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  • SlimDX Texture2D from DataRectangle array

    - by Rebekah Bryant
    I'm totally new to DirectX. I'm using SlimDX to create a texture consisting of 13046 DataRectangles. Here's my code. It's breaking on the Texture2D constructor with "E_INVALIDARG: An invalid parameter was passed to the returning function (-2147024809)." inParms is just a struct containing handle to a Panel. public Renderer(Parameters inParms, ref DataRectangle[] inShapes) { Texture2DDescription description = new Texture2DDescription() { Width = 500, Height = 500, MipLevels = 1, ArraySize = inShapes.Length, Format = Format.R32G32B32_Float, SampleDescription = new SampleDescription(1, 0), Usage = ResourceUsage.Default, BindFlags = BindFlags.RenderTarget | BindFlags.ShaderResource, CpuAccessFlags = CpuAccessFlags.None, OptionFlags = ResourceOptionFlags.None }; SwapChainDescription chainDescription = new SwapChainDescription() { BufferCount = 1, IsWindowed = true, Usage = Usage.RenderTargetOutput, ModeDescription = new ModeDescription(0, 0, new Rational(60, 1), Format.R8G8B8A8_UNorm), SampleDescription = new SampleDescription(1, 0), Flags = SwapChainFlags.None, OutputHandle = inParms.Handle, SwapEffect = SwapEffect.Discard }; Device.CreateWithSwapChain(DriverType.Hardware, DeviceCreationFlags.None, chainDescription, out mDevice, out mSwapChain); Texture2D texture = new Texture2D(Device, description, inShapes); } EDIT: Running with the Debug flag set, I got: D3D11 ERROR: ID3D11Device::CreateTexture2D: The format (0x6, R32G32B32_FLOAT) cannot be bound as a RenderTarget, or cast to a format that could be bound as a RenderTarget. This is because the current graphics implementation does not even support this Format. Therefore this format does not support D3D11_BIND_RENDER_TARGET. Use CheckFormatSupport to check Format support. [ STATE_CREATION ERROR #92: CREATETEXTURE2D_UNSUPPORTEDFORMAT] D3D11 ERROR: ID3D11Device::CreateTexture2D: Returning E_INVALIDARG, meaning invalid parameters were passed. [ STATE_CREATION ERROR #104: CREATETEXTURE2D_INVALIDARG_RETURN]

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  • Android threads trouble wrapping my head around design

    - by semajhan
    I am having trouble wrapping my head around game design. On the android platform, I have an activity and set its content view with a custom surface view. The custom surface view acts as my panel and I create instances of all classes and do all the drawing and calculation in there. Question: Should I instead create the instances of other classes in my activity? Now I create a custom thread class that handles the game loop. Question: How do I use this one class in all my activities? Or do I have to create a separate instance of the extended thread class each time? In my previous game, I had multiple levels that had to create an instance of the thread class and in the thread class I had to set constructor methods for each separate level and in the loop use a switch statement to check which level it needs to render and update. Sorry if that sounds confusing. I just want to know if the method I am using is inefficient (which it probably is) and how to go about designing it the correct way. I have read many tutorials out there and I am still having lots of trouble with this particular topic. Maybe a link to a some tutorials that explain this? Thanks.

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  • An ideal way to decode JSON documents in C?

    - by AzizAG
    Assuming I have an API to consume that uses JSON as a data transmission method, what is an ideal way to decode the JSON returned by each API resource? For example, in Java I'd create a class for each API resource then initiate an object of that class and consume data from it. for example: class UserJson extends JsonParser { public function UserJson(String document) { /*Initial document parsing goes here...*/ } //A bunch of getter methods . . . . } The probably do something like this: UserJson userJson = new UserJson(jsonString);//Initial parsing goes in the constructor String username = userJson.getName();//Parse JSON name property then return it as a String. Or when using a programming language with associative arrays(i.e., hash table) the decoding process doesn't require creating a class: (PHP) $userJson = json_decode($jsonString);//Decode JSON as key=>value $username = $userJson['name']; But, when I'm programming in procedural programming languages (C), I can't go with either method, since C is neither OOP nor supports associative arrays(by default, at least). What is the "correct" method of parsing pre-defined JSON strings(i.e., JSON documents specified by the API provider via examples or documentation)? The method I'm currently using is creating a file for each API resource to parse, the problem with this method is that it's basically a lousy version of the OOP method, as it looks exactly like the OOP method but doesn't provide any OOP benefits(e.g., can't pass an object of the parser, etc.). I've been thinking about encapsulating each API resource parser file in a publicly accessed structure(pointing all functions/publicly usable variables to the structure) then accessing the parser file code from within the structure(parser.parse(), parser.getName(), etc.). As this way looks a bit better than the my current method, it still just a rip off the OOP way, isn't it? Any suggestions for methods to parse JSON documents on procedural programming lanauges? Any comments on the methods I'm currently using(either 3 of them)?

