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• Need simple advice for graph solving problem

  - by sap

  Hi there, a collegue of mine proposed to me an exercise from an online judge website, which is basically a graph solving problem of an evacuation plan on a small town. i dont need the answer (nor do i want it) i just need an advice on which is the best approach to solving it since im kinda new to these kind of problems. the problem consists of town buildings with workers and fallout shelters in case of a nuclear attack. i have to build an algorithm that will assign the workers of each building to one or more fallout shelters but in a way that some shelters wont became too overcrowded while others remain almost empty (else i would just make the workers go to the nearest one). the problem is this: http://acm.timus.ru/problem.aspx?space=1&num=1237 in case its offline heres the google cached version of it: http://webcache.googleusercontent.com/search?q=cache:t2EPCzezs7AJ:acm.timus.ru/problem.aspx%3Fspace%3D1%26num%3D1237+vladimir+kotov+evacuation+problem&cd=1&hl=pt-PT&ct=clnk&gl=pt what i've done so far is for each building get the nearest shelter and move the number of workers from that build equal to the shelter capacity. then move to the next building. but sometimes the number of workers is greater than the shelter capacity, in that case after i iterate through every building, ill just iterate then again apllying the same algorithm until every building has 0 workers in it, problem is this is hardly the best way to solve it. any tip is welcome, please dont feel like im asking for the answer, i just want an advice in the right direction of solving it. thanks in advance.

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• Thread-local storage segfaults on NetBSD only?

  - by bortzmeyer

  Trying to run a C++ program, I get segmentation faults which appear to be specific to NetBSD. Bert Hubert wrote the simple test program (at the end of this message) and, indeed, it crashes only on NetBSD. % uname -a NetBSD golgoth 5.0.1 NetBSD 5.0.1 (GENERIC) #0: Thu Oct 1 15:46:16 CEST 2009 +stephane@golgoth:/usr/obj/sys/arch/i386/compile/GENERIC i386 % g++ --version g++ (GCC) 4.1.3 20080704 prerelease (NetBSD nb2 20081120) Copyright (C) 2006 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. % gdb thread-local-storage-powerdns GNU gdb 6.5 Copyright (C) 2006 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "i386--netbsdelf"... (gdb) run Starting program: /home/stephane/Programmation/C++/essais/thread-local-storage-powerdns Program received signal SIGSEGV, Segmentation fault. 0x0804881b in main () at thread-local-storage-powerdns.cc:20 20 t_a = new Bogo('a'); (gdb) On other Unix, it works fine. Is there a known issue in NetBSD with C++ thread-local storage? #include <stdio.h> class Bogo { public: explicit Bogo(char a) { d_a = a; } char d_a; }; __thread Bogo* t_a; int main() { t_a = new Bogo('a'); Bogo* b = t_a; printf("%c\n", b->d_a); }

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• error detection/correction/recovery in serial protocols

  - by Jason S

  I have some designing to do for a serial protocol and am running into some questions that I figure must have been considered elsewhere. So I'm wondering if there are some recommendations for best practices in designing serial protocols. (Please either state a fact that is easily verifiable, or cite a reputable source if you make a claim.) General recommendations for websites/books are also welcome. In particular I have to deal with issues like parsing a stream of bytes into packets verifying a packet is correct (easy with a CRC, for instance) identifying reasonable types of errors that can occur (e.g. in a point-to-point serial stream, sporadic single bit errors, and dropped series of bytes, are both likely, but extra phantom bytes are unlikely; whereas with a record stored in flash memory or on a disk drive the types of errors that predominate are different) error correction or recovery (if I detect an error in a packet, can I correct it? If not, can I resync to the boundary of the next packet?) how to make variable-length packets robust to error correction / recovery. Any suggestions?

