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• Is there any difference between BOOL and Boolean in Objective-C?

  - by Frost Li

  I know BOOL is actually a typedef of signed char. But what about Boolean? I am confused of bool, Boolean and BOOL.... Q Q

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• Using "as bool?" instead of "object something = ViewState["hi"]"

  - by Programmin Tool

  So I'm going through old code (2.0) and I came across this: object isReviewingValue = ViewState["IsReviewing"]; if (isReviewingValue is bool) { return (bool)isReviewingValue; } My first thought was to us the "as" keyword to avoid the unneeded (bool)isReviewingValue; But "as" only works with non value types. No problem, I just went ahead and did this: bool? isReviewingValue= ViewState["IsReviewing"] as bool?; if (isReviewingValue.HasValue) { return isReviewingValue.Value; } Question is: Besides looking a bit more readable, is this in fact better? EDIT: So this is getting more interesting. I decided to test it using a simple stopwatch and turns out that the second is much faster... Which after reading some of the responses here I didn't expect at all. I was thinking for sure my way was much slower. Tell me what I did wrong: public Stopwatch AsRun() { Stopwatch watch = new Stopwatch(); watch.Start(); for (Int32 loopCounter = 0; loopCounter < 10000; loopCounter++) { Boolean? test = true as Boolean?; if (test.HasValue) { Boolean something = test.Value; } } watch.Stop(); return watch; } public Stopwatch ObjectIsRun() { Stopwatch watch = new Stopwatch(); watch.Start(); for (Int32 loopCounter = 0; loopCounter < 10000; loopCounter++) { Object test = true; if (test is Boolean) { Boolean something = (Boolean)test; } } watch.Stop(); return watch; } Every time I run these methods against each other, the AsRun is twice as fast.

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• How can I set my screen resolution to match my TV?

  - by Scott Severance

  I have a computer in my classroom that's connected to an LG smart TV (that's actually not so smart. I wouldn't recommend buying one.). For the touch interface, the TV wants a resolution of 1920x1080 at 60Hz. However, I can't seem to set the computer to that resolution. The display settings only offer 1024x768 and 640x480. The computer dual boots with Windows XP, where widescreen options are available in approximately the required size, but the exact resolution -- or even aspect ratio-- isn't available in XP either. I tried the following command: xrandr -s 1920x1080 -r 60 The response was: Size 1920x1080 not found in available modes Back in the old days, the solution would be to edit xorg.conf. However, since that file no longer exists, and I haven't found up-to-date info, I don't know what else to do. If it helps, this machine will never be connected to a different display, so resolution flexibility isn't important. Here's the output of lshw: *-display:0 description: VGA compatible controller product: 4 Series Chipset Integrated Graphics Controller vendor: Intel Corporation physical id: 2 bus info: pci@0000:00:02.0 version: 03 width: 64 bits clock: 33MHz capabilities: vga_controller bus_master cap_list rom configuration: driver=i915 latency=0 resources: irq:42 memory:fe800000-febfffff memory:d0000000-dfffffff ioport:ecd8(size=8) *-display:1 UNCLAIMED description: Display controller product: 4 Series Chipset Integrated Graphics Controller vendor: Intel Corporation physical id: 2.1 bus info: pci@0000:00:02.1 version: 03 width: 64 bits clock: 33MHz According to the system settings, my graphics driver is unknown and my "experience" is standard. This is 64-bit Ubuntu 12.04 (Precise) Note: There are a number of similar questions to this one, but they didn't include any answers that helped me. Update After posting this question, I noticed one in the sidebar that I hadn't found through search but which appeared to contain the answer. Based on that question, I created the /etc/X11/xorg.conf file below: Section "ServerLayout" Identifier "X.org Configured" Screen 0 "Screen0" 0 0 InputDevice "Mouse0" "CorePointer" InputDevice "Keyboard0" "CoreKeyboard" EndSection Section "Files" ModulePath "/usr/lib/xorg/modules" FontPath "/usr/share/fonts/X11/misc" FontPath "/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType" FontPath "built-ins" EndSection Section "Module" Load "glx" Load "dri2" Load "dbe" Load "dri" Load "record" Load "extmod" EndSection Section "InputDevice" Identifier "Keyboard0" Driver "kbd" EndSection Section "InputDevice" Identifier "Mouse0" Driver "mouse" Option "Protocol" "auto" Option "Device" "/dev/input/mice" Option "ZAxisMapping" "4 5 6 7" EndSection Section "Monitor" Identifier "Monitor0" VendorName "LG" ModelName "Smart TV" EndSection Section "Device" ### Available Driver options are:- ### Values: <i>: integer, <f>: float, <bool>: "True"/"False", ### <string>: "String", <freq>: "<f> Hz/kHz/MHz", ### <percent>: "<f>%" ### [arg]: arg optional #Option "DRI" # [<bool>] #Option "ColorKey" # <i> #Option "VideoKey" # <i> #Option "FallbackDebug" # [<bool>] #Option "Tiling" # [<bool>] #Option "LinearFramebuffer" # [<bool>] #Option "Shadow" # [<bool>] #Option "SwapbuffersWait" # [<bool>] #Option "TripleBuffer" # [<bool>] #Option "XvMC" # [<bool>] #Option "XvPreferOverlay" # [<bool>] #Option "DebugFlushBatches" # [<bool>] #Option "DebugFlushCaches" # [<bool>] #Option "DebugWait" # [<bool>] #Option "HotPlug" # [<bool>] #Option "RelaxedFencing" # [<bool>] Identifier "Card0" Driver "intel" BusID "PCI:0:2:0" EndSection Section "Screen" Identifier "Screen0" Device "Card0" Monitor "Monitor0" DefaultDepth 24 #SubSection "Display" # Viewport 0 0 # Depth 1 #EndSubSection #SubSection "Display" # Viewport 0 0 # Depth 4 #EndSubSection #SubSection "Display" # Viewport 0 0 # Depth 8 #EndSubSection #SubSection "Display" # Viewport 0 0 # Depth 15 #EndSubSection #SubSection "Display" # Viewport 0 0 # Depth 16 #EndSubSection SubSection "Display" Viewport 0 0 Depth 24 Modes "1024x768" "1920x1080" EndSubSection EndSection According to /var/log/Xorg.0.log, my settings aren't being applied. In fact, I wonder if the config file is even being read. [ 1209.083] (**) intel(0): Depth 24, (--) framebuffer bpp 32 [ 1209.084] (==) intel(0): RGB weight 888 [ 1209.084] (==) intel(0): Default visual is TrueColor [ 1209.084] (II) intel(0): Integrated Graphics Chipset: Intel(R) G41 [ 1209.084] (--) intel(0): Chipset: "G41" [ 1209.084] (**) intel(0): Relaxed fencing enabled [ 1209.084] (**) intel(0): Wait on SwapBuffers? enabled [ 1209.084] (**) intel(0): Triple buffering? enabled [ 1209.084] (**) intel(0): Framebuffer tiled [ 1209.084] (**) intel(0): Pixmaps tiled [ 1209.084] (**) intel(0): 3D buffers tiled [ 1209.084] (**) intel(0): SwapBuffers wait enabled [ 1209.084] (==) intel(0): video overlay key set to 0x101fe [ 1209.172] (II) intel(0): Output VGA1 using monitor section Monitor0 [ 1209.260] (II) intel(0): EDID for output VGA1 [ 1209.260] (II) intel(0): Printing probed modes for output VGA1 [ 1209.260] (II) intel(0): Modeline "1024x768"x60.0 65.00 1024 1048 1184 1344 768 771 777 806 -hsync -vsync (48.4 kHz) [ 1209.260] (II) intel(0): Modeline "800x600"x60.3 40.00 800 840 968 1056 600 601 605 628 +hsync +vsync (37.9 kHz) [ 1209.260] (II) intel(0): Modeline "800x600"x56.2 36.00 800 824 896 1024 600 601 603 625 +hsync +vsync (35.2 kHz) [ 1209.260] (II) intel(0): Modeline "848x480"x60.0 33.75 848 864 976 1088 480 486 494 517 +hsync +vsync (31.0 kHz) [ 1209.260] (II) intel(0): Modeline "640x480"x59.9 25.18 640 656 752 800 480 489 492 525 -hsync -vsync (31.5 kHz) [ 1209.260] (II) intel(0): Output VGA1 connected [ 1209.260] (II) intel(0): Using user preference for initial modes [ 1209.260] (II) intel(0): Output VGA1 using initial mode 1024x768 [ 1209.260] (II) intel(0): Using default gamma of (1.0, 1.0, 1.0) unless otherwise stated. [ 1209.260] (II) intel(0): Kernel page flipping support detected, enabling [ 1209.260] (==) intel(0): DPI set to (96, 96)