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  • How to manage focus for a small set of simple widgets

    - by Christoph
    I'm developing a set of simple widgets for a small (128x128) display. For example I'd like to have a main screen with an overlay menu which I can use to toggle visibilty of main screen elements. Each option would be an icon with a box around it while it is selected. Button (left, up, right, down, enter) events should be given to the widget that has "focus". Focus is a simple thing to understand when using a GUI, but I'm having trouble implementing this. Can you suggest a simple concept for managing focus and input events? I have these simple ideas: Only one widget can have focus, so I need a single pointer to that widget. When this widget gets some kind of "cycle" input (as in "highlight the next item in this list"), the focus is given to a different widget. a widget must have a way of telling the application which widget the focus is given to next. if a widget cannot give a "next focus" hint, the application must be able to figure out where the focus should go. Widgets are currently structured like this: A widget can have a parent, which is passed to the constructor. Widgets are created statically, as I want to avoid dynamic memory allocation (I only have 16kB of RAM and I'd like to have control over that). widgets have siblings, implemented as an intrusive linked list (they have a next member). A parent has a pointer to the head of its list of children. Input events are arguments to the widgets buttonEvent methods which can accept or ignore that event. If it ignores the event, it can pass the event to its parent. My Questions: How can I manage focus for these widgets? Am I making this too complicated?

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  • Android threads trouble wrapping my head around design

    - by semajhan
    I am having trouble wrapping my head around game design. On the android platform, I have an activity and set its content view with a custom surface view. The custom surface view acts as my panel and I create instances of all classes and do all the drawing and calculation in there. Question: Should I instead create the instances of other classes in my activity? Now I create a custom thread class that handles the game loop. Question: How do I use this one class in all my activities? Or do I have to create a separate thread each time? In my previous game, I had multiple levels that had to create an instance of the thread class and in the thread class I had to set constructor methods for each separate level and in the loop use a switch statement to check which level it needs to render and update. Sorry if that sounds confusing. I just want to know if the method I am using is inefficient (which it probably is) and how to go about designing it the correct way. I have read many tutorials out there and I am still having lots of trouble with this particular topic. Maybe a link to a some tutorials that explain this? Thanks.

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  • Initializing OpenFeint for Android outside the main Application

    - by Ef Es
    I am trying to create a generic C++ bridge to use OpenFeint with Cocos2d-x, which is supposed to be just "add and run" but I am finding problems. OpenFeint is very exquisite when initializing, it requires a Context parameter that MUST be the main Application, in the onCreate method, never the constructor. Also, the main Apps name must be edited into the manifest. I am trying to fix this. So far I have tried to create a new Application that calls my Application to test if just the type is needed, but you do really need the main Android application. I also tried using a handler for a static initialization but I found pretty much the same problem. Has anybody been able to do it? This is my working-but-not-as-intended code snippet public class DerpHurr extends Application{ @Override public void onCreate() { super.onCreate(); initializeOpenFeint("TestApp", "edthedthedthedth", "aeyaetyet", "65462"); } public void initializeOpenFeint(String appname, String key, String secret, String id){ Map<String, Object> options = new HashMap<String, Object>(); options.put(OpenFeintSettings.SettingCloudStorageCompressionStrategy, OpenFeintSettings.CloudStorageCompressionStrategyDefault); OpenFeintSettings settings = new OpenFeintSettings(appname, key, secret, id, options); //RIGHT HERE OpenFeint.initialize(***this***, settings, new OpenFeintDelegate() { }); System.out.println("OpenFeint Started"); } } Manifest <application android:debuggable="true" android:label="@string/app_name" android:name=".DerpHurr">