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• ssh_exchange_identification: Connection closed by remote host under Git bash

  - by MoreFreeze

  I work at win7 and set up git server with sshd. I git --bare init myapp.git, and clone ssh://git@localhost/home/git/myapp.git in Cywgin correctly. But I need config git of Cygwin again, I want to git clone in Git Bash. I run "git clone ssh://git@localhost/home/git/myapp.git" and get following message ssh_exchange_identification: Connection closed by remote host then I run "ssh -vvv git@localhost" in Git Bash and get message debug2: ssh_connect: needpriv 0 debug1: Connecting to localhost [127.0.0.1] port 22. debug1: Connection established. debug1: identity file /c/Users/MoreFreeze/.ssh/identity type -1 debug3: Not a RSA1 key file /c/Users/MoreFreeze/.ssh/id_rsa. debug2: key_type_from_name: unknown key type '-----BEGIN' debug3: key_read: missing keytype debug3: key_read: missing whitespace // above it repeats 24 times debug2: key_type_from_name: unknown key type '-----END' debug3: key_read: missing keytype debug1: identity file /c/Users/MoreFreeze/.ssh/id_rsa type 1 debug1: identity file /c/Users/MoreFreeze/.ssh/id_dsa type -1 ssh_exchange_identification: Connection closed by remote host it seems my private keys has wrong format? And I find that there are exactly 25 line in private keys without "BEGIN" and "END". I'm confused why it said NOT RSA1 key, I totally ensure it is RSA 2 key. Any advises are welcome. btw, I have read first 3 pages on google about this problem.

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• Space-saving character encoding for japanese?

  - by Constantin

  In my opinion a common problem: character encoding in combination with a bitmap-font. Most multi-language encodings have an huge space between different character types and even a lot of unused code points there. So if I want to use them I waste a lot of memory (not only for saving multi-byte text - i mean specially for spaces in my bitmap-font) - and VRAM is mostly really valuable... So the only reasonable thing seems to be: Using an custom mapping on my texture for i.e. UTF-8 characters (so that no space is waste). BUT: This effort seems to be same with use an own proprietary character encoding (so also own order of characters in my texture). In my specially case I got texture space for 4096 different characters and need characters to display latin languages as well as japanese (its a mess with utf-8 that only support generall cjk codepages). Had somebody ever a similiar problem (I really wonder, if not)? If theres already any approach? Edit: The same Problem is described here http://www.tonypottier.info/Unicode_And_Japanese_Kanji/ but it doesnt provide an real solution how to save these bitmapfont mappings to utf-8 space efficent. So any further help is welcome!

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• Project Euler problem 214, How can i make it more efficient?

  - by Once

  I am becoming more and more addicted to the Project Euler problems. However since one week I am stuck with the #214. Here is a short version of the problem: PHI() is Euler's totient function, i.e. for any given integer n, PHI(n)=numbers of k<=n for which gcd(k,n)=1. We can iterate PHI() to create a chain. For example starting from 18: PHI(18)=6 = PHI(6)=2 = PHI(2)=1. So starting from 18 we get a chain of length 4 (18,6,2,1) The problem is to calculate the sum of all primes less than 40e6 which generate a chain of length 25. I built a function that calculates the chain length of any number and I tested it for small values: it works well and fast. sum of all primes<=20 which generate a chain of length 4: 12 sum of all primes<=1000 which generate a chain of length 10: 39383 Unfortunately my algorithm doesn't scale well. When I apply it to the problem, it takes several hours to calculate... so I stop it because the Project Euler problems must be solved in less than one minute. I thought that my prime detection function might be slow so I fed the program with a list of primes <40e6 to avoid the primality test... The code runs now a little bit faster, but there is still no way to get a solution in less than a few hours (and I don't want this). So is there any "magic trick" that I am missing here ? I really don't understand how to be more efficient on this one... I am not asking for the solution, because fighting with optimization is all the fun of Project Euler. However, any small hint that could put me on the right track would be welcome. Thanks !

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• Reducing moire when downsampling halftone comic images.

  - by drawnonward

  How can I reduce moire effects when downsampling halftone comic book images during live zoom on an iPhone or iPad? I am writing a comic book viewer. It would be nice to provide higher resolution images and allow the user to zoom in while reading the comic book. However, my client is averse to moire effects and will not allow this feature if there are noticeable moire artifacts while zooming, which of course there are. Modifying the images to be less susceptible to moire would only work if the modifications were not perceptible. Blur was specifically prohibited, as is anything that removes the beloved halftone dots. The images are black and white halftone and line art. The originals are 600 dpi but what we ship with the application will be half that at best, so probably 2500 pixels or less tall. So what are my options? If I write a custom downsampling algorithm would it be fast enough for real time on these devices? Are there other tricks I can do? Would it work to just avoid the size ratios that have the most visual moire effects? As you zoom in an out, there are definitely peaks where the moire effects are worst. Is there a way to calculate what those points are and just zoom to a nearby scale that is not as bad? Any suggestions are welcome. I have very little experience with image and signal processing, but am enjoying the opportunity to learn. I know nothing of wavelets and acutance and other jargon, so please be verbose.

