fonts packages installed via RPM. The strace utility told me that the crash happened shortly after cairo/pango attempted (and failed) to open some font configuration files. After installing some of the X11 font packages (and some others too), the crash went away. On 18 Oct 2012, at 09:55, malcolm.wallace wrote: Did you ever solve this? I have a similar message ( user error (out of memory) ) arising from a different app (not tplot) that uses the Haskell Chart library (and cairo underneath). On some linux machines, it crashes, on others it works fine. I can find no environment differences between the machines. The app does not use a lot of memory, and the machine is not running out of physical or swap. Regards, Malcolm On 04 Sep, 2012,at 04:01 PM, Eugene Kirpichov ekirpic...@gmail.com wrote: Hi Manish, Please provide the input file, I'll debug this. On Mon, Sep 3, 2012 at 1:06 PM, Manish Trivedi trivman...@gmail.com wrote: Hi, I am running into a weird out of memory issue. While running timeplot over an input file having ~800 rows. From below provided info, seems like machine has enough ram (1849MB). Please let me know if anyone has pointers. # free -m total used free shared buffers cached Mem: 3825 1975 1849 0 13 71 -/+ buffers/cache: 1891 1934 Swap: 4031 111 3920 #time tplot -o out.png -or 1024x768 -k 'CurrentPerHour' 'lines' -k 'RequiredPerHour' 'lines' -if adgroup_delivery_chart.input -tf 'date %Y-%m-%d %H:%M:%OS' tplot: user error (out of memory) real 0m0.026s user 0m0.018s sys 0m0.008s -Manish ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Eugene Kirpichov http://www.linkedin.com/in/eugenekirpichov ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Eugene Kirpichov http://www.linkedin.com/in/eugenekirpichov ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is anyone working on a sparse matrix library in Haskell?
Hi Mark I can work on couple of algorithms if you have anything specific in mind. May be first start with how to represent the matrix and then continue with algorithms. Mukesh Tiwari On Fri, Nov 30, 2012 at 3:33 AM, Mark Flamer m...@flamerassoc.com wrote: I am looking to continue to learn Haskell while working on something that might eventually be useful to others and get posted on Hackage. I have written quite a bit of Haskell code now, some useful and a lot just throw away for learning. In the past others have expressed interest in having a native Haskell sparse matrix and linear algebra library available(not just bindings to a C lib). This in combination with FEM is one of my interests. So my questions, is anyone currently working on a project like this? Does it seem like a good project/addition to the community? I'm also interested if anyone has any other project idea's, maybe even to collaborate on. Thanks -- View this message in context: http://haskell.1045720.n5.nabble.com/Is-anyone-working-on-a-sparse-matrix-library-in-Haskell-tp5721452.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.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] How to incrementally update list
On Sat, Dec 1, 2012 at 1:16 AM, Mark Thom markjordant...@gmail.com wrote: Is there a paper or other single resource that will help me thoroughly understand non-strictness in Haskell? If performance is utterly vital the best resource is Core, as in, the ability to read it. The order of evaluation is all laid out there. Don [1] and Johan [2] have written variously about it. [1] http://stackoverflow.com/questions/6121146/reading-ghc-core [2] http://blog.johantibell.com/2012/02/forcing-values-returned-from-monadic.html -- Kim-Ee On Sat, Dec 1, 2012 at 1:16 AM, Mark Thom markjordant...@gmail.com wrote: Haskell's laziness is tricky to understand coming from imperative languages, but once you figure out its evaluation rules, you'll begin to see the elegance. Is there a paper or other single resource that will help me thoroughly understand non-strictness in Haskell? Once my programs hit a certain level of complexity, their behaviour becomes much harder for me to predict. I've been using the wiki pages up to this point, but apparently they haven't pushed my understanding of laziness nearly far enough. ___ 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] Simple GUI Form
