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  • How can I generate signed distance fields (2D) in real time, fast?

    - by heishe
    In a previous question, it was suggested that signed distance fields can be precomputed, loaded at runtime and then used from there. For reasons I will explain at the end of this question (for people interested), I need to create the distance fields in real time. There are some papers out there for different methods which are supposed to be viable in real-time environments, such as methods for Chamfer distance transforms and Voronoi diagram-approximation based transforms (as suggested in this presentation by the Pixeljunk Shooter dev guy), but I (and thus can be assumed a lot of other people) have a very hard time actually putting them to use, since they're usually long, largely bloated with math and not very algorithmic in their explanation. What algorithm would you suggest for creating the distance fields in real-time (favourably on the GPU) especially considering the resulting quality of the distance fields? Since I'm looking for an actual explanation/tutorial as opposed to a link to just another paper or slide, this question will receive a bounty once it's eligible for one :-). Here's why I need to do it in real time: There's something else:

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  • How to refactor my design, if it seems to require multiple inheritance?

    - by Omega
    Recently I made a question about Java classes implementing methods from two sources (kinda like multiple inheritance). However, it was pointed out that this sort of need may be a sign of a design flaw. Hence, it is probably better to address my current design rather than trying to simulate multiple inheritance. Before tackling the actual problem, some background info about a particular mechanic in this framework: It is a simple game development framework. Several components allocate some memory (like pixel data), and it is necessary to get rid of it as soon as you don't need it. Sprites are an example of this. Anyway, I decided to implement something ala Manual-Reference-Counting from Objective-C. Certain classes, like Sprites, contain an internal counter, which is increased when you call retain(), and decreased on release(). Thus the Resource abstract class was created. Any subclass of this will obtain the retain() and release() implementations for free. When its count hits 0 (nobody is using this class), it will call the destroy() method. The subclass needs only to implement destroy(). This is because I don't want to rely on the Garbage Collector to get rid of unused pixel data. Game objects are all subclasses of the Node class - which is the main construction block, as it provides info such as position, size, rotation, etc. See, two classes are used often in my game. Sprites and Labels. Ah... but wait. Sprites contain pixel data, remember? And as such, they need to extend Resource. But this, of course, can't be done. Sprites ARE nodes, hence they must subclass Node. But heck, they are resources too. Why not making Resource an interface? Because I'd have to re-implement retain() and release(). I am avoiding this in virtue of not writing the same code over and over (remember that there are multiple classes that need this memory-management system). Why not composition? Because I'd still have to implement methods in Sprite (and similar classes) that essentially call the methods of Resource. I'd still be writing the same code over and over! What is your advice in this situation, then?

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  • Prevent gnome-shell's dash from listing Recent Items

    - by Vivek
    I am using gnome-shell in Ubuntu 11.10. I am getting annoyed when dash search lists Recent Items. I have tried many ways to prevent it like Deleting activity.sqlite and activity.sqlite-journal files under ~/.local/share/zeitgeist Adding all the possible entries in Activity Log Manager to prevent application logging Specifying time range in Activity Log Manager to forget my activities. But none of the methods are working. The recent items list is still populated. Is there any way to tell dash not to list Recent Items while searching, other than the above methods? Or is there any way to delete the recent items list?

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  • How can a collection class instantiate many objects with one database call?

    - by Buttle Butkus
    I have a baseClass where I do not want public setters. I have a load($id) method that will retrieve the data for that object from the db. I have been using static class methods like getBy($property,$values) to return multiple class objects using a single database call. But some people say that static methods are not OOP. So now I'm trying to create a baseClassCollection that can do the same thing. But it can't, because it cannot access protected setters. I don't want everyone to be able to set the object's data. But it seems that it is an all-or-nothing proposition. I cannot give just the collection class access to the setters. I've seen a solution using debug_backtrace() but that seems inelegant. I'm moving toward just making the setters public. Are there any other solutions? Or should I even be looking for other solutions?

