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  • Use crontab scheduling java application problem occurs

    - by koma
    The main method to start the java application. The main method initialize the log, and then determine whether the process is running. Every 10 minutes, scheduled to run through the linux crontab. Able to determine that the 10 minutes of this program must end. Under normal circumstances, will print the following log The beginning of the implementation of 10 minutes The end of the 10 minutes of normal The beginning of the implementation of 20 minutes The end of the 20 minutes of normal The beginning of the implementation of 30 minutes The end of the 30 minutes of normal ..... But now this situation: The beginning of the implementation of 10 minutes The end of the 10 minutes of normal Execution starts in 30 minutes, but detected already have a process in operation, the program exits. Start the execution of 40 points, but detected already have a process in operation, the program exits. ..... Very strange 20-minute log does not print, but the 20-minute program has been launched by the ps-ef | grep java view java thread, found in a 20-minute thread is locked. But why not see the log Check the linux dispatch log, not see scheduling a 20-minute log.

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  • Should I care about Junit redundancy when using setUp() with @Before annotation?

    - by c_maker
    Even though developers have switched from junit 3.x to 4.x I still see the following 99% of the time: @Before public void setUp(){/*some setup code*/} @After public void tearDown(){/*some clean up code*/} Just to clarify my point... in Junit 4.x, when the runners are set up correctly, the framework will pick up the @Before and @After annotations no matter the method name. So why do developers keep using the same conventional junit 3.x names? Is there any harm keeping the old names while also using the annotations (other than it makes me feel like devs do not know how this really works and just in case, use the same name AND annotate as well)? Is there any harm in changing the names to something maybe more meaningful, like eachTestMethod() (which looks great with @Before since it reads 'before each test method') or initializeEachTestMethod()? What do you do and why? I know this is a tiny thing (and may probably be even unimportant to some), but it is always in the back of my mind when I write a test and see this. I want to either follow this pattern or not but I want to know why I am doing it and not just because 99% of my fellow developers do it as well.

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  • FP for simulation and modelling

    - by heaptobesquare
    I'm about to start a simulation/modelling project. I already know that OOP is used for this kind of projects. However, studying Haskell made me consider using the FP paradigm for modelling a system of components. Let me elaborate: Let's say I have a component of type A, characterised by a set of data (a parameter like temperature or pressure,a PDE and some boundary conditions,etc.) and a component of type B, characterised by a different set of data(different or same parameter, different PDE and boundary conditions). Let's also assume that the functions/methods that are going to be applied on each component are the same (a Galerkin method for example). If I were to use an OOP approach, I would create two objects that would encapsulate each type's data, the methods for solving the PDE(inheritance would be used here for code reuse) and the solution to the PDE. On the other hand, if I were to use an FP approach, each component would be broken down to data parts and the functions that would act upon the data in order to get the solution for the PDE. This approach seems simpler to me assuming that linear operations on data would be trivial and that the parameters are constant. What if the parameters are not constant(for example, temperature increases suddenly and therefore cannot be immutable)? In OOP, the object's (mutable) state can be used. I know that Haskell has Monads for that. To conclude, would implementing the FP approach be actually simpler,less time consuming and easier to manage (add a different type of component or new method to solve the pde) compared to the OOP one? I come from a C++/Fortran background, plus I'm not a professional programmer, so correct me on anything that I've got wrong.

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  • OpenGL ES multiple objects not being rendered

    - by ladiesMan217
    I am doing the following to render multiple balls move around the screen but only 1 ball is seen to appear and function. I don't know why the rest (count-1) balls are not being drawn public void onDrawFrame(GL10 gl) { // TODO Auto-generated method stub gl.glDisable(GL10.GL_DITHER); gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); gl.glMatrixMode(GL10.GL_MODELVIEW); gl.glClientActiveTexture(DRAWING_CACHE_QUALITY_HIGH); gl.glLoadIdentity(); for(int i=0;i<mParticleSystem.getParticleCount();i++){ gl.glPushMatrix(); gl.glTranslatef(mParticleSystem.getPosX(i), mParticleSystem.getPosY(i), -3.0f); gl.glScalef(0.3f, 0.3f, 0.3f); gl.glColor4f(r.nextFloat(), r.nextFloat(), r.nextFloat(), 1); gl.glEnable(GL10.GL_TEXTURE_2D); mParticleSystem.getBall(i).draw(gl); gl.glPopMatrix(); } } Here is my void draw(GL10 gl) method public void draw(GL10 gl){ gl.glEnable(GL10.GL_CULL_FACE); gl.glEnable(GL10.GL_SMOOTH); gl.glEnable(GL10.GL_DEPTH_TEST); // gl.glTranslatef(0.2f, 0.2f, -3.0f); // gl.glScalef(size, size, 1.0f); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertBuff); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, points/2); gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); }