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• Static method , Abstract method , Interface method comparision ?

  - by programmerist

  When i choose these methods? i can not decide which one i must prefer or when will i use one of them?which one give best performance? First Type Usage public abstract class _AccessorForSQL { public virtual bool Save(string sp, ListDictionary ld, CommandType cmdType); public virtual bool Update(); public virtual bool Delete(); public virtual DataSet Select(); } class GenAccessor : _AccessorForSQL { DataSet ds; DataTable dt; public override bool Save(string sp, ListDictionary ld, CommandType cmdType) { } public override bool Update() { return true; } public override bool Delete() { return true; } public override DataSet Select() { DataSet dst = new DataSet(); return dst; } Second Type Usage Also i can write it below codes: public class GenAccessor { public Static bool Save() { } public Static bool Update() { } public Static bool Delete() { } } Third Type Usage Also i can write it below codes: public interface IAccessorForSQL { bool Delete(); bool Save(string sp, ListDictionary ld, CommandType cmdType); DataSet Select(); bool Update(); } public class _AccessorForSQL : IAccessorForSQL { private DataSet ds; private DataTable dt; public virtual bool Save(string sp, ListDictionary ld, CommandType cmdType) { } } } I can use first one below usage: GenAccessor gen = New GenAccessor(); gen.Save(); I can use second one below usage: GenAccessor.Save(); Which one do you prefer? When will i use them? which time i need override method ? which time i need static method?

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• How do I pass a bool into locationManager on iphone with startUpdatingLocation?

  - by user295944

  I want to pass a flag into my location manager function - (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation so it will look like - (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation andTweet:(Bool *)tweet but it started with the command [locmanager startUpdatingLocation]; So how can I pass the bool into the function?

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• How do I pass a bool into locationManager on iphone with stopUpdatingLocation?

  - by user295944

  I want to pass a flag into my location manager function - (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation so it will look like - (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation andTweet:(Bool *)tweet but it started with the command [locmanager stopUpdatingLocation]; So how can I pass the bool into the function?

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• How do I set a static bool in another app domain?

  - by Martin

  How do I programatically set the value of a static boolean in another app domain? I'm testing an application where I need to change a bool value. Problem is that the bool value exists as a static instance on a type hosted in another app domain. (I'm doing this for test purposes, it won't be used in production code)

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• C# Gui setting control.Enabled to false fires OnClick event???

  - by Daniel

  For some really weird reason when i set the .Enabled property to false on a simple text box on a small GUI, it fires a radio buttons OnClick event and its causing lots of problems. I have breakpointed the txtBox.Enabled = false; and after stepping over OR into it i jump straight to the OnClick event of the radio button control Here is the call stack as that happened: TestGUI.exe!TestGUI.frmMain.radiobuttonClicked(object sender = {Text = "Download Single Episode" Checked = true}, System.EventArgs e = {System.EventArgs}) Line 67 C# System.Windows.Forms.dll!System.Windows.Forms.Control.OnClick(System.EventArgs e) + 0x70 bytes System.Windows.Forms.dll!System.Windows.Forms.RadioButton.OnClick(System.EventArgs e) + 0x27 bytes System.Windows.Forms.dll!System.Windows.Forms.RadioButton.OnEnter(System.EventArgs e = {System.EventArgs}) + 0x3e bytes System.Windows.Forms.dll!System.Windows.Forms.Control.NotifyEnter() + 0x20 bytes System.Windows.Forms.dll!System.Windows.Forms.ContainerControl.UpdateFocusedControl() + 0x195 bytes System.Windows.Forms.dll!System.Windows.Forms.ContainerControl.AssignActiveControlInternal(System.Windows.Forms.Control value = {Text = "Download Single Episode" Checked = true}) + 0x54 bytes System.Windows.Forms.dll!System.Windows.Forms.ContainerControl.ActivateControlInternal(System.Windows.Forms.Control control, bool originator = false) + 0x76 bytes System.Windows.Forms.dll!System.Windows.Forms.ContainerControl.SetActiveControlInternal(System.Windows.Forms.Control value = {Text = "Download Single Episode" Checked = true}) + 0x73 bytes System.Windows.Forms.dll!System.Windows.Forms.ContainerControl.SetActiveControl(System.Windows.Forms.Control ctl) + 0x33 bytes System.Windows.Forms.dll!System.Windows.Forms.ContainerControl.ActiveControl.set(System.Windows.Forms.Control value) + 0x5 bytes System.Windows.Forms.dll!System.Windows.Forms.Control.Select(bool directed, bool forward) + 0x1b bytes System.Windows.Forms.dll!System.Windows.Forms.Control.SelectNextControl(System.Windows.Forms.Control ctl, bool forward, bool tabStopOnly, bool nested, bool wrap) + 0x7b bytes System.Windows.Forms.dll!System.Windows.Forms.Control.SelectNextControlInternal(System.Windows.Forms.Control ctl, bool forward, bool tabStopOnly, bool nested, bool wrap) + 0x4a bytes System.Windows.Forms.dll!System.Windows.Forms.Control.SelectNextIfFocused() + 0x61 bytes System.Windows.Forms.dll!System.Windows.Forms.Control.Enabled.set(bool value) + 0x42 bytes What the hell? It wouldn't have anything to do with the way i subscribe to the events would it? this.radioBtnMultipleDownload.Click += radiobuttonClicked; this.radioBtnSingleDownload.Click += radiobuttonClicked; this.radioCustomUrl.Click += radiobuttonClicked;

