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• In OpenGl ES 2, should I allocate multiple transformation matrices?

  - by thm4ter

  In OpenGl ES 2, should I declare just one transformation matrix, and share it across all objects or should I declare a transformation matrix in each object that needs it? for clarification... something like this: public class someclass{ public static float[16] transMatrix = new float[16]; ... public static void translate(int x, int y){ //do translation here } } public class someotherclass{ ... void draw(GL10 unused){ someclass.translate(10,10); //draw } } verses something like this: public class obj1{ public static float[16] transMatrix = new float[16]; ... void draw(GL10 unused){ //translate //draw } } public class obj2{ public static float[16] transMatrix = new float[16]; ... void draw(GL10 unused){ //translate //draw } }

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• Marching squares: Finding multiple contours within one source field?

  - by TravisG

  Principally, this is a follow-up-question to a problem from a few weeks ago, even though this is about the algorithm in general without application to my actual problem. The algorithm basically searches through all lines in the picture, starting from the top left of it, until it finds a pixel that is a border. In pseudo-C++: int start = 0; for(int i=0; i<amount_of_pixels; ++i) { if(pixels[i] == border) { start = i; break; } } When it finds one, it starts the marching squares algorithm and finds the contour to whatever object the pixel belongs to. Let's say I have something like this: Where everything except the color white is a border. And have found the contour points of the first blob: For the general algorithm it's over. It found a contour and has done its job. How can I move on to the other two blobs to find their contours as well?

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• design practice for business layer when supporting API versioning

  - by user1186065

  Is there any design pattern or practice recommended for business layer when dealing with multiple API version. For example, I have something like this. http://site.com/blogs/v1/?count=10 which calls business object method GetAllBlogs(int count) to get information http://site.com/blogs/v2/?blog_count=20 which calls business object method GetAllBlogs_v2(int blogCounts) Since parameter name is changed, I created another business method for version 2. This is just one example but it could have other breaking changes for which it requires me to create another method to support both version. Is there any design pattern or best practice for business/data access layer I should follow when supporting API Versioning?

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• Should accessible members of an internal class be internal too?

  - by Jeff Mercado

  I'm designing a set of APIs for some applications I'm working on. I want to keep the code style consistent in all the classes I write but I've found that there are a few inconsistencies that I'm introducing and I don't know what the best way to resolve them is. My example here is specific to C# but this would apply to any language with similar mechanisms. There are a few classes that I need for implementation purposes that I don't necessarily want to expose in the API so I make them internal whereever needed. Generally what I would do is design the class as I normally would (e.g., make members public/protected/private where necessary) and change the visibility level of the class itself to internal. So I might have a few classes that look like this: internal interface IMyItem { ItemSet AddTo(ItemSet set); } internal class _SmallItem : IMyItem { private readonly /* parameters */; public _SmallItem(/* small item parameters */) { /* ... */ } public ItemSet AddTo(ItemSet set) { /* ... */ } } internal abstract class _CompositeItem: IMyItem { private readonly /* parameters */; public _CompositeItem(/* composite item parameters */) { /* ... */ } public abstract object UsefulInformation { get; } protected void HelperMethod(/* parameters */) { /* ... */ } } internal class _BigItem : _CompositeItem { private readonly /* parameters */; public _BigItem(/* big item parameters */) { /* ... */ } public override object UsefulInformation { get { /* ... */ } } public ItemSet AddTo(ItemSet set) { /* ... */ } } In another generated class (part of a parser/scanner), there is a structure that contains fields for all possible values it can represent. The class generated is internal too but I have control over the visibility of the members and decided to make them internal as well. internal partial struct ValueType { internal string String; internal ItemSet ItemSet; internal IMyItem MyItem; } internal class TokenValue { internal static int EQ(ItemSetScanner scanner) { /* ... */ } internal static int NAME(ItemSetScanner scanner, string value) { /* ... */ } internal static int VALUE(ItemSetScanner scanner, string value) { /* ... */ } //... } To me, this feels odd because the first set of classes, I didn't necessarily have to make some members public, they very well could have been made internal. internal members of an internal type can only be accessed internally anyway so why make them public? I just don't like the idea that the way I write my classes has to change drastically (i.e., change all uses of public to internal) just because the class is internal. Any thoughts on what I should do here? It makes sense to me that I might want to make some members of a class declared public, internal. But it's less clear to me when the class is declared internal.

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• Displaying a grid based map using C++ and sdl

  - by user15386

  I am trying to create a roguelike game using c++ and SDL. However, I am having trouble getting it to display the map, which is represented by a 2d array of a tile class. Currently, my code is this: for (int y = 0; y!=MAPHEIGHT; y++) { for (int x = 0; x!=MAPWIDTH 1; x++) { apply_surface( x * TILEWIDTH, y * TILEHEIGHT, mymap[x][y].image, screen ); } } However, running this code causes it to both dither for a while before opening the SDL window, and (usually) tell me there is an access violation. How can I display my map?

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• Are closures with side-effects considered "functional style"?

