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  • Select all points in a matrix within 30m of another point

    - by pinnacler
    So if you look at my other posts, it's no surprise I'm building a robot that can collect data in a forest, and stick it on a map. We have algorithms that can detect tree centers and trunk diameters and can stick them on a cartesian XY plane. We're planning to use certain 'key' trees as natural landmarks for localizing the robot, using triangulation and trilateration among other methods, but programming this and keeping data straight and efficient is getting difficult using just Matlab. Is there a technique for sub-setting an array or matrix of points? Say I have 1000 trees stored over 1km (1000m), is there a way to say, select only points within 30m radius of my current location and work only with those? I would just use a GIS, but I'm doing this in Matlab and I'm unaware of any GIS plugins for Matlab. I forgot to mention, this code is going online, meaning it's going on a robot for real-time execution. I don't know if, as the map grows to several miles, using a different data structure will help or if calculating every distance to a random point is what a spatial database is going to do anyway. I'm thinking of mirroring two arrays, one sorted by X and the other by Y. Then bubble sorting to determine the 30m range in that. I do the same for both arrays, X and Y, and then have a third cross link table that will select the individual values. But I don't know, what that's called, how to program that and I'm sure someone already has so I don't want to reinvent the wheel. Cartesian Plane GIS

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  • c# sending sms from computer

    - by I__
    i have this code: private SerialPort port = new SerialPort("COM1", 115200, Parity.None, 8, StopBits.One); Console.WriteLine("Incoming Data:"); port.WriteTimeout = 5000; port.ReadTimeout = 5000; // Attach a method to be called when there is data waiting in the port's buffer port.DataReceived += new SerialDataReceivedEventHandler(port_DataReceived); // Begin communications port.Open(); #region PhoneSMSSetup port.Write("AT+CMGF=1\r\n"); Thread.Sleep(500); port.Write("AT+CNMI=2,2\r\n"); Thread.Sleep(500); port.Write("AT+CSCA=\"+4790002100\"\r\n"); Thread.Sleep(500); #endregion // Enter an application loop which keeps this thread alive Application.Run(); i got it from here: http://www.experts-exchange.com/Programming/Languages/C_Sharp/Q_22832563.html i have a new winforms empty application: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; namespace WindowsFormsApplication1 { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void Form1_Load(object sender, EventArgs e) { } } } can you please tell me: where exactly would i paste the code? how do i get the code to run? i am sending AT COMMANDS to my cell phone that is attached to the computer

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  • When to choose which machine learning classifier?

    - by LM
    Suppose I'm working on some classification problem. (Fraud detection and comment spam are two problems I'm working on right now, but I'm curious about any classification task in general.) How do I know which classifier I should use? (Decision tree, SVM, Bayesian, logistic regression, etc.) In which cases is one of them the "natural" first choice, and what are the principles for choosing that one? Examples of the type of answers I'm looking for (from Manning et al.'s "Introduction to Information Retrieval book": http://nlp.stanford.edu/IR-book/html/htmledition/choosing-what-kind-of-classifier-to-use-1.html): a. If your data is labeled, but you only have a limited amount, you should use a classifier with high bias (for example, Naive Bayes). [I'm guessing this is because a higher-bias classifier will have lower variance, which is good because of the small amount of data.] b. If you have a ton of data, then the classifier doesn't really matter so much, so you should probably just choose a classifier with good scalability. What are other guidelines? Even answers like "if you'll have to explain your model to some upper management person, then maybe you should use a decision tree, since the decision rules are fairly transparent" are good. I care less about implementation/library issues, though. Also, for a somewhat separate question, besides standard Bayesian classifiers, are there 'standard state-of-the-art' methods for comment spam detection (as opposed to email spam)? [Not sure if stackoverflow is the best place to ask this question, since it's more machine learning than actual programming -- if not, any suggestions for where else?]

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  • JBoss deployment throws 'java.util.zip.ZipException: error in opening zip file' on Linux?