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  • Example of persisting an inheritance relationship using ORM

    - by Schemer
    I have some experience with OOP and RDBs, but very little exposure to web programming. I am trying to understand what non-trivial types of problems are solved by ORM. Of course, I am familiar with the need for data persistence, but I have never encountered a need for persisting relationships between objects, a situation which is indicated in many online articles about ORM. I am not asking about the process of persisting a POJO to a database and restoring it later. Nor am I asking about why ORM frameworks are useful -- or a pain in the butt -- for doing so. I am particularly interested in how the need arises to persist and restore relationships between objects. In various documentation, I have seen many examples of persisting POJOs to a database, but the examples have all been for only very simple objects that are essentially nothing more than records anyway: a constructor, some private fields, and getter/setter methods. The motivation for persisting such an "object-record" seems obvious and trivial. This example: Hibernate ORM Tutorial offers such an example, but goes on to discuss mismatch issues of granularity, inheritance, identity, associations, and navigation that are not motivated by the example. If someone could offer a toy example of an instance where, say, the need arises to persist an inheritance relationship, I would be grateful. This might be blindingly obvious for anyone who has already encountered this situation but I have not and a great deal of searching and reading have not turned up any examples.

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  • OOP for unit testing : The good, the bad and the ugly

    - by Jeff
    I have recently read Miško Hevery's pdf guide to writing testable code in which its stated that you should limit your classes instanciations in your constructors. I understand that its what you should do because it allow you to easily mock you objects that are send as parameters to your class. But when it comes to writing actual code, i often end up with things like that (exemple is in PHP using Zend Framework but I think it's self explanatory) : class Some_class { private $_data; private $_options; private $_locale; public function __construct($data, $options = null) { $this->_data = $data; if ($options != null) { $this->_options = $options; } $this->_init(); } private function _init() { if(isset($this->_options['locale'])) { $locale = $this->_options['locale']; if ($locale instanceof Zend_Locale) { $this->_locale = $locale; } elseif (Zend_Locale::isLocale($locale)) { $this->_locale = new Zend_Locale($locale); } else { $this->_locale = new Zend_Locale(); } } } } Acording to my understanding of Miško Hevery's guide, i shouldn't instanciate the Zend_Local in my class but push it through the constructor (Which can be done through the options array in my example). I am wondering what would be the best practice to get the most flexibility for unittesing this code and aswell, if I want to move away from Zend Framework. Thanks in advance

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  • Designing Content-Based ETL Process with .NET and SFDC

    - by Patrick
    As my firm makes the transition to using SFDC as our main operational system, we've spun together a couple of SFDC portals where we can post customer-specific documents to be viewed at will. As such, we've had the need for pseudo-ETL applications to be implemented that are able to extract metadata from the documents our analysts generate internally (most are industry-standard PDFs, XML, or MS Office formats) and place in networked "queue" folders. From there, our applications scoop of the queued documents and upload them to the appropriate SFDC CRM Content Library along with some select pieces of metadata. I've mostly used DbAmp to broker communication with SFDC (DbAmp is a Linked Server provider that allows you to use SQL conventions to interact with your SFDC Org data). I've been able to create [console] applications in C# that work pretty well, and they're usually structured something like this: static void Main() { // Load parameters from app.config. // Get documents from queue. var files = someInterface.GetFiles(someFilterOrRegexPattern); foreach (var file in files) { // Extract metadata from the file. // Validate some attributes of the file; add any validation errors to an in-memory // structure (e.g. List<ValidationErrors>). if (isValid) { // Upload using some wrapper for an ORM an someInterface.Upload(meta.Param1, meta.Param2, ...); } else { // Bounce the file } } // Report any validation errors (via message bus or SMTP or some such). } And that's pretty much it. Most of the time I wrap all these operations in a "Worker" class that takes the needed interfaces as constructor parameters. This approach has worked reasonably well, but I just get this feeling in my gut that there's something awful about it and would love some feedback. Is writing an ETL process as a C# Console app a bad idea? I'm also wondering if there are some design patterns that would be useful in this scenario that I'm clearly overlooking. Thanks in advance!