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  • Detect Driver

    This article is the continue of the previously posted article Hide Driver. Some methods to detect hidden files and processes are described in it

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  • Create a kind of Interface c++ [migrated]

    - by Liuka
    I'm writing a little 2d rendering framework with managers for input and resources like textures and meshes (for 2d geometry models, like quads) and they are all contained in a class "engine" that interacts with them and with a directX class. So each class have some public methods like init or update. They are called by the engine class to render the resources, create them, but a lot of them should not be called by the user: //in pseudo c++ //the textures manager class class TManager { private: vector textures; .... public: init(); update(); renderTexture(); //called by the "engine class" loadtexture(); gettexture(); //called by the user } class Engine { private: Tmanager texManager; public: Init() { //initialize all the managers } Render(){...} Update(){...} Tmanager* GetTManager(){return &texManager;} //to get a pointer to the manager //if i want to create or get textures } In this way the user, calling Engine::GetTmanager will have access to all the public methods of Tmanager, including init update and rendertexture, that must be called only by Engine inside its init, render and update functions. So, is it a good idea to implement a user interface in the following way? //in pseudo c++ //the textures manager class class TManager { private: vector textures; .... public: init(); update(); renderTexture(); //called by the "engine class" friend class Tmanager_UserInterface; operator Tmanager_UserInterface*(){return reinterpret_cast<Tmanager_UserInterface*>(this)} } class Tmanager_UserInterface : private Tmanager { //delete constructor //in this class there will be only methods like: loadtexture(); gettexture(); } class Engine { private: Tmanager texManager; public: Init() Render() Update() Tmanager_UserInterface* GetTManager(){return texManager;} } //in main function //i need to load a texture //i always have access to Engine class engine-GetTmanger()-LoadTexture(...) //i can just access load and get texture; In this way i can implement several interface for each object, keeping visible only the functions i (and the user) will need. There are better ways to do the same?? Or is it just useless(i dont hide the "framework private functions" and the user will learn to dont call them)? Before i have used this method: class manager { public: //engine functions userfunction(); } class engine { private: manager m; public: init(){//call manager init function} manageruserfunciton() { //call manager::userfunction() } } in this way i have no access to the manager class but it's a bad way because if i add a new feature to the manager i need to add a new method in the engine class and it takes a lot of time. sorry for the bad english.

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  • How can I generate signed distance fields in real time, fast?

    - by heishe
    In a previous question, it was suggested that signed distance fields can be precomputed, loaded at runtime and then used from there. For reasons I will explain at the end of this question (for people interested), I need to create the distance fields in real time. There are some papers out there for different methods which are supposed to be viable in real-time environments, such as methods for Chamfer distance transforms and Voronoi diagram-approximation based transforms (as suggested in this presentation by the Pixeljunk Shooter dev guy), but I (and thus can be assumed a lot of other people) have a very hard time actually putting them to use, since they're usually long, largely bloated with math and not very algorithmic in their explanation. What algorithm would you suggest for creating the distance fields in real-time (favourably on the GPU) especially considering the resulting quality of the distance fields? Since I'm looking for an actual explanation/tutorial as opposed to a link to just another paper or slide, this question will receive a bounty once it's eligible for one :-). Here's why I need to do it in real time:

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  • Creating an object that is ready to be used & unset properties - with IoC