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• C# Type comparison

  - by Sean.C

  This has me pooped, is there any reason the following: public abstract class aExtension { public abstract bool LoadExtension(Constants c); // method required in inherit public abstract string AppliesToModule // property required in inherit { get; } public abstract string ExtensionName // property required in inherit { get; } public abstract string ExtensionDescription // property required in inherit { get; } } public class UK : aExtension { public override bool LoadExtension(Constants c) { return true; } public override string AppliesToModule { get { return "string"; } } public override string ExtensionName { get { return "string"; } } public override string ExtensionDescription { get { return "string"; } } } would return false for the following expressions: bool a = t.IsAssignableFrom(aExtension)); bool b = t.BaseType.IsAssignableFrom(aExtension)); bool c = typeof(aExtension).IsAssignableFrom(t); bool d = typeof(aExtension).IsAssignableFrom(t.BaseType); bool e = typeof(aExtension).IsSubclassOf(t); bool f = typeof(aExtension).IsSubclassOf(t.BaseType); bool g = t.IsSubclassOf(typeof(aExtension)); bool h = t.BaseType.IsSubclassOf(typeof(LBT.AdMeter.aExtension)); bool i = t.BaseType.Equals(typeof(aExtension)); bool j = typeof(aExtension).Equals(t.BaseType); T is the reflected Type from the calss UK. Stange thing is i do the exact same thing just on an external assembly in the same application and it works as expected...

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• XNA Screen Manager problem with transitions