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  • Why doesn't my cube hold a position?

    - by Christian Frantz
    I gave up a previous method of creating cubes so I went with a list to hold my cube objects. The list is being populated from an array like so: #region MAP float[,] map = { {0, 0, 0, 0, 0}, {0, 0, 0, 0, 0}, {0, 0, 0, 0, 0}, {0, 0, 0, 0, 0}, {0, 0, 0, 0, 0} }; #endregion MAP for (int x = 0; x < mapWidth; x++) { for (int z = 0; z < mapHeight; z++) { cubes.Add(new Cube(device, new Vector3(x, map[x,z], z), Color.Green)); } } The cube follows all the parameters of what I had before. This is just easier to deal with. But when I debug, every cube has a position of (0, 0, 0) and there's just one black cube in the middle of my screen. What could I be doing wrong here? public Vector3 cubePosition { get; set; } public Cube(GraphicsDevice graphicsDevice, Vector3 Position, Color color) { device = graphicsDevice; color = Color.Green; Position = cubePosition; SetUpIndices(); SetUpVerticesArray(); } That's the cube constructor. All variables are being passed correctly I think

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  • Discuss: PLs are characterised by which (iso)morphisms are implemented

    - by Yttrill
    I am interested to hear discussion of the proposition summarised in the title. As we know programming language constructions admit a vast number of isomorphisms. In some languages in some places in the translation process some of these isomorphisms are implemented, whilst others require code to be written to implement them. For example, in my language Felix, the isomorphism between a type T and a tuple of one element of type T is implemented, meaning the two types are indistinguishable (identical). Similarly, a tuple of N values of the same type is not merely isomorphic to an array, it is an array: the isomorphism is implemented by the compiler. Many other isomorphisms are not implemented for example there is an isomorphism expressed by the following client code: match v with | ((?x,?y),?z = x,(y,z) // Felix match v with | (x,y), - x,(y,z) (* Ocaml *) As another example, a type constructor C of int in Felix may be used directly as a function, whilst in Ocaml you must write a wrapper: let c x = C x Another isomorphism Felix implements is the elimination of unit values, including those in tuples: Felix can do this because (most) polymorphic values are monomorphised which can be done because it is a whole program analyser, Ocaml, for example, cannot do this easily because it supports separate compilation. For the same reason Felix performs type-class dispatch at compile time whilst Haskell passes around dictionaries. There are some quite surprising issues here. For example an array is just a tuple, and tuples can be indexed at run time using a match and returning a value of a corresponding sum type. Indeed, to be correct the index used is in fact a case of unit sum with N summands, rather than an integer. Yet, in a real implementation, if the tuple is an array the index is replaced by an integer with a range check, and the result type is replaced by the common argument type of all the constructors: two isomorphisms are involved here, but they're implemented partly in the compiler translation and partly at run time.

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  • Mock the window.setTimeout in a Jasmine test to avoid waiting

    - by Aligned
    Originally posted on: http://geekswithblogs.net/Aligned/archive/2014/08/21/mock-the-window.settimeout-in-a-jasmine-test-to-avoid-waiting.aspxJasmine has a clock mocking feature, but I was unable to make it work in a function that I’m calling and want to test. The example only shows using clock for a setTimeout in the spec tests and I couldn’t find a good example. Here is my current and slightly limited approach.   If we have a method we want to test: var test = function(){ var self = this; self.timeoutWasCalled = false; self.testWithTimeout = function(){ window.setTimeout(function(){ self.timeoutWasCalled = true; }, 6000); }; }; Here’s my testing code: var realWindowSetTimeout = window.setTimeout; describe('test a method that uses setTimeout', function(){ var testObject; beforeEach(function () { // force setTimeout to be called right away, no matter what time they specify jasmine.getGlobal().setTimeout = function (funcToCall, millis) { funcToCall(); }; testObject = new test(); }); afterEach(function() { jasmine.getGlobal().setTimeout = realWindowSetTimeout; }); it('should call the method right away', function(){ testObject.testWithTimeout(); expect(testObject.timeoutWasCalled).toBeTruthy(); }); }); I got a good pointer from Andreas in this StackOverflow question. This would also work for window.setInterval. Other possible approaches: create a wrapper module of setTimeout and setInterval methods that can be mocked. This can be mocked with RequireJS or passed into the constructor. pass the window.setTimeout function into the method (this could get messy)

