Re: [Haskell-cafe] Any Haskell events in Madrid next week?
Hi, There is a workshop on Functional Programming and also a conference on programming languages http://babel.ls.fi.upm.es/tpf2013/cfp_english.txt If interested, you can contact the organizers... Regards, Salvador. El 06/09/13 22:59, Joachim Breitner escribió: Hi, I'll be visiting Madrid next week (research visit) and I'm wondering if there are any Haskell or FP Group meeting or other events that might be interesting? I could possibly contribute a talk. (Both preferably in English.) Wednesday or Thursday evening might would most convenient. Greetings, Joachim ___ 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] Performance of delete-and-return-last-element
Suppose I need to get an element from a data structure, and also modify the data structure. For example, I might need to get and delete the last element of a list: darle xs = ((last xs), (rmlast xs)) where rmlast [_] = [] rmlast (y:ys) = y:(rmlast ys) There are probably other and better ways to write rmlast, but I want to focus on the fact that darle here, for lack of a better name off the top of my head, appears to traverse the list twice. Once to get the element, and once to remove it to produce a new list. This seems bad. Especially for large data structures, I don't want to be traversing twice to do what ought to be one operation. To fix it, I might be tempted to write something like: darle' [a] = (a, []) darle' (x:xs) = let (a, ys) = darle' xs in (a, (x:ys)) But this version has lost its elegance. It was also kind of harder to come up with, and for more complex data structures (like the binary search tree) the simpler expression is really desirable. Can a really smart compiler transform/optimize the first definition into something that traverses the data structure only once? Can GHC? - Lucas ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Examples of MVars usage
Hi Francisco, You can try GitHub's code search https://github.com/search?l=Haskellq=mvarref=cmdformtype=Code Cheers, --Lucas 2013/6/12 Francisco M. Soares Nt. xfrancisco.soa...@gmail.com Hello, everyone. I am looking for packages on hackage which use MVars extensively. Those which create plenty of MVars -- not just one or two for conditional synchronization or to keep track of a value throughout the program. My purpose is to analyze usage patterns of MVars. Does anybody have any suggestions? So far I have analyzed a few packages: * conjure (0.1) * distributed-process (0.4.2) * distributed-process-p2p (0.1.1.0) * leksah (0.12.1.3) * manatee-core (0.1.1) * urlcheck (0.1.1) Nonetheless, I feel like I still haven't covered a good enough range of usage, since some examples are small, and some use MVars just for a small number of cases, while the heavy lifting is done with STM. And surely because there are only 6 of them. Any suggestion will be very much appreciated. []'s -- Francisco Soares Nt. ___ 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] [ANN] Haskell-Paris meetup
Dear all, I'm happy to announce that the Haskell-Paris group will meet on June 25th in Paris. Please register (free) at http://www.meetup.com/haskell-paris/events/122515522/ . Program is not decided yet (contributions are welcome). We'll update once we know the lineup. I don't like to send spammy emails but I would like to take advantage of this announcement to invite any non-Parisian Haskellers to get in touch with us (email, twitter, or meetup page) if you are in town. We may an event scheduled close in time and we can anyway propose a get-together in a restaurant so that visitors can taste our great fooddrink and everyone can chat about her favorite programming language. I did this type of semi-planned dinners a few times with some Ruby folks and it's a good way to build ties :). Regards, --Lucas DiCioccio ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] [announce] second Haskell meetup in Paris
Hi, I am pleased to annouce that I'm bootstrapping a Haskell-enthusiastics group in Paris. We recently scheduled our second Haskell meetup in Paris. This meetup will take place next Monday (Monday, January 14, 2013). AF83 ( http://af83.com/ ) has been kind enough to offer us a room for our meeting. You don't have to, but it is recommended to, register for the meetup on http://meetup.haskell-paris.fr/ or by sending me an email. The website for our group is http://haskell-paris.fr/ (in French). You should pay it a click not only because it's written in Haskell but also to glance at our logo, propose a talk, or read the digest of past meetup(s). Regards, --Lucas DiCioccio ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] haskell platform - mac lion - installation error
Dear Peter, I recently had a similar problem with the same Haskell Platform version but on a Macmini (running Lion as well). I learnt that you have to install the 'command line tools' by using the 'preferences' of your XCode installation. After that, everything will work. Best regards, Salvador. El 10/03/12 10:15, Peter escribió: Hello - I'm a new user, having some trouble installing the Haskell Platform (2011.4.0.0 64bit.pkg) on a Macbook Pro (10.7.3). I installed Xcode 4.3.1 (4E1019), then the Haskell Platform. When I double-click on the Platform package icon, I get an installation dialogue with an error message reading Developer Tools Missing - Please install Xcode developer tools first. Are Xcode developer tools something distinct from Xcode itself? I'm mystified by this error message. Any assistance would be greatly appreciated - thank you. ___ 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] conflicting variable definitions in pattern