  - by NexAddo

  I'm having issues using the game statemanagement example in the game I am developing. I have no issues with my first three screens transitioning between one another. I have a main menu screen, a splash screen and a high score screen that cycle: mainMenuScreen->splashScreen->highScoreScreen->mainMenuScreen The screens change every 15 seconds. Transition times public MainMenuScreen() { TransitionOnTime = TimeSpan.FromSeconds(0.5); TransitionOffTime = TimeSpan.FromSeconds(0.0); currentCreditAmount = Global.CurrentCredits; } public SplashScreen() { TransitionOnTime = TimeSpan.FromSeconds(0.5); TransitionOffTime = TimeSpan.FromSeconds(0.5); } public HighScoreScreen() { TransitionOnTime = TimeSpan.FromSeconds(0.5); TransitionOffTime = TimeSpan.FromSeconds(0.5); } public GamePlayScreen() { TransitionOnTime = TimeSpan.FromSeconds(0.5); TransitionOffTime = TimeSpan.FromSeconds(0.5); } When a user inserts credits they can play the game after pressing start mainMenuScreen->splashScreen->highScoreScreen->(loops forever) || || || ===========Credits In============= || Start || \/ LoadingScreen || Start || \/ GamePlayScreen During each of these transitions, between screens, the same code is used, which exits(removes) all current active screens and respects transitions, then adds the new screen to the screen manager: foreach (GameScreen screen in ScreenManager.GetScreens()) screen.ExitScreen(); //AddScreen takes a new screen to manage and the controlling player ScreenManager.AddScreen(new NameOfScreenHere(), null); Each screen is removed from the ScreenManager with ExitScreen() and using this function, each screen transition is respected. The problem I am having is with my gamePlayScreen. When the current game is finished and the transition is complete for the gamePlayScreen, it should be removed and the next screens should be added to the ScreenManager. GamePlayScreen Code Snippet private void FinishCurrentGame() { AudioManager.StopSounds(); this.UnloadContent(); if (Global.SaveDevice.IsReady) Stats.Save(); if (HighScoreScreen.IsInHighscores(timeLimit)) { foreach (GameScreen screen in ScreenManager.GetScreens()) screen.ExitScreen(); Global.TimeRemaining = timeLimit; ScreenManager.AddScreen(new BackgroundScreen(), null); ScreenManager.AddScreen(new MessageBoxScreen("Enter your Initials", true), null); } else { foreach (GameScreen screen in ScreenManager.GetScreens()) screen.ExitScreen(); ScreenManager.AddScreen(new BackgroundScreen(), null); ScreenManager.AddScreen(new MainMenuScreen(), null); } } The problem is that when isExiting is set to true by screen.ExitScreen() for the gamePlayScreen, the transition never completes the transition and removes the screen from the ScreenManager. Every other screen that I use the same technique to add and remove each screen fully transitions On/Off and is removed at the appropriate time from the ScreenManager, but noy my GamePlayScreen. Has anyone that has used the GameStateManagement example experienced this issue or can someone see the mistake I am making? EDIT This is what I tracked down. When the game is done, I call foreach (GameScreen screen in ScreenManager.GetScreens()) screen.ExitScreen(); to start the transition off process for the gameplay screen. At this point there is only 1 screen on the ScreenManager stack. The gamePlay screen gets isExiting set to true and starts to transition off. Right after the above call to ExitScreen() I add a background screen and menu screen to the screenManager: ScreenManager.AddScreen(new background(), null); ScreenManager.AddScreen(new Menu(), null); The count of the ScreenManager is now 3. What I noticed while stepping through the updates for GameScreen and ScreenManager, the gameplay screen never gets to the point where the transistion process finishes so the ScreenManager can remove it from the stack. This anomaly does not happen to any of my other screens when I switch between them. Screen Manager Code #region File Description //----------------------------------------------------------------------------- // ScreenManager.cs // // Microsoft XNA Community Game Platform // Copyright (C) Microsoft Corporation. All rights reserved. //----------------------------------------------------------------------------- #endregion #define DEMO #region Using Statements using System; using System.Diagnostics; using System.Collections.Generic; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.Graphics; using PerformanceUtility.GameDebugTools; #endregion namespace GameStateManagement { /// <summary> /// The screen manager is a component which manages one or more GameScreen /// instances. It maintains a stack of screens, calls their Update and Draw /// methods at the appropriate times, and automatically routes input to the /// topmost active screen. /// </summary> public class ScreenManager : DrawableGameComponent { #region Fields List<GameScreen> screens = new List<GameScreen>(); List<GameScreen> screensToUpdate = new List<GameScreen>(); InputState input = new InputState(); SpriteBatch spriteBatch; SpriteFont font; Texture2D blankTexture; bool isInitialized; bool getOut; bool traceEnabled; #if DEBUG DebugSystem debugSystem; Stopwatch stopwatch = new Stopwatch(); bool debugTextEnabled; #endif #endregion #region Properties /// <summary> /// A default SpriteBatch shared by all the screens. This saves /// each screen having to bother creating their own local instance. /// </summary> public SpriteBatch SpriteBatch { get { return spriteBatch; } } /// <summary> /// A default font shared by all the screens. This saves /// each screen having to bother loading their own local copy. /// </summary> public SpriteFont Font { get { return font; } } public Rectangle ScreenRectangle { get { return new Rectangle(0, 0, GraphicsDevice.Viewport.Width, GraphicsDevice.Viewport.Height); } } /// <summary> /// If true, the manager prints out a list of all the screens /// each time it is updated. This can be useful for making sure /// everything is being added and removed at the right times. /// </summary> public bool TraceEnabled { get { return traceEnabled; } set { traceEnabled = value; } } #if DEBUG public bool DebugTextEnabled { get { return debugTextEnabled; } set { debugTextEnabled = value; } } public DebugSystem DebugSystem { get { return debugSystem; } } #endif #endregion #region Initialization /// <summary> /// Constructs a new screen manager component. /// </summary> public ScreenManager(Game game) : base(game) { // we must set EnabledGestures before we can query for them, but // we don't assume the game wants to read them. //TouchPanel.EnabledGestures = GestureType.None; } /// <summary> /// Initializes the screen manager component. /// </summary> public override void Initialize() { base.Initialize(); #if DEBUG debugSystem = DebugSystem.Initialize(Game, "Fonts/MenuFont"); #endif isInitialized = true; } /// <summary> /// Load your graphics content. /// </summary> protected override void LoadContent() { // Load content belonging to the screen manager. ContentManager content = Game.Content; spriteBatch = new SpriteBatch(GraphicsDevice); font = content.Load<SpriteFont>(@"Fonts\menufont"); blankTexture = content.Load<Texture2D>(@"Textures\Backgrounds\blank"); // Tell each of the screens to load their content. foreach (GameScreen screen in screens) { screen.LoadContent(); } } /// <summary> /// Unload your graphics content. /// </summary> protected override void UnloadContent() { // Tell each of the screens to unload their content. foreach (GameScreen screen in screens) { screen.UnloadContent(); } } #endregion #region Update and Draw /// <summary> /// Allows each screen to run logic. /// </summary> public override void Update(GameTime gameTime) { #if DEBUG debugSystem.TimeRuler.StartFrame(); debugSystem.TimeRuler.BeginMark("Update", Color.Blue); if (debugTextEnabled && getOut == false) { debugSystem.FpsCounter.Visible = true; debugSystem.TimeRuler.Visible = true; debugSystem.TimeRuler.ShowLog = true; getOut = true; } else if (debugTextEnabled == false) { getOut = false; debugSystem.FpsCounter.Visible = false; debugSystem.TimeRuler.Visible = false; debugSystem.TimeRuler.ShowLog = false; } #endif // Read the keyboard and gamepad. input.Update(); // Make a copy of the master screen list, to avoid confusion if // the process of updating one screen adds or removes others. screensToUpdate.Clear(); foreach (GameScreen screen in screens) screensToUpdate.Add(screen); bool otherScreenHasFocus = !Game.IsActive; bool coveredByOtherScreen = false; // Loop as long as there are screens waiting to be updated. while (screensToUpdate.Count > 0) { // Pop the topmost screen off the waiting list. GameScreen screen = screensToUpdate[screensToUpdate.Count - 1]; screensToUpdate.RemoveAt(screensToUpdate.Count - 1); // Update the screen. screen.Update(gameTime, otherScreenHasFocus, coveredByOtherScreen); if (screen.ScreenState == ScreenState.TransitionOn || screen.ScreenState == ScreenState.Active) { // If this is the first active screen we came across, // give it a chance to handle input. if (!otherScreenHasFocus) { screen.HandleInput(input); otherScreenHasFocus = true; } // If this is an active non-popup, inform any subsequent // screens that they are covered by it. if (!screen.IsPopup) coveredByOtherScreen = true; } } // Print debug trace? if (traceEnabled) TraceScreens(); #if DEBUG debugSystem.TimeRuler.EndMark("Update"); #endif } /// <summary> /// Prints a list of all the screens, for debugging. /// </summary> void TraceScreens() { List<string> screenNames = new List<string>(); foreach (GameScreen screen in screens) screenNames.Add(screen.GetType().Name); Debug.WriteLine(string.Join(", ", screenNames.ToArray())); } /// <summary> /// Tells each screen to draw itself. /// </summary> public override void Draw(GameTime gameTime) { #if DEBUG debugSystem.TimeRuler.StartFrame(); debugSystem.TimeRuler.BeginMark("Draw", Color.Yellow); #endif foreach (GameScreen screen in screens) { if (screen.ScreenState == ScreenState.Hidden) continue; screen.Draw(gameTime); } #if DEBUG debugSystem.TimeRuler.EndMark("Draw"); #endif #if DEMO SpriteBatch.Begin(); SpriteBatch.DrawString(font, "DEMO - NOT FOR RESALE", new Vector2(20, 80), Color.White); SpriteBatch.End(); #endif } #endregion #region Public Methods /// <summary> /// Adds a new screen to the screen manager. /// </summary> public void AddScreen(GameScreen screen, PlayerIndex? controllingPlayer) { screen.ControllingPlayer = controllingPlayer; screen.ScreenManager = this; screen.IsExiting = false; // If we have