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• Earmarks of a Professional PHP Programmer

  - by Scotty C.

  I'm a 19 year old student who really REALLY enjoys programming, and I'm hoping to glean from your years of experience here. At present, I'm studying PHP every chance I get, and have been for about 3 years, although I've never taken any formal classes. I'd love to some day be a programmer full time, and make a good career of it. My question to you is this: What do you consider to be the earmarks or traits of a professional programmer? Mainly in the field of PHP, but other, more generalized qualifications are also more than welcome, as I think PHP is more of a hobbyist language and may not be the language of choice in the eyes of potential employers. Please correct me if I'm wrong. Above all, I don't want to wast time on something that isn't worth while. I'm currently feeling pretty confident in my knowledge of PHP as a language, and I know that I could build just about anything I need and have it "work", but I feel sorely lacking in design concepts and code structure. I can even write object oriented code, but in my personal opinion, that isn't worth a hill of beans if it isn't organized well. For this reason, I bought Matt Zandstra's book "PHP Objects, Patterns, and Practice" and have been reading that a little every day. Anyway, I'm starting to digress a little here, so back to the original question. What advice would you give to an aspiring programmer who wants to make an impact in this field? Also, on a side note, I've been working on a project with a friend of mine that would give a fairly good idea of where I'm at coding wise. I'm gonna give a link, I don't want anyone to feel as though I'm pushing or spamming here, so don't click it if you don't want to. But if you are interested on giving some feedback there as well, you can see the code on github. I'm known as The Craw there. https://github.com/PureChat/PureChat--Beta-/tree/

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• Where to implement storable items

  - by James Hay

  I'm creating a multiplayer online trading game. The things that are traded range from raw items to complex products. For example Steel is a raw item. Mechanical Assembly is a more complex item that requires 2x Steel and maybe 1x Rubber. Then Hydraulics is an item that contains 2x Mechanical Assemblies and 1x Electronics (which is another complex item). So and so forth. These items will be created by me, players can't create their own items, so it doesn't need to be able to handle arbitrary layers of complexity for items. If my example isn't clear, think Minecraft. You have wooden planks, which can be made into sticks. From there the sticks - combined with metals - can be made into tools. My game is nothing to do with minecraft or any sandbox building game, but it uses a similar progressive complexity to creating items that I want to have in my game. My question is basically, how do you store something like this assuming that I will want to add more items in the future? Do you store it in a database or in a seperate library that the game uses? EDIT None of the items actually "do" anything, they are simply there to either sell, purchase, or combine with other items to make a more complex item, which can then be sold, purchased or combined... you get the idea. The items themselves would not have any properties, but the instances of the items would. For example an item that one player has would have a certain "quality" and if they were selling it a certain "price". An instance of that same item that a different player had would need to have a different "quality" and "price" if they were selling it. I think the price part will not be required on an individual item because instead I would have a "sale" object which was for a price and contained certain items.

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• A Console Application or Windows Application in VS 2010 for Sharepoint 2010 : A common Error

  - by Gino Abraham

  I have seen many Sharepoint Newbies cracking their head to create a Console/Windows  application in VS2010 and make it talk to Sharepoint 2010 Server. I had the same problem when i started with Sharepoint in the begining. It is important for you to acknowledge that SharePoint 2010 is based on .NET Framework version 3.5 and not version 4.0. In VS 2010 when you create a Console/Windows application, Make Sure you select .Net Framework 3.5 in the New Project Dialog Window.If you have missed while creating new Project Go to the Application tab of project properties and verify that .NET Framework Version 3.5 is select as the Target Framework. Now that you have selected the correct framework, will it work? Nope if the application is configured as x86 one it will not work. Sharepoint is a 64 Bit application and when you create a windows application to talk to Sharepoint it should also be a 64 Bit one. Go to Configuration Manager, Select x64. If x64 is not available select <New…> and in the New Solution Platform dialog box select x64 as the new platform copying settings from x86 and checking the Create new project platforms check box. This is not applicable if you are making a console application to talk to sharepoint with Client Object Model.