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• Why wont this compile its killing me. (java)

  - by Ryan The Leach

  import java.util.*; public class Caesar { public static void main(String [] args) { final boolean DEBUG = false; System.out.println("Welcome to the Caesar Cypher"); System.out.println("----------------------------"); Scanner keyboard = new Scanner (System.in); System.out.print("Enter a String : "); String plainText = keyboard.nextLine(); System.out.print("Enter an offset: "); int offset = keyboard.nextInt(); String cipherText = ""; for(int i=0;i<plainText.length();i++) { int chVal = plainText.charAt(i); if (DEBUG) {int debugchVal = chVal;} chVal +=offset; if (DEBUG) {System.out.print(chVal + "\t");} while (chVal <32 || chVal > 127) { if (chVal < 32) chVal += 96; if (chVal > 127) chVal -= 96; if(DEBUG) {System.out.print(chVal+" ");} } if (DEBUG) {System.out.println();} char c = (char) chVal; cipherText = cipherText + c; if (DEBUG) {System.out.println(i + "\t" + debugchVal + "\t" + chVal + "\t" + c + "\t" + cipherText);} } System.out.println(cipherText); } }

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• Python subprocess Popen.communicate() equivalent to Popen.stdout.read()?

  - by Christophe

  Very specific question (I hope): What are the differences between the following three codes? (I expect it to be only that the first does not wait for the child process to be finished, while the second and third ones do. But I need to be sure this is the only difference...) I also welcome other remarks/suggestions (though I'm already well aware of the shell=True dangers and cross-platform limitations) Note that I already read Python subprocess interaction, why does my process work with Popen.communicate, but not Popen.stdout.read()? and that I do not want/need to interact with the program after. Also note that I already read Alternatives to Python Popen.communicate() memory limitations? but that I didn't really get it... First code: from subprocess import Popen, PIPE def exe_f(command='ls -l', shell=True): "Function to execute a command and return stuff" process = Popen(command, shell=shell, stdout=PIPE, stderr=PIPE) stdout = process.stdout.read() stderr = process.stderr.read() return process, stderr, stdout Second code: from subprocess import Popen, PIPE from subprocess import communicate def exe_f(command='ls -l', shell=True): "Function to execute a command and return stuff" process = Popen(command, shell=shell, stdout=PIPE, stderr=PIPE) (stdout, stderr) = process.communicate() return process, stderr, stdout Third code: from subprocess import Popen, PIPE from subprocess import wait def exe_f(command='ls -l', shell=True): "Function to execute a command and return stuff" process = Popen(command, shell=shell, stdout=PIPE, stderr=PIPE) code = process.wait() stdout = process.stdout.read() stderr = process.stderr.read() return process, stderr, stdout Thanks.

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• Using layout view in Express with Consolidate and Mustache

  - by Raphael Caixeta

  I just started going through Node using Express and finally got Consolidate JS working properly to use Mustache as the templating view system per the instructions on the Consolidate JS Github page. Mustache is loading properly, but I'm now wondering how to include the layout file along in the rendering of the template. The default Jade system loads the content of the .render method inside of the layout.jade file. I'm just wondering how to do the same, but with Mustache. Any help is greatly appreciated! Code: index.js exports.index = function(req, res){ res.render('index', { title: "Work pl0x?" }); }); index.mustache Welcome to {{title}} I just want the index.mustache content to come in the "{{content}}" portion of the code below (layout.mustache). How can I do this? <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta charset="UTF-8" /> <title>Project Name | {{title}}</title> <link href="/stylesheets/style.css" rel="stylesheet" /> </head> <body> {{content}} </body> </html>

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• What java web application framework to use?