a graphics device, tell the screen to load content. if (isInitialized) { screen.LoadContent(); } screens.Add(screen); } /// <summary> /// Removes a screen from the screen manager. You should normally /// use GameScreen.ExitScreen instead of calling this directly, so /// the screen can gradually transition off rather than just being /// instantly removed. /// </summary> public void RemoveScreen(GameScreen screen) { // If we have a graphics device, tell the screen to unload content. if (isInitialized) { screen.UnloadContent(); } screens.Remove(screen); screensToUpdate.Remove(screen); } /// <summary> /// Expose an array holding all the screens. We return a copy rather /// than the real master list, because screens should only ever be added /// or removed using the AddScreen and RemoveScreen methods. /// </summary> public GameScreen[] GetScreens() { return screens.ToArray(); } /// <summary> /// Helper draws a translucent black fullscreen sprite, used for fading /// screens in and out, and for darkening the background behind popups. /// </summary> public void FadeBackBufferToBlack(float alpha) { Viewport viewport = GraphicsDevice.Viewport; spriteBatch.Begin(); spriteBatch.Draw(blankTexture, new Rectangle(0, 0, viewport.Width, viewport.Height), Color.Black * alpha); spriteBatch.End(); } #endregion } } Game Screen Parent of GamePlayScreen #region File Description //----------------------------------------------------------------------------- // GameScreen.cs // // Microsoft XNA Community Game Platform // Copyright (C) Microsoft Corporation. All rights reserved. //----------------------------------------------------------------------------- #endregion #region Using Statements using System; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Input; //using Microsoft.Xna.Framework.Input.Touch; using System.IO; #endregion namespace GameStateManagement { /// <summary> /// Enum describes the screen transition state. /// </summary> public enum ScreenState { TransitionOn, Active, TransitionOff, Hidden, } /// <summary> /// A screen is a single layer that has update and draw logic, and which /// can be combined with other layers to build up a complex menu system. /// For instance the main menu, the options menu, the "are you sure you /// want to quit" message box, and the main game itself are all implemented /// as screens. /// </summary> public abstract class GameScreen { #region Properties /// <summary> /// Normally when one screen is brought up over the top of another, /// the first screen will transition off to make room for the new /// one. This property indicates whether the screen is only a small /// popup, in which case screens underneath it do not need to bother /// transitioning off. /// </summary> public bool IsPopup { get { return isPopup; } protected set { isPopup = value; } } bool isPopup = false; /// <summary> /// Indicates how long the screen takes to /// transition on when it is activated. /// </summary> public TimeSpan TransitionOnTime { get { return transitionOnTime; } protected set { transitionOnTime = value; } } TimeSpan transitionOnTime = TimeSpan.Zero; /// <summary> /// Indicates how long the screen takes to /// transition off when it is deactivated. /// </summary> public TimeSpan TransitionOffTime { get { return transitionOffTime; } protected set { transitionOffTime = value; } } TimeSpan transitionOffTime = TimeSpan.Zero; /// <summary> /// Gets the current position of the screen transition, ranging /// from zero (fully active, no transition) to one (transitioned /// fully off to nothing). /// </summary> public float TransitionPosition { get { return transitionPosition; } protected set { transitionPosition = value; } } float transitionPosition = 1; /// <summary> /// Gets the current alpha of the screen transition, ranging /// from 1 (fully active, no transition) to 0 (transitioned /// fully off to nothing). /// </summary> public float TransitionAlpha { get { return 1f - TransitionPosition; } } /// <summary> /// Gets the current screen transition state. /// </summary> public ScreenState ScreenState { get { return screenState; } protected set { screenState = value; } } ScreenState screenState = ScreenState.TransitionOn; /// <summary> /// There are two possible reasons why a screen might be transitioning /// off. It could be temporarily going away to make room for another /// screen that is on top of it, or it could be going away for good. /// This property indicates whether the screen is exiting for real: /// if set, the screen will automatically remove itself as soon as the /// transition finishes. /// </summary> public bool IsExiting { get { return isExiting; } protected internal set { isExiting = value; } } bool isExiting = false; /// <summary> /// Checks whether this screen is active and can respond to user input. /// </summary> public bool IsActive { get { return !otherScreenHasFocus && (screenState == ScreenState.TransitionOn || screenState == ScreenState.Active); } } bool otherScreenHasFocus; /// <summary> /// Gets the manager that this screen belongs to. /// </summary> public ScreenManager ScreenManager { get { return screenManager; } internal set { screenManager = value; } } ScreenManager screenManager; public KeyboardState KeyboardState { get {return Keyboard.GetState();} } /// <summary> /// Gets the index of the player who is currently controlling this screen, /// or null if it is accepting input from any player. This is used to lock /// the game to a specific player profile. The main menu responds to input /// from any connected gamepad, but whichever player makes a selection from /// this menu is given control over all subsequent screens, so other gamepads /// are inactive until the controlling player returns to the main menu. /// </summary> public PlayerIndex? ControllingPlayer { get { return controllingPlayer; } internal set { controllingPlayer = value; } } PlayerIndex? controllingPlayer; /// <summary> /// Gets whether or not this screen is serializable. If this is true, /// the screen will be recorded into the screen manager's state and /// its Serialize and Deserialize methods will be called as appropriate. /// If this is false, the screen will be ignored during serialization. /// By default, all screens are assumed to be serializable. /// </summary> public bool IsSerializable { get { return isSerializable; } protected set { isSerializable = value; } } bool isSerializable = true; #endregion #region Initialization /// <summary> /// Load graphics content for the screen. /// </summary> public virtual void LoadContent() { } /// <summary> /// Unload content for the screen. /// </summary> public virtual void UnloadContent() { } #endregion #region Update and Draw /// <summary> /// Allows the screen to run logic, such as updating the transition position. /// Unlike HandleInput, this method is called regardless of whether the screen /// is active, hidden, or in the middle of a transition. /// </summary> public virtual void Update(GameTime gameTime, bool otherScreenHasFocus, bool coveredByOtherScreen) { this.otherScreenHasFocus = otherScreenHasFocus; if (isExiting) { // If the screen is going away to die, it should transition off. screenState = ScreenState.TransitionOff; if (!UpdateTransition(gameTime, transitionOffTime, 1)) { // When the transition finishes, remove the screen. ScreenManager.RemoveScreen(this); } } else if (coveredByOtherScreen) { // If the screen is covered by another, it should transition off. if (UpdateTransition(gameTime, transitionOffTime, 1)) { // Still busy transitioning. screenState = ScreenState.TransitionOff; } else { // Transition finished! screenState = ScreenState.Hidden; } } else { // Otherwise the screen should transition on and become active. if (UpdateTransition(gameTime, transitionOnTime, -1)) { // Still busy transitioning. screenState = ScreenState.TransitionOn; } else { // Transition finished! screenState = ScreenState.Active; } } } /// <summary> /// Helper for updating the screen transition position. /// </summary> bool UpdateTransition(GameTime gameTime, TimeSpan time, int direction) { // How much should we move by? float transitionDelta; if (time == TimeSpan.Zero) transitionDelta = 1; else transitionDelta = (float)(gameTime.ElapsedGameTime.TotalMilliseconds / time.TotalMilliseconds); // Update the transition position. transitionPosition += transitionDelta * direction; // Did we reach the end of the transition? if (((direction < 0) && (transitionPosition <= 0)) || ((direction > 0) && (transitionPosition >= 1))) { transitionPosition = MathHelper.Clamp(transitionPosition, 0, 1); return false; } // Otherwise we are still busy transitioning. return true; } /// <summary> /// Allows the screen to handle user input. Unlike Update, this method /// is only called when the screen is active, and not when some other /// screen has taken the focus. /// </summary> public virtual void HandleInput(InputState input) { } public KeyboardState currentKeyState; public KeyboardState lastKeyState; public bool IsKeyHit(Keys key) { if (currentKeyState.IsKeyDown(key) && lastKeyState.IsKeyUp(key)) return true; return false; } /// <summary> /// This is called when the screen should draw itself. /// </summary> public virtual void Draw(GameTime gameTime) { } #endregion #region Public Methods /// <summary> /// Tells the screen to serialize its state into the given stream. /// </summary> public virtual void Serialize(Stream stream) { } /// <summary> /// Tells the screen to deserialize its state from the given stream. /// </summary> public virtual void Deserialize(Stream stream) { } /// <summary> /// Tells the screen to go away. Unlike ScreenManager.RemoveScreen, which /// instantly kills the screen, this method respects the transition timings /// and will give the screen a chance to gradually transition off. /// </summary> public void ExitScreen() { if (TransitionOffTime == TimeSpan.Zero) { // If the screen has a zero transition time, remove it immediately. ScreenManager.RemoveScreen(this); } else { // Otherwise flag that it should transition off and then exit. isExiting = true; } } #endregion #region Helper Methods /// <summary> /// A helper method which loads assets using the screen manager's /// associated game content loader. /// </summary> /// <typeparam name="T">Type of asset.</typeparam> /// <param name="assetName">Asset name, relative to the loader root /// directory, and not including the .xnb extension.</param> /// <returns></returns> public T Load<T>(string assetName) { return ScreenManager.Game.Content.Load<T>(assetName); } #endregion } }