    - by GetFuzzy
    I have a question regarding the specifics of object creation and the usage of properties. A best practice is to put all the properties into a state such that the object is useful when its created. Object constructors help ensure that required dependencies are created. I've found myself following a pattern lately, and then questioning its appropriateness. The pattern looks like this... public class ThingProcesser { public List<Thing> CalculatedThings { get; set; } public ThingProcesser() { CalculatedThings = new List<Thing>(); } public double FindCertainThing() { CheckForException(); foreach (var thing in CalculatedThings) { //do some stuff with things... } } public double FindOtherThing() { CheckForException(); foreach (var thing in CalculatedThings) { //do some stuff with things... } } private void CheckForException() { if (CalculatedThings.Count < 2) throw new InvalidOperationException("Calculated things must have more than 2 items"); } } The list of items is not being changed, just looked through by the methods. There are several methods on the class, and to avoid having to pass the list of things to each function as a method parameter, I set it once on the class. While this works, does it violate the principle of least astonishment? Since starting to use IoC I find myself not sticking things into the constructor, to avoid having to use a factory pattern. For example, I can argue with myself and say well the ThingProcessor really needs a List to work, so the object should be constructed like this. public class ThingProcesser { public List<Thing> CalculatedThings { get; set; } public ThingProcesser(List<Thing> calculatedThings) { CalculatedThings = calculatedThings; } } However, if I did this, it would complicate things for IoC, and this scenario hardly seems appropriate for something like the factory pattern. So in summary, are there some good guidelines for when something should be part of the object state, vs. passed as a method parameter? When using IoC, is the factory pattern the best way to deal with objects that need created with state? If something has to be passed to multiple methods in a class, does that render it a good candidate to be part of the objects state?

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  • Why setter method when getter method enough in PHP OOP

    - by phphunger
    I am practicing OOP with PHP, and I am struck at setter and getter methods. I can directly access the class properties and methods with getter method then what's the use of setter method? See my example. <?php class MyClass{ public $classVar = "Its a class variable"; public function Getter(){ return $this -> classVar; } } $obj = new MyClass; echo $obj -> Getter(); ?>

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  • How to sell Agile development to clients [on hold]

    - by Sander Marechal
    Our development shop would really like to do more agile projects but we have a problem getting clients on board. Many clients want a budget and a deadline. It's hard to sell a client on an agile project when our competitors do come up with waterfall-based fixed deadlines and fixed prices. We know their fixed numbers are bad, but the client doesn't know that. So, we end up looking bad to the client because we can't fix the price or a deadline but our competitors can. So, how can you get your sales force to successfully sell a project that uses agile development methods, or a product that is developed using such methods? All the information I found seems to focus on project management and developers.

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  • Ubuntu 13.04 ERROR: /etc/apt/sources.list not found

    - by Richard Riley
    So, I tried uninstalling the LAMP stack I had following the Ubuntu documentation for it. I also manually removed dbconfig-common. Now, I'm unable to run apt-get update. When I do, I get the error message: E: The method driver /usr/lib/apt/methods/htp could not be found. After some digging, I've discovered that I no longer even have an /etc/apt/sources.list file. Also, I've received an error, when trying to run: sudo tasksel install lamp-server That aptitude can not be found. Does anyone have an idea of what I can do? I'm not able to find any documentation online that works - all the documentation out there is dated and no longer (or will not) work with 13.04. I followed this link previously prior to posting my question and it did not work for me: How do I fix a "E: The method driver /usr/lib/apt/methods/http could not be found." error?

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  • Best Practice to return responses from service

    - by A9S6
    I am writing a SOAP based ASP.NET Web Service having a number of methods to deal with Client objects. e.g: int AddClient(Client c) = returns Client ID when successful List GetClients() Client GetClientInfo(int clientId) In the above methods, the return value/object for each method corresponds to the "all good" scenario i.e. A client Id will be returned if AddClient was successful or a List< of Client objects will be returned by GetClients. But what if an error occurs, how do I convey the error message to the caller? I was thinking of having a Response class: Response { StatusCode, StatusMessage, Details } where Details will hold the actual response but in that case the caller will have to cast the response every time. What are your views on the above? Is there a better solution?

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  • How to sell Agile development to (waterfall) clients

    - by Sander Marechal
    Our development shop would really like to do more agile projects but we have a problem getting clients on board. Many clients want a budget and a deadline. It's hard to sell a client on an agile project when our competitors do come up with waterfall-based fixed deadlines and fixed prices. We know their fixed numbers are bad, but the client doesn't know that. So, we end up looking bad to the client because we can't fix the price or a deadline but our competitors can. So, how can you get your sales force to successfully sell a project that uses agile development methods, or a product that is developed using such methods? All the information I found seems to focus on project management and developers.