  - by Giorgio

  Many modern programming languages support some concept of closure, i.e. of a piece of code (a block or a function) that Can be treated as a value, and therefore stored in a variable, passed around to different parts of the code, be defined in one part of a program and invoked in a totally different part of the same program. Can capture variables from the context in which it is defined, and access them when it is later invoked (possibly in a totally different context). Here is an example of a closure written in Scala: def filterList(xs: List[Int], lowerBound: Int): List[Int] = xs.filter(x => x >= lowerBound) The function literal x => x >= lowerBound contains the free variable lowerBound, which is closed (bound) by the argument of the function filterList that has the same name. The closure is passed to the library method filter, which can invoke it repeatedly as a normal function. I have been reading a lot of questions and answers on this site and, as far as I understand, the term closure is often automatically associated with functional programming and functional programming style. The definition of function programming on wikipedia reads: In computer science, functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids state and mutable data. It emphasizes the application of functions, in contrast to the imperative programming style, which emphasizes changes in state. and further on [...] in functional code, the output value of a function depends only on the arguments that are input to the function [...]. Eliminating side effects can make it much easier to understand and predict the behavior of a program, which is one of the key motivations for the development of functional programming. On the other hand, many closure constructs provided by programming languages allow a closure to capture non-local variables and change them when the closure is invoked, thus producing a side effect on the environment in which they were defined. In this case, closures implement the first idea of functional programming (functions are first-class entities that can be moved around like other values) but neglect the second idea (avoiding side-effects). Is this use of closures with side effects considered functional style or are closures considered a more general construct that can be used both for a functional and a non-functional programming style? Is there any literature on this topic? IMPORTANT NOTE I am not questioning the usefulness of side-effects or of having closures with side effects. Also, I am not interested in a discussion about the advantages / disadvantages of closures with or without side effects. I am only interested to know if using such closures is still considered functional style by the proponent of functional programming or if, on the contrary, their use is discouraged when using a functional style.

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• Android - Force Close - Null Pointer on Canvas?

  - by user22241

  Please bear with me. I have a very odd problem. Basically, my app so far, has 3 activities (a main splash screen, an 'options/menu' screen and the main app). If I follow the very specific steps oulined below, I get a 'null pointer exception' in the 2nd activity) and the app force closes...... Here are the steps: Start the app (a game based on Surfaceview), tap through to the third activity so the game is running, then hit the home key so the game is paused and put to the background, the activity/app is ended through DDMS in the SDK then restarted on the device (all OK so far), now if I hit the back key on the device twice in quick succession, it happens. All other sequence of events is fine, even to the point of pressing the back key, waiting for the previous activity to show, then hitting back again - all OK. Only when the back key is pressed twice in quick succession following all the above steps does the problem occur. I'm assuming that the canvas isn't ready as it's showing as 'null' when this happens, but I'm not sure why this is happening as surely it's happening when I'm trying to go back to activity 1, but the logcat shows the error in activity 2. if I stop the activity running my 'doDraw' method (which referenced the canvas), then all is OK - so I can safely assume it is the canvas causing the problem. Also, if I skip my first activity (which is a very basic full-screen button which just displays a splashscreen and waits for the user to tap the screen), and make my 2nd activity the launch activity, again, it is OK. this is the part of the code that I think is probably relevant: @Override public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) { vheight = this.getHeight(); vwidth = this.getWidth(); } @Override public void surfaceCreated(SurfaceHolder holder) { vheight = this.getHeight(); vwidth = this.getWidth(); this.viewWidth = vwidth; this.viewHeight = vheight; if (runthread==false){ if (preThread.getState()==Thread.State.TERMINATED){ preThread = new OptionsThread(thisholder, thiscontext, thishandler); } preThread.setRunning(true); preThread.start();} } @Override public void surfaceDestroyed(SurfaceHolder holder) { preThread.setRunning(false); //Stop the loop boolean retry = true; //Stop the thread while (retry) { try { preThread.join(); retry = false; } catch (InterruptedException e) { } } Thank you all for any help you can offer

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• Commenting/In-Code Documentation Styles

  - by Maxpm

  This might be a stupid question, but it's been in the back of my head for a while and I can't find a decent answer anywhere else. I have a teacher who says we should explicitly list each parameter with a description, even if there's only one. This leads to a lot of repetition: double MyFunction(const int MyParam); // Function: MyFunction // Summary: Does stuff with MyParam. // Input: int MyParam - The number to do stuff with. // Output: MyParam with stuff done to it. When writing in-code documentation, how detailed are you?

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• Newbie in ASP.Net

  - by dnvThai

  I am learning ASP.Net and I am confusing between ASP.Net WebPages, ASP.Net WebForms and ASP.Net MVC. I have read a lot of articles and known the simple difference of their functions, but I don't know the differences of their code. E.g: When I look at int* p = new int(); ... I know that it's C++ style. and Dim A as String it have to be Visual Basic. [?1] I'm not able to detect like that in ASP.Net. How do they different in codes? I use Visual Studio 2010 Express Edition.I like to use C# (I also was learned VisualBasic in shool, but I don't like him). When I create a new project, there're too many types of project, then, I don't know which I should choose (I just want to make a simple site). [?2] What are they used to? Thanks

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• How are OpenGL ES 1 framebuffers and textures sized?