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• Retrieving Custom Attributes Using Reflection

  - by Scott Dorman

  The .NET Framework allows you to easily add metadata to your classes by using attributes. These attributes can be ones that the .NET Framework already provides, of which there are over 300, or you can create your own. Using reflection, the ways to retrieve the custom attributes of a type are: System.Reflection.MemberInfo public abstract object[] GetCustomAttributes(bool inherit); public abstract object[] GetCustomAttributes(Type attributeType, bool inherit); public abstract bool IsDefined(Type attributeType, bool inherit); System.Attribute public static Attribute[] GetCustomAttributes(MemberInfo member, bool inherit); public static bool IsDefined(MemberInfo element, Type attributeType, bool inherit); If you take the following simple class hierarchy: public abstract class BaseClass { private bool result;   [DefaultValue(false)] public virtual bool SimpleProperty { get { return this.result; } set { this.result = value; } } }   public class DerivedClass : BaseClass { public override bool SimpleProperty { get { return true; } set { base.SimpleProperty = value; } } } Given a PropertyInfo object (which is derived from MemberInfo, and represents a propery in reflection), you might expect that these methods would return the same result. Unfortunately, that isn’t the case. The MemberInfo methods strictly reflect the metadata definitions, ignoring the inherit parameter and not searching the inheritance chain when used with a PropertyInfo, EventInfo, or ParameterInfo object. It also returns all custom attribute instances, including those that don’t inherit from System.Attribute. The Attribute methods are closer to the implied behavior of the language (and probably closer to what you would naturally expect). They do respect the inherit parameter for PropertyInfo, EventInfo, and ParameterInfo objects and search the implied inheritance chain defined by the associated methods (in this case, the property accessors). These methods also only return custom attributes that inherit from System.Attribute. This is a fairly subtle difference that can produce very unexpected results if you aren’t careful. For example, to retrieve the custom  attributes defined on SimpleProperty, you could use code similar to this: PropertyInfo info = typeof(DerivedClass).GetProperty("SimpleProperty"); var attributeList1 = info.GetCustomAttributes(typeof(DefaultValueAttribute), true)); var attributeList2 = Attribute.GetCustomAttributes(info, typeof(DefaultValueAttribute), true));   The attributeList1 array will be empty while the attributeList2 array will contain the attribute instance, as expected. Technorati Tags: Reflection,Custom Attributes,PropertyInfo

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• Is it possible to coerce string values in xml to bool?

  - by Kugel

  Let's suppose I have xml like this one: <Server Active="No"> <Url>http://some.url</Url> </Server> C# class looks like this: public class Server { [XmlAttribute()] public string Active { get; set; } public string Url { get; set; } } Is it possible to change Active property to type bool and have XmlSerializer coerce "Yes" "No" to bool values? Edit: Xml is received, I cannot change it. So, in fact, i'm interested in deserialization only.

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• How to convert a function that returns a int to a function that returns a bool using boost::bind?

  - by user814628

  I have something like the following: struct A{ virtual int derp(){ if(herp()) return 1; else return 0; } void slurp(){ boost::function<bool(int x, int y> purp = /** boost bind derp to match lvalue sig **/; } } Any ideas? I want to create the function prup which basically calls derp and ignores the (x,y) passed in. I need something like bool purp(int x, int y){ return derp(); } but want to avoid creating it as a member function, and rather just create it locally if possible?

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• How to refactor and improve this XNA mouse input code?

  - by Andrew Price

  Currently I have something like this: public bool IsLeftMouseButtonDown() { return currentMouseState.LeftButton == ButtonState.Pressed && previousMouseSate.LeftButton == ButtonState.Pressed; } public bool IsLeftMouseButtonPressed() { return currentMouseState.LeftButton == ButtonState.Pressed && previousMouseSate.LeftButton == ButtonState.Released; } public bool IsLeftMouseButtonUp() { return currentMouseState.LeftButton == ButtonState.Released && previousMouseSate.LeftButton == ButtonState.Released; } public bool IsLeftMouseButtonReleased() { return currentMouseState.LeftButton == ButtonState.Released && previousMouseSate.LeftButton == ButtonState.Pressed; } This is fine. In fact, I kind of like it. However, I'd hate to have to repeat this same code five times (for right, middle, X1, X2). Is there any way to pass in the button I want to the function so I could have something like this? public bool IsMouseButtonDown(MouseButton button) { return currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } public bool IsMouseButtonPressed(MouseButton button) { return currentMouseState.IsPressed(button) && !previousMouseState.IsPressed(button); } public bool IsMouseButtonUp(MouseButton button) { return !currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } public bool IsMouseButtonReleased(MouseButton button) { return !currentMouseState.IsPressed(button) && previousMouseState.IsPressed(button); } I suppose I could create some custom enumeration and switch through it in each function, but I'd like to first see if there is a built-in solution or a better way.. Thanks!