  - by frohiky

  One of the main products of my company is an Oracle Forms (and Reports) based application, that "needs" to be re-written in another technology. Why? Users want a more rich interface experience, and we want, preferably, to reduce costs with an open source application server. For this (HUGE) project, we intend to use a java web application framework, keep these points in mind: We have: hundreds of tables on our database (the ORM must be as flexible as possible); some logic which is (and will still be) based on PL/SQL procedures/functions/packages; a lot of CRUDs (the application itself is of an considerable size); a demand to work with/generate documents and workflows; an intranet based user environment; We want: to offer a RIA interface experience; use (if possible) an open source app server; a rapid (as possible) development framework; a somewhat mature framework with a "wise" roadmap (and a considerable community support); a MVC approach combined with JS or GWT widgets (e.g. Vaadin or SmartGWT); Well, in the past weeks I've read a lot of posts, Q&As on stackoverflow, and much more: Wicket, JSF, Tapestry, Grails, GWT, Struts2, Play, Spring, Seam, Echo, .... the list goes on! I've even researched about Alfresco..! The obvious question: Which one to use? At this time, any insight, recommendation, shared experience, advice will be more then welcome!

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• Is It Incorrect to Make Domain Objects Aware of The Data Access Layer?

  - by Noah Goodrich

  I am currently working on rewriting an application to use Data Mappers that completely abstract the database from the Domain layer. However, I am now wondering which is the better approach to handling relationships between Domain objects: Call the necessary find() method from the related data mapper directly within the domain object Write the relationship logic into the native data mapper (which is what the examples tend to do in PoEAA) and then call the native data mapper function within the domain object. Either it seems to me that in order to preserve the 'Fat Model, Skinny Controller' mantra, the domain objects have to be aware of the data mappers (whether it be their own or that they have access to the other mappers in the system). Additionally it seems that Option 2 unnecessarily complicates the data access layer as it creates table access logic across multiple data mappers instead of confining it to a single data mapper. So, is it incorrect to make the domain objects aware of the related data mappers and to call data mapper functions directly from the domain objects? Update: These are the only two solutions that I can envision to handle the issue of relations between domain objects. Any example showing a better method would be welcome.

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• How to call a service operation at a REST style WCF endpoint uri?

  - by Dieter Domanski

  Hi, is it possible to call a service operation at a wcf endpoint uri with a self hosted service? I want to call some default service operation when the client enters the endpoint uri of the service. In the following sample these uris correctly call the declared operations (SayHello, SayHi): - http://localhost:4711/clerk/hello - http://localhost:4711/clerk/hi But the uri - http://localhost:4711/clerk does not call the declared SayWelcome operation. Instead it leads to the well known 'Metadata publishing disabled' page. Enabling mex does not help, in this case the mex page is shown at the endpoint uri. private void StartSampleServiceHost() { ServiceHost serviceHost = new ServiceHost(typeof(Clerk), new Uri( "http://localhost:4711/clerk/")); ServiceEndpoint endpoint = serviceHost.AddServiceEndpoint(typeof(IClerk), new WebHttpBinding(), ""); endpoint.Behaviors.Add(new WebHttpBehavior()); serviceHost.Open(); } [ServiceContract] public interface IClerk { [OperationContract, WebGet(UriTemplate = "")] Stream SayWelcome(); [OperationContract, WebGet(UriTemplate = "/hello/")] Stream SayHello(); [OperationContract, WebGet(UriTemplate = "/hi/")] Stream SayHi(); } public class Clerk : IClerk { public Stream SayWelcome() { return Say("welcome"); } public Stream SayHello() { return Say("hello"); } public Stream SayHi() { return Say("hi"); } private Stream Say(string what) { string page = @"<html><body>" + what + "</body></html>"; return new MemoryStream(Encoding.UTF8.GetBytes(page)); } } Is there any way to disable the mex handling and to enable a declared operation instead? Thanks in advance, Dieter

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• Easiest RPC client method in PHP

  - by T.K.