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  • How to write constructors which might fail to properly instantiate an object

    - by whitman
    Sometimes you need to write a constructor which can fail. For instance, say I want to instantiate an object with a file path, something like obj = new Object("/home/user/foo_file") As long as the path points to an appropriate file everything's fine. But if the string is not a valid path things should break. But how? You could: 1. throw an exception 2. return null object (if your programming language allows constructors to return values) 3. return a valid object but with a flag indicating that its path wasn't set properly (ugh) 4. others? I assume that the "best practices" of various programming languages would implement this differently. For instance I think ObjC prefers (2). But (2) would be impossible to implement in C++ where constructors must have void as a return type. In that case I take it that (1) is used. In your programming language of choice can you show how you'd handle this problem and explain why?

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  • Pattern for a class that does only one thing

    - by Heinzi
    Let's say I have a procedure that does stuff: void doStuff(initalParams) { ... } Now I discover that "doing stuff" is quite a compex operation. The procedure becomes large, I split it up into multiple smaller procedures and soon I realize that having some kind of state would be useful while doing stuff, so that I need to pass less parameters between the small procedures. So, I factor it out into its own class: class StuffDoer { private someInternalState; public Start(initalParams) { ... } // some private helper procedures here ... } And then I call it like this: new StuffDoer().Start(initialParams); or like this: new StuffDoer(initialParams).Start(); And this is what feels wrong. When using the .NET or Java API, I always never call new SomeApiClass().Start(...);, which makes me suspect that I'm doing it wrong. Sure, I could make StuffDoer's constructor private and add a static helper method: public static DoStuff(initalParams) { new StuffDoer().Start(initialParams); } But then I'd have a class whose external interface consists of only one static method, which also feels weird. Hence my question: Is there a well-established pattern for this type of classes that have only one entry point and have no "externally recognizable" state, i.e., instance state is only required during execution of that one entry point?

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  • Is there a name for the Builder Pattern where the Builder is implemented via interfaces so certain parameters are required?

    - by Zipper
    So we implemented the builder pattern for most of our domain to help in understandability of what actually being passed to a constructor, and for the normal advantages that a builder gives. The one twist was that we exposed the builder through interfaces so we could chain required functions and unrequired functions to make sure that the correct parameters were passed. I was curious if there was an existing pattern like this. Example below: public class Foo { private int someThing; private int someThing2; private DateTime someThing3; private Foo(Builder builder) { this.someThing = builder.someThing; this.someThing2 = builder.someThing2; this.someThing3 = builder.someThing3; } public static RequiredSomething getBuilder() { return new Builder(); } public interface RequiredSomething { public RequiredDateTime withSomething (int value); } public interface RequiredDateTime { public OptionalParamters withDateTime (DateTime value); } public interface OptionalParamters { public OptionalParamters withSeomthing2 (int value); public Foo Build ();} public static class Builder implements RequiredSomething, RequiredDateTime, OptionalParamters { private int someThing; private int someThing2; private DateTime someThing3; public RequiredDateTime withSomething (int value) {someThing = value; return this;} public OptionalParamters withDateTime (int value) {someThing = value; return this;} public OptionalParamters withSeomthing2 (int value) {someThing = value; return this;} public Foo build(){return new Foo(this);} } } Example of how it's called: Foo foo = Foo.getBuilder().withSomething(1).withDateTime(DateTime.now()).build(); Foo foo2 = Foo.getBuilder().withSomething(1).withDateTime(DateTime.now()).withSomething2(3).build();

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  • How to create a thread in XNA for pathfinding?