Of course. There is no reason to think that FRP is limited to real-time applications with complicated interactions. (...) there is a somewhat comprehensive tutorial [1] as well as lots of examples [2] linked from the wiki. Thank you for the links. I read it and looked at the examples. It seems you still need to build up the wx gui the same way as using wx directly and be sure it is in sync with the datatype. You just handle the logic with reactive-banana. As there really is almost no logic involved it gives too much overhead, needing to convert all the widgets to behaviors etc. I got the form working in wx, so I'll stick with that for now! Thanks! ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Simple GUI Form
I know it's not wx, but if you were willing to use GTK, you could simply install: http://hackage.haskell.org/package/gtk-jsinput and generate the form automatically as described in: https://github.com/timthelion/gtk-jsinput/blob/master/Graphics/UI/Gtk/Custom/JSInput.hs Cool! Would rather see it generated from the haskell data structure than from json, but you could of cause generate json from the data type. My understand is that GTK applications don't look and feel native on windows/mac, that's why I went for wx, but I could easily be wrong. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to incrementally update list
Why do you want to incrementally update this list a lot of times? The question would affect the answer you get; i.e. some context (non-monadically speaking). :D On Wed, Nov 28, 2012 at 3:43 AM, Branimir Maksimovic bm...@hotmail.com wrote: Problem is following short program: list = [1,2,3,4,5] advance l = map (\x - x+1) l run 0 s = s run n s = run (n-1) $ advance s main = do let s = run 5000 list putStrLn $ show s I want to incrementally update list lot of times, but don't know how to do this. Since Haskell does not have loops I have to use recursion, but problem is that recursive calls keep previous/state parameter leading to excessive stack.and memory usage. I don't know how to tell Haskell not to keep previous state rather to release so memory consumption becomes managable. Is there some solution to this problem as I think it is rather common? ___ 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
[Haskell-cafe] ANN: zeromq3-conduit, Conduit bindings for zeromq3-haskell
Hi, I published zeromq3-conduit, a small library which facilitates using zeromq3-haskell, a binding for ZeroMQ 3.x, in a Conduit-based application. The 'examples' folder in the source repository contains ports of the zeromq3-haskell examples. The library also contains a module which might ease using plain zeromq3-haskell: it lifts some of the IO actions into MonadIO and provides a ReaderT which carries a Context around, so sockets can be created without passing this around explicitly. Package is on Hackage [1] and Github [2]. Comments/feedback/pull requests/... welcome! Nicolas [1] http://hackage.haskell.org/package/zeromq3-conduit [2] https://github.com/NicolasT/zeromq3-conduit/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is anyone working on a sparse matrix library in Haskell?
Thanks for all the replies, It sounds like there is enough interest and even some potential collaborators out there. I have created a few data structures to represent sparse vectors and matrices. The vector was a simple binary tree and the matrix a quad tree. As I suspected a standard IntMap was around 3X as fast as my binary tree, so I have switched to the IntMap for now. I was hoping to hold on to my quad tree for the matrix rep. because I like the elegance of the recursive algorithms like Strassen’s for multiplication. In the end it will most likely be best to have a few different matrix representations anyway. For instance, I know that compressed row form is most efficient for certain algorithms. I have a Gauss iterative solver working currently and am thinking of moving on to a parallel Conjugate gradient or direct solver using LU decomposition. I’m no expert in Haskell or numeric methods but I do my best. I’ll clean up what I have and open up the project on Github or Bitbucket. Any other thoughts or ideas are welcome. I’m currently using the Matrix Market files for testing. It would be nice to benchmark this against an industry standard solver in C or Fortran, without having to do a lot of work to set it up. Does anyone know of an easy way to do this? I’m just trying to get results to compare in orders of magnitude for now. It would be motivating to see these comparisons. -- View this message in context: http://haskell.1045720.n5.nabble.com/Is-anyone-working-on-a-sparse-matrix-library-in-Haskell-tp5721452p5721556.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why Kleisli composition is not in the Monad signature?