  I've been asked to help a friend's company to bring up a web application. I have very limited time and I reluctantly accepted the request, at one condition. As most of the logic goes on in the back-end, I suggested that I would finish the complete back-end only, allowing a front-end developer to simply interface with my backend. I plan to do the back-end in Java EE or Python (with Pylons). It does not really matter at this point. I plan to have my back-end completely ready and unit-tested, so that my input will hardly be needed after my work is done. I know they have a PHP programmer, but as far as I could tell he is a real rookie. I want him to basically interface with my backend's services in the easiest possible way, with no way of him "stuffing" it up. It's basically a CRUD-only application. I could implement the backend as accessible through a webservice such as XML-RPC or SOAP. Even a RESTful API could be possible. However, my main objective is to make something that complete "noob" PHP programmer can easily interface with without getting confused. Preferably I do not even want to talk to him because I generally have an extremely busy schedule, and doing "support calls" is not something I am willing to do. Which approach should I choose? I would welcome any suggestions and inputs!

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• Which CMS do I need? Needs to be easy to post a certain kind of post

  - by Vian Esterhuizen

  Hi, I'm creating a site for a video store and it needs to be CMS. I'm doing this for free so I need to use a free CMS like Wordpress, Drupal or Joomla. Do I need a new CMS, a plugin or some PHP of my own? What I need: User accounts Categories Custom post Here's the site as it stands with WP: http://sundancevideo.ca. Right now an experimental site to try to work this out. What I've done now, is created a "Draft" that includes a template table with images and text and so on. The user would then have to copy everything, past into a new post and replace necessary. This really isn't working well. As you may notice by the condition of the posts. What I would prefer is if it was integrated into the WP UI. Like a field for "Description" and field for "Image" where they can upload the images as necessary. This would then generate post, with a table including all the information and images, for as many movies that were added in the UI. Please ask if I'm not being clear. Please help, any suggestions are welcome. Thank you, Vian

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• How can we best represent the SDLC process as a board game?

  - by Innogetics

  I recently got interested in financial board games and saw how they can be very useful in educating children about certain concepts. It got me thinking whether it was also possible to represent certain aspects of executing a software project via a boardgame and make it fun. Here are a few things that I have come up so far: human resources and tools / techniques are represented as cards. requirements are also represented as cards, which are dealt equally to each player, and the objective is to move all requirement cards through an "SDLC" board (one per player) that represent a series of squares grouped according to phases (design all the way to deployment) the passage of time is represented in a main square board like monopoly, and completing a trip around the board (passing "Go") allows the player to move each of the requirement cards a number of steps through the SDLC board depending on the capability of the resource cards (senior programmer allows one requirement to move two squares in the dev phase, junior programmer only one, etc.) players will start with play money representing the project budget, and at every pass at "Go" is payday. the player is out of the game if he runs out of funds. the main board also has "chance" / "risk" cards, which represent things that can mess up a project. damage is applied at the roll of a die, and chance modifiers depend on whether the user has "bought" tools / techniques. I haven't implemented this idea yet as I'm still looking at more play elements that can make the game more engaging, as well as soliciting for more ideas. I am planning to release this under Creative Commons license but haven't decided on the exact license yet. Any more game play suggestions are welcome. UPDATE: This was posted in BoardGameGeek and there's now an active discussion thread there. http://www.boardgamegeek.com/article/4436694

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• Calculate posterior distribution of unknown mis-classification with PRTools in MATLAB

  - by Samuel Lampa

  I'm using the PRTools MATLAB library to train some classifiers, generating test data and testing the classifiers. I have the following details: N: Total # of test examples k: # of mis-classification for each classifier and class I want to do: Calculate and plot Bayesian posterior distributions of the unknown probabilities of mis-classification (denoted q), that is, as probability density functions over q itself (so, P(q) will be plotted over q, from 0 to 1). I have that (math formulae, not matlab code!): P(q|k,N) = Posterior * Prior / Normalization constant = P(k|q,N) * P(q|N) / P(k|N) The prior is set to 1, so I only need to calculate the posterior and normalization constant. I know that the posterior can be expressed as (where B(N,k) is the binomial coefficient): P(k|q,N) = B(N,k) * q^k * (1-q)^(N-k) ... so the Normalization constant is simply an integral of the posterior above, from 0 to 1: P(k|N) = B(N,k) * integralFromZeroToOne( q^k * (1-q)^(N-k) ) (The Binomial coefficient ( B(N,k) ) can be omitted thoughappears in both the posterior and normalization constant, so it can be omitted.) Now, I've heard that the integral for the normalization constant should be able to be calculated as a series ... something like: k!(N-k)! / (N+1)! Is that correct? (I have some lecture notes from with this series, but can't figure out if it is for the normalization constant integral, or for the posterior distribution of mis-classification (q)) Also, hints are welcome as how to practically calculate this? (factorials are easily creating truncation errors right?) ... AND, how to practically calculate the final plot (the posterior distribution over q, from 0 to 1).