    - by Kaushalya
    I thought of posting both the question and the answer for others' knowledge. I deployed a large EAR (contained more than ~1024 jars/wars) on JBoss running with Java 6 on Linux, and the deployment process cried throwing the following exception: java.lang.RuntimeException: java.util.zip.ZipException: error in opening zip file) at org.jboss.deployment.DeploymentException.rethrowAsDeploymentException(DeploymentException.java:53) at org.jboss.deployment.MainDeployer.init(MainDeployer.java:901) at org.jboss.deployment.MainDeployer.init(MainDeployer.java:895) at org.jboss.deployment.MainDeployer.deploy(MainDeployer.java:809) at org.jboss.deployment.MainDeployer.deploy(MainDeployer.java:782) .... Caused by: java.lang.RuntimeException: java.util.zip.ZipException: error in opening zip file at org.jboss.util.file.JarArchiveBrowser.<init>(JarArchiveBrowser.java:74) at org.jboss.util.file.FileProtocolArchiveBrowserFactory.create(FileProtocolArchiveBrowserFactory.java:48) at org.jboss.util.file.ArchiveBrowser.getBrowser(ArchiveBrowser.java:57) at org.jboss.ejb3.EJB3Deployer.hasEjbAnnotation(EJB3Deployer.java:213) .... This was caused by the 'limit of number of open file descriptors' of Linux/Unix operating systems. The default is 1024. You can check the default value using: ulimit -n To increase the number of open file descriptors (say to 2048): ulimit -n 2048 Check the man page of ulimit for more details.

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  • Is Git ready to be recommended to my boss?

    - by Mike Weller
    I want to recomment Git to my boss as a new source control system, since we're stuck in the 90s with VSS (ouch), but are the tools and 3rd party support good enough yet? Specifically I'm talking about GUI front-ends similar to TortoiseSVN, decent visual diff/merge support, as well as stuff like email commit notifications and general support from 3rd parties like IDEs and build systems. Even though this will be used by programmers, we really need this kind of stuff in our team. I don't want to leave everyone stuck with a new tool, and even a new source control paradigm (distributed), with nothing but a command-line app and some online tutorials. This would be a step backwards. So what do you think... is Git ready? What decent tools exist for Git and what third party development apps support it? EDIT: My original question was pretty vague so I'm updating it to specifically ask for a list of available tools and 3rd party support for Git. Maybe we can get a community wiki post with a list of stuff. I also do not consider 'use subversion' to be an adequate answer. There are other reasons to use a distributed source control system other than offline editing - private and cheap branches being one of them.

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  • correct format for function prototype

    - by yCalleecharan
    Hi, I'm writing to a text file using the following declaration: void create_out_file(char file_name[],long double *z1){ FILE *out; int i; if((out = fopen(file_name, "w+")) == NULL){ fprintf(stderr, "***> Open error on output file %s", file_name); exit(-1); } for(i = 0; i < ARRAY_SIZE; i++) fprintf(out, "%.16Le\n", z1[i]); fclose(out); } Where z1 is an long double array of length ARRAY_SIZE. The calling function is: create_out_file("E:/first67/jz1.txt", z1); I defined the prototype as: void create_out_file(char file_name[], long double z1[]); which I'm putting before "int main" but after the preprocessor directives. My code works fine. I was thinking of putting the prototype as void create_out_file(char file_name[],long double *z1). Is this correct? *z1 will point to the first array element of z1. Is my declaration and prototype good programming practice? Thanks a lot...

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  • Is there a Scheduler/Calendar JS Widget library?

    - by Ravi Chhabra
    I am looking for some JavaScript based component to be used as a course scheduler which would be a cross between Google Calendar and the login time. I do not know if the right term for this is Course Scheduler but I shall describe this in more detail here. Course Scheduler The widget would be used to enter date and times of a course, as an example if I run a programming course 3 days a week on Mon, Tue and Wed every 7:00 am to 9:00am, 2 hours every day from 1st September to 30th November. I could answer various questions and the course data would be displayed in the calendar. It would also allow for non pattern based timings where each week is different from the other week etc. Question So would I end up creating something from scratch? Would it be sensible to use Google Calendar API for this? I did a Google search for some widgets, but I believe I need better keywords, as I could not find anything close to what I am looking for. Any tips? Commercial libraries would also work for me. Thanks.

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  • How to accommodate for the iPhone 4 screen resolution?