    - by Dan
    I am trying to create a separate thread for my enemy's A* pathfinder which will give me a list of points to get to the player. I have placed the thread in the update method of my enemy. However this seems to cause jittering in the game every-time the thread is called. I have tried calling just the method and this works fine. Is there any way I can sort this out so that I can have the pathfinder on its own thread? Do I need to remove the thread start from the update and start it in the constructor? Is there any way this can work? Here is the code at the moment: bool running = false; bool threadstarted; System.Threading.Thread thread; public void update() { if (running == false && threadstarted == false) { thread = new System.Threading.Thread(PathThread); //thread.Priority = System.Threading.ThreadPriority.Lowest; thread.IsBackground = true; thread.Start(startandendobj); //PathThread(startandendobj); threadstarted = true; } } public void PathThread(object Startandend) { object[] Startandendarray = (object[])Startandend; Point startpoint = (Point)Startandendarray[0]; Point endpoint = (Point)Startandendarray[1]; bool runnable = true; // Path find from 255, 255 to 0,0 on the map foreach(Tile tile in Map) { if(tile.Color == Color.Red) { if (tile.Position.Contains(endpoint)) { runnable = false; } } } if(runnable == true) { running = true; Pathfinder p = new Pathfinder(Map); pathway = p.FindPath(startpoint, endpoint); running = false; threadstarted = false; } }

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  • How do I separate codes with classes?

    - by Trycon
    I have this main class: package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.SlickException; import org.newdawn.slick.state.BasicGameState; import org.newdawn.slick.state.StateBasedGame; public class tests extends BasicGameState{ public boolean render=false; tests1 test = new tests1(); public tests(int test) { // TODO Auto-generated constructor stub } @Override public void init(GameContainer arg0, StateBasedGame arg1) throws SlickException { // TODO Auto-generated method stub } @Override public void render(GameContainer arg0, StateBasedGame arg1, Graphics g) throws SlickException { // TODO Auto-generated method stub if(render==true) { g.drawString("Hello",100,100); } } @Override public void update(GameContainer gc, StateBasedGame s, int delta) throws SlickException { // TODO Auto-generated method stub test.render=render; test.update(gc, s, delta); } @Override public int getID() { // TODO Auto-generated method stub return 1000; } } and its sub-class: package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Input; import org.newdawn.slick.state.StateBasedGame; public class tests1 { public boolean render; public void update(GameContainer gc, StateBasedGame s, int delta) { Input input = gc.getInput(); if(input.isKeyPressed(Input.KEY_X)) { render=true; } } } I was finding a way to prevent many codes in one class. I'm new to java. When I try running my game, then when I press X, it does not work. How am I suppose to fix that?

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  • XNA CustomModelAnimationSample problem

    - by Mentoliptus
    I downloaded the official tutorial from:CustomModelAnimationSample It works fine but when I try to replicate it in my project, it fails to load the Tag property in my model. Is found that the probelm is in the line: skinnedModel = Content.Load<Model>("DudeWalk"); This line loads the model from the DudeWalk.fbx file and with the custom SkinnedModelProcessor. It loads the animations data in the model. After the line the Tag property is full. I stepped into the method and it went to the custom ModelData class. I copied everything from the projects CustomModelAnimationWindows and CustomModelAnimationPipeline to my solution and set all the references. I tried the same line of code and couldn't step in the method. It called the default method or model constructor and after the line the model's Tag propetry was null. I have to load the model through my custom SkinnedModelProcessor class, but how I tell the game to use this class? In the tutroail CustomModelClass the line is changed to: model = Content.Load<CustomModel>("tank"); So I assumed that I have to set the generic type to a custom model class, but the first example works without it. If anyone has some useful advice or some other helpful link, I'll be happy to try it.

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  • How do you encode Algebraic Data Types in a C#- or Java-like language?