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• Matrix.CreateBillboard centre rotation problem

  - by Chris88

  I'm having an issue with Matrix.CreateBillboard and a textured Quad where the center axis seems to be positioned incorrectly to the quad object which is rotating around a center point: Using: BasicEffect quadEffect; Drawing the quad shape: Left = Vector3.Cross(Normal, Up); Vector3 uppercenter = (Up * height / 2) + origin; LowerLeft = uppercenter + (Left * width / 2); LowerRight = uppercenter - (Left * width / 2); UpperLeft = LowerLeft - (Up * height); UpperRight = LowerRight - (Up * height); Where height and width are float values passed in (it draws a square) Draw method: quadEffect.View = camera.view; quadEffect.Projection = camera.projection; quadEffect.World = Matrix.CreateBillboard(Origin, camera.cameraPosition, Vector3.Up, camera.cameraDirection); GraphicsDevice.BlendState = BlendState.Additive; foreach (EffectPass pass in quadEffect.CurrentTechnique.Passes) { pass.Apply(); GraphicsDevice.DrawUserIndexedPrimitives <VertexPositionNormalTexture>( PrimitiveType.TriangleList, Vertices, 0, 4, Indexes, 0, 2); } GraphicsDevice.BlendState = BlendState.Opaque; In the screenshots below i draw the image at Vector3(32f, 0f, 32f) The screenshots below show you the position of the quad in relation to the red cross. The red cross shows where it should be drawn http://i.imgur.com/YwRYj.jpg http://i.imgur.com/ZtoHL.jpg It rotates around the red cross position

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• How can I get started using TDD to code some simple functionality?

  - by Gabriel

  I basically have the gist of TDD. I'm sold that it's useful and I've got a reasonable command of the MSTEST framework. However, to date I have not been able to graduate to using it as a primary development method. Mostly, I use it as a surrogate for writing console apps as test drivers (my traditional approach). The most useful thing about it for me is the way it absorbs the role of regression testing. I have not yet built anything yet that specifically isolates various testable behaviors, which is another big part of the picture I know. So this question is to ask for pointers on what the first test(s) I might write for the following development task: I want to produce code that encapsulates task execution in the fashion of producer/consumer. I stopped and decided to write this question after I wrote this code (wondering if I could actually use TDD for real this time) Code: interface ITask { Guid TaskId { get; } bool IsComplete { get; } bool IsFailed { get; } bool IsRunning { get; } } interface ITaskContainer { Guid AddTask(ICommand action); } interface ICommand { string CommandName { get; } Dictionary<string, object> Parameters { get; } void Execute(); }

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• Add control to grid from code behind in Silverlight

  - by Emanuele Bartolesi

  In this post I show how you can easily add a control to a silverlight grid layout from code behind. First you draw the grid in the xaml. <Grid x:Name="LayoutRoot" Background="Red"> <Grid.RowDefinitions> <RowDefinition Height="20"> </RowDefinition> </Grid.RowDefinitions> <Grid.ColumnDefinitions> <ColumnDefinition Width="300"> </ColumnDefinition> </Grid.ColumnDefinitions> </Grid> Now in the page constructor add the following code. public MainPage() { InitializeComponent(); var myButton = new Button { Name = "btnOk", Content = "Ok", }; myButton.SetValue(Grid.RowProperty, 1); myButton.SetValue(Grid.ColumnProperty, 1); myButton.Click += myButton_Click; LayoutRoot.Children.Add(myButton); } Also add the evento of the button. void myButton_Click(object sender, RoutedEventArgs e) { } The code needs no comment because it’s very simple. The only important thing is the method SetValue because it is used to set XAML attribute of element. For a better understanding I have created an example that you can download from here.

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• How can I use the dualforward parameter in my unity shader to use lightmaps and normal maps together?