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• Efficient Clojure workflow?

  - by Alex B

  I am developing a pet project with Clojure, but wonder if I can speed up my workflow a bit. My current workflow (with Compojure) is: Start Swank with lein swank. Go to Emacs, connect with M-x slime-connect. Load all existing source files one by one. This also starts a Jetty server and an application. Write some code in REPL. When satisfied with experiments, write a full version of a construct I had in mind. Eval (C-c C-c) it. Switch REPL to namespace where this construct resides and test it. Switch to browser and reload browser tab with the affected page. Tweak the code, eval it, check in the browser. Repeat any of the above. There are a number of annoyances with it: I have to switch between Emacs and the browser (or browsers if I am testing things like templating with multiple browsers) all the time. Is there a common idiom to automate this? I used to have a JavaScript bit that reloads the page continuously, but it's of limited utility, obviously, when I have to interact with the page for more than a few seconds. My JVM instance becomes "dirty" when I experiment and write test functions. Basically namespaces become polluted, especially if I'm refactoring and moving the functions between namespaces. This can lead to symbol collisions and I need to restart Swank. Can I undef a symbol? I load all source files one by one (C-c C-k) upon restarting Swank. I suspect I'm doing it all wrong. Switching between the REPL and the file editor can be a bit irritating, especially when I have a lot of Emacs tabs open, alongside the browser(s). I'm looking for ways to improve the above points and the entire workflow in general, so I'd appreciate if you'd share yours. P. S. I have also used Vimclojure before, so Vimclojure-based workflows are welcome too.

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• Questions on method to use: Facebook Business Page with Flash or Facebook Application?

  - by Jay

  Hi there, I'm new to Facebook's Graph API / FBML / etc. So if at any point in my post I make a mistake or wrong assumption, please point them out. One of the projects that I am working on has a need to get data/info from an existing web site in addition to the friends list and such that FB can provide. This is for a platform that allows people from all over the world to help out in small scale projects that will benefit various communities. These projects are usually to help out people in unfortunate / less than ideal situations / living conditions so that their environment improves. You can read about it in detail at http://www.getitdone.org. The initial idea was to develop a Business Page (this is the same as a Fan Page right?) for each Project with a Static FBML tag to do the displaying. However, iframes are not allowed in Pages (as far as I know, iframes are only allowed in an FB Application). So it is no longer possible to get data from the web site to be displayed in the FB Page. So one of the options is to embed a Flash in the Page's Tab. I am fairly certain that the Flash can retrieve data on the User's friends and connections in an Application's context (because of all of those darn FB games that I'm addicted to :p). However, I would like to confirm if it can do the same if it's embedded in a Business Page's Tab. Could someone please confirm on this issue? The other option that we arrived at was (if the earlier options fails) to have an Application built instead. However, this means that we would need to create an Application for each Project. Not an ideal situation. Is there any other option that we have missed that can help us achieve the desired result with as little hassle as possible? Any help that you can provide on this matter is most welcome. Thank you.

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• Which version of Grady Booch's OOA/D book should I buy?

  - by jackj

  Grady Booch's "Object-Oriented Analysis and Design with Applications" is available brand new in both the 2nd edition (1993) and the 3rd edition (2007), while many used copies of both editions are available. Here are my concerns: 1) The 2nd edition uses C++: given that I just finished reading my first two C++ books (Accelerated C++ and C++ Primer) I guess practical tips can only help, so the 2nd edition is probably best (I think the 3rd edition has absolutely no code). On the other hand, the C++ books I read insist on the importance of using standard C++, whereas Booch's 2nd edition was published before the 1998 standard. 2) The 2nd edition is shorter (608 pages vs. 720) so, I guess, it will be slightly easier to get through. 3) The 3rd edition uses UML 2.0, whereas the 2nd edition is pre-UML. Some reviews say that the notation in the 2nd edition is close enough to UML, so it doesn't matter, but I don't know if I should be worrying about this or not. 4) The 2nd edition is available in good-shape used copies for considerably less than what the 3rd one goes for. Given all the above factors, do you think I should buy the 2nd or the 3rd edition? Recommendations on other books are also welcome but I would prefer it if whoever answers has read at least one of the versions of Booch's book (preferably both!). I have already bought but not read GoF and Riel's books. I also know that I should practice a lot with real-life code. Thanks.