    - by Jörg W Mittag
    There are some problems which are easily solved by Algebraic Data Types, for example a List type can be very succinctly expressed as: data ConsList a = Empty | ConsCell a (ConsList a) consmap f Empty = Empty consmap f (ConsCell a b) = ConsCell (f a) (consmap f b) l = ConsCell 1 (ConsCell 2 (ConsCell 3 Empty)) consmap (+1) l This particular example is in Haskell, but it would be similar in other languages with native support for Algebraic Data Types. It turns out that there is an obvious mapping to OO-style subtyping: the datatype becomes an abstract base class and every data constructor becomes a concrete subclass. Here's an example in Scala: sealed abstract class ConsList[+T] { def map[U](f: T => U): ConsList[U] } object Empty extends ConsList[Nothing] { override def map[U](f: Nothing => U) = this } final class ConsCell[T](first: T, rest: ConsList[T]) extends ConsList[T] { override def map[U](f: T => U) = new ConsCell(f(first), rest.map(f)) } val l = (new ConsCell(1, new ConsCell(2, new ConsCell(3, Empty))) l.map(1+) The only thing needed beyond naive subclassing is a way to seal classes, i.e. a way to make it impossible to add subclasses to a hierarchy. How would you approach this problem in a language like C# or Java? The two stumbling blocks I found when trying to use Algebraic Data Types in C# were: I couldn't figure out what the bottom type is called in C# (i.e. I couldn't figure out what to put into class Empty : ConsList< ??? >) I couldn't figure out a way to seal ConsList so that no subclasses can be added to the hierarchy What would be the most idiomatic way to implement Algebraic Data Types in C# and/or Java? Or, if it isn't possible, what would be the idiomatic replacement?

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  • Nested entities in Google App Engine. Do I do it right?

    - by Aleksandr Makov
    Trying to make most of the GAE Datastore entities concept, but some doubts drill my head. Say I have the model: class User(ndb.Model): email = ndb.StringProperty(indexed=True) password = ndb.StringProperty(indexed=False) first_name = ndb.StringProperty(indexed=False) last_name = ndb.StringProperty(indexed=False) created_at = ndb.DateTimeProperty(auto_now_add=True) @classmethod def key(cls, email): return ndb.Key(User, email) @classmethod def Add(cls, email, password, first_name, last_name): user = User(parent=cls.key(email), email=email, password=password, first_name=first_name, last_name=last_name) user.put() UserLogin.Record(email) class UserLogin(ndb.Model): time = ndb.DateTimeProperty(auto_now_add=True) @classmethod def Record(cls, user_email): login = UserLogin(parent=User.key(user_email)) login.put() And I need to keep track of times of successful login operations. Each time user logs in, an UserLogin.Record() method will be executed. Now the question — do I make it right? Thanks. EDIT 2 Ok, used the typed arguments, but then it raised this: Expected Key instance, got User(key=Key('User', 5418393301680128), created_at=datetime.datetime(2013, 6, 27, 10, 12, 25, 479928), email=u'[email protected]', first_name=u'First', last_name=u'Last', password=u'password'). It's clear to understand, but I don't get why the docs are misleading? They implicitly propose to use: # Set Employee as Address entity's parent directly... address = Address(parent=employee) But Model expects key. And what's worse the parent=user.key() swears that key() isn't callable. And I found out the user.key works. EDIT 1 After reading the example form the docs and trying to replicate it — I got type error: TypeError('Model constructor takes no positional arguments.'). This is the exacto code used: user = User('[email protected]', 'password', 'First', 'Last') user.put() stamp = UserLogin(parent=user) stamp.put() I understand that Model was given the wrong argument, BUT why it's in the docs?

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  • Check parameters annotated with @Nonnull for null?

    - by David Harkness
    We've begun using FindBugs with and annotating our parameters with @Nonnull appropriately, and it works great to point out bugs early in the cycle. So far we have continued checking these arguments for null using Guava's checkNotNull, but I would prefer to check for null only at the edges--places where the value can come in without having been checked for null, e.g., a SOAP request. // service layer accessible from outside public Person createPerson(@CheckForNull String name) { return new Person(Preconditions.checkNotNull(name)); } ... // internal constructor accessed only by the service layer public Person(@Nonnull String name) { this.name = Preconditions.checkNotNull(name); // remove this check? } I understand that @Nonnull does not block null values itself. However, given that FindBugs will point out anywhere a value is transferred from an unmarked field to one marked @Nonnull, can't we depend on it to catch these cases (which it does) without having to check these values for null everywhere they get passed around in the system? Am I naive to want to trust the tool and avoid these verbose checks? Bottom line: While it seems safe to remove the second null check below, is it bad practice? This question is perhaps too similar to Should one check for null if he does not expect null, but I'm asking specifically in relation to the @Nonnull annotation.