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• Template inheritence c++

  - by Chris Condy

  I have made a template singleton class, I have also made a data structure that is templated. My question is; how do I make my templated data structure inherit from a singleton so you can only have one float type of this structure? I have tested both seperate and have found no problems. Code provided under... (That is the problem) template <class Type> class AbstractRManagers : public Singleton<AbstractRManagers<Type> > The problem is the code above doesn't work I get alot of errors. I cant get it to no matter what I do template a templated singleton class... I was asking for maybe advice or maybe if the code above is incorrect guidence? #ifndef SINGLETON_H #define SINGLETON_H template <class Type> class Singleton { public: virtual ~Singleton(); Singleton(); static Type* m_instance; }; template <class Type> Type* Singleton<Type>::m_instance = 0; #include "Singleton.cpp" #endif #ifndef SINGLETON_CPP #define SINGLETON_CPP #include "Singleton.h" template <class Type> Singleton<Type>::Singleton() { } template <class Type> Singleton<Type>::~Singleton() { } template <class Type> Type* Singleton<Type>::getInstance() { if(m_instance==nullptr) { m_instance = new Type; } return m_instance; } #endif #ifndef ABSTRACTRMANAGERS_H #define ABSTRACTRMANAGERS_H #include <vector> #include <map> #include <stack> #include "Singleton.h" template <class Type> class AbstractRManagers : public Singleton<AbstractRManagers<Type> > { public: virtual ~AbstractRManagers(); int insert(Type* type, std::string name); Type* remove(int i); Type* remove(std::string name); Type* get(int i); Type* getS(std::string name); int get(std::string name); int get(Type* i); bool check(std::string name); int resourceSize(); protected: private: std::vector<Type*> m_resources; std::map<std::string,int> m_map; std::stack<int> m_freePos; }; #include "AbstractRManagers.cpp" #endif #ifndef ABSTRACTRMANAGERS_CPP #define ABSTRACTRMANAGERS_CPP #include "AbstractRManagers.h" template <class Type> int AbstractRManagers<Type>::insert(Type* type, std::string name) { int i=0; if(!check(name)) { if(m_freePos.empty()) { m_resources.push_back(type); i = m_resources.size()-1; m_map[name] = i; } else { i = m_freePos.top(); m_freePos.pop(); m_resources[i] = type; m_map[name] = i; } } else i = -1; return i; } template <class Type> int AbstractRManagers<Type>::resourceSize() { return m_resources.size(); } template <class Type> bool AbstractRManagers<Type>::check(std::string name) { std::map<std::string,int>::iterator it; it = m_map.find(name); if(it==m_map.end()) return false; return true; } template <class Type> Type* AbstractRManagers<Type>::remove(std::string name) { Type* temp = m_resources[m_map[name]]; if(temp!=NULL) { std::map<std::string,int>::iterator it; it = m_map[name]; m_resources[m_map[name]] = NULL; m_freePos.push(m_map[name]); delete (*it).second; delete (*it).first; return temp; } return NULL; } template <class Type> Type* AbstractRManagers<Type>::remove(int i) { if((i < m_resources.size())&&(i > 0)) { Type* temp = m_resources[i]; m_resources[i] = NULL; m_freePos.push(i); std::map<std::string,int>::iterator it; for(it=m_map.begin();it!=m_map.end();it++) { if((*it).second == i) { delete (*it).second; delete (*it).first; return temp; } } return temp; } return NULL; } template <class Type> int AbstractRManagers<Type>::get(Type* i) { for(int i2=0;i2<m_resources.size();i2++) { if(i == m_resources[i2]) { return i2; } } return -1; } template <class Type> Type* AbstractRManagers<Type>::get(int i) { if((i < m_resources.size())&&(i >= 0)) { return m_resources[i]; } return NULL; } template <class Type> Type* AbstractRManagers<Type>::getS(std::string name) { return m_resources[m_map[name]]; } template <class Type> int AbstractRManagers<Type>::get(std::string name) { return m_map[name]; } template <class Type> AbstractRManagers<Type>::~AbstractRManagers() { } #endif #include "AbstractRManagers.h" struct b { float x; }; int main() { b* a = new b(); AbstractRManagers<b>::getInstance()->insert(a,"a"); return 0; } This program produces next errors when compiled : 1> main.cpp 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1> c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(124) : while compiling class template member function 'bool std::less<_Ty>::operator ()(const _Ty &,const _Ty &) const' 1> with 1> [ 1> _Ty=std::string 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\map(71) : see reference to class template instantiation 'std::less<_Ty>' being compiled 1> with 1> [ 1> _Ty=std::string 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(451) : see reference to class template instantiation 'std::_Tmap_traits<_Kty,_Ty,_Pr,_Alloc,_Mfl>' being compiled 1> with 1> [ 1> _Kty=std::string, 1> _Ty=int, 1> _Pr=std::less<std::string>, 1> _Alloc=std::allocator<std::pair<const std::string,int>>, 1> _Mfl=false 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(520) : see reference to class template instantiation 'std::_Tree_nod<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(659) : see reference to class template instantiation 'std::_Tree_val<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\map(81) : see reference to class template instantiation 'std::_Tree<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\users\chris\desktop\311\ideas\idea1\idea1\abstractrmanagers.h(28) : see reference to class template instantiation 'std::map<_Kty,_Ty>' being compiled 1> with 1> [ 1> _Kty=std::string, 1> _Ty=int 1> ] 1> c:\users\chris\desktop\311\ideas\idea1\idea1\abstractrmanagers.h(30) : see reference to class template instantiation 'AbstractRManagers<Type>' being compiled 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2676: binary '<' : 'const std::string' does not define this operator or a conversion to a type acceptable to the predefined operator ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

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• (C++) Linking with namespaces causes duplicate symbol error