  - by jens

  I am trying to draw to a texture using a framebuffer using OpenGL ES 1.1 on Android, Java. Afterwords I want to overlay this texture full-screen over my game. In theory, this works like a charm, but somehow the coordinates are off. For testing I drew something at (0,0) with width and height 200, and it partly is off-screen. This is how I create the framebuffer: fb = new int[1]; depthRb = new int[1]; renderTex = new int[1]; gl11ep.glGenFramebuffersOES(1, fb, 0); gl11ep.glGenRenderbuffersOES(1, depthRb, 0); // the depth buffer gl.glGenTextures(1, renderTex, 0);// generate texture gl.glBindTexture(GL10.GL_TEXTURE_2D, renderTex[0]); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_LINEAR); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_REPEAT); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_REPEAT); texBuffer = ByteBuffer.allocateDirect(buf.length*4).order(ByteOrder.nativeOrder()).asIntBuffer(); gl.glTexImage2D(GL10.GL_TEXTURE_2D, 0, GL10.GL_LUMINANCE, texW, texH, 0, GL10.GL_LUMINANCE, GL10.GL_UNSIGNED_BYTE, texBuffer); gl11ep.glBindRenderbufferOES(GL11ExtensionPack.GL_RENDERBUFFER_OES, depthRb[0]); gl11ep.glRenderbufferStorageOES(GL11ExtensionPack.GL_RENDERBUFFER_OES, GL11ExtensionPack.GL_DEPTH_COMPONENT16, texW, texH); Before I draw, I do this: gl11ep.glBindFramebufferOES(GL11ExtensionPack.GL_FRAMEBUFFER_OES, fb[0]); gl.glClearColor(0f, 0f, 0f, 0f); // specify texture as color attachment gl11ep.glFramebufferTexture2DOES(GL11ExtensionPack.GL_FRAMEBUFFER_OES, GL11ExtensionPack.GL_COLOR_ATTACHMENT0_OES, GL10.GL_TEXTURE_2D, renderTex[0], 0); // attach render buffer as depth buffer gl11ep.glFramebufferRenderbufferOES(GL11ExtensionPack.GL_FRAMEBUFFER_OES, GL11ExtensionPack.GL_DEPTH_ATTACHMENT_OES, GL11ExtensionPack.GL_RENDERBUFFER_OES, depthRb[0]); I set texW = 1024 and texH = 512. When rendering this texture fullscreen, with a lightmask (size 200x200) placed at (0, 0) and (texW/2, texH/2). You can see that it seems like the coordinate system doesnt start at (0,0) as that light overlaps the screen and the images are not drawn as squares (my lightcone-texture is a circle, not an ellipse). So, how is the coordinate system of this offscreen-drawn texture defined? Thanks

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• Need help with a method to randomly lay mines in a minesweeper game

  - by avatarX

  So my Java minesweeper game is represented as a int[][] where -1 represents a mine. When I initialize my game I need to randomly place x amount of mines. What is an elegant way of doing this? I was thinking of using an ArrayList with the coordinates of each cell, randomly selecting it, changing the state of the int[][] and then removing that Point. This would ensure that no point is selected twice. Is there a more elegant way of doing this?

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• Render graphics using Doubles in Graphics2D

  - by thedeadlybutter

  Currently, I have a JFrame for my game to render in, and I'm using Graphics2D for drawing (The games graphics are fairly simple 2D sprites). However, my delta variable is a double, and all of the Graphics 2D methods (And Grpahics) use int. I tried to type cast the delta to an int, but it just rounds down to 0. So my question is, how can I render graphics using Graphics2D in Java with coordinates that are doubles. Can I convert it to work with Graphics2D if there is no built in way? Or, is there a graphics library that can support doubles for coordinates?

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• If there's no problem treating a statement as an expression, why was there a distinction in the first place in some programming languages?

  - by cdmckay

  Why do we have the distinction between statements and expressions in most programming languages? For example, in Java, assuming f and g return ints, this still won't compile because it's a statement and statements don't return values. // won't compile int i = if (pred) { f(x); } else { g(x); } but in Scala, it's very happy with treating if as an expression. // compiles fine val i: Int = if (pred) f(x) else g(x) So if there's no problem treating an if statement as an expression, why was there a distinction in the first place?

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• Am I violating LSP if the condition can be checked?

  - by William

  This base class for some shapes I have in my game looks like this. Some of the shapes can be resized, some of them can not. private Shape shape; public virtual void SetSizeOfShape(int x, int y) { if (CanResize()){ shape.Width = x; shape.Height = y; } else { throw new Exception("You cannot resize this shape"); } } public virtual bool CanResize() { return true; } In a sub class of a shape that I don't ever want to resize I am overriding the CanResize() method so a piece of client code can check before calling the SetSizeOfShape() method. public override bool CanResize() { return false; } Here's how it might look in my client code: public void DoSomething(Shape s) { if(s.CanResize()){ s.SetSizeOfShape(50, 70); } } Is this violating LSP?

