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• Help to solve "Robbery Problem"

  - by peiska

  Hello, Can anybody help me with this problem in C or Java? The problem is taken from here: http://acm.pku.edu.cn/JudgeOnline/problem?id=1104 Inspector Robstop is very angry. Last night, a bank has been robbed and the robber has not been caught. And this happened already for the third time this year, even though he did everything in his power to stop the robber: as quickly as possible, all roads leading out of the city were blocked, making it impossible for the robber to escape. Then, the inspector asked all the people in the city to watch out for the robber, but the only messages he got were of the form "We don't see him." But this time, he has had enough! Inspector Robstop decides to analyze how the robber could have escaped. To do that, he asks you to write a program which takes all the information the inspector could get about the robber in order to find out where the robber has been at which time. Coincidentally, the city in which the bank was robbed has a rectangular shape. The roads leaving the city are blocked for a certain period of time t, and during that time, several observations of the form "The robber isn't in the rectangle Ri at time ti" are reported. Assuming that the robber can move at most one unit per time step, your program must try to find the exact position of the robber at each time step. Input The input contains the description of several robberies. The first line of each description consists of three numbers W, H, t (1 <= W,H,t <= 100) where W is the width, H the height of the city and t is the time during which the city is locked. The next contains a single integer n (0 <= n <= 100), the number of messages the inspector received. The next n lines (one for each of the messages) consist of five integers ti, Li, Ti, Ri, Bi each. The integer ti is the time at which the observation has been made (1 <= ti <= t), and Li, Ti, Ri, Bi are the left, top, right and bottom respectively of the (rectangular) area which has been observed. (1 <= Li <= Ri <= W, 1 <= Ti <= Bi <= H; the point (1, 1) is the upper left hand corner, and (W, H) is the lower right hand corner of the city.) The messages mean that the robber was not in the given rectangle at time ti. The input is terminated by a test case starting with W = H = t = 0. This case should not be processed. Output For each robbery, first output the line "Robbery #k:", where k is the number of the robbery. Then, there are three possibilities: If it is impossible that the robber is still in the city considering the messages, output the line "The robber has escaped." In all other cases, assume that the robber really is in the city. Output one line of the form "Time step : The robber has been at x,y." for each time step, in which the exact location can be deduced. (x and y are the column resp. row of the robber in time step .) Output these lines ordered by time . If nothing can be deduced, output the line "Nothing known." and hope that the inspector will not get even more angry. Output a blank line after each processed case.

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• What are the Open Source alternatives to WPF/XAML?

  - by Evan Plaice

  If we've learned anything from HTML/CSS it's that, declarative languages (like XML) work best to describe User Interfaces because: It's easy to build code preprocessors that can template the code effectively. The code is in a well defined well structured (ideally) format so it's easy to parse. The technology to effectively parse or crawl an XML based source file already exists. The UIs scripted code becomes much simpler and easier to understand. It simple enough that designers are able to design the interface themselves. Programmers suck at creating UIs so it should be made easy enough for designers. I recently took a look at the meat of a WPF application (ie. the XAML) and it looks surprisingly familiar to the declarative language style used in HTML. It's apparent to me that the current state of desktop UI development is largely fractionalized, otherwise there wouldn't be so much duplicated effort in the domain of graphical user interface design (IE. GTK, XUL, Qt, Winforms, WPF, etc). There are 45 GUI platforms for Python alone It's seems reasonable to me that there should be a general purpose, open source, standardized, platform independent, markup language for designing desktop GUIs. Much like what the W3C made HTML/CSS into. WPF, or more specifically XAML seems like a pretty likely step in the right direction. Now that the 'browser wars' are over should we look forward to a future of 'desktop gui wars?' Note: This topic is relatively subjective in the attempt to be 'future-thinking.' I think that desktop GUI development in its current state sucks ((really)hard) and, even though WPF is still in it's infancy, it presents a likely solution to the problem. Update: Thanks a lot for the info, keep it comin'. Here's are the options I've gathered from the comments and answers. GladeXML Editor: Glade Interface Designer OS Platforms: All GUI Platform: GTK+ Languages: C (libglade), C++, C# (Glade#), Python, Ada, Pike, Perl, PHP, Eiffel, Ruby XRC (XML Resource) Editors: wxGlade, XRCed, wxDesigner, DialogBlocks (non-free) OS Platforms: All GUI Platform: wxWidgets Languages: C++, Python (wxPython), Perl (wxPerl), .NET (wx.NET) XML based formats that are either not free, not cross-platform, or language specific XUL Editor: Any basic text editor OS Platforms: Any OS running a browser that supports XUL GUI Platform: Gecko Engine? Languages: C++, Python, Ruby as plugin languages not base languages Note: I'm not sure if XUL deserves mentioning in this list because it's less of a desktop GUI language and more of a make-webapps-run-on-the-desktop language. Plus, it requires a browser to run. IE, it's 'DHTML for the desktop.' CookSwing Editor: Eclipse via WindowBuilder, NetBeans 5.0 (non-free) via Swing GUI Builder aka Matisse OS Platforms: All GUI Platform: Java Languages: Java only XAML (Moonlight) Editor: MonoDevelop OS Platforms: Linux and other Unix/X11 based OSes only GUI Platforms: GTK+ Languages: .NET Note: XAML is not a pure Open Source format because Microsoft controls its terms of use including the right to change the terms at any time. Moonlight can not legally be made to run on Windows or Mac. In addition, the only platform that is exempt from legal action is Novell. See this for a full description of what I mean.

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• DEV C ++ Error: expected declaration before '}' token

  - by Francesca

  What does this mean? My program goes like this: (NOTE: The line that has the error was the line coming before case 2.) case 1: { cout<< "C * H * E * M * I * S * T * R * Y \n\n"; cout<< "1) What is the valence electron configuration of Selenium (Se)?\n\n"; cout<< "\na) 1s2 2s2 2p6 3s2\n\n"; cout<< "\nb) 1s2 2s2 2p2\n\n"; cout<< "\nc)4s2 4p4\n\n"; cout<< "\nd) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5\n\n"; cout<< "Enter your answer:\n"; cin>> answer; if (answer == 'c') { cout<<"Your answer is correct. Please press the enter key to proceed to the next question.\n\n"; } else cout<< "The correct answer is C. Please press the enter key to proceed to the next question.\n\n"; getch (); } getch (); cout<< "2) Which element yields the biggest atomic radius?\n\n"; cout<< "\na) Ca\n\n"; cout<< "\nb) Xe\n\n"; cout<< "\nc) B\n\n"; cout<< "\nd) Cs\n\n"; cout<< "Enter your answer:\n"; cin>> answer; if (answer == 'd') { cout<< "Your answer is correct. Please press the enter key to proceed to the next question.\n\n"; } else cout<< "The correct answer is D. Please press the enter key to proceed to the next question.\n\n"; getch (); } cout<< "3) Name the ionic compound K2 Cr2 O7\n\n"; cout<< "\na) potassium chloride\n\n"; cout<< "\nb) potassium carbonate\n\n"; cout<< "\nc) potassium chromite\n\n"; cout<< "\nd) potassium chromate\n\n"; cout<< "Enter your answer:\n"; cin>> answer; if (answer == 'd') { cout<< "Your answer is correct. Please press the enter key to proceed to the next question.\n\n"; } else cout<< "The correct answer is D. Please press the enter key to proceed to the next question.\n\n"; getch (); } } case 2: { cout<< "G * E * O * M * E * T * R * Y \n\n"; The error, as noted in the title is expected declaration before '}' token at the line noted in my opening paragraph.

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• Strange intermittent SQL connection error, fixes on reboot, comes back after 3-5 days (ASP.NET)

  - by Ryan

  For some reason every 3-5 days our web app loses the ability to open a connection to the db with the following error, the strange thing is that all we have to do is reboot the container (it is a VPS) and it is restored to normal functionality. Then a few days later or so it happens again. Has anyone ever had such a problem? I have noticed a lot of ANONYMOUS LOGONs in the security log in the middle of the night from our AD server which is strange, and also some from an IP in Amsterdam. I am not sure how to tell what exactly they mean or if it is related or not. Server Error in '/ntsb' Application. A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Data.SqlClient.SqlException: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) Source Error: Line 11: Line 12: Line 13: dbConnection.Open() Line 14: Line 15: Source File: C:\Inetpub\wwwroot\includes\connection.ascx Line: 13 Stack Trace: [SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)] System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +248 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +245 System.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Boolean encrypt, Boolean trustServerCert, Boolean integratedSecurity, SqlConnection owningObject) +475 System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject) +260 System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart) +2445449 System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance) +2445144 System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance) +354 System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection) +703 System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options) +54 System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject) +2414696 System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject) +92 System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) +1657 System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +84 System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +1645687 System.Data.SqlClient.SqlConnection.Open() +258 ASP.includes_connection_ascx.getConnection() in C:\Inetpub\wwwroot\includes\connection.ascx:13 ASP.default_aspx.Page_Load(Object sender, EventArgs e) in C:\Inetpub\wwwroot\Default.aspx:16 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +25 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +42 System.Web.UI.Control.OnLoad(EventArgs e) +132 System.Web.UI.Control.LoadRecursive() +66 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2428 Version Information: Microsoft .NET Framework Version:2.0.50727.3053; ASP.NET Version:2.0.50727.3053