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  • A Web Service to collect data from local servers every hour

    - by anilerduran
    I'm trying to find a way to collect data from different servers around the world. Here are the details: There is only one single PowerShell script on servers that encrypts data (simple csv file) and sends with preferred method (HTTP/HTTPS Post could be) There is no more control on that servers. Can't install any service, process etc. Just I can configure script to execute every hour. This script also will have encrypted username/password/license key for every server. Script will compress data and send to me with these information. So I need a service (I'm not sure if Web Service is the rigth solution) on the cloud that will help me to: Will get data that is sent from servers using a method. Will authenticate request to recognize sender using license key/username/password and most importantly, Will redirect/send this filecab to my SQL Server on the cloud (Azure). Also it should seperate data according to customer information in license key. So every data for every customer will be stored in dedicated DB/Tables on my SQL All the processes above should be completed automatically. No way for manual steps. Question: A Web Service (SOAP or Restful) is the rigth solution for that?

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  • Complex string matching with fuzzywuzzy

    - by That1Guy
    I'm attempting to write a process that matches obscure strings to a single 'master string' for further processing. I have a lot of data that looks something like this: Basketball Basket Ball Football BasketBallR BBall BBall - r FootB ...and so on. These need to be mapped to a master record like so: Basketball = Basket Ball, BBall Basketball - R = BasketBallR, BBall - r I also have instances of data resembling this format: Football -r FootBall - r-g/H,Q,HH These situations need to be separated into different categories before being mapped. For example FootBall - r-g/H,Q,HH should be: Football - r Football - g Football - H Football - Q Football - HH At this point, it still needs to be mapped to a master record... I've tried several different combinations of fuzzywuzzy matching methods, Levenshtein Distance measurements, regex, etc. and can't seem to find a reliable method to logically associate different naming styles of a single item with a master name. I'm throwing my hands up in desperation. Are there any existing python resources than can help sort out my problem? Are there other options? Can anybody point out an obvious option that I might have overlooked? Basically, any suggestion, solution, resource or alternative method is greatly appreciated.

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  • Command Query Separation

    - by Liam McLennan
    Command query separation is a strategy, proposed by Bertrand Meyer, that each of an object’s methods should be either a command or a query. A command is an operation that changes the state of a system, and a query is an operation that returns a value. This is not the same thing as CQRS, hence why I think that CQRS is poorly named. An Example of Command Query Separation Consider a system that models books and shelves. There is a rule that a shelf may not be removed if it holds any books. One way to implement the removal is to write a method Shelf.Remove() that internally checks to make sure that the shelf is empty before removing it. If the shelf is not empty then it is not removed and an error is returned. To implement this feature following the principle of command query separation would require two methods, one to query the shelf and determine if it is empty and a second method to remove the shelf. Separating the query from the command makes the shelf class simpler to use because the state change is clear and explicit.

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  • What is the most efficient way to add and remove Slick2D sprites?