  - by Raphaeltm

  I'm using the free version of unity and I would like to combine lightmaps with specularity and normal maps. After doing a -bunch- of research, I've figured out that there doesn't seem to be any easy way to do this in the free version of unity, which doesn't support deferred rendering/easy use of dual lightmaps. However, it looks like it's possible, by writing a custom shader, using the "dualforward" parameter in a shader, switching the lightmapping mode to "dual lightmaps" and turning on "Use in forward ren." (basically, writing a shader that specifies the use of dual lightmaps, which should allow for a combination of lightmaps and normal maps) So I downloaded the source code for the default shaders (because all I need is a normal specular bumped shader) and added "dualforward" to the parameters: Shader "Bumped Specular Dual Lightmaps" { Properties { _Color ("Main Color", Color) = (1,1,1,1) _SpecColor ("Specular Color", Color) = (0.5, 0.5, 0.5, 1) _Shininess ("Shininess", Range (0.03, 1)) = 0.078125 _MainTex ("Base (RGB) Gloss (A)", 2D) = "white" {} _BumpMap ("Normalmap", 2D) = "bump" {} } SubShader { Tags { "RenderType"="Opaque" } LOD 400 CGPROGRAM #pragma surface surf BlinnPhong dualforward sampler2D _MainTex; sampler2D _BumpMap; fixed4 _Color; half _Shininess; struct Input { float2 uv_MainTex; float2 uv_BumpMap; }; void surf (Input IN, inout SurfaceOutput o) { fixed4 tex = tex2D(_MainTex, IN.uv_MainTex); o.Albedo = tex.rgb * _Color.rgb; o.Gloss = tex.a; o.Alpha = tex.a * _Color.a; o.Specular = _Shininess; o.Normal = UnpackNormal(tex2D(_BumpMap, IN.uv_BumpMap)); } ENDCG } FallBack "Specular" } This, however, doesn't seem to work. When I keep the "dualforward" param, every object that uses it seems to be lit by the one directional light in the scene. When I remove the "dualforward" param, it they look like normal lightmapped objects with no normal maps or specularity. I noticed that the support for "dualforward" seems to be new in v.3.4.2, so I made sure to download it (I was running 3.4.1), but it still doesn't work. Anybody have any advice for me?

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• Is this an acceptable approach to undo/redo in Python?

  - by Codemonkey

  I'm making an application (wxPython) to process some data from Excel documents. I want the user to be able to undo and redo actions, even gigantic actions like processing the contents of 10 000 cells simultaneously. I Googled the topic, and all the solutions I could find involves a lot of black magic or is overly complicated. Here is how I imagine my simple undo/redo scheme. I write two classes - one called ActionStack and an abstract one called Action. Every "undoable" operation must be a subclass of Action and define the methods do and undo. The Action subclass is passed the instance of the "document", or data model, and is responsible for committing the operation and remembering how to undo the change. Now, every document is associated with an instance of the ActionStack. The ActionStack maintains a stack of actions (surprise!). Every time actions are undone and new actions are performed, all undone actions are removed for ever. The ActionStack will also automatically remove the oldest Action when the stack reaches the configurable maximum amount. I imagine the workflow would produce code looking something like this: class TableDocument(object): def __init__(self, table): self.table = table self.action_stack = ActionStack(history_limit=50) # ... def delete_cells(self, cells): self.action_stack.push( DeleteAction(self, cells) ) def add_column(self, index, name=''): self.action_stack.push( AddColumnAction(self, index, name) ) # ... def undo(self, count=1): self.action_stack.undo(count) def redo(self, count=1): self.action_stack.redo(count) Given that none of the methods I've found are this simple, I thought I'd get the experts' opinion before I go ahead with this plan. More specifically, what I'm wondering about is - are there any glaring holes in this plan that I'm not seeing?

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• How do I architect 2 plugins that share a common component?

  - by James

  I have an object that takes in data and spits out a transformed output, called IBaseItem. I also have two parsers, IParserA and IParserB. These parsers transform external data (in format dataA and dataB respectively) to a format usable by my IBaseItem (baseData). I want to create 2 systems, one that works with dataA and one that works with dataB. They will allow the user to enter data and match it to the right plugins/implementations and transform the data to outData. I want to write these traffic cops myself, but have other people provide the parsers and baseitem logic, and and as such am implementing these items as plugins (hence the use of interfaces). Other programmers can choose to implement 1 or both parsers. Q: How should I structure the way base items and parsers are associated, stored, and loaded into each of my programs? Class Relations: What I've Tried: Initially I though there should be a different dll for each of my 2 traffic cops, that each have a parser and baseitem in them. However, the duplication of baseitem logic doesn't seem right (especially if the base item logic changes). I then thought the base items could all have their own dll, and then somehow associate parsers and baseitems (guids?), but I don't know if implementing the overhead id/association is adding too much complexion.