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• Silverlight and WCF caching

  - by subodhnpushpak

  There are scenarios where Silverlight client calls WCF (or REST) service for data. Now, if the data is cached on the WCF layer, the calls can take considerable resources at the server if NOT cached. Keeping that in mind along with the fact that cache is an cross-cutting aspect, and therefore it should be as easy as possible to put Cache wherever required. The good thing about the solution is that it caches based on the inputs. The input can be basic type of any complex type. If input changes the data is fetched and then cached for further used. If same input is provided again, data id fetched from the cache. The cache logic itself is implemented as PostSharp aspect, and it is as easy as putting an attribute over service call to switch on cache. Notice how clean the code is:        [OperationContract]       [CacheOnArgs(typeof(int))] // based on actual value of cache        public string DoWork(int value)        {            return string.Format("You entered: {0} @ cached time {1}", value, System.DateTime.Now);        } The cache is implemented as POST Sharp as below 1: public override void OnInvocation(MethodInvocationEventArgs eventArgs) 2: { 3: try 4: { 5: object value = new object(); 6: object[] args = eventArgs.GetArgumentArray(); 7: if (args != null || args.Count() > 0) 8: { 9:   10: string key = string.Format("{0}_{1}", eventArgs.Method.Name, XMLUtility<object>.GetDataContractXml(args[0], null));// Compute the cache key (details omitted). 11:   12: 13: value = GetFromCache(key); 14: if (value == null) 15: { 16: eventArgs.Proceed(); 17: value = XMLUtility<object>.GetDataContractXml(eventArgs.ReturnValue, null); 18: value = eventArgs.ReturnValue; 19: AddToCache(key, value); 20: return; 21: } 22:   23:   24: Log(string.Format("Data returned from Cache {0}",value)); 25: eventArgs.ReturnValue = value; 26: } 27: } 28: catch (Exception ex) 29: { 30: //ApplicationLogger.LogException(ex.Message, Source.UtilityService); 31: } 32: } 33:   34: private object GetFromCache(string inputKey) { if (ServerConfig.CachingEnabled) { return WCFCache.Current[inputKey]; } return null; }private void AddToCache(string inputKey,object outputValue) 35: { 36: if (ServerConfig.CachingEnabled) 37: { 38: if (WCFCache.Current.CachedItemsNumber < ServerConfig.NumberOfCachedItems) 39: { 40: if (ServerConfig.SlidingExpirationTime <= 0 || ServerConfig.SlidingExpirationTime == int.MaxValue) 41: { 42: WCFCache.Current[inputKey] = outputValue; 43: } 44: else 45: { 46: WCFCache.Current.Insert(inputKey, outputValue, new TimeSpan(0, 0, ServerConfig.SlidingExpirationTime), true); 47:   48: // _bw.DoWork += bw_DoWork; 49: //string arg = string.Format("{0}|{1}", inputKey,outputValue); 50: //_bw.RunWorkerAsync(inputKey ); 51: } 52: } 53: } 54: }     The cache class can be extended to support Velocity / memcahe / Nache. the attribute can be used over REST services as well. Hope the above helps. Here is the code base for the same.   Please do provide your inputs / comments.

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• Practices for domain models in Javascript (with frameworks)

  - by AndyBursh

  This is a question I've to-and-fro'd with for a while, and searched for and found nothing on: what're the accepted practices surrounding duplicating domain models in Javascript for a web application, when using a framework like Backbone or Knockout? Given a web application of a non-trivial size with a set of domain models on the server side, should we duplicate these models in the web application (see the example at the bottom)? Or should we use the dynamic nature to load these models from the server? To my mind, the arguments for duplicating the models are in easing validation of fields, ensuring that fields that expected to be present are in fact present etc. My approach is to treat the client-side code like an almost separate application, doing trivial things itself and only relying on the server for data and complex operations (which require data the client-side doesn't have). I think treating the client-side code like this is akin to separation between entities from an ORM and the models used with the view in the UI layer: they may have the same fields and relate to the same domain concept, but they're distinct things. On the other hand, it seems to me that duplicating these models on the server side is a clear violation of DRY and likely to lead to differing results on the client- and server-side (where one piece gets updated but the other doesn't). To avoid this violation of DRY we can simply use Javascripts dynamism to get the field names and data from the server as and when they're neeed. So: are there any accepted guidelines around when (and when not) to repeat yourself in these situations? Or this a purely subjective thing, based on the project and developer(s)? Example Server-side model class M { int A DateTime B int C int D = (A*C) double SomeComplexCalculation = ServiceLayer.Call(); } Client-side model function M(){ this.A = ko.observable(); this.B = ko.observable(); this.C = ko.observable(); this.D = function() { return A() * C(); } this.SomeComplexCalculation = ko.observalbe(); return this; }l M.GetComplexValue = function(){ this.SomeComplexCalculation(Ajax.CallBackToServer()); }; I realise this question is quite similar to this one, but I think this is more about almost wholly untying the web application from the server, where that question is about doing this only in the case of complex calculation.