    - by kirchhoff
    I'm making a game in Java with Slick2D and I want to create planes which shoots: int maxBullets = 40; static int bullet = 0; Missile missile[] = new Missile[maxBullets]; I want to create/move my missiles in the most efficient way, I would appreciate your advise: public void shoot() throws SlickException{ if(bullet<maxBullets){ if(missile[bullet] != null){ missile[bullet].resetLocation(plane.getCenterX(), plane.getCenterY(), plane.image.getRotation()); }else{ missile[bullet] = new Missile("resources/missile.png", plane.getCenterX(), plane.getCenterY(), plane.image.getRotation()); } }else{ bullet = 0; missile[bullet].resetLocation(plane.getCenterX(), plane.getCenterY(), plane.image.getRotation()); } bullet++; } I created the method resetLocation in my Missile class in order to avoid loading again the resource. Is it correct? In the update method I've got this to move all the missiles: if(bullet > 0 && bullet < maxBullets){ float hyp = 0.4f * delta; if(bullet == 1){ missile[0].move(hyp); }else{ for(int x = 0; x<bullet; x++){ missile[x].move(hyp); } } }

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  • Understanding interfaces [closed]

    - by user985482
    Possible Duplicate: When to use abstract classes instead of interfaces and extension methods in C#? Why are interfaces useful? What is the point of an interface? What other reasons are there to write interfaces rather than abstract classes? What is the point of having every service class have an interface? Is it bad habit not using interfaces? I am reading Microsoft Visual C# 2010 Step by Step which I feel it is a very good book on introducing you to the C# language. I have just finished reading a chapter on interfaces and although I understood the syntax of creating and using interfaces I have trouble of understanding the point on why should I use them? Correct me If I am wrong but in an interface you can only declare methods names and parameters.The body of the method should be declared in the class that inherits the interface. So in this case why should I declare an interface if I am going to declare the entire method in the class that inherits that interface? What is the point? Does this have something to do with the fact that a class can inherit multiple interfaces?

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  • Storage of leftover values in a situation of having to round down

    - by jt0dd
    I'm writing an app (client and server side) where the number of sales required by each employee must be kept track of in round-number form. Each month, the employees are required to sell a certain number, and this app needs to keep track of how many sales must be made for each 12 hour interval during the work week. Because I have to round the values down to a whole number, I must keep track of leftovers in the rounding process and ensure that they are always carried over. My method must ensure the storage of the leftover value even when client and server side crash, restart, close, etc. Right now, I'm working on doing this by storing the leftovers in a field in the user's account row in the database each time a value is rounded, reading the stored value, removing any portion that is used (when a whole number is reached, most of the leftover is used up), and storing the new value. This practice seems weird because while the leftovers are calculated on the client side, it's the same number for each employee, and every employee using the app is storing a copy of the same leftover data. Alternatively, I could have all clients store the data at once into the same data field on a general table, but this is just as weird. Is there a better way that this can be handled or is my method correct?

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  • Fun programming or something else?

    - by gion_13
    I've recently heard about android's isUserAGoat method and I didn't know what to think. At first I laughed my brains out, than I was embarrassed for my lack of professionalism and tried to look into it and see if it makes any normal sense. As it turns out it is a joke (as stated here) and it appears that other languages/apis have these sort of easter eggs implemented in their core. While I personally like them and feel they can be a fresh breath sometimes, I think that they also can be both frustrating and confusing (and you begin to ask yourself : "can users be goats?" or "I get it! "goat" is slang for.... wait.."). My question is are there any other examples of these kind of programming jokes and what are their intends? Should they be considered harmless or not (how do programmers feel about it) ? Do they reach their goal (if any other than to laugh) ? Where do you draw a line between a good joke and a disaster? (what if the method was called isUserStupid?)

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  • Informing GUI objects about screen size - Designing

    - by Mosquito
    I have a problem with designing classes for my game which I create. In my app, there is: class CGame which contains all the information about game itself, e.g. screen width, screen height, etc. In the main() function I create a pointer to CGame instance. class CGUIObject which includes fields specifying it's position and draw() method, which should know how to draw an object according to screen size. class CGUIManager which is a singleton and it includes a list of CGUIObject's. For each object in a list it just calls draw() method. For clarity's sake, I'll put some simple code: class CGame { int screenWidth; int screenHeight; }; class CGUIObject { CPoint position; void draw(); // this one needs to know what is a screen's width and height }; class CGUIManager // it's a singleton { vector<CGUIObject*> guiObjects; void drawObjects(); }; And the main.cpp: CGame* g; int main() { g = new CGame(); while(1) { CGUIManager::Instance().drawObjects(); } return 0; } Now the problem is, that each CGUIObject needs to know the screen size which is held by CGame, but I find it very dumb to include pointer to CGame instance in every object. Could anyone, please, tell me what would be the best approach to achieve this?