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  • The sign of a true manager is delegation (C# style)

    - by MarkPearl
    Today I thought I would write a bit about delegates in C#. Up till recently I have managed to side step any real understanding of what delegates do and why they are useful – I mean, I know roughly what they do and have used them a lot, but I have never really got down dirty with them and mucked about. Recently however with my renewed interest in Silverlight delegates came up again as a possible solution to a particular problem, and suddenly I found myself opening a bland little console application to just see exactly how far I could take delegates with my limited knowledge. So, let’s first look at the MSDN definition of delegates… A delegate declaration defines a reference type that can be used to encapsulate a method with a specific signature. A delegate instance encapsulates a static or an instance method. Delegates are roughly similar to function pointers in C++; however, delegates are type-safe and secure. Well, don’t you love MSDN for such a useful definition. I must give it credit though… later on it really explains it a bit better by saying “A delegate lets you pass a function as a parameter. The type safety of delegates requires the function you pass as a delegate to have the same signature as the delegate declaration.” A little more reading up on delegates mentions that delegates are similar to interfaces in that they enable the separation of specification and implementation. A delegate declares a single method, while an interface declares a group of methods. So enough reading - lets look at some code and see a basic example of a delegate… Let’s assume we have a console application with a simple delegate declared called AdjustValue like below… class Program { private delegate int AdjustValue(int val); static void Main(string[] args) { } } In a sense, all we have said is that we will be creating one or more methods that follow the same pattern as AdjustValue – i.e. they will take one input value of type int and return an integer. We could then expand our code to have various methods that match the structure of our delegate AdjustValue (remember the structure is int xxx (int xxx)) class Program { private delegate int AdjustValue(int val); private static int Dbl(int val) { return val * 2; } private static int AlwaysOne(int val) { return 1; } static void Main(string[] args) { } }  Above I have expanded my project to have two methods, one called Dbl and the other AlwaysOne. Dbl always returns double the input val and AlwaysOne always returns 1. I could now declare a variable and assign it to be one of those functions, like the following… class Program { private delegate int AdjustValue(int val); private static int Dbl(int val) { return val * 2; } private static int AlwaysOne(int val) { return 1; } static void Main(string[] args) { AdjustValue myDelegate; myDelegate = Dbl; Console.WriteLine(myDelegate(1).ToString()); Console.ReadLine(); } } In this instance I have declared an instance of the AdjustValue delegate called myDelegate; I have then told myDelegate to point to the method Dbl, and then called myDelegate(1). What would the result be? Yes, in this instance it would be exactly the same as me calling the following code… static void Main(string[] args) { Console.WriteLine(Dbl(1).ToString()); Console.ReadLine(); }   So why all the extra work for delegates when we could just do what we did above and call the method directly? Well… that separation of specification to implementation comes to mind. So, this all seems pretty simple. Let’s take a slightly more complicated variation to the console application. Assume that my project is the same as the one previously except that my main method is adjusted as follows… static void Main(string[] args) { AdjustValue myDelegate; myDelegate = Dbl; myDelegate = AlwaysOne; Console.WriteLine(myDelegate(1).ToString()); Console.ReadLine(); } What would happen in this scenario? Quite simply “1” would be written to the console, the reason being that myDelegate was last pointing to the AlwaysOne method before it was called. Make sense? In a way, the myDelegate is a variable method that can be swapped and changed when needed. Let’s make the code a little more confusing by using a delegate in the declaration of another delegate as shown below… class Program { private delegate int AdjustValue(InputValue val); private delegate int InputValue(); private static int Dbl(InputValue val) { return val()*2; } private static int GetInputVal() { Console.WriteLine("Enter a whole number : "); return Convert.ToInt32(Console.ReadLine()); } static void Main(string[] args) { AdjustValue myDelegate; myDelegate = Dbl; Console.WriteLine(myDelegate(GetInputVal).ToString()); Console.ReadLine(); } }   Now it gets really interesting because it looks like we have passed a method into a function in the main method by declaring… Console.WriteLine(myDelegate(GetInputVal).ToString()); So, what it the output? Well, try take a guess on what will happen – then copy the code and see if you got it right. Well that brings me to the end of this short explanation of Delegates. Hopefully it made sense!