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• Designing business objects, and gui actions

  - by fozz

  Developing a product ordering system using Java SE 6. The previous implementations used combo boxes, text fields, and check boxes. Preforming validation on action events from the GUI. The validation includes limiting existing combo boxes items, or even availability. The issue in the old system was that the action was received and all rules were applied to the entire business object. This resulted in a huge event change as options were changed multiple times. To be honest I have no idea how an infinite loop wasn't produced. Through the next iteration I stepped in and attempted to limit the chaos by controlling the order in which the selections could be made. Making configuration of BO's a top down approach. I implemented custom box models, action events, beans/binding, and an MVC pattern. However I still am unable to fully isolate action even chains. I'm thinking that I've approached the whole concept backwards in an attempt to stay closest to what was already in place. So the question becomes what do I design instead? I'm currently considering an implementation of Interfaces, Beans, Property Change Listeners to manage the back and forth. Other thoughts were validation exceptions, dynamic proxies.... I'm sure there are a ton of different ways. To say that one way is right is crazy, and I'm sure it will take a blending of multiple patterns. My knowledge of swing/awt validation is limited, previously I did backend logic only. Other considerations are were some sort of binding(jgoodies or otherwise) to directly bind GUI state to BO's.

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• How to determine the end of list has been reached?

  - by Sweta Dwivedi

  I'm trying to animate my object according to a set of recorded values from kinect skeleton stream by saving the (x,y,z) stream from the skeletal data into a list and then set my objects x and y position from the x,y of the list. However, once the list end has been reached it starts to animate again from the start. I don't want that - I just want the model position to keep going in the positive X direction. Is there any way I can check if end of the list has been reached and to just update the model position in x direction? Or is there any other way to continue moving my sprite once the points in the list are over... i dont want it to start animating all the way again.. protected override void Update(GameTime gameTime) { //position += spriteSpeed * (float)gameTime.ElapsedGameTime.TotalSeconds; //// TODO: Add your update logic here using (StreamReader r = new StreamReader(f)) { string line; Viewport view = graphics.GraphicsDevice.Viewport; int maxWidth = view.Width; int maxHeight = view.Height; while((line = r.ReadLine()) != null) { string[] temp = line.Split(','); int x = (int) Math.Floor(((float.Parse(temp[0]) * 0.5f) + 0.5f) * maxWidth); int y = (int) Math.Floor(((float.Parse(temp[1]) * -0.5f) + 0.5f) * maxHeight); motion_2.Add(new Point(x, y)); } } position.X = motion_2[i].X; position.Y = motion_2[i].Y; i++; a_butterfly_up.Update(gameTime); a_butterfly_side.Update(gameTime); G_vidPlayer.Play(mossV); base.Update(gameTime); }

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• Microsoft Public License Question

  - by ryanzec

  Let preface this by saying that I understand that any advice I may receive is not to be taken as 100% correct, I am just looking for what people's understand of what this license is. I have been looking for a library that allow be to deal with archived compressed files (like zip files) and so far the best one I have found is DotNetZip. The only concern I have is that I am not familiar with the Microsoft Public License. While I plan to release a portion of my project (a web application platform) freely (MIT/BSD style) there are a few things. One is that I don't plan on actually releasing the source code, just the compiled project. Another thing is that I don't plan on releasing everything freely, only a subset of the application. Those are reason why I stay away form (L)GPL code. Is this something allowed while using 3rd party libraries that are licensed under the Microsoft Public License? EDIT The part about the Microsoft license that concerns me is Section 3 (D) which says (full license here): If you distribute any portion of the software in source code form, you may do so only under this license by including a complete copy of this license with your distribution. If you distribute any portion of the software in compiled or object code form, you may only do so under a license that complies with this license. I don't know what is meant by 'software'. My assumption would be that 'software' only refers to the library included under the license (being DotNetZip) and that is doesn't extends over to my code which includes the DotNetZip library. If that is the case then everything is fine as I have no issues keeping the license for DotNetZip when release this project in compiled form while having my code under its own license. If 'software' also include my code that include the DotNetZip library then that would be an issue (as it would basically act like GPL with the copyleft sense).