    - by dontWatchMyProfile
    This is a programming question! Read on before you vote to close! According to Apple, the iPhone 4 has a new and better screen resolution: 3.5-inch (diagonal) widescreen Multi-Touch display 960-by-640-pixel resolution at 326 ppi This little detail affects our apps in a heavy way. Most of the demo apps on the net have one thing in common: They position views in the believe that the screen has a fixed size of 320 x 480 pixels. So what most -if not all- developers do is: They designed everything in such a way, that a touchable area is -for example- 50 x 50 pixels big. Just enough to tap it. Things have been positioned relative to the upper left, to reach a specific position on screen - let's say the center, or somewhere at the bottom. Edit: It seems Apple has integrated an switch that allows to tell if an app is highRes or not. Nice. When we develop high-resolution apps, they probably won't work on older devices. And if they do, they would suffer a lot from 4-times the size of any image, having to scale them down in memory.

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  • OOP - Handling Automated Instances of a Class - PHP

    - by dscher
    This is a topic that, as a beginner to PHP and programming, sort of perplexes me. I'm building a stockmarket website and want users to add their own stocks. I can clearly see the benefit of having each stock be a class instance with all the methods of a class. What I am stumped on is the best way to give that instance a name when I instantiate it. If I have: class Stock() { ....doing stuff..... } what is the best way to give my instances of it a name. Obviously I can write: $newStock = new Stock(); $newStock.getPrice(); or whatever, but if a user adds a stock via the app, where can the name of that instance come from? I guess that there is little harm in always creating a new child with $newStock = new Stock() and then storing that to the DB which leads me to my next question! What would be the best way to retrieve 20 user stocks(for example) into instances of class Stock()? Do I need to instantiate 20 new instances of class Stock() every time the user logs in or is there something I'm missing? I hope someone answers this and more important hope a bunch of people answer this and it somehow helps someone else who is having a hard time wrapping their head around what probably leads to a really elegant solution. Thanks guys!

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  • git crlf configuration in mixed environment

    - by Jonas Byström
    I'm running a mixed environment, and keep a central, bare repository where I pull and push most of my stuff. This centralized repository runs on Linux, and I check out to Windows XP/7, Mac and Linux. In all repositories I put the following line in my .git/config: [core] autocrlf = true I don't have the flag safecrlf=true anywhere. First time when I modify stuff on my one Windows machine (XP) there is no problem and when I look at the diff, it looks fine. But when I do the same on the other Windows machine (7), all lines are shown as changed but local line endings are \r\n as expected (when checked in a hex editor). The same applies to a MacOSX can. Sometimes I get the feeling that the different systems wrestle on line endings, but I can't be sure (I'm loosing track of all the times I change specific files). I didn't use to have the autocrlf set, but set the flag many months back. Could that be causing my current problems? Do I need to clone everything again to loose some old baggage? Or are there other things that needs configuring too? I tried git checkout -- . about a million times, but with no success.

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  • With a browser, how do I know which decimal separator does the client use?

    - by Quassnoi
    I'm developing a web application. I need to display some decimal data correctly so that it can be copied and pasted into a certain GUI application that is not under my control. The GUI application is locale sensitive and it accepts only the correct decimal separator which is set in the system. I can guess the decimal separator from Accept-Language and the guess will be correct in 95% cases, but sometimes it fails. Is there any way to do it on server side (preferably, so that I can collect statistics), or on client side? Update: The whole point of the task is doing it automatically. In fact, this webapp is a kind of online interface to a legacy GUI which helps to fill the forms correctly. The kind of users that use it mostly have no idea on what a decimal separator is. The Accept-Language solution is implemented and works, but I'd like to improve it. Update2: I need to retrive a very specific setting: decimal separator set in Control Panel / Regional and Language Options / Regional Options / Customize. I deal with four kinds of operating systems: Russian Windows with a comma as a DS (80%). English Windows with a period as a DS (15%). Russian Windows with a period as a DS to make poorly written English applications work (4%). English Windows with a comma as a DS to make poorly written Russian applications work (1%). All 100% of clients are in Russia and the legacy application deals with Russian goverment-issued forms, so asking for a country will yield 100% of Russian Federation, and GeoIP will yield 80% of Russian Federation and 20% of other, incorrect answers.