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  • Collision Systems Implementation

    - by hrr4
    Just curious what might be a good way to implement a decent collision system. As a class inherited by a base Entity class? Currently I'm stuck and could just use a couple better ideas than my own. Any help is appreciated! Edit: Sorry, it's 2D Collisioning but honestly, I'm not looking for specific collision methods. I'm looking more about the lines of implementation. Just curious of some of the common methods of how to implement collision systems such as: Should the entire collision system be it's own class? What, if anything, should be inheritable? These are some of my questions. Sorry for the confusion.

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  • Type Conversion in JPA 2.1

    - by delabassee
    The Java Persistence 2.1 specification (JSR 338) adds support for various new features such as schema generation, stored procedure invocation, use of entity graphs in queries and find operations, unsynchronized persistence contexts, injection into entity listener classes, etc. JPA 2.1 also add support for Type Conversion methods, sometime called Type Converter. This new facility let developers specify methods to convert between the entity attribute representation and the database representation for attributes of basic types. For additional details on Type Conversion, you can check the JSR 338 Specification and its corresponding JPA 2.1 Javadocs. In addition, you can also check those 2 articles. The first article ('How to implement a Type Converter') gives a short overview on Type Conversion while the second article ('How to use a JPA Type Converter to encrypt your data') implements a simple use-case (encrypting data) to illustrate Type Conversion. Mission critical applications would probably rely on transparent database encryption facilities provided by the database but that's not the point here, this use-case is easy enough to illustrate JPA 2.1 Type Conversion.

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  • More elegant way to avoid hard coding the format of a a CSV file?

    - by dsollen
    I know this is trivial issue, but I just feel this can be more elegant. So I need to write/read data files for my program, lets say they are CSV for now. I can implement the format as I see fit, but I may have need to change that format later. The simply thing to do is something like out.write(For.getValue()+","+bar.getMinValue()+","+fi.toString()); This is easy to write, but obviously is guilty of hard coding and the general 'magic number' issue. The format is hard-coded, requires parsing of the code to figure out the file format, and changing the format requires changing multiple methods. I could instead have my constants specifying the location that I want each variable to be saved in the CSV file to remove some of the 'magic numbers'; then save/load into the an array at the location specified by the constants: int FOO_LOCATION=0; int BAR_MIN_VAL_LOCATION=1; int FI_LOCATION=2 int NUM_ARGUMENTS=3; String[] outputArguments=new String[NUM_ARGUMENTS]; outputArguments[FOO_LOCATION] = foo.getValue(); outputArgumetns[BAR_MIN_VAL_LOCATION] = bar.getMinValue(); outptArguments[FI_LOCATOIN==fi.toString(); writeAsCSV(outputArguments); But this is...extremely verbose and still a bit ugly. It makes it easy to see the format of existing CSV and to swap the location of variables within the file easily. However, if I decide to add an extra value to the csv I need to not only add a new constant, but also modify the read and write methods to add the logic that actually saves/reads the argument from the array; I still have to hunt down every method using these variables and change them by hand! If I use Java enums I can clean this up slightly, but the real issue is still present. Short of some sort of functional programming (and java's inner classes are too ugly to be considered functional) I still have no obvious way of clearly expressing what variable is associated with each constant short of writing (and maintaining) it in the read/write methods. For instance I still need to write somewhere that the FOO_LOCATION specifies the location of foo.getValue(). It seems as if there should be a prettier, easier to maintain, manner for approaching this? Incidentally, I'm working in java at the moment, however, I am interested conceptually about the design approach regardless of language. Some library in java that does all the work for me is definitely welcome (though it may prove more hassle to get permission to add it to the codebase then to just write something by hand quickly), but what I'm really asking is more about how to write elegant code if you had to do this by hand.