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• C#: Inheritence, Overriding, and Hiding

  - by Rosarch

  I'm having difficulty with an architectural decision for my C# XNA game. The basic entity in the world, such as a tree, zombie, or the player, is represented as a GameObject. Each GameObject is composed of at least a GameObjectController, GameObjectModel, and GameObjectView. These three are enough for simple entities, like inanimate trees or rocks. However, as I try to keep the functionality as factored out as possible, the inheritance begins to feel unwieldy. Syntactically, I'm not even sure how best to accomplish my goals. Here is the GameObjectController: public class GameObjectController { protected GameObjectModel model; protected GameObjectView view; public GameObjectController(GameObjectManager gameObjectManager) { this.gameObjectManager = gameObjectManager; model = new GameObjectModel(this); view = new GameObjectView(this); } public GameObjectManager GameObjectManager { get { return gameObjectManager; } } public virtual GameObjectView View { get { return view; } } public virtual GameObjectModel Model { get { return model; } } public virtual void Update(long tick) { } } I want to specify that each subclass of GameObjectController will have accessible at least a GameObjectView and GameObjectModel. If subclasses are fine using those classes, but perhaps are overriding for a more sophisticated Update() method, I don't want them to have to duplicate the code to produce those dependencies. So, the GameObjectController constructor sets those objects up. However, some objects do want to override the model and view. This is where the trouble comes in. Some objects need to fight, so they are CombatantGameObjects: public class CombatantGameObject : GameObjectController { protected new readonly CombatantGameModel model; public new virtual CombatantGameModel Model { get { return model; } } protected readonly CombatEngine combatEngine; public CombatantGameObject(GameObjectManager gameObjectManager, CombatEngine combatEngine) : base(gameObjectManager) { model = new CombatantGameModel(this); this.combatEngine = combatEngine; } public override void Update(long tick) { if (model.Health <= 0) { gameObjectManager.RemoveFromWorld(this); } base.Update(tick); } } Still pretty simple. Is my use of new to hide instance variables correct? Note that I'm assigning CombatantObjectController.model here, even though GameObjectController.Model was already set. And, combatants don't need any special view functionality, so they leave GameObjectController.View alone. Then I get down to the PlayerController, at which a bug is found. public class PlayerController : CombatantGameObject { private readonly IInputReader inputReader; private new readonly PlayerModel model; public new PlayerModel Model { get { return model; } } private float lastInventoryIndexAt; private float lastThrowAt; public PlayerController(GameObjectManager gameObjectManager, IInputReader inputReader, CombatEngine combatEngine) : base(gameObjectManager, combatEngine) { this.inputReader = inputReader; model = new PlayerModel(this); Model.Health = Constants.PLAYER_HEALTH; } public override void Update(long tick) { if (Model.Health <= 0) { gameObjectManager.RemoveFromWorld(this); for (int i = 0; i < 10; i++) { Debug.WriteLine("YOU DEAD SON!!!"); } return; } UpdateFromInput(tick); // .... } } The first time that this line is executed, I get a null reference exception: model.Body.ApplyImpulse(movementImpulse, model.Position); model.Position looks at model.Body, which is null. This is a function that initializes GameObjects before they are deployed into the world: public void Initialize(GameObjectController controller, IDictionary<string, string> data, WorldState worldState) { controller.View.read(data); controller.View.createSpriteAnimations(data, _assets); controller.Model.read(data); SetUpPhysics(controller, worldState, controller.Model.BoundingCircleRadius, Single.Parse(data["x"]), Single.Parse(data["y"]), bool.Parse(data["isBullet"])); } Every object is passed as a GameObjectController. Does that mean that if the object is really a PlayerController, controller.Model will refer to the base's GameObjectModel and not the PlayerController's overriden PlayerObjectModel?

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• OSGI Declarative Services (DS): What is a good way of using service component instances

  - by Christoph

  I am just getting started with OSGI and Declarative Services (DS) using Equinox and Eclipse PDE. I have 2 Bundles, A and B. Bundle A exposes a component which is consumed by Bundle B. Both bundles also expose this service to the OSGI Service registry again. Everything works fine so far and Equinox is wireing the components together, which means the Bundle A and Bundle B are instanciated by Equinox (by calling the default constructor) and then the wireing happens using the bind / unbind methods. Now, as Equinox is creating the instances of those components / services I would like to know what is the best way of getting this instance? So assume there is third class class which is NOT instantiated by OSGI: Class WantsToUseComponentB{ public void doSomethingWithComponentB(){ // how do I get componentB??? Something like this maybe? ComponentB component = (ComponentB)someComponentRegistry.getComponent(ComponentB.class.getName()); } I see the following options right now: 1. Use a ServiceTracker in the Activator to get the Service of ComponentBundleA.class.getName() (I have tried that already and it works, but it seems to much overhead to me) and make it available via a static factory methods public class Activator{ private static ServiceTracker componentBServiceTracker; public void start(BundleContext context){ componentBServiceTracker = new ServiceTracker(context, ComponentB.class.getName(),null); } public static ComponentB getComponentB(){ return (ComponentB)componentBServiceTracker.getService(); }; } 2. Create some kind of Registry where each component registers as soon as the activate() method is called. public ComponentB{ public void bind(ComponentA componentA){ someRegistry.registerComponent(this); } or public ComponentB{ public void activate(ComponentContext context){ someRegistry.registerComponent(this); } } } 3. Use an existing registry inside osgi / equinox which has those instances? I mean OSGI is already creating instances and wires them together, so it has the objects already somewhere. But where? How can I get them? Conclusion Where does the class WantsToUseComponentB (which is NOT a Component and NOT instantiated by OSGI) get an instance of ComponentB from? Are there any patterns or best practises? As I said I managed to use a ServiceTracker in the Activator, but I thought that would be possible without it. What I am looking for is actually something like the BeanContainer of Springframework, where I can just say something like Container.getBean(ComponentA.BEAN_NAME). But I don't want to use Spring DS. I hope that was clear enough. Otherwise I can also post some source code to explain in more detail. Thanks Christoph UPDATED: Answer to Neil's comment: Thanks for clarifying this question against the original version, but I think you still need to state why the third class cannot be created via something like DS. Hmm don't know. Maybe there is a way but I would need to refactor my whole framework to be based on DS, so that there are no "new MyThirdClass(arg1, arg2)" statements anymore. Don't really know how to do that, but I read something about ComponentFactories in DS. So instead of doing a MyThirdClass object = new MyThirdClass(arg1, arg2); I might do a ComponentFactory myThirdClassFactory = myThirdClassServiceTracker.getService(); // returns a if (myThirdClassFactory != null){ MyThirdClass object = objectFactory.newInstance(); object.setArg1("arg1"); object.setArg2("arg2"); } else{ // here I can assume that some service of ComponentA or B went away so MyThirdClass Componenent cannot be created as there are missing dependencies? } At the time of writing I don't know exactly how to use the ComponentFactories but this is supposed to be some kind of pseudo code :) Thanks Christoph

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• Win32: IProgressDialog will not disappear until you mouse over it.

  - by Ian Boyd

  i'm using the Win32 progress dialog. The damnest thing is that when i call: progressDialog.StopProgressDialog(); it doesn't disappear. It stays on screen until the user moves her mouse over it - then it suddenly disappers. The call to StopProgressDialog returns right away (i.e. it's not a synchronous call). i can prove this by doing things after the call has returned: private void button1_Click(object sender, EventArgs e) { //Force red background to prove we've started this.BackColor = Color.Red; this.Refresh(); //Start a progress dialog IProgressDialog pd = (IProgressDialog)new ProgressDialog(); pd.StartProgressDialog(this.Handle, null, PROGDLG.Normal, IntPtr.Zero); //The long running operation System.Threading.Thread.Sleep(10000); //Stop the progress dialog pd.SetLine(1, "Stopping Progress Dialog", false, IntPtr.Zero); pd.StopProgressDialog(); pd = null; //Return form to normal color to prove we've stopped. this.BackColor = SystemColors.Control; this.Refresh(); } The form: starts gray turns red to show we've stared turns back to gray color to show we've called stop So the call to StopProgressDialog has returned, except the progress dialog is still sitting there, mocking me, showing the message: Stopping Progress Dialog Doesn't Appear for 10 seconds Additionally, the progress dialog does not appear on screen until the System.Threading.Thread.Sleep(10000); ten second sleep is over. Not limited to .NET WinForms The same code also fails in Delphi, which is also an object wrapper around Window's windows: procedure TForm1.Button1Click(Sender: TObject); var pd: IProgressDialog; begin Self.Color := clRed; Self.Repaint; pd := CoProgressDialog.Create; pd.StartProgressDialog(Self.Handle, nil, PROGDLG_NORMAL, nil); Sleep(10000); pd.SetLine(1, StringToOleStr('Stopping Progress Dialog'), False, nil); pd.StopProgressDialog; pd := nil; Self.Color := clBtnFace; Self.Repaint; end; PreserveSig An exception would be thrown if StopProgressDialog was failing. Most of the methods in IProgressDialog, when translated into C# (or into Delphi), use the compiler's automatic mechanism of converting failed COM HRESULTS into a native language exception. In other words the following two signatures will throw an exception if the COM call returned an error HRESULT (i.e. a value less than zero): //C# void StopProgressDialog(); //Delphi procedure StopProgressDialog; safecall; Whereas the following lets you see the HRESULT's and react yourself: //C# [PreserveSig] int StopProgressDialog(); //Delphi function StopProgressDialog: HRESULT; stdcall; HRESULT is a 32-bit value. If the high-bit is set (or the value is negative) it is an error. i am using the former syntax. So if StopProgressDialog is returning an error it will be automatically converted to a language exception. Note: Just for SaG i used the [PreserveSig] syntax, the returned HRESULT is zero; MsgWait? The symptom is similar to what Raymond Chen described once, which has to do with the incorrect use of PeekMessage followed by MsgWaitForMultipleObjects: "Sometimes my program gets stuck and reports one fewer record than it should. I have to jiggle the mouse to get the value to update. After a while longer, it falls two behind, then three..." But that would mean that the failure is in IProgressDialog, since it fails equally well on CLR .NET WinForms and native Win32 code.