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  • Methods for getting static data from obj-c to Parse (database)

    - by Phil
    I'm starting out thinking out how best to code my latest game on iOS, and I want to use parse.com to store pretty much everything, so I can easily change things. What I'm not sure about is how to get static data into parse, or at least the best method. I've read about using NSMutableDictionary, pLists, JSON, XML files etc. Let's say for example in AS3 I could create a simple data object like so... static var playerData:Object = {position:{startX:200, startY:200}}; Stick it in a static class, and bingo I've got my static data to use how I see fit. Basically I'm looking for the best method to do the same thing in Obj-c, but the data is not to be stored directly in the iOS game, but to be sent to parse.com to be stored on their database there. The game (at least the distribution version) will only load data from the parse database, so however I'm getting the static data into parse I want to be able to remove it from being included in the eventual iOS file. So any ideas on the best methods to sort that? If I had longer on this project, it might be nice to use storyboards and create a simple game editor to send data to parse....actually maybe that's a good idea, it's just I'm new to obj-c and I'm looking for the most straightforward (see quickest) way to achieve things. Thanks for any advice.

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  • XNA- Transforming children

    - by user1806687
    So, I have a Model stored in MyModel, that is made from three meshes. If you loop thrue MyModel.Meshes the first two are children of the third one. And was just wondering, if anyone could tell me where is the problem with my code. This method is called whenever I want to programmaticly change the position of a whole model: public void ChangePosition(Vector3 newPos) { Position = newPos; MyModel.Root.Transform = Matrix.CreateScale(VectorMathHelper.VectorMath(CurrentSize, DefaultSize, '/')) * Matrix.CreateFromAxisAngle(MyModel.Root.Transform.Up, MathHelper.ToRadians(Rotation.Y)) * Matrix.CreateFromAxisAngle(MyModel.Root.Transform.Right, MathHelper.ToRadians(Rotation.X)) * Matrix.CreateFromAxisAngle(MyModel.Root.Transform.Forward, MathHelper.ToRadians(Rotation.Z)) * Matrix.CreateTranslation(Position); Matrix[] transforms = new Matrix[MyModel.Bones.Count]; MyModel.CopyAbsoluteBoneTransformsTo(transforms); int count = transforms.Length - 1; foreach (ModelMesh mesh in MyModel.Meshes) { mesh.ParentBone.Transform = transforms[count]; count--; } } This is the draw method: foreach (ModelMesh mesh in MyModel.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.View = camera.view; effect.Projection = camera.projection; effect.World = mesh.ParentBone.Transform; effect.EnableDefaultLighting(); } mesh.Draw(); } The thing is when I call ChangePosition() the first time everything works perfectlly, but as soon as I call it again and again. The first two meshes(children meshes) start to move away from the parent mesh. Another thing I wanted to ask, if I change the scale/rotation/position of a children mesh, and then do CopyAbsoluteBoneTransforms() will children meshes be positioned properlly(at the proper distance) or would achieving that require more math/methods? Thanks in advance

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  • Crash when trying to detect touch

    - by iQue
    I've got a character in a 2D game using surfaceView that I want to be able to move using a button (eventually a joystick), but my game crashes as soon as I try to move my sprite. This is my onTouch-method for my steering button: public void handleActionDown(int eventX, int eventY) { if (eventX >= (x - bitmap.getWidth() / 2) && (eventX <= (x + bitmap.getWidth()/2))) { if (eventY >= (y - bitmap.getHeight() / 2) && (y <= (y + bitmap.getHeight() / 2))) { setTouched(true); } else { setTouched(false); } } else { setTouched(false); } And if I try to put this in my update-method: public void update() { x += (speed.getXv() * speed.getxDirection()); y += (speed.getYv() * speed.getyDirection()); } The sprite moves on its own just fine, but as soon as I add: public void update() { if(steering.isTouched()){ x += (speed.getXv() * speed.getxDirection()); y += (speed.getYv() * speed.getyDirection()); } the game crashes. Does anyone know why this is or how to fix it? I cannot figure it out. I'm using MotionEvent.ACTION_DOWN to check if the user if pressing the screen.