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  • Adding 2D vector movement with rotation applied

    - by Michael Zehnich
    I am trying to apply a slight sine wave movement to objects that float around the screen to make them a little more interesting. I would like to apply this to the objects so that they oscillate from side to side, not front to back (so the oscillation does not affect their forward velocity). After reading various threads and tutorials, I have come to the conclusion that I need to create and add vectors, but I simply cannot come up with a solution that works. This is where I'm at right now, in the object's update method (updated based on comments): Vector2 oldPosition = new Vector2(spritePos.X, spritePos.Y); //note: newPosition is initially set in the constructor to spritePos.x/y Vector2 direction = newPosition - oldPosition; Vector2 perpendicular = new Vector2(direction.Y, -direction.X); perpendicular.Normalize(); sinePosAng += 0.1f; perpendicular.X += 2.5f * (float)Math.Sin(sinePosAng); spritePos.X += velocity * (float)Math.Cos(radians); spritePos.Y += velocity * (float)Math.Sin(radians); spritePos += perpendicular; newPosition = spritePos;

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  • Generated Methods with Type Hints

    - by Ondrej Brejla
    Hi all! Today we would like to introduce you just another feature from upcoming NetBeans 7.3. It's about generating setters, constructors and type hints of their parameters. For years, you can use Insert Code action to generate setters, getters, constructors and such. Nothing new. But from NetBeans 7.3 you can generate Fluent Setters! What does it mean? Simply that $this is returned from a generated setter. This is how it looks like: But that's not everything :) As you know, before a method is generated, you have to choose a field, which will be associated with that method (in case of constructors, you choose fileds which should be initialized by that constructor). And from NetBeans 7.3, type hints are generated automatically for these parameters! But only if a proper PHPDoc is used in a corresponding field declaration, of course. Here is how it looks like. And that's all for today and as usual, please test it and if you find something strange, don't hesitate to file a new issue (product php, component Editor). Thanks a lot!

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  • Java Applet Tower Defence Game needs tweeking

    - by Ephiras
    Hello :) i have made a tower defence Game for my computer science class as one of my major projects, but have encountered some rather fatal roadblocks. here they are creating a menu screen (class Menu) that can set the total number of enimies, the max number of towers, starting money and the map. i tried creating a constructor in my Main class that sets all the values to whatever the Menu class passes in. I want the Menu screen to close after a difficulty has been selected and the main class to begin. Another problem i would really like some help with is instead of having to write entire arrays i would like to create a small segment of code that runs through an entire picture and sets up an array based on that pixels color.this way i can have multiple levels just dragged into a level folder and have the program read through them. users can even create their own. so a 1 if its yellow, a two if blue and a 3 if purple, then everything else = 0; you can download all the classes and code uif you'd like here sorry about having to redirect you but i wasn't sure how to efficently add a code spoiler. help is greatly appreciated

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  • Dynamically setting a value in XAML page:

    - by kaleidoscope
    This is find that I came across while developing the Silverlight screen for MSFT BPO Invoice project. Consider an instance wherein I am calling a xaml page as a popup in my parent xaml. And suppose we wanted to dynamically set a textbox field in the parent page with the  values that we select from the popup xaml. I tried the following approaches to achieve the above scenario: 1. Creating an object of the parent page within the popup xaml and initializing its textbox field.         ParentPage p = new ParentPage();         ParentPage.txtCompCode.Text = selectedValue; 2. Using App app = (App)Application.Current and storing the selected value in app. 3. Using IsolatedStorage All the above approaches failed to produce the desired effect since in the first case I did not want the parent page to get initialized over and over again and furthermore in all the approaches the value was not spontaneously rendered on the parent page. After a couple of trials and errors I decided to tweak the g.cs file of the Parent xaml. *.g.cs files are autogenerated and their purpose is to wire xaml-element with the code-behind file. This file is responsible for having reference to xaml-elements with the x:Name-property in code-behind. So I changed the access modifier of supposed textbox fields to 'static' and then directly set the value in popup xaml page as so: ParentPage.txtCompCode.Text = selectedValue; This seemed to work perfectly. We can access any xaml's g.cs file by going to the definition of InitializeComponent() present in the constructor of the xaml. PS: I may have failed to explore other more efficient ways of getting this done. So if anybody does find a better alternative please feel free to get back to me. Tinu

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