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• The counter doesnt seem to increase when ever the edittext changes

  - by Mabulhuda

  Im using Edit-texts and i need when ever an edit-text is changed to increment a counter by one but the counter isnt working , I mean the app starts and everything but the counter doesnt seem to change please help here is the code public class Numersys extends Activity implements TextWatcher { EditText mark1 ,mark2, mark3,mark4,mark5,mark6 , hr1 ,hr2,hr3,hr4,hr5,hr6; EditText passed, currentavg; TextView tvnewavg ; Button calculate; double marks , curAVG , NewAVG ; String newCumAVG; int counter , hrs , curHr , NewHr; @Override protected void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); setContentView(R.layout.numersys); mark1=(EditText)findViewById(R.id.mark1n); mark2=(EditText)findViewById(R.id.mark2n); mark3=(EditText)findViewById(R.id.mark3n); mark4=(EditText)findViewById(R.id.mark4n); mark5=(EditText)findViewById(R.id.mark5n); mark6=(EditText)findViewById(R.id.mark6n); hr1=(EditText)findViewById(R.id.ethour1); hr2=(EditText)findViewById(R.id.ethour2); hr3=(EditText)findViewById(R.id.ethour3); hr4=(EditText)findViewById(R.id.ethour4); hr5=(EditText)findViewById(R.id.ethour5); hr6=(EditText)findViewById(R.id.ethour6); passed=(EditText)findViewById(R.id.etPassCn); currentavg=(EditText)findViewById(R.id.etCavgn); tvnewavg=(TextView)findViewById(R.id.tvcAVGn); mark1.addTextChangedListener(this); mark2.addTextChangedListener(this); mark3.addTextChangedListener(this); mark4.addTextChangedListener(this); mark5.addTextChangedListener(this); mark6.addTextChangedListener(this); calculate=(Button)findViewById(R.id.bAvgCalcn); @Override public void onClick(View arg0) { // TODO Auto-generated method stub switch(arg0.getId()) { case 0: break; case 1: hrs=Integer.valueOf(hr1.getText().toString()); marks=Double.valueOf(mark1.getText().toString())*Integer.valueOf(hr1.getText().toString()); curHr=Integer.valueOf(passed.getText().toString()); curAVG=Double.valueOf(currentavg.getText().toString())*curHr; NewHr= curHr+hrs; NewAVG= (marks+curAVG)/NewHr; break; case 2: hrs=Integer.valueOf(hr1.getText().toString())+Integer.valueOf(hr2.getText().toString()); marks=Double.valueOf(mark1.getText().toString())*Integer.valueOf(hr1.getText().toString()) +Double.valueOf(mark2.getText().toString())*Integer.valueOf(hr2.getText().toString()); curHr=Integer.valueOf(passed.getText().toString()); curAVG=Double.valueOf(currentavg.getText().toString())*curHr; NewHr= curHr+hrs; NewAVG= (marks+curAVG)/NewHr; break; case 3: hrs=Integer.valueOf(hr1.getText().toString())+Integer.valueOf(hr2.getText().toString()) +Integer.valueOf(hr3.getText().toString()); marks=Double.valueOf(mark1.getText().toString())*Integer.valueOf(hr1.getText().toString()) +Double.valueOf(mark2.getText().toString())*Integer.valueOf(hr2.getText().toString()) +Double.valueOf(mark3.getText().toString())*Integer.valueOf(hr3.getText().toString()); curHr=Integer.valueOf(passed.getText().toString()); curAVG=Double.valueOf(currentavg.getText().toString())*curHr; NewHr= curHr+hrs; NewAVG= (marks+curAVG)/NewHr; break; case R.id.bAvgCalcn: newCumAVG=String.valueOf(NewAVG); tvnewavg.setText(newCumAVG); } } }); } @Override public void afterTextChanged(Editable arg0) { // TODO Auto-generated method stub } @Override public void beforeTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) { // TODO Auto-generated method stub } @Override public void onTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) { // TODO Auto-generated method stub if(mark1.hasFocus()) { counter = counter+1; } if(mark2.hasFocus()) { counter = counter+1; } if(mark3.hasFocus()) { counter = counter+1; } if(mark4.hasFocus()) { counter = counter+1; } if(mark5.hasFocus()) { counter = counter+1; } if(mark6.hasFocus()) { counter = counter+1; } }

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• What is "elegant" code?

  - by Breton

  I see a lot of lip service and talk about the most "elegant" way to do this or that. I think if you spend enough time programming you begin to obtain a sort of intuitive feel for what it is we call "elegance". But I'm curious. Even if we can look at a bit of code, and say instinctively "That's elegant", or "That's messy", I wonder if any of us really understands what that means. Is there a precise definition for this "elegance" we keep referring to? If there is, what is it? Now, what I mean by a precise definition, is a series of statements which can be used to derive questions about a peice of code, or a program as a whole, and determine objectively, or as objectively as possible, whether that code is "elegant" or not. May I assert, that perhaps no such definition exists, and it's all just personal preference. In this case, I ask you a slightly different question: Is there a better word for "elegance", or a better set of attributes to use for judging code quality that is perhaps more objective than merely appealing to individual intuition and taste? Perhaps code quality is a matter of taste, and the answer to both of my questions is "no". But I can't help but feel that we could be doing better than just expressing wishy washy feelings about our code quality. For example, user interface design is something that to a broad range of people looks for all the world like a field of study that oughtta be 100% subjective matter of taste. But this is shockingly and brutally not the case, and there are in fact many objective measures that can be applied to a user interface to determine its quality. A series of tests could be written to give a definitive and repeatable score to user interface quality. (See GOMS, for instance). Now, okay. is Elegance simply "code quality" or is it something more? Is it something that can be measured? Or is it a matter of taste? Does our profession have room for taste? Maybe I'm asking the wrong questions altogether. Help me out here. Bonus Round If there is such a thing as elegance in code, and that concept is useful, do you think that justifies classifying the field of programming as an "Art" capital A, or merely a "craft". Or is it just an engineering field populated by a bunch of wishful thinking humans? Consider this question in the light of your thoughts about the elegance question. Please note that there is a distinction between code which is considered "art" in itself, and code that was written merely in the service of creating an artful program. When I ask this question, I ask if the code itself justifies calling programming an art. Bounty Note I liked the answers to this question so much, I think I'd like to make a photographic essay book from it. Released as a free PDF, and published on some kind of on demand printing service of course, such as "zazz" or "tiggle" or "printley" or something . I'd like some more answers, please!

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• Lock-Free, Wait-Free and Wait-freedom algorithms for non-blocking multi-thread synchronization.