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  • Rendering multiple squares fast?

    - by Sam
    so I'm doing my first steps with openGL development on android and I'm kinda stuck at some serious performance issues... What I'm trying to do is render a whole grid of single colored squares on to the screen and I'm getting framerates of ~7FPS. The squares are 9px in size right now with one pixel border in between, so I get a few thousand of them. I have a class "Square" and the Renderer iterates over all Squares every frame and calls the draw() method of each (just the iteration is fast enough, with no openGL code the whole thing runs smootlhy at 60FPS). Right now the draw() method looks like this: // Prepare the square coordinate data GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, vertexStride, vertexBuffer); // Set color for drawing the square GLES20.glUniform4fv(mColorHandle, 1, color, 0); // Draw the square GLES20.glDrawElements(GLES20.GL_TRIANGLES, drawOrder.length, GLES20.GL_UNSIGNED_SHORT, drawListBuffer); So its actually only 3 openGL calls. Everything else (loading shaders, filling buffers, getting appropriate handles, etc.) is done in the Constructor and things like the Program and the handles are also static attributes. What am I missing here, why is it rendering so slow? I've also tried loading the buffer data into VBOs, but this is actually slower... Maybe I did something wrong though. Any help greatly appreciated! :)

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  • What is the standard technique for shifting the frames of a sprite according to user input?

    - by virtual__
    From my own experience, I developed two techniques for changing the sprites of a character that's reacting to user input -- this in the context of a classic 2D platformer. The first one is to store all character's pixmaps in a list, putting the index of the currently used pixmap in an ordinary variable. This way, every time the player presses a key -- say the right arrow for moving the character forward -- the graphics engine sees what's the next pixmap to draw, draws it, and increments the index counter. That's a pretty common approach I believe, the problem is that in this case the animation's quality depends not only on the number of sprites available but also on how often your engine listens to user input. The second technique is to actually play an animation every key press event. For this you can use any sort of animation framework you want. It's only necessary to set the timer, the animation steps and to call the animation's play() method on your key press event handler. The problem with that approach is that is lacks responsiveness, since the character won't react to any input while the current animation is still being played. What I want to know is whether you are using one of these techniques -- or something similar -- in your games, or whether there's a standard method for animating sprites out there that's widely known by everybody but me.

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  • Creating a steady rhythm for music-based game in XNA

    - by A-Type
    I'm looking to develop a game for Windows Phone to explore an idea I had which involves the user building notes into a sequencer while playing a puzzle game. The issue I'm running into is that, while my implementation is very close to being on-beat, there is the occasional pause between beats which makes the whole thing sound sloppy. I'm just not sure how to get around this inside XNA's infrastructure. Currently I'm running this code in the Update method of my GameBoard: public void Update(GameTime gameTime) { onBeat = IsOnBeat(gameTime); [...] if (onBeat) BeatUpdate(); } private bool IsOnBeat(GameTime gameTime) { beatTime += gameTime.ElapsedGameTime.TotalSeconds; if (Math.Abs(beatTime - beatLength) < 0.0166666) { beatTime -= beatLength; return true; } return false; } private void BeatUpdate() { cursor.BeatUpdate(); board.CursorPass((int)cursor.CursorPosition % Board.GRID_WIDTH); } Update checks to see if the time is on beat, and if it is, it calls the BeatUpdate method which moves the cursor over the board (sequencer). The cursor reports its X position to the board, which then plays any notes which are in that position on the sequencer. Notes are SoundEffectInstances, preloaded and ready to play. Oh, and TargetElapsedTime is set to 166666, or 60FPS target. Obviously totaling up the time and then subtracting isn't the most accurate way to go but I can't figure out a way to work within XNA's system in order to overcome this issue. This current system is just horribly unstable. Beats lag and fire too early and it's obvious. I thought about perhaps some sort of threaded solution but I'm not familiar enough with multithreading to figure out how that would work. Any ideas?

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  • Updating entities in response to collisions - should this be in the collision-detection class or in the entity-updater class?