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• Antenna Aligner part 2: Finding the right direction

  - by Chris George

  Last time I managed to get "my first app(tm)" built, published and running on my iPhone. This was really cool, a piece of my code running on my very own device. Ok, so I'm easily pleased! The next challenge was actually trying to determine what it was I wanted this app to do, and how to do it. Reverting back to good old paper and pen, I started sketching out designs for the app. I knew I wanted it to get a list of transmitters, then clicking on a transmitter would display a compass type view, with an arrow pointing the right way. I figured there would not be much point in continuing until I know I could do the graphical part of the project, i.e. the rotating compass, so armed with that reasoning (plus the fact I just wanted to get on and code!), I once again dived into visual studio. Using my friend (google) I found some example code for getting the compass data from the phone using the PhoneGap framework. // onSuccess: Get the current heading // function onSuccess(heading) {    alert('Heading: ' + heading); } navigator.compass.getCurrentHeading(onSuccess, onError); Using the ripple mobile emulator this showed that it was successfully getting the compass heading. But it didn't work when uploaded to my phone. It turns out that the examples I had been looking at were for PhoneGap 1.0, and Nomad uses PhoneGap 1.4.1. In 1.4.1, getCurrentHeading provides a compass object to onSuccess, not just a numeric value, so the code now looks like // onSuccess: Get the current magnetic heading // function onSuccess(heading) {    alert('Heading: ' + heading.magneticHeading); }; navigator.compass.getCurrentHeading(onSuccess, onError); So the lesson learnt from this... read the documentation for the version you are actually using! This does, however, lead to compatibility problems with ripple as it only supports 1.0 which is a real pain. I hope that the ripple system is updated sometime soon.

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• On developing deep programming knowledge

  - by Robert Harvey

  Occasionally I see questions about edge cases and other weirdness on Stack Overflow that are easily answered by the likes of Jon Skeet and Eric Lippert, demonstrating a deep knowledge of the language and its many intricacies, like this one: You might think that in order to use a foreach loop, the collection you are iterating over must implement IEnumerable or IEnumerable<T>. But as it turns out, that is not actually a requirement. What is required is that the type of the collection must have a public method called GetEnumerator, and that must return some type that has a public property getter called Current and a public method MoveNext that returns a bool. If the compiler can determine that all of those requirements are met then the code is generated to use those methods. Only if those requirements are not met do we check to see if the object implements IEnumerable or IEnumerable<T>. That's cool stuff to know. I can understand why Eric knows this; he's on the compiler team, so he has to know. But what about those who demonstrate such deep knowledge who are not insiders? How do mere mortals (who are not on the C# compiler team) find out about stuff like this? Specifically, are there methods these folks use to systematically root out such knowledge, explore it and internalize it (make it their own)?

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• Best Method of function parameter validation

  - by Aglystas

  I've been dabbling with the idea of creating my own CMS for the experience and because it would be fun to run my website off my own code base. One of the decisions I keep coming back to is how best to validate incoming parameters for functions. This is mostly in reference to simple data types since object validation would be quite a bit more complex. At first I debated creating a naming convention that would contain information about what the parameters should be, (int, string, bool, etc) then I also figured I could create options to validate against. But then in every function I still need to run some sort of parameter validation that parses the parameter name to determine what the value can be then validate against it, granted this would be handled by passing the list of parameters to function but that still needs to happen and one of my goals is to remove the parameter validation from the function itself so that you can only have the actual function code that accomplishes the intended task without the additional code for validation. Is there any good way of handling this, or is it so low level that typically parameter validation is just done at the start of the function call anyway, so I should stick with doing that.

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• What is the proper response to lousy error message?

  - by William Pursell

  I've just come across (for the 47 millionth time) some code that looks like this: except IOError, e: print "Problems reading file: %s." % filename sys.exit( 1 ) My first reaction is very visceral: the person who coded this is a complete idiot. How hard is it to print error messages to stderr and to include the system error message in the string? I haven't used python in years, and it took me all of 4 minutes to track down the documentation to figure out how to get the error message from the exception object e and the syntax for printing to stderr. My "complete idiot" reaction was slightly lessened since at least a non-zero value is passed to sys.exit, but I still find this code offensive. My prime thought is that the developer who wrote this is a complete novice for whom I have zero respect. Am I over-reacting? Surely there are excuses for all sorts of bad coding practices, but is there anything that can possibly excuse this sort of $#|t? I guess there are two question here: one is a duplicate of What are developer's problems with helpful error messages?, and the other is "am I over-reacting, or is it valid to conclude that the author of the above code is a novice?"