  - by GJ

  In multi thread programming we can find different terms for data transfer synchronization between two or more threads/tasks. When exactly we can say that some algorithem is: 1)Lock-Free 2)Wait-Free 3)Wait-Freedom I understand what means Lock-free but when we can say that some synchronization algorithm is Wait-Free or Wait-Freedom? I have made some code (ring buffer) for multi-thread synchronization and it use Lock-Free methods but: 1) Algorithm predicts maximum execution time of this routine. 2) Therad which call this routine at beginning set unique reference, what mean that is inside of this routine. 3) Other threads which are calling the same routine check this reference and if is set than count the CPU tick count (measure time) of first involved thread. If that time is to long interrupt the current work of involved thread and overrides him job. 4) Thread which not finished job because was interrupted from task scheduler (is reposed) at the end check the reference if not belongs to him repeat the job again. So this algorithm is not really Lock-free but there is no memory lock in use, and other involved threads can wait (or not) certain time before overide the job of reposed thread. Added RingBuffer.InsertLeft function: function TgjRingBuffer.InsertLeft(const link: pointer): integer; var AtStartReference: cardinal; CPUTimeStamp : int64; CurrentLeft : pointer; CurrentReference: cardinal; NewLeft : PReferencedPtr; Reference : cardinal; label TryAgain; begin Reference := GetThreadId + 1; //Reference.bit0 := 1 with rbRingBuffer^ do begin TryAgain: //Set Left.Reference with respect to all other cores :) CPUTimeStamp := GetCPUTimeStamp + LoopTicks; AtStartReference := Left.Reference OR 1; //Reference.bit0 := 1 repeat CurrentReference := Left.Reference; until (CurrentReference AND 1 = 0)or (GetCPUTimeStamp - CPUTimeStamp > 0); //No threads present in ring buffer or current thread timeout if ((CurrentReference AND 1 <> 0) and (AtStartReference <> CurrentReference)) or not CAS32(CurrentReference, Reference, Left.Reference) then goto TryAgain; //Calculate RingBuffer NewLeft address CurrentLeft := Left.Link; NewLeft := pointer(cardinal(CurrentLeft) - SizeOf(TReferencedPtr)); if cardinal(NewLeft) < cardinal(@Buffer) then NewLeft := EndBuffer; //Calcolate distance result := integer(Right.Link) - Integer(NewLeft); //Check buffer full if result = 0 then //Clear Reference if task still own reference if CAS32(Reference, 0, Left.Reference) then Exit else goto TryAgain; //Set NewLeft.Reference NewLeft^.Reference := Reference; SFence; //Try to set link and try to exchange NewLeft and clear Reference if task own reference if (Reference <> Left.Reference) or not CAS64(NewLeft^.Link, Reference, link, Reference, NewLeft^) or not CAS64(CurrentLeft, Reference, NewLeft, 0, Left) then goto TryAgain; //Calcolate result if result < 0 then result := Length - integer(cardinal(not Result) div SizeOf(TReferencedPtr)) else result := cardinal(result) div SizeOf(TReferencedPtr); end; //with end; { TgjRingBuffer.InsertLeft } RingBuffer unit you can find here: RingBuffer, CAS functions: FockFreePrimitives, and test program: RingBufferFlowTest Thanks in advance, GJ

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• Using boost locks for RAII access to a semaphore

  - by dan

  Suppose I write a C++ semaphore class with an interface that models the boost Lockable concept (i.e. lock(); unlock(); try_lock(); etc.). Is it safe/recommended to use boost locks for RAII access to such an object? In other words, do boost locks (and/or other related parts of the boost thread library) assume that the Lockable concept will only be modeled by mutex-like objects which are locked and unlocked from the same thread? My guess is that it should be OK to use a semaphore as a model for Lockable. I've browsed through some of the boost source and it "seems" OK. The locks don't appear to store explicit references to this_thread or anything like that. Moreover, the Lockable concept doesn't have any function like whichThreadOwnsMe(). It also looks like I should even be able to pass a boost::unique_lock<MySemaphore> reference to boost::condition_variable_any::wait. However, the documentation is not explicitly clear about the requirements. To illustrate what I mean, consider a bare-bones binary semaphore class along these lines: class MySemaphore{ bool locked; boost::mutex mx; boost::condition_variable cv; public: void lock(){ boost::unique_lock<boost::mutex> lck(mx); while(locked) cv.wait(lck); locked=true; } void unlock(){ { boost::lock_guard<boost::mutex> lck(mx); if(!locked) error(); locked=false; } cv.notify_one(); } // bool try_lock(); void error(); etc. } Now suppose that somewhere, either on an object or globally, I have MySemaphore sem; I want to lock and unlock it using RAII. Also I want to be able to "pass" ownership of the lock from one thread to another. For example, in one thread I execute void doTask() { boost::unique_lock<MySemaphore> lock(sem); doSomeWorkWithSharedObject(); signalToSecondThread(); waitForSignalAck(); lock.release(); } While another thread is executing something like { waitForSignalFromFirstThread(); ackSignal(); boost::unique_lock<MySemaphore>(sem,boost::adopt_lock_t()); doMoreWorkWithSameSharedObject(); } The reason I am doing this is that I don't want anyone else to be able to get the lock on sem in between the time that the first thread executes doSomeWorkWithSharedObject() and the time the second executes doMoreWorkWithSameSharedObject(). Basically, I'm splitting one task into two parts. And the reason I'm splitting the task up is because (1) I want the first part of the task to get started as soon as possible, (2) I want to guarantee that the first part is complete before doTask() returns, and (3) I want the second, more time-consuming part of the task to be completed by another thread, possibly chosen from a pool of slave threads that are waiting around to finish tasks that have been started by master threads. NOTE: I recently posted this same question (sort of) here http://stackoverflow.com/questions/2754884/unlocking-a-mutex-from-a-different-thread-c but I confused mutexes with semaphores, and so the question about using boost locks didn't really get addressed.

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• nextSibling issues...

  - by SoLoGHoST

  Ok, this has been killing me all night, I mean I've been working on this code for atleast 8 hours now. What is the problem with this, argggg. I am trying to update all <span id="column_[some number]"> to increment it by one after the next id="row_" tr element, but for some god knows what reason, it gives me issues. It's updating the same <span> tag 2x, and this changes it from the desired value to 1 more than it should be... argggg. Here's my code someone please help me here... // Reorder all columns, if any, in the other rows after this 1. if (aRowId != 0 && lId.indexOf("tr_" + aRowId) == 0 && rowComplete != aRowId) { var tempTr = lTable.childNodes[i].childNodes[p]; while(tempTr.nodeType == 1 && tempTr.nextSibling != null) { var tempId = tempTr.getAttribute("id"); if (!tempId) continue; if (tempId.indexOf("row_") == 0) { // All done this row, set it to completed! rowComplete = aRowId; break; } if (tempTr.hasChildNodes) { var doneChilds = false; // grab the id where tdcolumn_{aRowId}.indexOf = 0. for (fcTd = 0; fcTd<tempTr.childNodes.length; fcTd++) { if (tempTr.childNodes[fcTd].nodeName == '#text') continue; var tempfcId = tempTr.childNodes[fcTd].getAttribute("id"); if (!tempfcId) continue; if (tempfcId.indexOf("tdcolumn_" + aRowId) != 0) continue; // looping through the children in the <td> element here. if (tempTr.childNodes[fcTd].hasChildNodes) { for (x = tempTr.childNodes[fcTd].childNodes.length-1; x>0; x--) { if (tempTr.childNodes[fcTd].childNodes[x].nodeName == '#text') continue; var tempSpanId = tempTr.childNodes[fcTd].childNodes[x].getAttribute("id"); if (!tempSpanId) continue; if (tempSpanId.indexOf("column_") != 0) continue; // alert(tempSpanId); alert(tempTr.childNodes[fcTd].childNodes[x].nodeName); var tSpanId = new Array(); tSpanId = tempSpanId.split("_"); if (currColumnId == 0) { currColumnId = parseInt(tSpanId[1]); var incCol = currColumnId; } incCol++; // alert("currColumnId = " + currColumnId + "\n\ntSpanId[1] = " + tSpanId[1] + "\n\nincCol = " + incCol); // Set the new Id's and Text, after which we can exit the for loop. tempTr.childNodes[fcTd].childNodes[x].setAttribute("id", "column_" + incCol); tempTr.childNodes[fcTd].childNodes[x].setAttribute("class", "dp_edit_column"); tempTr.childNodes[fcTd].childNodes[x].innerHTML = oColumnText + " " + incCol; // tempTr.childNodes[fcTd].setAttribute("id", "tdcolumn_" + aRowId + "_" + (parseInt(tSpanId[1])+1) + "_" + tSpanId[3]); doneChilds = true; break; } } else continue; if (doneChilds = true) continue; } } else continue; tempTr = tempTr.nextSibling; } } Please help me, thanks.

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• Pure JSP without mixing HTML, by writing html as Java-like code

  - by ADTC

  Please read before answering. This is a fantasy programming technique I'm dreaming up. I want to know if there's anything close in real life. The following JSP page: <% html { head { title {"Pure fantasy";} } body { h1 {"A heading with double quote (\") character";} p {"a paragraph";} String s = "a paragraph in string. the date is "; p { s; new Date().toString(); } table (Border.ZERO, new Padding(27)) { tr { for (int i = 0; i < 10; i++) { td {i;} } } } } } %> could generate the following HTML page: <html> <head> <title>Pure fantasy</title> </head> <body> <h1>A heading with double quote (") character</h1> <p>a paragraph</p> <p>a paragraph in string. the date is 11 December 2012</p> <table border="0" padding="27"> <tr> <td>0</td> <td>1</td> <td>2</td> <td>3</td> <td>4</td> <td>5</td> <td>6</td> <td>7</td> <td>8</td> <td>9</td> </tr> </table> </body> </html> The thing about this fantasy is it reuses the same old Java programming language technique that enable customized keywords used in a way similar to if-else-then, while, try-catch etc to represent html tags in a non-html way that can easily be checked for syntactic correctness, and most importantly can easily be mixed up with regular Java code without being lost in a sea of <%, %>, <%=, out.write(), etc. An added feature is that strings can directly be placed as commands to print out into generated HTML, something Java doesn't support (where pure strings have to be assigned to variables before use). Is there anything in real life that comes close? If not, is it possible to define customized keywords in Java or JSP? Or do I have to create an entirely new programming language for that? What problems do you see with this kind of setup? PS: I know you can use HTML libraries to construct HTML using Java code, but the problem with such libraries is, the source code itself doesn't have a readable HTML representation like the code above does - if you get what I mean.