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  • Avoid loading unnecessary data from db into objects (web pages)

    - by GmGr
    Really newbie question coming up. Is there a standard (or good) way to deal with not needing all of the information that a database table contains loaded into every associated object. I'm thinking in the context of web pages where you're only going to use the objects to build a single page rather than an application with longer lived objects. For example, lets say you have an Article table containing id, title, author, date, summary and fullContents fields. You don't need the fullContents to be loaded into the associated objects if you're just showing a page containing a list of articles with their summaries. On the other hand if you're displaying a specific article you might want every field loaded for that one article and maybe just the titles for the other articles (e.g. for display in a recent articles sidebar). Some techniques I can think of: Don't worry about it, just load everything from the database every time. Have several different, possibly inherited, classes for each table and create the appropriate one for the situation (e.g. SummaryArticle, FullArticle). Use one class but set unused properties to null at creation if that field is not needed and be careful. Give the objects access to the database so they can load some fields on demand. Something else? All of the above seem to have fairly major disadvantages. I'm fairly new to programming, very new to OOP and totally new to databases so I might be completely missing the obvious answer here. :)

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  • c++ callback syntax in a class

    - by Mr Bell
    I am trying to figure out the syntax to register a callback with this 3rd party software. I think it is probably a basic question, I just am not too familiar with c++. They have a method for registering a callback function so their code can call a function in my code when an event happens. They provided a working example that registers the callback from the main file, but I want to know how to do it when working inside a class Their method signature: smHTRegisterHeadPoseCallback(smEngineHandle engine_handle, void *user_data, smHTHeadPoseCallback callback_fun); Working example from the main file: void STDCALL receiveHeadPose(void *,smEngineHeadPoseData head_pose, smCameraVideoFrame video_frame) { ... } void main() { ... smHTRegisterHeadPoseCallback(engine_handle,0,receiveHeadPose) ... } But I want to use this from my class MyClass.h class FaceEngine { public: void STDCALL receiveFaceData(void *, smEngineFaceData face_data, smCameraVideoFrame video_frame); ... MyClass.cpp void FaceEngine::Start(void) { rc = smHTRegisterFaceDataCallback(hFaceAPIEngine,0,&FaceEngine::receiveFaceData); ... Results in this compiler error: Error 1 error C2664: 'smHTRegisterFaceDataCallback' : cannot convert parameter 3 from 'void (__stdcall FaceEngine::* )(void *,smEngineFaceData,smCameraVideoFrame)' to 'smHTFaceDataCallback' d:\stuff\programming\visual studio 2008\projects\tut02_vertices\faceengine.cpp 43 Beard If my question isn't clear please let me know how I can clarify.

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  • Properly design a code editor application

    - by Hemaulo
    I'm working on personal project which is basically a code editor. Imagine standard File menu with menu items New, Open, Save, Save As, Save All, Close, Close All. I'm stuck with proper design. Currently I have: A Document class which represents a document - code editing control, respective tab in tab bar and various properties such as Caption, Filename, IsModified etc. A Documents class which represents all open documents. Contains methods like New, Open(FileName), ... The problem is that I can't figure out which class / menu command is responsible for which tasks. For example, with File-New menu command is simple - call Documents.New and that's it. But what for File-Open? The Documents.Open method expects filename as a parameter. So before calling this method I need to open an file selection dialog, let user select files and for each file call Documents.Open(FileName). Where is best place for this supporting code, in menu command, rewrite Documents.Open and put it there? The same with Save actions. Which is responsible for saving? Is it Documents class which uses Document.Editor.SaveToFile(FileName) or better create Save method in Document class? Somewhere in the middle also need to ask user if he wants to save current document... I'm stuck. Any ideas? Edited: The programming language is Delphi.

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  • What's a good Java-based Master-Slave communication mechanism?