    - by Prog
    In a game I'm working on, there's a class responsible for collision detection. It's method detectCollisions(List<Entity> entities) is called from the main gameloop. The code to update the entities (i.e. where the entities 'act': update their positions, invoke AI, etc) is in a different class, in the method updateEntities(List<Entity> entities). Also called from the gameloop, after the collision detection. When there's a collision between two entities, usually something needs to be done. For example, zero the velocity of both entities in the collision, or kill one of the entities. It would be easy to have this code in the CollisionDetector class. E.g. in psuedocode: for(Entity entityA in entities){ for(Entity entityB in entities){ if(collision(entityA, entityB)){ if(entityA instanceof Robot && entityB instanceof Robot){ entityA.setVelocity(0,0); entityB.setVelocity(0,0); } if(entityA instanceof Missile || entityB instanceof Missile){ entityA.die(); entityB.die(); } } } } However, I'm not sure if updating the state of entities in response to collision should be the job of CollisionDetector. Maybe it should be the job of EntityUpdater, which runs after the collision detection in the gameloop. Is it okay to have the code responding to collisions in the collision detection system? Or should the collision detection class only detect collisions, report them to some other class and have that class affect the state of the entities?

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  • Choosing the correct network protocol for my type of game (its Wc3 Warlock style)

    - by Moritz
    I need to code a little game for a school project. The type of the game is like the Warcraft 3 map "Warlock", if anyone doesnt know it, here is a short description: up to ten players spawn into an arena filled with lava, the goal of each player is to push the other players into the lava with spells (basically variations of missiles, aoe nukes, moba spells etc) http://www.youtube.com/watch?v=c3PoO-gcJik&feature=related we need to provide multiplayer-support over the internet, for that reason I am looking for the best network protocol for this type of game (udp, tcp, lock step, client-server...) what the requirements are: - same/stable simulation on all clients - up to ten players - up to ~100 missiles on the field - very low latency since its reaction based (i dont know the method wc3 used, but it was playable with the old servers) what would be nice (if even possible, since the traffic might be too big): - support for soft bodies over the network (with bullet physics), but this is no real requirement I read several articles about the lock step method used for RTS games, this seems to be great, but does it fit for real-time action games too (ping-related)? If anyone has run into the same problems/questions like me, I would be very happy about any help

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  • Collision Detection Problems

    - by MrPlosion
    So I'm making a 2D tile based game but I can't quite get the collisions working properly. I've taken the code from the Platformer Sample and implemented it into my game as seen below. One problem I'm having is when I'm on the ground for some strange reason I can't move to the left. Now I'm pretty sure this problem is from the HandleCollisions() method because when I stop running it I can smoothly move around with no problems. Another problem I'm having is when I'm close to a tile the character jitters very strangely. I will try to post a video if necessary. Here is the HandleCollisions() method: Thanks. void HandleCollisions() { Rectangle bounds = BoundingRectangle; int topTile = (int)Math.Floor((float)bounds.Top / World.PixelTileSize); int bottomTile = (int)Math.Ceiling((float)bounds.Bottom / World.PixelTileSize) - 1; int leftTile = (int)Math.Floor((float)bounds.Left / World.PixelTileSize); int rightTile = (int)Math.Ceiling((float)bounds.Right / World.PixelTileSize) - 1; isOnGround = false; for(int x = leftTile; x <= rightTile; x++) { for(int y = topTile; y <= bottomTile; y++) { if(world.Map[y, x].Collidable == true) { Rectangle tileBounds = new Rectangle(x * World.PixelTileSize, y * World.PixelTileSize, World.PixelTileSize, World.PixelTileSize); Vector2 depth = RectangleExtensions.GetIntersectionDepth(bounds, tileBounds); if(depth != Vector2.Zero) { if(Math.Abs(depth.Y) < Math.Abs(depth.X)) { isOnGround = true; position = new Vector2(position.X, position.Y + depth.Y); } else { position = new Vector2(position.X + depth.X, position.Y); } bounds = BoundingRectangle; } } } }

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  • How to choose between Tell don't Ask and Command Query Separation?