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• Do you think Scala will be the dominant JVM langauge, ie be the next Java? [on hold]

  - by user1037729

  From what I've read about Scala do far I think it has some nice features but I do not think it should be "the next Java". It might however end up being the next Java (due to fashion rather than fact) but lets not hope it does not... To me adds a lot of complexity over Java which is a simple and scalable language. Scala Pattern matching allows you to perform some type/value checking in a more concise way, this is possible in Java, Scala's pattern matching has a limit to it, you cannot continuously match deeper and deeper down the object graph, so why not just stick to Java and use decent invariants? Scala provides tuples, easy enough to make in Java, create a static factory method and it all reads nicely too. Scala provides mixins, why not just use composition? I believe Scala implicit's are bad, they can lead to code becoming complex and hard to maintain, explicitness is good. Scala provides closures, well they will be in Java 8 too. Scala has lazy keyword for lazy instantiation, this is easy enough to do in Java by calling a getter which creates the instance when needed, no hidden magic here. Scala can be used with AKKA, well so can Java, there is an Java AKKA implementation. Scala offers addition functional features but these can all be created in Java, there are many frameworks with have implemented functional features in Java. All in all Scala seems to offer is addition complexity and thats it...

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• Unity calendar lens not showing events in Ubuntu 12.04

  - by David_G

  I'm trying to get proper/useful calendar integration into Ubuntu 12.04. I have a Google Calendar (& account) and I want to be able to use this without opening the browser. I want to get the Unity Calendar lens working, so that it shows events coming up, and it allows me a quick way to add new events. However, after installing it, it does not find any events, nor allow me to add a new event. Note that I've installed Lightning 1.4, Evolution mirror 0.2.3, Evolution, and unity-calendar lens. I've also installed Calendar-indicator. I suspect that somehow the lens is not getting the calendar information from thunderbird via evolution. A bit of searching around led me to try this command: /usr/lib/calendar-lens/calendar-lens-daemon.py. With this result: /usr/lib/python2.7/dist-packages/gobject/constants.py:24: Warning: g_boxed_type_register_static: assertion `g_type_from_name (name) == 0' failed import gobject._gobject Traceback (most recent call last): File "/usr/lib/calendar-lens/calendar-lens-daemon.py", line 324, in daemon = Daemon() File "/usr/lib/calendar-lens/calendar-lens-daemon.py", line 80, in init for calendar in evolution.ecal.list_calendars(): AttributeError: 'NoneType' object has no attribute 'list_calendars' Any ideas?

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• How to remove a box2d body when collision happens?

  - by Ayham

  I’m still new to java and android programming and I am having so much trouble Removing an object when collision happens. I looked around the web and found that I should never handle removing BOX2D bodies during collision detection (a contact listener) and I should add my objects to an arraylist and set a variable in the User Data section of the body to delete or not and handle the removing action in an update handler. So I did this: First I define two ArrayLists one for the faces and one for the bodies: ArrayList<Sprite> myFaces = new ArrayList<Sprite>(); ArrayList<Body> myBodies = new ArrayList<Body>(); Then when I create a face and connect that face to its body I add them to their ArrayLists like this: face = new AnimatedSprite(pX, pY, pWidth, pHeight, this.mBoxFaceTextureRegion); Body BoxBody = PhysicsFactory.createBoxBody(mPhysicsWorld, face, BodyType.DynamicBody, objectFixtureDef); mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(face, BoxBody, true, true)); myFaces.add(face); myBodies.add(BoxBody); now I add a contact listener and an update handler in the onloadscene like this: this.mPhysicsWorld.setContactListener(new ContactListener() { private AnimatedSprite face2; @Override public void beginContact(final Contact pContact) { } @Override public void endContact(final Contact pContact) { } @Override public void preSolve(Contact contact,Manifold oldManifold) { } @Override public void postSolve(Contact contact,ContactImpulse impulse) { } }); scene.registerUpdateHandler(new IUpdateHandler() { @Override public void reset() { } @Override public void onUpdate(final float pSecondsElapsed) { } }); My plan is to detect which two bodies collided in the contact listener by checking a variable from the user data section of the body, get their numbers in the array list and finally use the update handler to remove these bodies. The questions are: Am I using the arraylist correctly? How to add a variable to the User Data (the code please). I tried removing a body in this update handler but it still throws me NullPointerException , so what is the right way to add an update handler and where should I add it. Any other advices to do this would be great. Thanks in advance.

