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• Game network physics collision

  - by Jonas Byström

  How to simulating two client-controlled vehicles colliding (sensibly) in a typical client/server setup for a network game? I did read this eminent blog post on how to do distributed network physics in general (without traditional client prediction), but this question is specifically on how to handle collisions of owned objects. Example Say client A is 20 ms ahead of server, client B 300 ms ahead of server (counting both latency and maximum jitter). This means that when the two vehicles collide, both clients will see the other as 320 ms behind - in the opposite direction of the velocity of the other vehicle. Head-to-head on a Swedish highway means a difference of 16 meters/17.5 yards! What not to try It is virtually impossible to extrapolate the positions, since I also have very complex vehicles with joints and bodies all over, which in turn have linear and angular positions, velocities and accelerations, not to mention states from user input.

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• Using std::bad_alloc for C pointers

  - by otibom

  I'm using a library written in C in a C++ project. I'd like to use C++ exceptions to handle C errors. In particular, it would be nice to have an exception thrown if an allocation fails. I can do this in constructors of classes which hold C-style pointers to C structs : if (c_object == NULL) throw std::bad_alloc(); But if the class is responsible for several C objects they are no ways of free-ing all already allocated pointers since the destructor isn't called. I have a feeling I could use smart-pointers, but I don't have much experience with them. What's more, I have to have access to the original C pointers to use the C api properly. Is there an elegant solution to this ?

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• Does invoking System.gc() in java suggest garbage collection of the tenured generation as well as th

  - by Markus Jevring

  When invoking System.gc() in java (via JMX), it will dutifully (attempt to) clean the young generation. This generally works very well. I have never seen it attempt to clean the tenured generation, though. This leads me to two questions: Can the tenured generation even be collected (i.e. is there actually garbage in this generation, or do all objects in the tenured generation actually still have live references to them)? If the tenured generation can be collected, can this be done via System.gc(), or is there another way to do it (unlikely), or will I simply have to wait until I run out of space in the tenured generation?

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• Is base method able to use derived base data members?

  - by iTayb

  Lets assume we have the following code: abstract class Base1 { protected int num; } class Der1:Base1 { protected Color color; protected string name; } class Der2:Base1 { protected DateTime dthen; } and so on. An array of base1 type exists and includes many objects created out of classes that are derived from base1. Is it possible to define the toString() method in the base class only? something like: public override string toString() { if (this is Der1) return "num = " + this.num + "color = " + this.color.toString() + " name = " this.name; if (this is Der2) return "num = " + this.num + "dthen = " + this.dthen.toString(); // and so on ... } Thank you very much :) P.S. This is not an homework question. I've just wondered about.

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• Managing test data for Junit tests.

  - by nobody

  Hi, We are facing one problem in managing test data(xmls which is used to create mock objects). The data which we have currently has been evolved over a long period of time. Each time we add a new functionality or test case we add new data to test that functionality. Now, the problem is when the business requirement changes the format( like length or format of a variable) or any change which the test data doesn't support , we need to change the entire test data which is 100s of MBs in size. Could anyone suggest a better method or process to overcome this problem? Any suggestion would be appreciated.

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• Struts2 scriptlet

  - by Bret

  Using struts2 with jsp with standard struts tag libraries. I'm trying to dynamically hide a DIV on page load, but still send it to the browser. This is so I can show it later via javascript. The request objects one and two are not easily referenced via a jsp:usebean tag. (They are enums and cannot be instantiated) I tried using a combination of s:if tags or c:if tags and it just looks ugly. <% String displayStr = "display: none;"; if(request.getAttribute("one") != null || request.getAttribute("two") != null ) { displayStr = "display: block;"; } %> <div id="next" style="<%=displayStr %>"> Any suggestions for a better way to do this?

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• iOS Development: Can I store an array of integers in a Core Data object without creating a new table to represent the array?