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• Entity Framework 5, separating business logic from model - Repository?

  - by bnice7

  I am working on my first public-facing web application and I’m using MVC 4 for the presentation layer and EF 5 for the DAL. The database structure is locked, and there are moderate differences between how the user inputs data and how the database itself gets populated. I have done a ton of reading on the repository pattern (which I have never used) but most of my research is pushing me away from using it since it supposedly creates an unnecessary level of abstraction for the latest versions of EF since repositories and unit-of-work are already built-in. My initial approach is to simply create a separate set of classes for my business objects in the BLL that can act as an intermediary between my Controllers and the DAL. Here’s an example class: public class MyBuilding { public int Id { get; private set; } public string Name { get; set; } public string Notes { get; set; } private readonly Entities _context = new Entities(); // Is this thread safe? private static readonly int UserId = WebSecurity.GetCurrentUser().UserId; public IEnumerable<MyBuilding> GetList() { IEnumerable<MyBuilding> buildingList = from p in _context.BuildingInfo where p.Building.UserProfile.UserId == UserId select new MyBuilding {Id = p.BuildingId, Name = p.BuildingName, Notes = p.Building.Notes}; return buildingList; } public void Create() { var b = new Building {UserId = UserId, Notes = this.Notes}; _context.Building.Add(b); _context.SaveChanges(); // Set the building ID this.Id = b.BuildingId; // Seed 1-to-1 tables with reference the new building _context.BuildingInfo.Add(new BuildingInfo {Building = b}); _context.GeneralInfo.Add(new GeneralInfo {Building = b}); _context.LocationInfo.Add(new LocationInfo {Building = b}); _context.SaveChanges(); } public static MyBuilding Find(int id) { using (var context = new Entities()) // Is this OK to do in a static method? { var b = context.Building.FirstOrDefault(p => p.BuildingId == id && p.UserId == UserId); if (b == null) throw new Exception("Error: Building not found or user does not have access."); return new MyBuilding {Id = b.BuildingId, Name = b.BuildingInfo.BuildingName, Notes = b.Notes}; } } } My primary concern: Is the way I am instantiating my DbContext as a private property thread-safe, and is it safe to have a static method that instantiates a separate DbContext? Or am I approaching this all wrong? I am not opposed to learning up on the repository pattern if I am taking the total wrong approach here.

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• Context Menu for add and remove datalist column [migrated]

  - by Kadir Ozgur

  When I right click on Datalist Columns then a context menu appears whose items are add columns, remove column etc. When I removed a column and if I want to remove one more column then it shows me to remove previous column. Everytime, it shows me to remove the previous ones. if (mnu.Name.StartsWith("Rem")) { //getview(); //datalist.Items.Refresh(); //rows.Clear(); //datalist.ItemsSource = rows; int id = listwork.dispidx(util.valint(/*mnu.Name.Substring(3)*/util.valint(mnu.Tag)), ListWork.eArtIdx.dispord); int delid = listwork.delcol(id); GridViewColumnCollection gw = getview().Columns; if (delid >= 0 && delid < gw.Count) gw.RemoveAt(delid); listsortnr = 0; //weil wir ja Colonnen gelöschte haben showsortlist(listwork.querydef.Sortcol); //rows.Clear(); DoRefresh(); }

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• Checking timeouts made more readable

  - by Markus

  I have several situations where I need to control timeouts in a technical application. Either in a loop or as a simple check. Of course – handling this is really easy, but none of these is looking cute. To clarify, here is some C# (Pseudo) code: private DateTime girlWentIntoBathroom; girlWentIntoBathroom = DateTime.Now; do { // do something } while (girlWentIntoBathroom.AddSeconds(10) > DateTime.Now); or if (girlWentIntoBathroom.AddSeconds(10) > DateTime.Now) MessageBox.Show("Wait a little longer"); else MessageBox.Show("Knock louder"); Now I was inspired by something a saw in Ruby on StackOverflow: Now I’m wondering if this construct can be made more readable using extension methods. My goal is something that can be read like “If girlWentIntoBathroom is more than 10 seconds ago” 1st attempt if (girlWentIntoBathroom > (10).Seconds().Ago()) MessageBox.Show("Wait a little longer"); else MessageBox.Show("Knock louder"); So I wrote an extension for integer that converts the integer into a TimeSpan public static TimeSpan Seconds(this int amount) { return new TimeSpan(0, 0, amount); } After that, I wrote an extension for TimeSpan like this: public static DateTime Ago(this TimeSpan diff) { return DateTime.Now.Add(-diff); } This works fine so far, but has a great disadvantage. The logic is inverted! Since girlWentIntoBathroom is a timestamp in the past, the right side of the equation needs to count backwards: impossible. Just inverting the equation is no solution, because it will invert the read sentence as well. 2nd attempt So I tried something new: if (girlWentIntoBathroom.IsMoreThan(10).SecondsAgo()) MessageBox.Show("Knock louder"); else MessageBox.Show("Wait a little longer"); IsMoreThan() needs to transport the past timestamp as well as the span for the extension SecondsAgo(). It could be: public static DateWithIntegerSpan IsMoreThan(this DateTime baseTime, int span) { return new DateWithIntegerSpan() { Date = baseTime, Span = span }; } Where DateWithIntegerSpan is simply: public class DateWithIntegerSpan { public DateTime Date {get; set;} public int Span { get; set; } } And SecondsAgo() is public static bool SecondsAgo(this DateWithIntegerSpan dateAndSpan) { return dateAndSpan.Date.Add(new TimeSpan(0, 0, dateAndSpan.Span)) < DateTime.Now; } Using this approach, the English sentence matches the expected behavior. But the disadvantage is, that I need a helping class (DateWithIntegerSpan). Has anyone an idea to make checking timeouts look more cute and closer to a readable sentence? Am I a little too insane thinking about something minor like this?