    - by Dakotah North
    The principle Tell Don't Ask says: you should endeavor to tell objects what you want them to do; do not ask them questions about their state, make a decision, and then tell them what to do. The problem is that, as the caller, you should not be making decisions based on the state of the called object that result in you then changing the state of the object. The logic you are implementing is probably the called object’s responsibility, not yours. For you to make decisions outside the object violates its encapsulation. A simple example of "Tell, don't Ask" is Widget w = ...; if (w.getParent() != null) { Panel parent = w.getParent(); parent.remove(w); } and the tell version is ... Widget w = ...; w.removeFromParent(); But what if I need to know the result from the removeFromParent method? My first reaction was just to change the removeFromParent to return a boolean denoting if the parent was removed or not. But then I came across Command Query Separation Pattern which says NOT to do this. It states that every method should either be a command that performs an action, or a query that returns data to the caller, but not both. In other words, asking a question should not change the answer. More formally, methods should return a value only if they are referentially transparent and hence possess no side effects. Are these two really at odds with each other and how do I choose between the two? Do I go with the Pragmatic Programmer or Bertrand Meyer on this?

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  • How to offset particles from point of origin

    - by Sun
    Hi I'm having troubles off setting particles from a point of origin. I want my particles to spread out after a certain radius from a the point of origin. For example, this is what I have right now: All particles emitted from a point of origin. What I want is this: Particles are offset from the point of origin by some amount, i.e after the circle. What is the best way to achieve this? At the moment, I have the point of origin, the position of each particle and its rotation angle. Sorry for the poor illustrations. Edit: I was mistaken, when a particle is created, I have only the point of origin. When the particle is created I am able to calculate the rotation of the particle in the update method after it has moved to a new location using atan2() method. This is how I create/manage particles: Created new particle at enemy ship death location, for every new particle which is added to the list, call Update and Draw to update its position, calculate new angle and draw it.

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  • How to input data into user defined variables into MySql query

    - by user292791
    Simple Shell script echo "Enter 1 for month of March" echo "Enter 2 for month of April" echo "Enter 3 for month of May" read Month case "$Month" in 1) echo "enter establishment name" read a; mysql -u root -p $a < "March.sql";; 2) echo "enter establishment name" read b; mysql -u root -p $b < "April.sql";; 3) echo "enter establishment name" read c; mysql -u root -p $c < "May.sql";; esac done In this i have three other query files March.sql, April.sql, May.sql. i'm linking this in shell script . Example of .sql file: SELECT DISTINCT substr( a.case_no, 3, 2 ), b.case_type, b.type_name, a.case_no into outfile '/tmp/April.csv' FIELDS TERMINATED BY ',' ENCLOSED BY '"' LINES TERMINATED BY '\r\n' FROM Civil_t AS a, Case_type_t AS b, disposal_proc AS c WHERE substr( a.case_no, 3, 2 ) = b.case_type AND a.date_of_decision BETWEEN '2014-04-01' AND '2014-04-30' AND a.case_no = c.case_no AND a.court_no =1; I have to alter the .sql script every time. Is there any method to read the variables from shell script and use it in mysql. For example:- echo "enter date" read a #input date Now i have read a "date" and i want to use it in March.sql query in where clause. Is there is any method of using this variable in .sql query.

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  • Is sending data to a server via a script tag an outdated paradigm?

    - by KingOfHypocrites
    I inherited some old javascript code for a website tracker that submits data to the server using a script url: var src = "http://domain.zzz/log/method?value1=x&value2=x" var e = document.createElement('script'); e.src = src; I guess the idea was that cross domain requests didn't haven't to be enabled perhaps. Also it was written back in 2005. I'm not sure how well XmlHttpRequests were supported at the time. Anyone could stick this on their website and send data to our server for logging and it ideally would work in most any browser with javascript. The main limitation is all the server can do is send back javascript code and each request has to wait for a response from the server (in the form of a generic acknowledgement javascript method call) to know it was received, then it sends the next. I can't find anyone doing this online or any metrics as to whether this faster or more secure than XmlHttpRequests. I don't know if this is just an old way of doing things or it's still the best way to send data to the server when you are mostly trying to send data one way and you need the best performance possible. So in summary is sending data via a script tag an outdated paradigm? Should I abandon in favor of using XmlHttpRequsts?

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