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• Trying to draw a dynamic rectangle in SVG

  - by Shaun

  To be more specific, here are the steps I need: onmousedown - set x and y of rect as mouse coordinates onmousemove - using the current x and y mouse coordinates calculate height and width of the rect, set these and append onmouseup - remove the rectangle, and call a function based off some calculations from the rect. Here is what I have but isn't quite working (right now I have it drawing a line to make it simpler): onmousedown: startbox(evt) function startbox(evt) { if(evt.button === 0) { x1 = evt.clientX + div.scrollLeft-5; y1 = evt.clientY + div.scrollTop-30; obj.setAttributeNS(null, "x1", x1); obj.setAttributeNS(null, "y1", y1); Root.setAttributeNS(null, "onmousemove", "updatebox(evt)"); } } onmousemove: updatebox(evt) function updatebox(evt) { if(evt.button === 0) { x2 = evt.clientX + div.scrollLeft-5; y2 = evt.clientY + div.scrollTop-30; Root.appendChild(.obj); w = Math.abs(x2-x1); h = Math.abs(y2-y1); var strokecolor; if(w>20 && h>20) { strokecolor = "green"; validbox = true; } else { strokecolor = "red"; validbox = false; } var Attr={ x2:x2, y2:y2, stroke:strokecolor } assignAttr(obj, Attr); //just loops thru adding multiple attributes } } onmouseup: endbox() function endbox(evt) { if(evt.button===0) { Root.setAttributeNS(null, "onmousemove", ""); Root.removeChild(obj); if(validbox) { //do stuff validbox = !validbox; } } } Some of my problems with this are: Its slow in Chrome making drawing the line/rect feel sluggish. It won't work two times in a row. This is the real problem that I can't fix. Any and all feedback is welcome.

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• Timer Service in ejb 3.1 - schedule calling timeout problem

  - by Greg

  Hi Guys, I have created simple example with @Singleton, @Schedule and @Timeout annotations to try if they would solve my problem. The scenario is this: EJB calls 'check' function every 5 secconds, and if certain conditions are met it will create single action timer that would invoke some long running process in asynchronous fashion. (it's sort of queue implementation type of thing). It then continues to check, but as long as long running process is there it won't start another one. Below is the code I came up with, but this solution does not work, because it looks like asynchronous call I'm making is in fact blocking my @Schedule method. @Singleton @Startup public class GenerationQueue { private Logger logger = Logger.getLogger(GenerationQueue.class.getName()); private List<String> queue = new ArrayList<String>(); private boolean available = true; @Resource TimerService timerService; @Schedule(persistent=true, minute="*", second="*/5", hour="*") public void checkQueueState() { logger.log(Level.INFO,"Queue state check: "+available+" size: "+queue.size()+", "+new Date()); if (available) { timerService.createSingleActionTimer(new Date(), new TimerConfig(null, false)); } } @Timeout private void generateReport(Timer timer) { logger.info("!!--timeout invoked here "+new Date()); available = false; try { Thread.sleep(1000*60*2); // something that lasts for a bit } catch (Exception e) {} available = true; logger.info("New report generation complete"); } What am I missing here or should I try different aproach? Any ideas most welcome :) Testing with Glassfish 3.0.1 latest build - forgot to mention

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• starting oracle 10g on ubuntu, Listener failed to start.