Dear Martin, I think that the (practical) reason is avoiding equality checks during pattern matching. For instance, how do you evaluate this: foo ((+1):(1+):[])? Both expressions in the first and second entries of the list are semantically equivalent, but from an operational point of view, you have to ensure the equality of two functions over an infinite domain (of integer numbers). Best regards, Salvador. Martin Hofmann escribió: It is pretty clear, that the following is not a valid Haskell pattern: foo (x:x:xs) = x:xs My questions is _why_ this is not allowed. IMHO, the semantics should be clear: The pattern is expected to succeed, iff 'x' is each time bound to the same term. Isn't this allowed, because this would require a strict evaluation of the 'x' variables? Thanks, Martin ___ 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] Program using 500MB RAM to process 5MB file
On Fri, Apr 03, 2009 at 10:22:07AM +0200, Ketil Malde wrote: lu...@die.net.au writes: I'm relatively new to haskell so as one does, I am rewriting an existing program in haskell to help learn the language. However, it eats up all my RAM whenever I run the program. This typically happens to me when I parse large files and either am a) using a parser that is too strict (like Luke says) or b) using a parser that is too lazy - or rather, it parses into a lazy data structure which is then populated with unevaluated thunks holding onto the input data. Thanks for all the help everyone . I've decided to dump Parsec, as the file structure is simple enough to implement using basic list manipulation (which is, I've read, one of haskell's strong points) and has turned out to be much simpler code. I think I was reading the write your own scheme tutorial when I started writing that code, so natually started using parsec. As a side note, I was reading the I/O section of RWH last night and came across the lazy vs. strict I/O part, however it didn't occur to me that Parsec was strict. Anyway, thanks for all the help and suggestions. -- Lucas Hazel lu...@die.net.au pgp5StOlyFrnV.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Program using 500MB RAM to process 5MB file
On Fri, Apr 03, 2009 at 10:27:08PM +1100, lu...@die.net.au wrote: On Fri, Apr 03, 2009 at 10:22:07AM +0200, Ketil Malde wrote: lu...@die.net.au writes: I'm relatively new to haskell so as one does, I am rewriting an existing program in haskell to help learn the language. However, it eats up all my RAM whenever I run the program. Thanks for all the help everyone . I've decided to dump Parsec, as the file structure is simple enough to implement using basic list manipulation (which is, I've read, one of haskell's strong points) and has turned out to be much simpler code. Using lazy I/O has reduced run time by 75% and RAM consumption to 3MB Thank you :) -- Lucas Hazel lu...@die.net.au pgpPMNEI3nA3B.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Program using 500MB RAM to process 5MB file
I'm relatively new to haskell so as one does, I am rewriting an existing program in haskell to help learn the language. However, it eats up all my RAM whenever I run the program. http://hpaste.org/fastcgi/hpaste.fcgi/view?id=3175#a3175 Obviously I'm doing something wrong, but without my magical FP pants I don't know what that might be. -- Lucas Hazel lu...@die.net.au pgpCpy889Gy8E.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Program using 500MB RAM to process 5MB file
On Thu, Apr 02, 2009 at 07:55:07PM -0400, Rick R wrote: You could profile your app for memory usage. Then you could figure out just what function is blowing up the mem usage and figure out how to optimize it. http://book.realworldhaskell.org/read/profiling-and-optimization.html 2009/4/2 lu...@die.net.au I'm relatively new to haskell so as one does, I am rewriting an existing program in haskell to help learn the language. However, it eats up all my RAM whenever I run the program. http://hpaste.org/fastcgi/hpaste.fcgi/view?id=3175#a3175 Obviously I'm doing something wrong, but without my magical FP pants I don't know what that might be. I ran some profiling as suggested, [SNIP] total time =8.36 secs (418 ticks @ 20 ms) total alloc = 3,882,593,720 bytes (excludes profiling overheads) COST CENTREMODULE %time %alloc line PkgDb 89.7 93.5 COST CENTRE MODULE no. entries %time %alloc %time %alloc linePkgDb 305 109771 89.7 93.3 89.7 93.3 [SNIP] The line function is part of the file parser line :: Parser String line = anyChar `manyTill` newline files' :: Parser Files files' = line `manyTill` newline Perhaps I should also explain the structure of the file. It's for a simple package manager called pkgutils, used for CRUX[1]. The file contains information for all the packages installed and is structured as follows package name package version file file ... file package name ... From profiling it shows that the memory is simple consumed by reading in all the lines, the graph from using -p -hd shows an almost Ologn2 growth of the heap as the collection of lines grows. Is there a better way to do this? [1] http://crux.nu -- Lucas Hazel lu...@die.net.au pgplYxxA2pBsy.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Question on case x of g when g is a function
Because both bit0 and bit1 are free *local* variables within the case expression. So, they have nothing to do with your defined functions bit0 and bit1. Best regards, Salvador. [EMAIL PROTECTED] wrote: Can a kind soul please enlighten me on why f bit0 and f bit1 both return 0? bit0 = False bit1 = True f x = case x of bit0 - 0 bit1 - 1 ___ 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