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• android alarm not able to launch alarm activity

  - by user965830

  I am new to android programming and am trying to make this simple alarm app. I have my code written and it is compiled with no errors. The app runs in the emulator, that is the main activity asks the date and time, but when i click on the confirm button, it displays the message - "Unfortunately, Timer1 has stopped working." The code for my main activity is as follows: public void onClick(View v) { EditText date = (EditText) findViewById(R.id.editDate); EditText month = (EditText) findViewById(R.id.editMonth); EditText hour = (EditText) findViewById(R.id.editHour); EditText min = (EditText) findViewById(R.id.editMin); int dt = Integer.parseInt(date.getText().toString()); int mon = Integer.parseInt(month.getText().toString()); int hr = Integer.parseInt(hour.getText().toString()); int mnt = Integer.parseInt(min.getText().toString()); Intent myIntent = new Intent(MainActivity.this, AlarmActivity.class); pendingIntent = PendingIntent.getService(MainActivity.this, 0, myIntent, 0); AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE); Calendar calendar = Calendar.getInstance(); calendar.set(Calendar.DATE, dt); calendar.set(Calendar.MONTH, mon); calendar.set(Calendar.HOUR, hr); calendar.set(Calendar.MINUTE, mnt); alarmManager.set(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), pendingIntent); } I do not understand what all the errors in logcat mean, so i am posting them: 06-25 16:03:32.175: I/Process(566): Sending signal. PID: 566 SIG: 9 06-25 16:03:53.775: I/dalvikvm(612): threadid=3: reacting to signal 3 06-25 16:03:54.046: I/dalvikvm(612): Wrote stack traces to '/data/anr/traces.txt' 06-25 16:03:54.255: I/dalvikvm(612): threadid=3: reacting to signal 3 06-25 16:03:54.305: I/dalvikvm(612): Wrote stack traces to '/data/anr/traces.txt' 06-25 16:03:54.735: I/dalvikvm(612): threadid=3: reacting to signal 3 06-25 16:03:54.785: I/dalvikvm(612): Wrote stack traces to '/data/anr/traces.txt' 06-25 16:03:54.925: D/gralloc_goldfish(612): Emulator without GPU emulation detected. 06-25 16:05:09.605: D/AndroidRuntime(612): Shutting down VM 06-25 16:05:09.605: W/dalvikvm(612): threadid=1: thread exiting with uncaught exception (group=0x409c01f8) 06-25 16:05:09.685: E/AndroidRuntime(612): FATAL EXCEPTION: main 06-25 16:05:09.685: E/AndroidRuntime(612): java.lang.NumberFormatException: Invalid int: "android.widget.EditText@41030b40" 06-25 16:05:09.685: E/AndroidRuntime(612): at java.lang.Integer.invalidInt(Integer.java:138) 06-25 16:05:09.685: E/AndroidRuntime(612): at java.lang.Integer.parse(Integer.java:375) 06-25 16:05:09.685: E/AndroidRuntime(612): at java.lang.Integer.parseInt(Integer.java:366) 06-25 16:05:09.685: E/AndroidRuntime(612): at java.lang.Integer.parseInt(Integer.java:332) 06-25 16:05:09.685: E/AndroidRuntime(612): at com.kapymay.tversion1.MainActivity$1.onClick(MainActivity.java:34) 06-25 16:05:09.685: E/AndroidRuntime(612): at android.view.View.performClick(View.java:3511) 06-25 16:05:09.685: E/AndroidRuntime(612): at android.view.View$PerformClick.run(View.java:14105) 06-25 16:05:09.685: E/AndroidRuntime(612): at android.os.Handler.handleCallback(Handler.java:605) 06-25 16:05:09.685: E/AndroidRuntime(612): at android.os.Handler.dispatchMessage(Handler.java:92) 06-25 16:05:09.685: E/AndroidRuntime(612): at android.os.Looper.loop(Looper.java:137) 06-25 16:05:09.685: E/AndroidRuntime(612): at android.app.ActivityThread.main(ActivityThread.java:4424) 06-25 16:05:09.685: E/AndroidRuntime(612): at java.lang.reflect.Method.invokeNative(Native Method) 06-25 16:05:09.685: E/AndroidRuntime(612): at java.lang.reflect.Method.invoke(Method.java:511) 06-25 16:05:09.685: E/AndroidRuntime(612): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 06-25 16:05:09.685: E/AndroidRuntime(612): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 06-25 16:05:09.685: E/AndroidRuntime(612): at dalvik.system.NativeStart.main(Native Method) 06-25 16:05:10.445: I/dalvikvm(612): threadid=3: reacting to signal 3 06-25 16:05:10.575: I/dalvikvm(612): Wrote stack traces to '/data/anr/traces.txt'

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• Need some help deciphering a line of assembler code, from .NET JITted code

  - by Lasse V. Karlsen

  In a C# constructor, that ends up with a call to this(...), the actual call gets translated to this: 0000003d call dword ptr ds:[199B88E8h] What is the DS register contents here? I know it's the data-segment, but is this call through a VMT-table or similar? I doubt it though, since this(...) wouldn't be a call to a virtual method, just another constructor. I ask because the value at that location seems to be bad in some way, if I hit F11, trace into (Visual Studio 2008), on that call-instruction, the program crashes with an access violation. The code is deep inside a 3rd party control library, where, though I have the source code, I don't have the assemblies compiled with enough debug information that I can trace it through C# code, only through the disassembler, and then I have to match that back to the actual code. The C# code in question is this: public AxisRangeData(AxisRange range) : this(range, range.Axis) { } Reflector shows me this IL code: .maxstack 8 L_0000: ldarg.0 L_0001: ldarg.1 L_0002: ldarg.1 L_0003: callvirt instance class DevExpress.XtraCharts.AxisBase DevExpress.XtraCharts.AxisRange::get_Axis() L_0008: call instance void DevExpress.XtraCharts.Native.AxisRangeData::.ctor(class DevExpress.XtraCharts.ChartElement, class DevExpress.XtraCharts.AxisBase) L_000d: ret It's that last call there, to the other constructor of the same class, that fails. The debugger never surfaces inside the other method, it just crashes. The disassembly for the method after JITting is this: 00000000 push ebp 00000001 mov ebp,esp 00000003 sub esp,14h 00000006 mov dword ptr [ebp-4],ecx 00000009 mov dword ptr [ebp-8],edx 0000000c cmp dword ptr ds:[18890E24h],0 00000013 je 0000001A 00000015 call 61843511 0000001a mov eax,dword ptr [ebp-4] 0000001d mov dword ptr [ebp-0Ch],eax 00000020 mov eax,dword ptr [ebp-8] 00000023 mov dword ptr [ebp-10h],eax 00000026 mov ecx,dword ptr [ebp-8] 00000029 cmp dword ptr [ecx],ecx 0000002b call dword ptr ds:[1889D0DCh] // range.Axis 00000031 mov dword ptr [ebp-14h],eax 00000034 push dword ptr [ebp-14h] 00000037 mov edx,dword ptr [ebp-10h] 0000003a mov ecx,dword ptr [ebp-0Ch] 0000003d call dword ptr ds:[199B88E8h] // this(range, range.Axis)? 00000043 nop 00000044 mov esp,ebp 00000046 pop ebp 00000047 ret Basically what I'm asking is this: What the purpose of the ds:[ADDR] indirection here? VMT-table is only for virtual isn't it? and this is constructor Could the constructor have yet to be JITted, which could mean that the call would actually call through a JIT shim? I'm afraid I'm in deep water here, so anything might and could help. Edit: Well, the problem just got worse, or better, or whatever. We are developing the .NET feature in a C# project in a Visual Studio 2008 solution, and debugging and developing through Visual Studio. However, in the end, this code will be loaded into a .NET runtime hosted by a Win32 Delphi application. In order to facilitate easy experimentation of such features, we can also configure the Visual Studio project/solution/debugger to copy the produced dll's to the Delphi app's directory, and then execute the Delphi app, through the Visual Studio debugger. Turns out, the problem goes away if I run the program outside of the debugger, but during debugging, it crops up, every time. Not sure that helps, but since the code isn't slated for production release for another 6 months or so, then it takes some of the pressure off of it for the test release that we have soon. I'll dive into the memory parts later, but probably not until over the weekend, and post a followup.