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• Uses of persistent data structures in non-functional languages

  - by Ray Toal

  Languages that are purely functional or near-purely functional benefit from persistent data structures because they are immutable and fit well with the stateless style of functional programming. But from time to time we see libraries of persistent data structures for (state-based, OOP) languages like Java. A claim often heard in favor of persistent data structures is that because they are immutable, they are thread-safe. However, the reason that persistent data structures are thread-safe is that if one thread were to "add" an element to a persistent collection, the operation returns a new collection like the original but with the element added. Other threads therefore see the original collection. The two collections share a lot of internal state, of course -- that's why these persistent structures are efficient. But since different threads see different states of data, it would seem that persistent data structures are not in themselves sufficient to handle scenarios where one thread makes a change that is visible to other threads. For this, it seems we must use devices such as atoms, references, software transactional memory, or even classic locks and synchronization mechanisms. Why then, is the immutability of PDSs touted as something beneficial for "thread safety"? Are there any real examples where PDSs help in synchronization, or solving concurrency problems? Or are PDSs simply a way to provide a stateless interface to an object in support of a functional programming style?

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• Name for Osherove's modified singleton pattern?

  - by Kazark

  I'm pretty well sold on the "singletons are evil" line of thought. Nevertheless, there are limited occurrences when you want to limit the creation of an object. Roy Osherove advises, If you're planning to use a singleton in your design, separate the logic of the singleton class and the logic that makes it a singleton (the part that initializes a static variables, for example) into two separate classes. That way, you can keep the single responsibility principle (SRP) and also have a way to override singleton logic. (The Art of Unit Testing 261-262) This pattern still perpetuates the global state. However, it does result in a testable design, so it seems to me to be a good pattern for mitigating the damage of a singleton. However, Osherove does not give a name to this pattern; but naming a pattern, according to the Gang of Four, is important: Naming a pattern immediately increases our design vocabulary. It lets us design at a higher level of abstraction. (3) Is there a standard name for this pattern? It seems different enough from a standard singleton to deserve a separate name. Decoupled Singleton, perhaps?

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• Multiplayer online game engine/pipeline

  - by Slav

  I am implementing online multiplayer game where client must be written in AS3 (Flash) to embed game into browser and server in C++ (abstract part of which is already written and used with other games). Networking models may differ from each other, but currently I'm looking toward game's logic run on both client and server parts but they're written on different languages while it's not the main problem. My previous game (pretty big one - was implemented with efforts of ~5 programmers in 1.5 years) was mainly "written" within electronic tables as structured objects with implemented inheritance: was written standalone tool which generated AS3 and C++ (languages of platforms to which the game was published) using specified electronic tables file (.xls or .ods). That file contained ~50 tables with ~50 rows and ~50 columns each and was mainly written by game designers which do not know any programming languages. But that game was single-player. Having declared problem with my currently implementing MMO, I'm looking toward some vast pipeline, where will be resolved such problems like: game objects descriptions (which starships exist within game, how much HP they have, how fast move, what damage deal...) actions descriptions (what players or NPCs can do: attack each other, collect resources, build structures, move, teleport, cast spells) - actions are transmitted through server between clients influences (what happens when specified action applied on specified object, e.i "Ship A attacked Ship B: field "HP" of Ship B reduced by amount of field "damage" of Ship A" Influences can be much more difficult, yes, e.i. "damage is twice it's size when Ship has =5 allies around him in a 200 units range during night" and so on. If to be able to write such logic within some "design document" it will be easily possible to: let designers to do their job without programmer's intervention or any bug-prone programming validate described logic transfer (transform, convert) to any programming language where it will be executed Did somebody worked on something like that? Is there some tools/engines/pipelines which concernes with it? How to handle all of this problems simultaneously in a best way or do I properly imagine my tasks and problems to myself?