    - by plecong
    I'm creating a Java application that requires master-slave communication between JVMs, possibly residing on the same physical machine. There will be a "master" server running inside a JEE application server (i.e. JBoss) that will have "slave" clients connect to it and dynamically register itself for communication (that is the master will not know the IP addresses/ports of the slaves so cannot be configured in advance). The master server acts as a controller that will dole work out to the slaves and the slaves will periodically respond with notifications, so there would be bi-directional communication. I was originally thinking of RPC-based systems where each side would be a server, but it could get complicated, so I'd prefer a mechanism where there's an open socket and they talk back and forth. I'm looking for a communication mechanism that would be low-latency where the messages would be mostly primitive types, so no serious serialization is necessary. Here's what I've looked at: RMI JMS: Built-in to Java, the "slave" clients would connect to the existing ConnectionFactory in the application server. JAX-WS/RS: Both master and slave would be servers exposing an RPC interface for bi-directional communication. JGroups/Hazelcast: Use shared distributed data structures to facilitate communication. Memcached/MongoDB: Use these as "queues" to facilitate communication, though the clients would have to poll so there would be some latency. Thrift: This does seem to keep a persistent connection, but not sure how to integrate/embed a Thrift server into JBoss WebSocket/Raw Socket: This would work, but require a lot more custom code than I'd like. Is there any technology I'm missing? Edit: Also looked at: JMX: Have the client connect to JBoss' JMX server and receive JMX notifications for bidirectional comms.

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  • Flex 4 front end connecting to Java Jersey Web Service

    - by user305801
    I created a Java REST service using Jersey. I use three of the HTTP "verbs" GET, POST and DELETE. I want to create several prototype front ends for the service. After much research, a lot dating to 2008 and 2009, I have been unable to find anything remotely simple. My three options are: 1) resthttpservice. This project hasn't been updated in a year. The only activity are one off suggestions that individual users have implemented. http://code.google.com/p/resthttpservice/ 2) Create an AIR application. This isn't unfeasible. 3) Writing my own socket level code but there is a security restriction with flash players and I need to implement a policy server. I have already read the question posted about asking whether using Flex for REST services were worth it. That information is old as well. I want to introduce REST services to my company but Flex's limited support for HTTP PUT and DELETE are discouraging. My service also uses the Accept header to determine if JSON or XML will be returned to the client. I can't seem to change HTTP headers without doing socket programming. I'm fine with that but the security policy thing is annoying. Is there an easy way to use Flex 4 with RESTful services that uses PUT/DELETE and the Accept HTTP header? Please help. I'm very frustrated.

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  • Cobol web development/hosting resources

    - by felixm
    Hello, I'm employed at a fairly big company here in Germany and got the job to create the main website for it which will feature: Static contents; Information and Presentations An employee area (around 6000 employees) featuring various things from calenders, job descriptions, some sort of groups Too many other dynamic things I can't list here I have decided to use COBOL for the job, it may be very underrated but it is a very powerful language, especially for business apps and, as my co-workers say, web (2.0) development too. I also need to use COBOL because all the backend and transactions system of the company is programmed in it (some small parts were programmed in LISP too, idk exactly why). I also have received an API that makes it possible to use COBOL with MySQL easily. This is a big project and it will probably take more than 2 months programming it. What do I have to expect when building a huge web app in COBOL? Are there web frameworks for COBOL available? Some sort of MVC? Are there any good resources for practical web-development with COBOL? Thanks in advance

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  • Computing "average" of two colors

    - by Francisco P.
    This is only marginally programming related - has much more to do w/ colors and their representation. I am working on a very low level app. I have an array of bytes in memory. Those are characters. They were rendered with anti-aliasing: they have values from 0 to 255, 0 being fully transparent and 255 totally opaque (alpha, if you wish). I am having trouble conceiving an algorithm for the rendering of this font. I'm doing the following for each pixel: // intensity is the weight I talked about: 0 to 255 intensity = glyphs[text[i]][x + GLYPH_WIDTH*y]; if (intensity == 255) continue; // Don't draw it, fully transparent else if (intensity == 0) setPixel(x + xi, y + yi, color, base); // Fully opaque, can draw original color else { // Here's the tricky part // Get the pixel in the destination for averaging purposes pixel = getPixel(x + xi, y + yi, base); // transfer is an int for calculations transfer = (int) ((float)((float) (255.0 - (float) intensity/255.0) * (float) color.red + (float) pixel.red)/2); // This is my attempt at averaging newPixel.red = (Byte) transfer; transfer = (int) ((float)((float) (255.0 - (float) intensity/255.0) * (float) color.green + (float) pixel.green)/2); newPixel.green = (Byte) transfer; // transfer = (int) ((float) ((float) 255.0 - (float) intensity)/255.0 * (((float) color.blue) + (float) pixel.blue)/2); transfer = (int) ((float)((float) (255.0 - (float) intensity/255.0) * (float) color.blue + (float) pixel.blue)/2); newPixel.blue = (Byte) transfer; // Set the newpixel in the desired mem. position setPixel(x+xi, y+yi, newPixel, base); } The results, as you can see, are less than desirable. That is a very zoomed in image, at 1:1 scale it looks like the text has a green "aura". Any idea for how to properly compute this would be greatly appreciated. Thanks for your time!