Gershom Bazerman wrote: On 11/30/12 10:44 AM, Dan Doel wrote: Lists! The finite kind. This could mean Seq for instance. On Nov 30, 2012 9:53 AM, Brent Yorgey byor...@seas.upenn.edu mailto:byor...@seas.upenn.edu wrote: Any data type which admits structures of arbitrary but *only finite* size has a natural zippy Apply instance but no Applicative (since pure would have to be an infinite structure). The Map instance I mentioned above falls in this category. Though I guess I'm having trouble coming up with other examples, but I'm sure some exist. Maybe Edward knows of other examples. Another common case would be an embedded DSL representing code in a different language, targeting a different platform (or even an FPGA or the like), etc. You can apply `OtherLang (a - b)` to an `OtherLang a` and get an `OtherLang b`, but you clearly can't promote (or lower, I guess) an arbitrary Haskell function into a function in your target language. This is the same reason that GArrows remove the `arr` function (http://www.cs.berkeley.edu/~megacz/garrows/). A fine example! And I am getting the drift... yes, this could be a useful abstraction. Now, on to Bind: the standard finite structure example for Bind is most probably the substitution thingy, i.e. if m :: m a, f :: a - m b, then m = f means replace all elements x :: a in m with f x and then flatten the result so it's an m b again. Like concatMap for lists, right? So, there is no return for that in the Map case for exactly the same reason as with Apply: the unit would have have value id for every possible key, so cannot be finite. So what about an example for Bind\\Monad that is not yet another variation of the finite structure theme? Cheers -- Ben Franksen () ascii ribbon campaign - against html e-mail /\ www.asciiribbon.org - against proprietary attachments ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is anyone working on a sparse matrix library in Haskell?
I look forward to see what comes of this! On Fri, Nov 30, 2012 at 4:58 PM, Mark Flamer m...@flamerassoc.com wrote: Thanks for all the replies, It sounds like there is enough interest and even some potential collaborators out there. I have created a few data structures to represent sparse vectors and matrices. The vector was a simple binary tree and the matrix a quad tree. As I suspected a standard IntMap was around 3X as fast as my binary tree, so I have switched to the IntMap for now. I was hoping to hold on to my quad tree for the matrix rep. because I like the elegance of the recursive algorithms like Strassen’s for multiplication. In the end it will most likely be best to have a few different matrix representations anyway. For instance, I know that compressed row form is most efficient for certain algorithms. I have a Gauss iterative solver working currently and am thinking of moving on to a parallel Conjugate gradient or direct solver using LU decomposition. I’m no expert in Haskell or numeric methods but I do my best. I’ll clean up what I have and open up the project on Github or Bitbucket. Any other thoughts or ideas are welcome. I’m currently using the Matrix Market files for testing. It would be nice to benchmark this against an industry standard solver in C or Fortran, without having to do a lot of work to set it up. Does anyone know of an easy way to do this? I’m just trying to get results to compare in orders of magnitude for now. It would be motivating to see these comparisons. -- View this message in context: http://haskell.1045720.n5.nabble.com/Is-anyone-working-on-a-sparse-matrix-library-in-Haskell-tp5721452p5721556.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.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] computation over containers, greatly simplified notation.
Dear everyone, After a number of attempts [1] I'm starting to think that my initial approach was ill-directed. After all, Functor, Applicative, Zip are three different classes. Functors are type constructors where you can map unary functions over them. Applicatives are those with map-over of zero-ary functions (pure,) unary functions, binary functions, ternary functions, ... etc. Zip are those with unary, binary, ternary ... mapover, but not zero-ary map-over. Repa Arrays and Vectors belong to Zip because there's no trivial unique way to implement pure. What the customer really needed [2] seems to be the following series of functions: forLiftZ1 :: Zip f = f a - (a - b) - f b forLiftZ2 :: Zip f = f a - f b - (a - b - c) - f c forLiftZ3 :: Zip f = f a - f b - f c - (a - b - c - d) - f d Now I'm trying if it's possible to implement the series in a single shot [3] . I'm reporting my progress for anyone who might be still thinking for me. Thank you!! [1] https://github.com/nushio3/practice/tree/master/free-objects [2] http://www.projectcartoon.com/cartoon/3 [3] https://github.com/nushio3/practice/blob/master/free-objects/printf6.hs 2012/11/29 Takayuki Muranushi muranu...