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• Unable to list contents/remove directory (linux ext3)

  - by RedKrieg

  System is CentOS5 x86_64, completely up to date. I've got a folder that can't be listed (ls just hangs, eating memory until it is killed). The directory size is nearly 500k: root@server [/home/user/public_html/domain.com/wp-content/uploads/2010/03]# stat . File: `.' Size: 458752 Blocks: 904 IO Block: 4096 directory Device: 812h/2066d Inode: 44499071 Links: 2 Access: (0755/drwxr-xr-x) Uid: ( 3292/ user) Gid: ( 3287/ user) Access: 2012-06-29 17:31:47.000000000 -0400 Modify: 2012-10-23 14:41:58.000000000 -0400 Change: 2012-10-23 14:41:58.000000000 -0400 I can see the file names if I use ls -1f, but it just repeats the same 48 files ad infinitum, all of which have non-ascii characters somewhere in the file name: La-critic\363-al-servicio-la-privacidad-300x160.jpg When I try to access the files (say to copy them or remove them) I get messages like the following: lstat("/home/user/public_html/domain.com/wp-content/uploads/2010/03/Sebast\355an-Pi\361era-el-balc\363n-150x120.jpg", 0x7fff364c52c0) = -1 ENOENT (No such file or directory) I tried altering the code found on this man page and modified the code to call unlink for each file. I get the same ENOENT error from the unlink call: unlink("/home/user/public_html/domain.com/wp-content/uploads/2010/03/Marca-naci\363n-Madrid-150x120.jpg") = -1 ENOENT (No such file or directory) I also straced a "touch", grabbed the syscalls it makes and replicated them, then tried to unlink the resulting file by name. This works fine, but the folder still contains an entry by the same name after the operation completes and the program runs for an arbitrarily long time (strace output ended up at 20GB after 5 minutes and I stopped the process). I'm stumped on this one, I'd really prefer not to have to take this production machine (hundreds of customers) offline to fsck the filesystem, but I'm leaning toward that being the only option at this point. If anyone's had success using other methods for removing files (by inode number, I can get those with the getdents code) I'd love to hear them. (Yes, I've tried find . -inum <inode> -exec rm -fv {} \; and it still has the problem with unlink returning ENOENT) For those interested, here's the diff between that man page's code and mine. I didn't bother with error checking on mallocs, etc because I'm lazy and this is a one-off: root@server [~]# diff -u listdir-orig.c listdir.c --- listdir-orig.c 2012-10-23 15:10:02.000000000 -0400 +++ listdir.c 2012-10-23 14:59:47.000000000 -0400 @@ -6,6 +6,7 @@ #include <stdlib.h> #include <sys/stat.h> #include <sys/syscall.h> +#include <string.h> #define handle_error(msg) \ do { perror(msg); exit(EXIT_FAILURE); } while (0) @@ -17,7 +18,7 @@ char d_name[]; }; -#define BUF_SIZE 1024 +#define BUF_SIZE 1024*1024*5 int main(int argc, char *argv[]) { @@ -26,11 +27,16 @@ struct linux_dirent *d; int bpos; char d_type; + int deleted; + int file_descriptor; fd = open(argc > 1 ? argv[1] : ".", O_RDONLY | O_DIRECTORY); if (fd == -1) handle_error("open"); + char* full_path; + char* fd_path; + for ( ; ; ) { nread = syscall(SYS_getdents, fd, buf, BUF_SIZE); if (nread == -1) @@ -55,7 +61,24 @@ printf("%4d %10lld %s\n", d->d_reclen, (long long) d->d_off, (char *) d->d_name); bpos += d->d_reclen; + if ( d_type == DT_REG ) + { + full_path = malloc(strlen((char *) d->d_name) + strlen(argv[1]) + 2); //One for the /, one for the \0 + strcpy(full_path, argv[1]); + strcat(full_path, (char *) d->d_name); + + //We're going to try to "touch" the file. + //file_descriptor = open(full_path, O_WRONLY|O_CREAT|O_NOCTTY|O_NONBLOCK, 0666); + //fd_path = malloc(32); //Lazy, only really needs 16 + //sprintf(fd_path, "/proc/self/fd/%d", file_descriptor); + //utimes(fd_path, NULL); + //close(file_descriptor); + deleted = unlink(full_path); + if ( deleted == -1 ) printf("Error unlinking file\n"); + break; //Break on first try + } } + break; //Break on first try } exit(EXIT_SUCCESS);