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  • Useful design patterns for working with FragmentManager on Android

    - by antman8969
    When working with fragments, I have been using a class composed of static methods that define actions on fragments. For any given project, I might have a class called FragmentActions, which contains methods similar to the following: public static void showDeviceFragment(FragmentManager man){ String tag = AllDevicesFragment.getFragmentTag(); AllDevicesFragment fragment = (AllDevicesFragment)man.findFragmentByTag(tag); if(fragment == null){ fragment = new AllDevicesFragment(); } FragmentTransaction t = man.beginTransaction(); t.add(R.id.main_frame, fragment, tag); t.commit(); } I'll usually have one method per application screen. I do something like this when I work with small local databases (usually SQLite) so I applied it to fragments, which seem to have a similar workflow; I'm not married to it though. How have you organized your applications to interface with the Fragments API, and what (if any) design patterns do you think apply do this?

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  • Useful design patterns for working with FragmentManger on Android

    - by antman8969
    When working with fragments, I have been using a class composed of static methods that define actions on fragments. For any given project, I might have a class called FragmentActions, which contains methods similar to the following: public static void showDeviceFragment(FragmentManager man){ String tag = AllDevicesFragment.getFragmentTag(); AllDevicesFragment fragment = (AllDevicesFragment)man.findFragmentByTag(tag); if(fragment == null){ fragment = new AllDevicesFragment(); } FragmentTransaction t = man.beginTransaction(); t.add(R.id.main_frame, fragment, tag); t.commit(); } I'll usually have one method per application screen. I do something like this when I work with small local databases (usually SQLite) so I applied it to fragments, which seem to have a similar workflow; I'm not married to it though. How have you organized your applications to interface with the Fragments API, and what (if any) design patterns do you think apply do this?

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  • Is it okay to have many Abstract classes in your application?

    - by JoseK
    We initially wanted to implement a Strategy pattern with varying implementations of the methods in a commmon interface. These will get picked up at runtime based on user inputs. As it's turned out, we're having Abstract classes implementing 3 - 5 common methods and only one method left for a varying implementation i.e. the Strategy. Update: By many abstract classes I mean there are 6 different high level functionalities i.e. 6 packages , and each has it's Interface + AbstractImpl + (series of Actual Impl). Is this a bad design in any way? Any negative views in terms of later extensibility - I'm preparing for a code/design review with seniors.

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  • Try/Catch or test parameters

    - by Ondra Morský
    I was recently on a job interview and I was given a task to write simple method in C# to calculate when the trains meet. The code was simple mathematical equation. What I did was that I checked all the parameters on the beginning of the method to make sure, that the code will not fail. My question is: Is it better to check the parameters, or use try/catch? Here are my thoughts: Try/catch is shorter Try/catch will work always even if you forget about some condition Catch is slow in .NET Testing parameters is probably cleaner code (Exceptions should be exceptional) Testing parameters gives you more control over return values I would prefer testing parameters in methods longer than +/- 10 lines, but what do you think about using try/catch in simple methods just like this – i.e. return (a*b)/(c+d); There are many similar questions on stackexchnage, but I am interested in this particular scenario.

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  • How to configure simple game AI setting with jtable

    - by Asgard
    I'm developing an application that has methods of this kind: attackIfIsFar(); protectIfIsNear(); helpAfterDeadOf(); helpBeforeAttackOf(); etc. The initialization of my application for n players is something like player1.attackIfIsFar(player2); player2.protectIfIsNear(player4); player3.helpAfterDeadOf(player1); player4.helpBeforeAttackOf(player3); etc. I don't know how to configure a jtable that that can allow me to set the equivalent of this code-block In others words I need simply a way to create a jtable with 3 column and n row, were I can set in the column 1 and 3, the player, and in the central column one of the available methods that each player on the column 1 must invoke on each player of column 3

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