  - by BeachRunnerJoe

  Hello. I'm using Core Data and I'm trying to figure out the simplest way to store an array of integers in one of my Core Data entities. Currently, my entities contain various arrays of objects that are more complex than a single number, so it makes sense to represent those arrays as tables in my DB and attach them using relationships. If I want to store a simple array of integers, do I need to create a new table with a single column and attach it using a one-to-many relationship? Or is there a more simple way? Thanks in advance for your wisdom!

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• why assert_equal() in Ruby on Rails sometimes seem to compare by Identity and sometimes by value?

  - by Jian Lin

  it was very weird that yesterday, I was do an integration test in Rails and assert_equal array_of_obj1, array_of_obj2 # obj1 from db, obj2 created in test and it failed. The values shown inside the array and objects were identical. If I change the test to assert array_of_obj1 == array_of_obj2 Then it will pass. But today, the first test actually passed. What reason could it be? Is assert_equal always using == or .equal? in Rails 2.2 or 2.3.5?

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• C++ enforce conditions on inherited classes

  - by user231536

  I would like to define an abstract base class X and enforce the following: a) every concrete class Y that inherits from X define a constructor Y(int x) b) it should be possible to test whether two Y objects are equal. For a, one not very good solution is to put a pure virtual fromInt method in X which concrete class will have to define. But I cannot enforce construction. For b), I cannot seem to use a pure virtual method in X bool operator == (const X& other) const =0; because in overridden classes this remains undefined. It is not enough to define bool operator == (const Y& other) const { //stuff} because the types don't match. How do I solve these problems?

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• in_array() - help on what specifically would return true

  - by Kerri

  I am using in_array, and I'm trying to use it in a way where it will only return true if it's an exact match of one of the objects in the array, not just if it's "in" the array. e.g. 1. $sample_array = array('123', '234', '345'); 2. $sample_array = array('23', '34', '45'); in_array('23', $sample_array); In the above example, I would only want version 2 to return true, because it has the exact string, '23'. Version 1 returns true as well though, because the array contains instances of the string '23'. How would I get this to work so that only version 2 returns true? Am I even using the right function?

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• Offsite data storage for simple app, or a similar supported persistence mechanism?

  - by jdk

  Question Is there a usable facebook entry point to the Data Storage API that facebook lists on their app admin page for developers, or should I consider an alternate mechanism? What alternative mechanisms exist to simply persist my information offsite (away from my server app) without stuffing it into a cookie that's prone to expire? ... Background The facebook Data Store Admin tool is made available in a facebook App's Settings as seen here: (continue reading below) However when I visit the DataStoreAdmin link nothing works (i.e. clicking the buttons to define the data store types and objects does nothing - I have tried different browsers). The Wiki page for Data Store API hasn't been updated recently and the second last update says the beta Data Store was taken offline. It seems odd the link would be readily available and highly visible at the top of the App configuration area if indeed it's defunct. I was hoping some kind of key/value pair solution to remove the data calls from my own server.

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• Filtering NSMutableArray based on enum property

  - by Marty

  I've got an NSMutableArray filled with objects of type "GameObject". GameObject has a number of properties, one of which being "gameObjectType" . "gameObjectType" is of type GameObjectTypeEnum. I want to be able to filter this NSMutableArray so only GameObjects of a certain type are returned. I've got the following in place, but it's giving me a "BAD ACCESS" error: NSPredicate *predicate = [NSPredicate predicateWithFormat:@"gameObjectType = %@", gameObjectType]; return [gameObjects filteredArrayUsingPredicate:predicate]; Is it possible to pass a "custom" type (ie, this enum I've defined) into the predicateWithFormat call?

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• Facebook Open Graph Debugger Error

  - by Darshanjit Badrain

  Hi I am new to programming and have tried to make a facebook app with open graph beta tutorial. I have done exactly as described in the tutorial but when i try to use the debug tool it gives me an error: Extraneous Property: Objects of this type do not allow properties named og:app_id. I have noticed and searched that its doing this because the tag needs to be <fb:app_id>. I checked my file it says fb:app_id only, but the raw data that pulls up on the debug tool shows meta property="og:app_id" content="267029796703617" even though i have changed and uploaded with fb:app_id. I have checked my page several times and tried some possible solutions but have had no success. Can someone help me fix this.