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• Round-twice error in .NET's Double.ToString method

  - by Jeppe Stig Nielsen

  Mathematically, consider for this question the rational number 8725724278030350 / 2**48 where ** in the denominator denotes exponentiation, i.e. the denominator is 2 to the 48th power. (The fraction is not in lowest terms, reducible by 2.) This number is exactly representable as a System.Double. Its decimal expansion is 31.0000000000000'49'73799150320701301097869873046875 (exact) where the apostrophes do not represent missing digits but merely mark the boudaries where rounding to 15 resp. 17 digits is to be performed. Note the following: If this number is rounded to 15 digits, the result will be 31 (followed by thirteen 0s) because the next digits (49...) begin with a 4 (meaning round down). But if the number is first rounded to 17 digits and then rounded to 15 digits, the result could be 31.0000000000001. This is because the first rounding rounds up by increasing the 49... digits to 50 (terminates) (next digits were 73...), and the second rounding might then round up again (when the midpoint-rounding rule says "round away from zero"). (There are many more numbers with the above characteristics, of course.) Now, it turns out that .NET's standard string representation of this number is "31.0000000000001". The question: Isn't this a bug? By standard string representation we mean the String produced by the parameterles Double.ToString() instance method which is of course identical to what is produced by ToString("G"). An interesting thing to note is that if you cast the above number to System.Decimal then you get a decimal that is 31 exactly! See this Stack Overflow question for a discussion of the surprising fact that casting a Double to Decimal involves first rounding to 15 digits. This means that casting to Decimal makes a correct round to 15 digits, whereas calling ToSting() makes an incorrect one. To sum up, we have a floating-point number that, when output to the user, is 31.0000000000001, but when converted to Decimal (where 29 digits are available), becomes 31 exactly. This is unfortunate. Here's some C# code for you to verify the problem: static void Main() { const double evil = 31.0000000000000497; string exactString = DoubleConverter.ToExactString(evil); // Jon Skeet, http://csharpindepth.com/Articles/General/FloatingPoint.aspx Console.WriteLine("Exact value (Jon Skeet): {0}", exactString); // writes 31.00000000000004973799150320701301097869873046875 Console.WriteLine("General format (G): {0}", evil); // writes 31.0000000000001 Console.WriteLine("Round-trip format (R): {0:R}", evil); // writes 31.00000000000005 Console.WriteLine(); Console.WriteLine("Binary repr.: {0}", String.Join(", ", BitConverter.GetBytes(evil).Select(b => "0x" + b.ToString("X2")))); Console.WriteLine(); decimal converted = (decimal)evil; Console.WriteLine("Decimal version: {0}", converted); // writes 31 decimal preciseDecimal = decimal.Parse(exactString, CultureInfo.InvariantCulture); Console.WriteLine("Better decimal: {0}", preciseDecimal); // writes 31.000000000000049737991503207 } The above code uses Skeet's ToExactString method. If you don't want to use his stuff (can be found through the URL), just delete the code lines above dependent on exactString. You can still see how the Double in question (evil) is rounded and cast.

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• How do I get confidence intervals without inverting a singular Hessian matrix?

  - by AmalieNot

  Hello. I recently posted this to reddit and it was suggested I come here, so here I am. I'm a student working on an epidemiology model in R, using maximum likelihood methods. I created my negative log likelihood function. It's sort of gross looking, but here it is: NLLdiff = function(v1, CV1, v2, CV2, st1 = (czI01 - czV01), st2 = (czI02 - czV02), st01 = czI01, st02 = czI02, tt1 = czT01, tt2 = czT02) { prob1 = (1 + v1 * CV1 * tt1)^(-1/CV1) prob2 = ( 1 + v2 * CV2 * tt2)^(-1/CV2) -(sum(dbinom(st1, st01, prob1, log = T)) + sum(dbinom(st2, st02, prob2, log = T))) } The reason the first line looks so awful is because most of the data it takes is inputted there. czI01, for example, is already declared. I did this simply so that my later calls to the function don't all have to have awful vectors in them. I then optimized for CV1, CV2, v1 and v2 using mle2 (library bbmle). That's also a bit gross looking, and looks like: ml.cz.diff = mle2 (NLLdiff, start=list(v1 = vguess, CV1 = cguess, v2 = vguess, CV2 = cguess), method="L-BFGS-B", lower = 0.0001) Now, everything works fine up until here. ml.cz.diff gives me values that I can turn into a plot that reasonably fits my data. I also have several different models, and can get AICc values to compare them. However, when I try to get confidence intervals around v1, CV1, v2 and CV2 I have problems. Basically, I get a negative bound on CV1, which is impossible as it actually represents a square number in the biological model as well as some warnings. The warnings are this: http://i.imgur.com/B3H2l.png . Is there a better way to get confidence intervals? Or, really, a way to get confidence intervals that make sense here? What I see happening is that, by coincidence, my hessian matrix is singular for some values in the optimization space. But, since I'm optimizing over 4 variables and don't have overly extensive programming knowledge, I can't come up with a good method of optimization that doesn't rely on the hessian. I have googled the problem - it suggested that my model's bad, but I'm reconstructing some work done before which suggests that my model's really not awful (the plots I make using the ml.cz.diff look like the plots of the original work). I have also read the relevant parts of the manual as well as Bolker's book Ecological Models in R. I have also tried different optimization methods, which resulted in a longer run time but the same errors. The "SANN" method didn't finish running within an hour, so I didn't wait around to see the result. tl;dr : my confidence intervals are bad, is there a relatively straightforward way to fix them in R. My vectors are: czT01 = c(5, 5, 5, 5, 5, 5, 5, 25, 25, 25, 25, 25, 25, 25, 50, 50, 50, 50, 50, 50, 50) czT02 = c(5, 5, 5, 5, 5, 10, 10, 10, 10, 10, 25, 25, 25, 25, 25, 50, 50, 50, 50, 50, 75, 75, 75, 75, 75) czI01 = c(25, 24, 22, 22, 26, 23, 25, 25, 25, 23, 25, 18, 21, 24, 22, 23, 25, 23, 25, 25, 25) czI02 = c(13, 16, 5, 18, 16, 13, 17, 22, 13, 15, 15, 22, 12, 12, 13, 13, 11, 19, 21, 13, 21, 18, 16, 15, 11) czV01 = c(1, 4, 5, 5, 2, 3, 4, 11, 8, 1, 11, 12, 10, 16, 5, 15, 18, 12, 23, 13, 22) czV02 = c(0, 3, 1, 5, 1, 6, 3, 4, 7, 12, 2, 8, 8, 5, 3, 6, 4, 6, 11, 5, 11, 1, 13, 9, 7) and I get my guesses by: v = -log((c(czI01, czI02) - c(czV01, czV02))/c(czI01, czI02))/c(czT01, czT02) vguess = mean(v) cguess = var(v)/vguess^2 It's also possible that I'm doing something else completely wrong, but my results seem reasonable so I haven't caught it.

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• How do I make these fields autopopulate from the database?

  - by dmanexe

  I have an array, which holds values like this: $items_pool = Array ( [0] => Array ( [id] => 1 [quantity] => 1 ) [1] => Array ( [id] => 2 [quantity] => 1 ) [2] => Array ( [id] => 72 [quantity] => 6 ) [3] => Array ( [id] => 4 [quantity] => 1 ) [4] => Array ( [id] => 5 [quantity] => 1 ) [5] => Array ( [id] => 7 [quantity] => 1 ) [6] => Array ( [id] => 8 [quantity] => 1 ) [7] => Array ( [id] => 9 [quantity] => 1 ) [8] => Array ( [id] => 19 [quantity] => 1 ) [9] => Array ( [id] => 20 [quantity] => 1 ) [10] => Array ( [id] => 22 [quantity] => 1 ) [11] => Array ( [id] => 29 [quantity] => 0 ) ) Next, I have a form that I am trying to populate. It loops through the item database, prints out all the possible items, and checks the ones that are already present in $items_pool. <?php foreach ($items['items_poolpackage']->result() as $item): ?> <input type="checkbox" name="measure[<?=$item->id?>][checkmark]" value="<?=$item->id?>"> <?php endforeach; ?> I know what logically I'm trying to accomplish here, but I can't figure out the programming. What I'm looking for, written loosely is something like this (not real code): <input type="checkbox" name="measure[<?=$item->id?>][checkmark]" value="<?=$item->id?>" <?php if ($items_pool['$item->id']) { echo "SELECTED"; } else { }?>> Specifically this conditional loop through the array, through all the key values (the ID) and if there's a match, the checkbox is selected. <?php if ($items_pool['$item->id']) { echo "SELECTED"; } else { }?> I understand from a loop structured like this that it may mean a lot of 'extra' processing. TL;DR - I need to echo within a loop if the item going through the loop exists within another array.