@gmail.com Dear all, I came up with an idea to greatly simplify some kinds of array computations. It should work well with many kinds of arrays. Is this new? https://gist.github.com/4162375 These few days, I've been trying to rewrite a hydrodynamic simulation code that used Data.Vector (~250 lines), to Repa [1] . It seemed promising, but soon I realized that I needed to use Repa.map and Repa.zipWith almost everywhere. I need careful thinking to transform every lines (that used vector's indexing) to Repa's point-free stile. Is there any better ways? Then I realized that I was the author of Paraiso [2], a DSL for stencil computation. One of its feature is to write down array computation just as if it were scalar computation. Basically what I need is ZipList-like Applicative instances for vectors and Repa arrays. Why not they support ZipVector? Because 'pure' of zipList was an infinite list and you can't do infinite vectors. Then I came up with this idea. https://gist.github.com/4162375 the wrapper W does several things: it represents the 'pure,' homogeneous array in a space-efficient manner, and also serves as a newtype-wrapper of Num (and possibly Fractional, Floating...) instances. Questions are: is this technology new? or promising? doomed? It seems to me like a free-Applicative, like the free-Monad theory. Are they related? The function 'backend' helps to mix in the non-zip-like computations. How can we remove the 'undefined' in the 'backend?' Some of Repa computations are Monads. W needs to be a monad transformer to incooperate this. Also I'm grateful to past cafe discussion on existing Zippable implementations [3][4] . [1] hackage.haskell.org/package/repa [2] http://hackage.haskell.org/package/Paraiso [3] http://www.haskell.org/pipermail/haskell-cafe/2009-July/064403.html [4] http://hackage.haskell.org/packages/archive/category-extras/latest/doc/html/Control-Functor-Zip.html -- Takayuki MURANUSHI The Hakubi Center for Advanced Research, Kyoto University http://www.hakubi.kyoto-u.ac.jp/02_mem/h22/muranushi.html -- Takayuki MURANUSHI The Hakubi Center for Advanced Research, Kyoto University http://www.hakubi.kyoto-u.ac.jp/02_mem/h22/muranushi.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] computation over containers, greatly simplified notation.
You might find this paper an interesting read: http://www.brics.dk/RS/01/10/ On Fri, Nov 30, 2012 at 4:43 PM, Takayuki Muranushi muranu...@gmail.comwrote: Dear everyone, After a number of attempts [1] I'm starting to think that my initial approach was ill-directed. After all, Functor, Applicative, Zip are three different classes. Functors are type constructors where you can map unary functions over them. Applicatives are those with map-over of zero-ary functions (pure,) unary functions, binary functions, ternary functions, ... etc. Zip are those with unary, binary, ternary ... mapover, but not zero-ary map-over. Repa Arrays and Vectors belong to Zip because there's no trivial unique way to implement pure. What the customer really needed [2] seems to be the following series of functions: forLiftZ1 :: Zip f = f a - (a - b) - f b forLiftZ2 :: Zip f = f a - f b - (a - b - c) - f c forLiftZ3 :: Zip f = f a - f b - f c - (a - b - c - d) - f d Now I'm trying if it's possible to implement the series in a single shot [3] . I'm reporting my progress for anyone who might be still thinking for me. Thank you!! [1] https://github.com/nushio3/practice/tree/master/free-objects [2] http://www.projectcartoon.com/cartoon/3 [3] https://github.com/nushio3/practice/blob/master/free-objects/printf6.hs 2012/11/29 Takayuki Muranushi muranu...@gmail.com Dear all, I came up with an idea to greatly simplify some kinds of array computations. It should work well with many kinds of arrays. Is this new? https://gist.github.com/4162375 These few days, I've been trying to rewrite a hydrodynamic simulation code that used Data.Vector (~250 lines), to Repa [1] . It seemed promising, but soon I realized that I needed to use Repa.map and Repa.zipWith almost everywhere. I need careful thinking to transform every lines (that used vector's indexing) to Repa's point-free stile. Is there any better ways? Then I realized that I was the author of Paraiso [2], a DSL for stencil computation. One of its feature is to write down array computation just as if it were scalar computation. Basically what I need is ZipList-like Applicative instances for vectors and Repa arrays. Why not they support ZipVector? Because 'pure' of zipList was an infinite list and you can't do infinite vectors. Then I came up with this idea. https://gist.github.com/4162375 the wrapper W does several things: it represents the 'pure,' homogeneous array in a space-efficient manner, and also serves as a newtype-wrapper of Num (and possibly Fractional, Floating...) instances. Questions are: is this technology new? or promising? doomed? It seems to me like a free-Applicative, like the free-Monad theory. Are they related? The function 'backend' helps to mix in the non-zip-like computations. How can we remove the 'undefined' in the 'backend?' Some of Repa computations are Monads. W needs to be a monad transformer to incooperate this. Also I'm grateful to past cafe discussion on existing Zippable implementations [3][4] . [1] hackage.haskell.org/package/repa [2] http://hackage.haskell.org/package/Paraiso [3] http://www.haskell.org/pipermail/haskell-cafe/2009-July/064403.html [4] http://hackage.haskell.org/packages/archive/category-extras/latest/doc/html/Control-Functor-Zip.html -- Takayuki MURANUSHI The Hakubi Center for Advanced Research, Kyoto University http://www.hakubi.kyoto-u.ac.jp/02_mem/h22/muranushi.html -- Takayuki MURANUSHI The Hakubi Center for Advanced Research, Kyoto University http://www.hakubi.kyoto-u.ac.jp/02_mem/h22/muranushi.html ___ 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] Can a GC delay TCP connection formation?