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• Encrypt images before uploading to Dropbox [migrated]

  - by Cherry

  I want to encrypt a file first before the file will be uploaded to the dropbox. So i have implement the encryption inside the uploading of the codes. However, there is an error after i integrate the codes together. Where did my mistake go wrong? Error at putFileOverwriteRequest and it says The method putFileOverwriteRequest(String, InputStream, long, ProgressListener) in the type DropboxAPI is not applicable for the arguments (String, FileOutputStream, long, new ProgressListener(){}) Another problem is that this FileOutputStream fis = new FileOutputStream(new File("dont know what to put in this field")); i do not know where to put the file so that after i read the file, it will call the path and then upload to the Dropbox. Anyone is kind to help me in this? As time is running out for me and i still cant solve the problem. Thank you in advance. The full code is as below. public class UploadPicture extends AsyncTask<Void, Long, Boolean> { private DropboxAPI<?> mApi; private String mPath; private File mFile; private long mFileLen; private UploadRequest mRequest; private Context mContext; private final ProgressDialog mDialog; private String mErrorMsg; public UploadPicture(Context context, DropboxAPI<?> api, String dropboxPath, File file) { // We set the context this way so we don't accidentally leak activities mContext = context.getApplicationContext(); mFileLen = file.length(); mApi = api; mPath = dropboxPath; mFile = file; mDialog = new ProgressDialog(context); mDialog.setMax(100); mDialog.setMessage("Uploading " + file.getName()); mDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL); mDialog.setProgress(0); mDialog.setButton("Cancel", new OnClickListener() { public void onClick(DialogInterface dialog, int which) { // This will cancel the putFile operation mRequest.abort(); } }); mDialog.show(); } @Override protected Boolean doInBackground(Void... params) { try { KeyGenerator keygen = KeyGenerator.getInstance("DES"); SecretKey key = keygen.generateKey(); //generate key //encrypt file here first byte[] plainData; byte[] encryptedData; Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding"); cipher.init(Cipher.ENCRYPT_MODE, key); //File f = new File(mFile); //read file FileInputStream in = new FileInputStream(mFile); //obtains input bytes from a file plainData = new byte[(int)mFile.length()]; in.read(plainData); //Read bytes of data into an array of bytes encryptedData = cipher.doFinal(plainData); //encrypt data FileOutputStream fis = new FileOutputStream(new File("dont know what to put in this field")); //upload to a path first then call the path so that it can be uploaded up to the dropbox //save encrypted file to dropbox // By creating a request, we get a handle to the putFile operation, // so we can cancel it later if we want to //FileInputStream fis = new FileInputStream(mFile); String path = mPath + mFile.getName(); mRequest = mApi.putFileOverwriteRequest(path, fis, mFile.length(), new ProgressListener() { @Override public long progressInterval() { // Update the progress bar every half-second or so return 500; } @Override public void onProgress(long bytes, long total) { publishProgress(bytes); } }); if (mRequest != null) { mRequest.upload(); return true; } } catch (DropboxUnlinkedException e) { // This session wasn't authenticated properly or user unlinked mErrorMsg = "This app wasn't authenticated properly."; } catch (DropboxFileSizeException e) { // File size too big to upload via the API mErrorMsg = "This file is too big to upload"; } catch (DropboxPartialFileException e) { // We canceled the operation mErrorMsg = "Upload canceled"; } catch (DropboxServerException e) { // Server-side exception. These are examples of what could happen, // but we don't do anything special with them here. if (e.error == DropboxServerException._401_UNAUTHORIZED) { // Unauthorized, so we should unlink them. You may want to // automatically log the user out in this case. } else if (e.error == DropboxServerException._403_FORBIDDEN) { // Not allowed to access this } else if (e.error == DropboxServerException._404_NOT_FOUND) { // path not found (or if it was the thumbnail, can't be // thumbnailed) } else if (e.error == DropboxServerException._507_INSUFFICIENT_STORAGE) { // user is over quota } else { // Something else } // This gets the Dropbox error, translated into the user's language mErrorMsg = e.body.userError; if (mErrorMsg == null) { mErrorMsg = e.body.error; } } catch (DropboxIOException e) { // Happens all the time, probably want to retry automatically. mErrorMsg = "Network error. Try again."; } catch (DropboxParseException e) { // Probably due to Dropbox server restarting, should retry mErrorMsg = "Dropbox error. Try again."; } catch (DropboxException e) { // Unknown error mErrorMsg = "Unknown error. Try again."; } catch (FileNotFoundException e) { } return false; } @Override protected void onProgressUpdate(Long... progress) { int percent = (int)(100.0*(double)progress[0]/mFileLen + 0.5); mDialog.setProgress(percent); } @Override protected void onPostExecute(Boolean result) { mDialog.dismiss(); if (result) { showToast("Image successfully uploaded"); } else { showToast(mErrorMsg); } } private void showToast(String msg) { Toast error = Toast.makeText(mContext, msg, Toast.LENGTH_LONG); error.show(); } }

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• Getting data from csv file and returning objects in collections

  - by Jacob

  I have very simple class of person as below: public class Person { int ID; Gender gender; Date dateOfBirth; public Person(final int iD, final Gender gender,final Date dateOfBirth) { ID = iD; this.gender = gender; this.dateOfBirth = dateOfBirth; } } Gender is enum : public enum Gender { Male, Female } In CSV file i will have data, for example: 1;Male;23-02-2001 2;Female;11-06-1989 3;Male;02-12-1999 Is in java any simple way to get all persons from csv file and return it as ArrayList<Person> persons ?