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• Calling system commands from Perl

  - by Dan J

  In an older version of our code, we called out from Perl to do an LDAP search as follows: # Pass the base DN in via the ldapsearch-specific environment variable # (rather than as the "-b" paramater) to avoid problems of shell # interpretation of special characters in the DN. $ENV{LDAP_BASEDN} = $ldn; $lcmd = "ldapsearch -x -T -1 -h $gLdapServer" . <snip> " > $lworkfile 2>&1"; system($lcmd); if (($? != 0) || (! -e "$lworkfile")) { # Handle the error } The code above would result in a successful LDAP search, and the output of that search would be in the file $lworkfile. Unfortunately, we recently reconfigured openldap on this server so that a "BASE DC=" is specified in /etc/openldap/ldap.conf and /etc/ldap.conf. That change seems to mean ldapsearch ignores the LDAP_BASEDN environment variable, and so my ldapsearch fails. I've tried a couple of different fixes but without success so far: (1) I tried going back to using the "-b" argument to ldapsearch, but escaping the shell metacharacters. I started writing the escaping code: my $ldn_escaped = $ldn; $ldn_escaped =~ s/\/\\/g; $ldn_escaped =~ s/`/\`/g; $ldn_escaped =~ s/$/\$/g; $ldn_escaped =~ s/"/\"/g; That threw up some Perl errors because I haven't escaped those regexes properly in Perl (the line number matches the regex with the backticks in). Backticks found where operator expected at /tmp/mycommand line 404, at end of line At the same time I started to doubt this approach and looked for a better one. (2) I then saw some Stackoverflow questions (here and here) that suggested a better solution. Here's the code: print("Processing..."); # Pass the arguments to ldapsearch by invoking open() with an array. # This ensures the shell does NOT interpret shell metacharacters. my(@cmd_args) = ("-x", "-T", "-1", "-h", "$gLdapPool", "-b", "$ldn", <snip> ); $lcmd = "ldapsearch"; open my $lldap_output, "-|", $lcmd, @cmd_args; while (my $lline = <$lldap_output>) { # I can parse the contents of my file fine } $lldap_output->close; The two problems I am having with approach (2) are: a) Calling open or system with an array of arguments does not let me pass > $lworkfile 2>&1 to the command, so I can't stop the ldapsearch output being sent to screen, which makes my output look ugly: Processing...ldap_bind: Success (0) additional info: Success b) I can't figure out how to choose which location (i.e. path and file name) to the file handle passed to open, i.e. I don't know where $lldap_output is. Can I move/rename it, or inspect it to find out where it is (or is it not actually saved to disk)? Based on the problems with (2), this makes me think I should return back to approach (1), but I'm not quite sure how to

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• When should I use indexed arrays of OpenGL vertices?

  - by Tartley

  I'm trying to get a clear idea of when I should be using indexed arrays of OpenGL vertices, drawn with gl[Multi]DrawElements and the like, versus when I should simply use contiguous arrays of vertices, drawn with gl[Multi]DrawArrays. (Update: The consensus in the replies I got is that one should always be using indexed vertices.) I have gone back and forth on this issue several times, so I'm going to outline my current understanding, in the hopes someone can either tell me I'm now finally more or less correct, or else point out where my remaining misunderstandings are. Specifically, I have three conclusions, in bold. Please correct them if they are wrong. One simple case is if my geometry consists of meshes to form curved surfaces. In this case, the vertices in the middle of the mesh will have identical attributes (position, normal, color, texture coord, etc) for every triangle which uses the vertex. This leads me to conclude that: 1. For geometry with few seams, indexed arrays are a big win. Follow rule 1 always, except: For geometry that is very 'blocky', in which every edge represents a seam, the benefit of indexed arrays is less obvious. To take a simple cube as an example, although each vertex is used in three different faces, we can't share vertices between them, because for a single vertex, the surface normals (and possible other things, like color and texture co-ord) will differ on each face. Hence we need to explicitly introduce redundant vertex positions into our array, so that the same position can be used several times with different normals, etc. This means that indexed arrays are of less use. e.g. When rendering a single face of a cube: 0 1 o---o |\ | | \ | | \| o---o 3 2 (this can be considered in isolation, because the seams between this face and all adjacent faces mean than none of these vertices can be shared between faces) if rendering using GL_TRIANGLE_FAN (or _STRIP), then each face of the cube can be rendered thus: verts = [v0, v1, v2, v3] colors = [c0, c0, c0, c0] normal = [n0, n0, n0, n0] Adding indices does not allow us to simplify this. From this I conclude that: 2. When rendering geometry which is all seams or mostly seams, when using GL_TRIANGLE_STRIP or _FAN, then I should never use indexed arrays, and should instead always use gl[Multi]DrawArrays. (Update: Replies indicate that this conclusion is wrong. Even though indices don't allow us to reduce the size of the arrays here, they should still be used because of other performance benefits, as discussed in the comments) The only exception to rule 2 is: When using GL_TRIANGLES (instead of strips or fans), then half of the vertices can still be re-used twice, with identical normals and colors, etc, because each cube face is rendered as two separate triangles. Again, for the same single cube face: 0 1 o---o |\ | | \ | | \| o---o 3 2 Without indices, using GL_TRIANGLES, the arrays would be something like: verts = [v0, v1, v2, v2, v3, v0] normals = [n0, n0, n0, n0, n0, n0] colors = [c0, c0, c0, c0, c0, c0] Since a vertex and a normal are often 3 floats each, and a color is often 3 bytes, that gives, for each cube face, about: verts = 6 * 3 floats = 18 floats normals = 6 * 3 floats = 18 floats colors = 6 * 3 bytes = 18 bytes = 36 floats and 18 bytes per cube face. (I understand the number of bytes might change if different types are used, the exact figures are just for illustration.) With indices, we can simplify this a little, giving: verts = [v0, v1, v2, v3] (4 * 3 = 12 floats) normals = [n0, n0, n0, n0] (4 * 3 = 12 floats) colors = [c0, c0, c0, c0] (4 * 3 = 12 bytes) indices = [0, 1, 2, 2, 3, 0] (6 shorts) = 24 floats + 12 bytes, and maybe 6 shorts, per cube face. See how in the latter case, vertices 0 and 2 are used twice, but only represented once in each of the verts, normals and colors arrays. This sounds like a small win for using indices, even in the extreme case of every single geometry edge being a seam. This leads me to conclude that: 3. When using GL_TRIANGLES, one should always use indexed arrays, even for geometry which is all seams. Please correct my conclusions in bold if they are wrong.

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• Link Error : xxx is already defined in *****.LIB :: What exactly is wrong?

  - by claws

  Problem: I'm trying to use a library named DCMTK which used some other external libraries ( zlib, libtiff, libpng, libxml2, libiconv ). I've downloaded these external libraries (*.LIB & *.h files ) from the same website. Now, when I compile the DCMTK library I'm getting link errors (793 errors) like this: Error 2 error LNK2005: __encode_pointer already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 3 error LNK2005: __decode_pointer already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 4 error LNK2005: __CrtSetCheckCount already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 5 error LNK2005: __invoke_watson already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 6 error LNK2005: __errno already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 7 error LNK2005: __configthreadlocale already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 8 error LNK2005: _exit already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Documentation: This seems to be a popular error for this library so, they do have a FAQ entry addressing this issue which ( http://forum.dcmtk.org/viewtopic.php?t=35 ) says: The problem is that the linker tries to combine different, incompatible versions of the Visual C++ runtime library into a single binary. This happens when not all parts of your project and the libraries you link against are generated with the same code generation options in Visual C++. Do not use the /NODEFAULTLIB workaround, because strange software crashes may follow. Fix the problem! DCMTK is by default compiled with the "Multithreaded" or "Multithreaded Debug" code generation option (the latter for Debug mode). Either change the project settings of all of your code to use these code generation options, or change the code generation for all DCMTK modules and re-compile. MFC users beware: DCMTK should be compiled with "Multithreaded DLL" or "Multithreaded DLL Debug" settings if you want to link the libraries into an MFC application. Solution to same problem for others: http://stackoverflow.com/questions/2259697/vscopengl-huge-amount-of-linker-issues-with-release-build-only says: It seems that your release build is trying to link to something that was built debug. You probably have a broken dependency in your build, (or you missed rebuilding something to release by hand if your project is normally built in pieces). More technically, you seem to be linking projects built with different C Run Time library settings, one with "Multi-Threaded", another one with "Multi-Threaded Debug". Adjust the settings for all the projects to use the very same flavour of the library and the issue should go away Questions: Till now I used to think that Name mangling is the only problem that may cause linking failures if its not been standardized. Just now I knew there are other things also which can cause same effect. Whats up with the "Debug Mode" (Multi-Threaded Debug) and "Release Mode" (Multi-Threaded)? What exactly is happening under the hood? Why exactly this thing is causing linking error? I wonder if there is something called "Single-Threaded Debug" and "Single-Threaded" which again causes the same thing. Documentation talks something about "Code Generation Options". What Code Generation Options? WTH are they? Documentation specifically warns us not to use /NODEFAULTLIB workaround. (example /NODEFAULTLIB :msvcrt ). Why? How would I cause troubles? what exactly is it? Please explain the last point in the documentation for MFC users. Because I'm going to use MFC later in this project. Explain Why should we do it? What troubles would it cause if I don't. Anything more you'd like to mention? I mean regarding similar errors. I'm very interested in Linker & its problems. So, if there are any similar things you can mentions them or some keywords atleast.

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• ublas::bounded_vector<> being resized?