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  • Upgrade .NET 1.1 WinForm/Service to what?

    - by Conor
    Hi Folks, We have a current WinForm/Windows Service running in .NET 1.1 out on various customer sites that is getting data from internal systems, transforming it and then calling a Web Service synchronously. This client app will no longer work in Vista or Windows 7 etc.. and its time to update!! I was looking for ideas on what I could do here, I didn't write the App and I have the Business team telling me they want the world but I need to be realistic :) Things the service must be able to do: - Handle multiple formats from internal system and transform to a schema SAP, ERP etc.. - Run silently and just work on customer sites (it does currently albeit .NET 1.1) - The Customers are unable to call our web service from their sites as they are not technical enough. - Upgrade it's self when updates occur (currently don't have this capability) Is there anything I can do here other than upgrade the service to run in .NET and add a few more transformation capabilities e..g they want the customer to be able to give us a flat file, an xml file, a csv and the service transforms it and calls the Web Service? I was hoping in this day and age we could use the Web, but automating this 100% rules it out in my eyes? I could be totally wrong!! Any help would be gratefully appreciated! Cheers. Conor

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  • Idea for a small project, should I use Python?

    - by Robb
    I have a project idea, but unsure if using Python would be a good idea. Firstly, I'm a C++ and C# developer with some SQL experience. My day job is C++. I have a project idea i'd like to create and was considering developing it in a language I don't know. Python seems to be popular and has piqued my interests. I definitely use OOP in programming and I understand Python would work fine with that style. I could be way off on this, I've only read small bits and pieces about the language. The project won't be public or anything, just purely something of my own creation do dabble in at home. So the project would essentially represent a simple game idea I have. The game would consist roughly these things: Data structures to hold specific information (would be strongly typed). A way to output the gamestate for the players. This is completely up in the air, it can be graphical or text based, I don't really care at this point. A way to save off game data for the players in something like a database or file system. A relatively easy way for me to input information and a 'GO' button which processes the changes and obviously creates a new gamestate. The game would function similar to a board game. Really nothing out of the ordinary when I look back at that list. Would this be a fun way to learn Python or should I select another language?

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  • Someone selling my GPL theme

    - by PaKK
    I'm having a tough time trying to figure out the best way to handle this. I've created a few themes last year, released them under a GPL license, and pretty much forgot about them. My goal was to put them out publicly as samples of my work. I've recently come across a site and was shocked they are selling one of my themes among several other themes (not mine) and other support and package systems. Anyway needless to say I'm not happy about this. I did not intend for those themes to be sold, and if they are to be sold, at least I would expect a percentage of those sales. I contacted the website asking how many they sold and that I'm the author of one of the themes they were selling. I eventually received a reply that my theme is a GPL theme and that this license allows them to sell it without compensation to me. WTF? Just the way the reply was worded pissed me off. There is no way to comment on the site to inform possible buyers that those themes can be downloaded from my site. What can I do about this? I realize now it was a bad choice to release them under that license. Is it possible to take back the theme from public distribution or is it out forever. Can I change it from GPL to another license at this point? Will that be sufficient to stop the sale of my theme in the future? Any insights are appreciated.

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  • How to access hidden template in unnamed namespace?

    - by Johannes Schaub - litb
    Here is a tricky situation, and i wonder what ways there are to solve it namespace { template <class T> struct Template { /* ... */ }; } typedef Template<int> Template; Sadly, the Template typedef interferes with the Template template in the unnamed namespace. When you try to do Template<float> in the global scope, the compiler raises an ambiguity error between the template name and the typedef name. You don't have control over either the template name or the typedef-name. Now I want to know whether it is possible to: Create an object of the typedefed type Template (i.e Template<int>) in the global namespace. Create an object of the type Template<float> in the global namespace. You are not allowed to add anything to the unnamed namespace. Everything should be done in the global namespace. This is out of curiosity because i was wondering what tricks there are for solving such an ambiguity. It's not a practical problem i hit during daily programming.