On 11/30/2012 1:29 PM, Bryan O'Sullivan wrote: On Tue, Nov 27, 2012 at 11:02 AM, Jeff Shaw shawj...@gmail.com mailto:shawj...@gmail.com wrote: Once each minute, a thread of my program updates a global state, stored in an IORef, and updated with atomicModifyIORef', based on query results via HDBC-obdc. Incidentally, what kind of database are you talking to? Issues of FFI correctness aside, HDBC is in general terribly slow compared to some of the more DB-specific bindings. I'm connecting to a MS SQL Server 2008 R2 DBMS via Free TDS. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why Kleisli composition is not in the Monad signature?
Ben, Now, on to Bind: the standard finite structure example for Bind is most probably the substitution thingy ... Danger of conflating a bunch of things here: (1) the substitution monadic effect is always also applicative and always also unital/pointed because monads are always applicative and pointed. (2) the zippy applicative effect is NOT monadic (see main applicative paper) (3) for finite structures, there's even a pre-applicative-but-still-zippy-ish Apply effect that's apparently NOT unital/pointed. I don't know of any results that crystallize this intuition about finite/infinite cleanly distributing itself into Applicative and Apply bins. (4) all the above has thus far been functors! Gershom has explained a use case where Apply isn't even one. HTH, -- Kim-Ee On Sat, Dec 1, 2012 at 5:00 AM, Ben Franksen ben.frank...@online.de wrote: Gershom Bazerman wrote: On 11/30/12 10:44 AM, Dan Doel wrote: Lists! The finite kind. This could mean Seq for instance. On Nov 30, 2012 9:53 AM, Brent Yorgey byor...@seas.upenn.edu mailto:byor...@seas.upenn.edu wrote: Any data type which admits structures of arbitrary but *only finite* size has a natural zippy Apply instance but no Applicative (since pure would have to be an infinite structure). The Map instance I mentioned above falls in this category. Though I guess I'm having trouble coming up with other examples, but I'm sure some exist. Maybe Edward knows of other examples. Another common case would be an embedded DSL representing code in a different language, targeting a different platform (or even an FPGA or the like), etc. You can apply `OtherLang (a - b)` to an `OtherLang a` and get an `OtherLang b`, but you clearly can't promote (or lower, I guess) an arbitrary Haskell function into a function in your target language. This is the same reason that GArrows remove the `arr` function (http://www.cs.berkeley.edu/~megacz/garrows/). A fine example! And I am getting the drift... yes, this could be a useful abstraction. Now, on to Bind: the standard finite structure example for Bind is most probably the substitution thingy, i.e. if m :: m a, f :: a - m b, then m = f means replace all elements x :: a in m with f x and then flatten the result so it's an m b again. Like concatMap for lists, right? So, there is no return for that in the Map case for exactly the same reason as with Apply: the unit would have have value id for every possible key, so cannot be finite. So what about an example for Bind\\Monad that is not yet another variation of the finite structure theme? Cheers -- Ben Franksen () ascii ribbon campaign - against html e-mail /\ www.asciiribbon.org - against proprietary attachments ___ 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