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• How to use mount points in MilkShape models?

  - by vividos

  I have bought the Warriors & Commoners model pack from Frogames and the pack contains (among other formats) two animated models and several non-animated objects (axe, shield, pilosities, etc.) in MilkShape3D format. I looked at the official "MilkShape 3D Viewer v2.0" (msViewer2.zip at http://www.chumba.ch/chumbalum-soft/ms3d/download.html) source code and implemented loading the model, calculating the joint matrices and everything looks fine. In the model there are several joints that are designated as the "mount points" for the static objects like axe and shield. I now want to "put" the axe into the hand of the animated model, and I couldn't quite figure out how. I put the animated vertices in a VBO that gets updated every frame (I know I should do this with a shader, but I didn't have time to do this yet). I put the static vertices in another VBO that I want to keep static and not updated every frame. I now tried to render the animated vertices first, then use the joint matrix for the "mount joint" to calculate the location of the static object. I tried many things, and what about seems to be right is to transpose the joint matrix, then use glMatrixMult() to transform the modelview matrix. For some objects like the axe this is working, but not for others, e.g. the pilosities. Now my question: How is this generally implemented when using bone/joint models, and especially with MilkShape3D models? Am I on the right track?

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• DataContractSerializer truncated string when used with MemoryStream,but works with StringWriter

  - by Michael Freidgeim

  We've used the following DataContractSerializeToXml method for a long time, but recently noticed, that it doesn't return full XML for a long object, but  truncated it and returns XML string with the length of  multiple-of-1024 , but the reminder is not included. internal static string DataContractSerializeToXml<T>(T obj) { string strXml = ""; Type type= obj.GetType();//typeof(T) DataContractSerializer serializer = new DataContractSerializer(type); System.IO.MemoryStream aMemStr = new System.IO.MemoryStream(); System.Xml.XmlTextWriter writer = new System.Xml.XmlTextWriter(aMemStr, null); serializer.WriteObject(writer, obj); strXml = System.Text.Encoding.UTF8.GetString(aMemStr.ToArray()); return strXml; }   I tried to debug and searched Google for similar problems, but didn't find explanation of the error. The most closed http://forums.codeguru.com/showthread.php?309479-MemoryStream-allocates-size-multiple-of-1024-( talking about incorrect length, but not about truncated string.fortunately replacing MemoryStream to StringWriter according to http://billrob.com/archive/2010/02/09/datacontractserializer-converting-objects-to-xml-string.aspxfixed the issue.   1: var serializer = new DataContractSerializer(tempData.GetType());   2: using (var backing = new System.IO.StringWriter())   3: using (var writer = new System.Xml.XmlTextWriter(backing))   4: {   5:     serializer.WriteObject(writer, tempData);   6:     data.XmlData = backing.ToString();   7: }v

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• Boolean checks with a single quadtree, or multiple quadtrees?

  - by Djentleman

  I'm currently developing a 2D sidescrolling shooter game for PC (think metroidvania but with a lot more happening at once). Using XNA. I'm utilising quadtrees for my spatial partitioning system. All objects will be encompassed by standard bounding geometry (box or sphere) with possible pixel-perfect collision detection implemented after geometry collision (depends on how optimised I can get it). These are my collision scenarios, with < representing object overlap (multiplayer co-op is the reason for the player<player scenario): Collision scenarios (true = collision occurs): Player <> Player = false Enemy <> Enemy = false Player <> Enemy = true PlayerBullet <> Enemy = true PlayerBullet <> Player = false PlayerBullet <> EnemyBullet = true PlayerBullet <> PlayerBullet = false EnemyBullet <> Player = true EnemyBullet <> Enemy = false EnemyBullet <> EnemyBullet = false Player <> Environment = true Enemy <> Environment = true PlayerBullet <> Environment = true EnemyBullet <> Environment = true Going off this information and the fact that were will likely be several hundred objects rendering on-screen at any given time, my question is as follows: Which method is likely to be the most efficient/optimised and why: Using a single quadtree with boolean checks for collision between the different types of objects. Using three quadtrees at once (player, enemy, environment), only testing the player and enemy trees against each other while testing both the player and enemy trees against the environment tree.

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