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  • What is the preferred way in C++ for converting a builtin type (int) to bool?

    - by Martin
    When programming with Visual C++, I think every developer is used to see the warning warning C4800: 'BOOL' : forcing value to bool 'true' or 'false' from time to time. The reason obviously is that BOOL is defined as int and directly assigning any of the built-in numerical types to bool is considered a bad idea. So my question is now, given any built-in numerical type (int, short, ...) that is to be interpreted as a boolean value, what is the/your preferred way of actually storing that value into a variable of type bool? Note: While mixing BOOL and bool is probably a bad idea, I think the problem will inevitably pop up whether on Windows or somewhere else, so I think this question is neither Visual-C++ nor Windows specific. Given int nBoolean; I prefer this style: bool b = nBoolean?true:false; The following might be alternatives: bool b = !!nBoolean; bool b = (nBoolean != 0); Is there a generally preferred way? Rationale? I should add: Since I only work with Visual-C++ I cannot really say if this is a VC++ specific question or if the same problem pops up with other compilers. So it would be interesting to specifically hear from g++ or users how they handle the int-bool case. Regarding Standard C++: As David Thornley notes in a comment, the C++ Standard does not require this behavior. In fact it seems to explicitly allow this, so one might consider this a VC++ weirdness. To quote the N3029 draft (which is what I have around atm.): 4.12 Boolean conversions [conv.bool] A prvalue of arithmetic, unscoped enumeration, pointer, or pointer to member type can be converted to a prvalue of type bool. A zero value, null pointer value, or null member pointer value is converted to false; any other value is converted to true. (...)

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  • Objective-C and NSURL: where am I supposed to declare receivedData?

    - by jthomas
    I have a two classes, a controller called "AppController" and a class called "URLDelegate" that encapsulates the sample NSURL code from Apple's URL Loading System Programming Guide. The guide repeatedly mentions declaring the receivedData instance variable "elsewhere." I assume this means outside of the URLDelagate class, because if I declare it in the URLDelegate class, my controller class can't "see" the data that has been downloaded. I know that data is received, because in my connectionDidFinishLoading function, I have NSLog display the results: NSLog(@"Succeeded! Received %d bytes of data",[receivedData length]); receivedText=[[NSString alloc] initWithData:receivedData encoding: NSASCIIStringEncoding]; NSLog(@"receivedText=%@",receivedText); So I'm a bit stumped with the following questions: Where should I declare receivedData? My controller class? A third class? Can I just declare it like any normal NSMutableData variable? How do I give my URLDelegate class "access" to this variable? E.g., if I declare receivedData in my AppController class, wouldn't I have to instantiate AppController within URLDelegate? But how would this possible if it's the AppController class which is instantiating the URLDelegate class in the first place? Especially with regard to the last question, I feel like I must be overlooking something blindingly obvious and fundamental. If anyone could point me in the right direction, I would really appreciate it. Thank you!

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  • ADO.NET Multiple simultaneous reads from an open database.

    - by Deverill
    Answer not needed - my logic was wrong and this question is invalid. Charles helped me see where I went off-tracks. Thanks I have a utility that moves data from one source to another. In the process of writing the record I check to see if it exists and do an update/insert as necessary. The difficulty I have is that as I'm writing the main record info there is a 2nd table for "custom data" that I have to check to see if it exists and do an update/insert for that as well. Example: I may be loading a pencil sharpener that may or may not exist. While I'm writing it into destination it has characteristics such as style, color, etc. and each of them may or may not exist. As written I seem to need to have 2 DataReaders open, one for the sharpener and one to check for and update color. I am new to ADO.NET, but not to programming and it's more complicated than I listed but for sanity's sake I didn't put all the details. My question is: What am I missing? You can't have 2 readers open at the same time on a connection, yet I can't close the first if I'm stepping through all products. It seems inefficient to have 2 connections, readers, etc. for this. Is there a feature of ADO.NET DBs that I'm missing? How would you do it? Thanks!

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