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• Updating a database periodically with Java

  - by MSR

  I would like to perform updates to a MySQL database using two separate classes (that do different things) -- one doing so every 10 seconds, and the second every minute. I have a few gaps in my Java knowledge and I'm wondering what the best way to achieve it is. Importantly, if connectivity to the database is lost, I need reconnection attempts to occur indefinitely, and I'm guessing the use of Prepared Statements will make queries more efficient. Should the connection to the database be left open all the time or closed between the updates being run? Maybe I also need to think about clearing objects/resources out of memory if the class instances are going to be run indefinitely.

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• How do I compare vectors in C++?

  - by Sam Phelps

  I am trying to compare two vector objects, and return a single vector containing all the chars which appear in both vectors. How would I go about this without writing some horribly complex manual method which compares every char in the first vector to every char in the second vector and using an if to add it to a third vector (which would be returned) if they match. Maybe my lack of real experience with vectors is making me imagine this will be harder than it really is, but I suspect there is some simplier way which I have been unable to find through searching.

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• (conditional) Multiple Event Handlers C#

  - by gjk

  A portion of my program requires a "flag" retrieval, that is I am fetching a value that is either True or False, and based on this return value two things could follow. 1) The flag is true, aka "go ahead", and I retrieve data from a database. 2) The flag is false, and I want to prevent the data from being retrieved. Now, this check has to be performed before any function that would call upon the database in question. I decided to implement this check in the form of an event handler attached to GUI objects that would trigger this data inquiry. This check event handler is called first upon necessary events, and my question is: How do I stop subsequent event handlers from firing if the FIRST event handler (my flag checker) comes up FALSE? Thanks

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• How to get and set dynamic or runtime input in XStream

  - by RSR

  i am getting xml tags as input in java web services. i need that to parsed to java objects i had tried everything like XStream,XMLEncoder, JaxB Concepts also. But I don't know what is the problem. i am having pojo class for that input but it is not working. example for xml tags : 1034|Chromepet|Chennai|117.97.24.32 first to extract data : i need only data from .... and then Using Xstream or XmlEncoder i have to parse it like i want only devsrlno:101 signalstrength : 30 devicedatetime:01/24/2010 10:10:23 AM gprsdatetime:01/24/2010 10:10:23 AM debug:yes autoip :1034|Chromepet|Chennai|117.97.24.32. please tell me how to do it

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• Why are Objective-C instance variables declared in an interface?

  - by Chase

  I'm just getting into Objective-C (Java is my primary OO language). Defining an object's instance variables in the interface instead of the class seems strange. I'm used to an interface being a public API definition with nothing besides method signatures (not counting constants here). Is there some reason that state is defined in an interface (even if it is private) and behaviour is defined in a class. It just seems odd that since objects are state+behavior that the definition would be split into two separate places. Is it a design benefit is some way? A pain in the rear issue that you are just forced to deal with in Objective-C? A non-issue, just different? Any background on why it's done this way? Or can you put object state in a class and I just haven't hit that part in my book yet?

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• IB z-order on simulator 6.0

  - by Stanley

  Consider the above's IB objects listing. Siblings further down the list should be on top of the siblings listed further up when rendered on the screen. Under Xcode 4.5.2, everything is ok if iphone simulator 5.1 is used. But for simulator 6.0 the map just covers everything. The same if using actual devices (phones) for testing. Hope that somebody knowledgeable could help. Please also add comments if you do not find such a problem on simulator 6.0. Because chances are the problem is related to how my project is setup. Update : Have setup a test project with the iOS 6 map view. There seems to be no problem with the z-order. So the problem should relate to my code.

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• Why does the assignment operator return a value and not a reference?