  - by n2liquid

  Now, seriously... I'll refrain from using bad words here because we're talking about the Boost fellows. It MUST be my mistake to see things this way, but I can't understand why, so I'll ask it here; maybe someone can enlighten me in this matter. Here it goes: uBLAS has this nice class template called bounded_vector<> that's used to create fixed-size vectors (or so I thought). From the Effective uBLAS wiki (http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl?Effective_UBLAS): The default uBLAS vector and matrix types are of variable size. Many linear algebra problems involve vectors with fixed size. 2 and 3 elements are common in geometry! Fixed size storage (akin to C arrays) can be implemented efficiently as it does not involve the overheads (heap management) associated with dynamic storage. uBLAS implements fixed sizes by changing the underling storage of a vector/matrix to a "bounded_array" from the default "unbounded_array". Alright, this bounded_vector<> thing is used to free you from specifying the underlying storage of the vector to a bounded_array<> of the specified size. Here I ask you: doesn't it look like this bounded vector thing has fixed size to you? Well, it doesn't have. At first I felt betrayed by the wiki, but then I reconsidered the meaning of "bounded" and I think I can let it pass. But in case you, like me (I'm still uncertain), is still wondering if this makes sense, what I found out is that the bounded_vector<> actually can be resized, it may only not be greater than the size specified as template parameter. So, first off, do you think they've had a good reason not to make a real fixed<< size vector or matrix type? Do you think it's okay to "sell" this bounded -- as opposed to fixed-size -- vector to the users of my library as a "fixed-size" vector replacement, even named "Vector3" or "Vector2", like the Effective uBLAS wiki did? Do you think I should somehow implement a vector with fixed size for this purpose? If so, how? (Sorry, but I'm really new to uBLAS; just tried it today) I am developing a 3D game. Should uBLAS be used for the calculations involved in this ("hey, geometry!", per Effective uBLAS wiki)? What replacement would you suggest, if not? -- edit And just in case, yes, I've read this warning: It should be noted that this only changes the storage uBLAS uses for the vector3. uBLAS will still use all the same algorithm (which assume a variable size) to manipulate the vector3. In practice this seems to have no negative impact on speed. The above runs just as quickly as a hand crafted vector3 which does not use uBLAS. The only negative impact is that the vector3 always store a "size" member which in this case is redundant [or isn't it? I mean......]. I see it uses the same algorithm, assuming a variable size, but if an operation were to actually change its size, shouldn't it be stopped (assertion)? ublas::bounded_vector<float,3> v3; ublas::bounded_vector<float,2> v2; v3 = v2; std::cout << v3.size() << '\n'; // prints 2 Oh, come on, isn't this just plain betrayal?

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• Win32 -- Object cleanup and global variables

  - by KaiserJohaan

  Hello, I've got a question about global variables and object cleanup in c++. For example, look at the code here; case WM_PAINT: paintText(&hWnd); break; void paintText(HWND* hWnd) { PAINTSTRUCT ps; HBRUSH hbruzh = CreateSolidBrush(RGB(0,0,0)); HDC hdz = BeginPaint(*hWnd,&ps); char s1[] = "Name"; char s2[] = "IP"; SelectBrush(hdz,hbruzh); SelectFont(hdz,hFont); SetBkMode(hdz,TRANSPARENT); TextOut(hdz,3,23,s1,sizeof(s1)); TextOut(hdz,10,53,s2,sizeof(s2)); EndPaint(*hWnd,&ps); DeleteObject(hdz); DeleteObject(hbruzh); // bad? DeleteObject(ps); // bad? } 1)First of all; which objects are good to delete and which ones are NOT good to delete and why? Not 100% sure of this. 2)Since WM_PAINT is called everytime the window is redrawn, would it be better to simply store ps, hdz and hbruzh as global variables instead of re-initializing them everytime? The downside I guess would be tons of global variables in the end _ but performance-wise would it not be less CPU-consuming? I know it won't matter prolly but I'm just aiming for minimalistic as possible for educational purposes. 3) What about libraries that are loaded in? For example: // // Main // int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) { // initialize vars HWND hWnd; WNDCLASSEX wc; HINSTANCE hlib = LoadLibrary("Riched20.dll"); ThishInstance = hInstance; ZeroMemory(&wc,sizeof(wc)); // set WNDCLASSEX props wc.cbSize = sizeof(WNDCLASSEX); wc.lpfnWndProc = WindowProc; wc.hInstance = ThishInstance; wc.hIcon = LoadIcon(hInstance,MAKEINTRESOURCE(IDI_MYICON)); wc.lpszMenuName = MAKEINTRESOURCE(IDR_MENU1); wc.hCursor = LoadCursor(NULL, IDC_ARROW); wc.hbrBackground = (HBRUSH)COLOR_WINDOW; wc.lpszClassName = TEXT("PimpClient"); RegisterClassEx(&wc); // create main window and display it hWnd = CreateWindowEx(NULL, wc.lpszClassName, TEXT("PimpClient"), 0, 300, 200, 450, 395, NULL, NULL, hInstance, NULL); createWindows(&hWnd); ShowWindow(hWnd,nCmdShow); // loop message queue MSG msg; while (GetMessage(&msg, NULL,0,0)) { TranslateMessage(&msg); DispatchMessage(&msg); } // cleanup? FreeLibrary(hlib); return msg.wParam; } 3cont) is there a reason to FreeLibrary at the end? I mean when the process terminates all resources are freed anyway? And since the library is used to paint text throughout the program, why would I want to free before that? Cheers

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• Get mutually and non mutually existening Fields in same table in Two columns

  - by ranabra

  This is a question similar to another question I posted here but is a little different. I am trying to get a list of all instances of mutual and non-mutual existing Users. What I mean is that the returned result from the query will return a list of users along with their co-worker. It is similar to the question here, but the difference is that non mutual users will be returned too and with out the "duplicity" mutually existing users return in the list (See image below in-order simplify it all). I took the original answer from Thomas (Thanx again Thomas) Select D1.u_username, U1.Permission, U1.Grade, D1.f_username, U2.Permission, U2.Gradefrom tblDynamicUserList As D1    Join tblDynamicUserList As D2        On D2.u_username = D1.f_username            And D2.f_username = D1.u_username    Join tblUsers As U1        On U1.u_username = D1.u_username    Join tblUsers As U2        On U2.u_username = D2.u_username and after some several trials I commented out 2 lines (Below). The returned result are exactly as described in the beginning of this question, but with the "duplicity" returned by mutually existing users in the table. How can I eliminate this duplicity? Select D1.u_username, U1.Permission, U1.Grade, D1.f_username, U2.Permission, U2.Gradefrom tblDynamicUserList As D1    Join tblDynamicUserList As D2        On D2.u_username = D1.f_username            /* And D2.f_username = D1.u_username */    Join tblUsers As U1        On U1.u_username = D1.u_username    Join tblUsers As U2        On U2.u_username = D2.u_username /* WHERE D1.U_userName < D1.f_username */ *Screenshot that hopefully helps explain it all. Database is SQL 2005. Many thanx in advance

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• How to represent a Board Panel in Java for a game ? [+code]

  - by FILIaS

  I wanna fix a 2D board for a game. I've already fixed other panels for the Gui and everything goes well. But the panel for the board cant be printed on the window. I'm a bit confused about it as i think i've followed the same ideas as for the others panels i need. Here's what i've done: EDIT:*EDIT* what i'm trying to do is fix a board panel for the game according to the dimensions of the it,hold every square in an array in order to use it after wherever it;s needed. I draw each little square of it with the method draw and put it back to the panel. So, each square on the board is a panel. This is the idea. But as u can see. There are troubles/errors on it. EDIT: code updated. just found a part of the problem. i thought first that i had set background to squared, but i didnt. with this one it appears on the panel a wide black "column". Unfortunately,still none squares. :( One More EDIT: Also,i realized that draw method is never called. when i put the draw method in the following method i can see the squares but they remain small. I redefine them with setSize but still no change. /** *Method used to construct the square in the area of the *gui's grid. In this stage a GUISquare array is being constructed, * used in the whole game as *a mean of changing a square graphical state. *@param squares is the squares array from whom the gui grid will be *constructed. *@see getSquare about the correspondance beetween a squareModel and * a GUISquare. */ private void initBoardPanel(SquareModel[][] squares){ BoardPanel.setLayout(new GridLayout(height ,width )); //set layout SquareRenderer[][] Squares; JPanel[][] grid; Squares=new GUISquare[height][width()]; grid=new JPanel[height()][width()]; for (int i=0; i<height(); i++){ for (int j=0; j<width() ; j++){ grid[i][j] = new JPanel( ); SquareRenderer kout=new SquareRenderer(i,j); koutaki.setSquare(myGame.getSquares()[i][j]); if (myGame.getSquares()[i][j] instanceof SimpleSquareModel){ kout.draw(i,j,"");} else { kout.draw(i,j); } kout.setVisible(true); kout.setBackground(Color.BLACK); kout.setSize(50,50); Squares[i][j]= kout; grid[i][j].setSize(50,50); grid[i][j].setVisible(true); grid[i][j].setBackground(Color.BLACK); BoardPanel.add(kout); BoardPanel.setVisible(true); BoardPanel.setBackground(Color.WHITE); } } this.add(BoardPanel,BorderLayout.WEST); // this.pack(); //sets appropriate size for frame this.setVisible(true); //makes frame visible } IMPLEMENTED BY SQUARERENDERER: /** * Transformer for Snake/Ladder * <br>This method is used to display a square on the screen. */ public void draw(int i,int j) { JPanel panel = new JPanel(); panel.setLayout(new BorderLayout()); JLabel label1 = new JLabel("Move To"+myGame.getSquares()[i][j].getGoTo()); JLabel label2 = new JLabel(""+myGame.getSquares()[i][j].getSquare()); JSeparator CellSeparator = new JSeparator(orientation); panel.add(CellSeparator); panel.setForeground(Color.ORANGE); panel.add(label2, BorderLayout.NORTH); panel.add(label1, BorderLayout.CENTER); }

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