  - by tsegay

  I have installed oracle 10g on a ubuntu 10.x, This is my first time installation. After installing I tried to start it with the command below. tsegay@server-name:/u01/app/oracle/product/10.2.0/db_1/bin$ lsnrctl LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 29-DEC-2010 22:46:51 Copyright (c) 1991, 2005, Oracle. All rights reserved. Welcome to LSNRCTL, type "help" for information. LSNRCTL> start Starting /u01/app/oracle/product/10.2.0/db_1/bin/tnslsnr: please wait... TNSLSNR for Linux: Version 10.2.0.1.0 - Production System parameter file is /u01/app/oracle/product/10.2.0/db_1/network/admin/listener.ora Log messages written to /u01/app/oracle/product/10.2.0/db_1/network/log/listener.log Error listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1))) TNS-12555: TNS:permission denied TNS-12560: TNS:protocol adapter error TNS-00525: Insufficient privilege for operation Linux Error: 1: Operation not permitted Listener failed to start. See the error message(s) above... my listener.ora file looks like this: # listener.ora Network Configuration File: /u01/app/oracle/product/10.2.0/db_1/network/admin/listener.ora # Generated by Oracle configuration tools. SID_LIST_LISTENER = (SID_LIST = (SID_DESC = (SID_NAME = PLSExtProc) (ORACLE_HOME = /u01/app/oracle/product/10.2.0/db_1) (PROGRAM = extproc) ) ) LISTENER = (DESCRIPTION_LIST = (DESCRIPTION = (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1)) (ADDRESS = (PROTOCOL = TCP)(HOST = acct-vmserver)(PORT = 1521)) ) ) I can guess the problem is with permission issue, But i dont know where I have to do the change on permission. Any help is appreciated ...

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• Change classes instantiated with loadNibNamed

  - by Nick H247

  I am trying to change the class of objects created with a nib with the iPhone SDK. The reason for this is; i dont know until runtime what the class is that i want the nib object to be (though they will have the same UIView based super class), and i dont want to create a different nib for every eventuality - as the .nib will be the same for each, apart from the class of one object. I have been successful, with a couple of methods, but either have some knock on effects or am unsure of how safe the methods I have used are: Method 1: Override alloc, on the super class and set a c variable to the class I require: + (id) alloc { if (theClassIWant) { id object = [theClassIWant allocWithZone:NSDefaultMallocZone()]; theClassIWant = nil; return object; } return [BaseClass allocWithZone:NSDefaultMallocZone()]; } this works well, and i assume is 'reasonably' safe, though if I alloc a subclass myself (without setting 'theClassIWant') - an object of the base class is created. I also dont really like the idea of overriding alloc... Method 2: use object_setClass(self,theClassIWant) in initWithCoder (before calling initWithCoder on the super class): - (id) initWithCoder:(NSCoder *)aDecoder { if (theClassIWant) { // the framework doesn't like this: //[self release]; //self = [theClassIWant alloc]; // whoa now! object_setClass(self,theClassIWant); theClassIWant = nil; return [self initWithCoder:aDecoder]; } if (self = [super initWithCoder:aDecoder]) { ... this also works well, but not all the subclasses are necessarily going to be the same size as the super class, so this could be very unsafe! To combat this i tried releasing and re-allocing to the correct type within initWithCoder, but i got the following error from the framework: "This coder requires that replaced objects be returned from initWithCoder:" dont quite get what this means! i am replacing an object in initWithCoder... Any comments on the validity of these methods, or suggestions of improvements or alternatives welcome!

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• Boost lambda: Invoke method on object

  - by ckarras

  I'm looking at boost::lambda as a way to to make a generic algorithm that can work with any "getter" method of any class. The algorithm is used to detect duplicate values of a property, and I would like for it to work for any property of any class. In C#, I would do something like this: class Dummy { public String GetId() ... public String GetName() ... } IEnumerable<String> FindNonUniqueValues<ClassT> (Func<ClassT,String> propertyGetter) { ... } Example use of the method: var duplicateIds = FindNonUniqueValues<Dummy>(d => d.GetId()); var duplicateNames = FindNonUniqueValues<Dummy>(d => d.GetName()); I can get the for "any class" part to work, using either interfaces or template methods, but have not found yet how to make the "for any method" part work. Is there a way to do something similar to the "d = d.GetId()" lambda in C++ (either with or without Boost)? Alternative, more C++ian solutions to make the algorithm generic are welcome too. I'm using C++/CLI with VS2008, so I can't use C++0x lambdas.

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