  - by Nick Lowman

  I saw the example below explained on this site and thought both answers would be 20 and not the 10 that is returned. He wrote that both the comma and assignment returns a value, not a reference. I don't quite understand what that means. I understand it in relation to passing variables into functions or methods i.e primitive types are passed in by value and objects by reference but I'm not sure how it applies in this case. I also understand about context and the value of 'this' (after help from stackoverflow) but I thought in both cases I would still be invoking it as a method, foo.bar() which would mean foo is the context but it seems both result in a function call bar(). Why is that and what does it all mean? var x = 10; var foo = { x: 20, bar: function () {return this.x;} }; (foo.bar = foo.bar)();//returns 10 (foo.bar, foo.bar)();//returns 10

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• Adobe After Efects Plugin With Cocoa (Overriding malloc)

  - by mustISignUp

  Messing about a bit, i have a working Adobe After Effects plugin with a bit of Obj-c / Cocoa in it (NSArray and custom objects - not ui stuff). The SDK guide states:- Always use After Effects memory allocation functions. In low-memory conditions (such as during RAM preview), it’s very important that plug-ins not compete with After Effects for OS memory, and deal gracefully with out-of-memory conditions. Failing to use our functions can cause lock-ups, crashes, and tech support calls. Don’t do that. If you’re wrapping existing C++ code, overloading new and delete to use our functions will save substantial reimplementation. On Windows, derive all classes from a common base class which implements new and delete. so my question.. is something compatible with the above statement possible in Obj-c?

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• Java swing doesn't show changes to source

  - by out_sider

  I'm using Java Swing graphical editor with netbeans to make my project...but using it brings some limitations like I can't add to a jpanel an image,using java swing options. So i'll need to code it, implementing a new jPanel. My problem is that the code generated by the java swing graphical editor can't be edited so instead of adding the new JPanel code in the initComponents() section I'm doing it after this function is called in the constructor of my main JPanel. But any code I add is not recognized by the "Designer" which means that after making my coded objects I can't use them in the "Designer" and everything must be coded, which is a pain considering how much easier is previewing and moving elements in the "Designer" tool. How can I code what I want but steel appear in the "DEsigner"? Thx in advance

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• will destroyed() be emitted if the constructor of a class derived from QObject throws?

  - by PorkyBrain

  Ive seen Qt GUI syntax like the following all over the place: myDialog::myDialog(QWidget *parent, Qt::WFlags flags):QDialog(parent, flags) { QPushButton *button = new QPushButton("&Download", this); QVBoxLayout *layout = new QVBoxLayout(this); //something that can throw here layout ->addWidget(button ); setLayout(layout); } I've always wondered if this can leak in the event of an exception because the "this" I'm giving as a parent to button and layout is not fully constructed so it might not destroy its children. I tried it out in MSVC2010 Qt4.8.3 and it looks like as soon as the base QObject class is fully created (which is done first of course) it is ok to pass "this" to other objects in the constructor, they will destroyed correctly. I haven't found the spot in the Qt docs guaranteeing this though, can someone point me to it so I have assurance that this will not change in the future?

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• unit testing methods with arrays as argument

  - by Ryan

  I am porting over some C++ assembly to VB that performs demodulation of various waveforms. I decided to go the unit test route instead of building a test app to get a feel for how testing is performed. The original demodulation code accepts an array that is the waveform along with some other arguments. How should one go about performing a test on something that has an array as an argument? Is it acceptable to generate fake data in a file and read it in at the beginning of the test? On a side note - The original C++ code was written because we were performing math that we couldn't do in VB6 so we had to cross boundaries between C++ and VB6 and arrays were used. Is there a "better" way of handling large amounts of data in the .NET world that us VB6 programmers may not yet be privy to? Or if we aren't crossing that managed/un-managed boundary, should we be representing our data as objects instead? Thanks all!

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• Trying to re-create UI object from the native iPhone Calendar Notes

  - by FrankOS

  Probably a lame question for a start but i'm trying to re-create the ui object that's used in Apple's native Calendar to create notes. It's the basic text-field but with multiple lines. Sort of a text-area. Now i know that anything from the calendar in terms of ui objects isn't available but i have seen this in quite few apps so i'm guessing it's some sort of standard component. I must be dumb but i just cannot find it. Help please... Thx :)

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