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• Better way for calculating project euler's 2nd problem Fibonacci sequence)

  - by firephil

  object Problem_2 extends App { def fibLoop():Long = { var x = 1L var y = 2L var sum = 0L var swap = 0L while(x < 4000000) { if(x % 2 ==0) sum +=x swap = x x = y y = swap + x } sum } def fib:Int = { lazy val fs: Stream[Int] = 0 #:: 1 #:: fs.zip(fs.tail).map(p => p._1 + p._2) fs.view.takeWhile(_ <= 4000000).filter(_ % 2 == 0).sum } val t1 = System.nanoTime() val res = fibLoop val t2 = (System.nanoTime() - t1 )/1000 println(s"The result is: $res time taken $t2 ms ") } Is there a better functional way for calculating the fibonaci sequence and taking the sum of the the even values below 4million ? (projecteuler.net - problem 2) The imperative method is 1000x faster ?

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• while(true) and loop-breaking - anti-pattern?

  - by KeithS

  Consider the following code: public void doSomething(int input) { while(true) { TransformInSomeWay(input); if(ProcessingComplete(input)) break; DoSomethingElseTo(input); } } Assume that this process involves a finite but input-dependent number of steps; the loop is designed to terminate on its own as a result of the algorithm, and is not designed to run indefinitely (until cancelled by an outside event). Because the test to see if the loop should end is in the middle of a logical set of steps, the while loop itself currently doesn't check anything meaningful; the check is instead performed at the "proper" place within the conceptual algorithm. I was told that this is bad code, because it is more bug-prone due to the ending condition not being checked by the loop structure. It's more difficult to figure out how you'd exit the loop, and could invite bugs as the breaking condition might be bypassed or omitted accidentally given future changes. Now, the code could be structured as follows: public void doSomething(int input) { TransformInSomeWay(input); while(!ProcessingComplete(input)) { DoSomethingElseTo(input); TransformInSomeWay(input); } } However, this duplicates a call to a method in code, violating DRY; if TransformInSomeWay were later replaced with some other method, both calls would have to be found and changed (and the fact that there are two may be less obvious in a more complex piece of code). You could also write it like: public void doSomething(int input) { var complete = false; while(!complete) { TransformInSomeWay(input); complete = ProcessingComplete(input); if(!complete) { DoSomethingElseTo(input); } } } ... but you now have a variable whose only purpose is to shift the condition-checking to the loop structure, and also has to be checked multiple times to provide the same behavior as the original logic. For my part, I say that given the algorithm this code implements in the real world, the original code is the most readable. If you were going through it yourself, this is the way you'd think about it, and so it would be intuitive to people familiar with the algorithm. So, which is "better"? is it better to give the responsibility of condition checking to the while loop by structuring the logic around the loop? Or is it better to structure the logic in a "natural" way as indicated by requirements or a conceptual description of the algorithm, even though that may mean bypassing the loop's built-in capabilities?

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• Object Oriented Design of a Small Java Game

  - by user2733436

  This is the problem i am dealing with. I have to make a simple game of NIM. I am learning java using a book so far i have only coded programs that deal with 2 classes. This program would have about 4 classes i guess including the main class. My problem is i am having a difficult time designing classes how they will interact with each other. I really want to think and use a object oriented approach. So the first thing i did was design the Pile CLASS as it seemed the easiest and made the most sense to me in terms of what methods go in it. Here is what i have got down for the Pile Class so far. package Nim; import java.util.Random; public class Pile { private int initialSize; public Pile(){ } Random rand = new Random(); public void setPile(){ initialSize = (rand.nextInt(100-10)+10); } public void reducePile(int x){ initialSize = initialSize - x; } public int getPile(){ return initialSize; } public boolean hasStick(){ if(initialSize>0){ return true; } else { return false; } } } Now i need help in designing the Player Class. By that i mean i am not asking for anyone to write code for me as that defeats the purpose of learning i was just wondering how would i design the player class and what would go on it. My guess is that the player class would contain method for choosing move for computer and also receiving the move human user makes. Lastly i am guessing in the Game class i am guessing the turns would be handeled. I am really lost right now so i was wondering if someone can help me think through this problem it would be great. Starting with the player class would be appreciated. I know there are some solutions for this problem online but i refuse to look at because i want to develop my own approach to such problems and i am confident if i can get through this problem i can solve other problems. I apologize if this question is a bit poor but in specific i need help in designing the Player class.

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