  - by user577072

  Hello. For the past few days, I have been trying to figure out how to link the files for a CLI gaming project I have been working on. There are two halves of the project, the Client and the Server code. The client needs two libraries I've made. The first is a general purpose game board. This is split between GameEngine.h and GameEngine.cpp. The header file looks something like this namespace gfdGaming { // struct sqr_size { // Index x; // Index y; // }; typedef struct { Index x, y; } sqr_size; const sqr_size sPos = {1, 1}; sqr_size sqr(Index x, Index y); sqr_size ePos; class board { // Prototypes / declarations for the class } } And the CPP file is just giving everything content #include "GameEngine.h" type gfdGaming::board::functions The client also has game-specific code (in this case, TicTacToe) split into declarations and definitions (TTT.h, Client.cpp). TTT.h is basically #include "GameEngine.h" #define TTTtar "localhost" #define TTTport 2886 using namespace gfdGaming; void* turnHandler(void*); namespace nsTicTacToe { GFDCON gfd; const char X = 'X'; const char O = 'O'; string MPhostname, mySID; board TTTboard; bool PlayerIsX = true, isMyTurn; char Player = X, Player2 = O; int recon(string* datHolder = NULL, bool force = false); void initMP(bool create = false, string hn = TTTtar); void init(); bool isTie(); int turnPlayer(Index loc, char lSym = Player); bool checkWin(char sym = Player); int mainloop(); int mainloopMP(); }; // NS I made the decision to put this in a namespace to group it instead of a class because there are some parts that would not work well in OOP, and it's much easier to implement later on. I have had trouble linking the client in the past, but this setup seems to work. My server is also split into two files, Server.h and Server.cpp. Server.h contains exactly: #include "../TicTacToe/TTT.h" // Server needs a full copy of TicTacToe code class TTTserv; struct TTTachievement_requirement { Index id; Index loc; bool inUse; }; struct TTTachievement_t { Index id; bool achieved; bool AND, inSameGame; bool inUse; bool (*lHandler)(TTTserv*); char mustBeSym; int mustBePlayer; string name, description; TTTachievement_requirement steps[safearray(8*8)]; }; class achievement_core_t : public GfdOogleTech { public: // May be shifted to private TTTachievement_t list[safearray(8*8)]; public: achievement_core_t(); int insert(string name, string d, bool samegame, bool lAnd, int lSteps[8*8], int mbP=0, char mbS=0); }; struct TTTplayer_t { Index id; bool inUse; string ip, sessionID; char sym; int desc; TTTachievement_t Ding[8*8]; }; struct TTTgame_t { TTTplayer_t Player[safearray(2)]; TTTplayer_t Spectator; achievement_core_t achievement_core; Index cTurn, players; port_t roomLoc; bool inGame, Xused, Oused, newEvent; }; class TTTserv : public gSserver { TTTgame_t Game; TTTplayer_t *cPlayer; port_t conPort; public: achievement_core_t *achiev; thread threads[8]; int parseit(string tDat, string tsIP); Index conCount; int parseit(string tDat, int tlUser, TTTplayer_t** retval); private: int parseProto(string dat, string sIP); int parseProto(string dat, int lUser); int cycleTurn(); void setup(port_t lPort = 0, bool complete = false); public: int newEvent; TTTserv(port_t tlPort = TTTport, bool tcomplete = true); TTTplayer_t* userDC(Index id, Index force = false); int sendToPlayers(string dat, bool asMSG = false); int mainLoop(volatile bool *play); }; // Other void* userHandler(void*); void* handleUser(void*); And in the CPP file I include Server.h and provide main() and the contents of all functions previously declared. Now to the problem at hand I am having issues when linking my server. More specifically, I get a duplicate symbol error for every variable in nsTicTacToe (and possibly in gfdGaming as well). Since I need the TicTacToe functions, I link Client.cpp ( without main() ) when building the server ld: duplicate symbol nsTicTacToe::PlayerIsX in Client.o and Server.o collect2: ld returned 1 exit status Command /Developer/usr/bin/g++-4.2 failed with exit code 1 It stops once a problem is encountered, but if PlayerIsX is removed / changed temporarily than another variable causes an error Essentially, I am looking for any advice on how to better organize my code to hopefully fix these errors. Disclaimers: -I apologize in advance if I provided too much or too little information, as it is my first time posting -I have tried using static and extern to fix these problems, but apparently those are not what I need Thank you to anyone who takes the time to read all of this and respond =)

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• ASP.NET MVC2 Implementing Custom RoleManager problem

  - by ile

  To create a custom membership provider I followed these instructions: http://stackoverflow.com/questions/2771094/asp-net-mvc2-custom-membership and these: http://mattwrock.com/post/2009/10/14/Implementing-custom-Membership-Provider-and-Role-Provider-for-Authinticating-ASPNET-MVC-Applications.aspx So far, I've managed to implement custom membership provider and that part works fine. RoleManager still needs some modifications... Project structure: SAMembershipProvider.cs: public class SAMembershipProvider : MembershipProvider { #region - Properties - private int NewPasswordLength { get; set; } private string ConnectionString { get; set; } public bool enablePasswordReset { get; set; } public bool enablePasswordRetrieval { get; set; } public bool requiresQuestionAndAnswer { get; set; } public bool requiresUniqueEmail { get; set; } public int maxInvalidPasswordAttempts { get; set; } public int passwordAttemptWindow { get; set; } public MembershipPasswordFormat passwordFormat { get; set; } public int minRequiredNonAlphanumericCharacters { get; set; } public int minRequiredPasswordLength { get; set; } public string passwordStrengthRegularExpression { get; set; } public override string ApplicationName { get; set; } public override bool EnablePasswordRetrieval { get { return enablePasswordRetrieval; } } public override bool EnablePasswordReset { get { return enablePasswordReset; } } public override bool RequiresQuestionAndAnswer { get { return requiresQuestionAndAnswer; } } public override int MaxInvalidPasswordAttempts { get { return maxInvalidPasswordAttempts; } } public override int PasswordAttemptWindow { get { return passwordAttemptWindow; } } public override bool RequiresUniqueEmail { get { return requiresUniqueEmail; } } public override MembershipPasswordFormat PasswordFormat { get { return passwordFormat; } } public override int MinRequiredPasswordLength { get { return minRequiredPasswordLength; } } public override int MinRequiredNonAlphanumericCharacters { get { return minRequiredNonAlphanumericCharacters; } } public override string PasswordStrengthRegularExpression { get { return passwordStrengthRegularExpression; } } #endregion #region - Methods - public override void Initialize(string name, NameValueCollection config) { throw new NotImplementedException(); } public override bool ChangePassword(string username, string oldPassword, string newPassword) { throw new NotImplementedException(); } public override bool ChangePasswordQuestionAndAnswer(string username, string password, string newPasswordQuestion, string newPasswordAnswer) { throw new NotImplementedException(); } public override MembershipUser CreateUser(string username, string password, string email, string passwordQuestion, string passwordAnswer, bool isApproved, object providerUserKey, out MembershipCreateStatus status) { throw new NotImplementedException(); } public override bool DeleteUser(string username, bool deleteAllRelatedData) { throw new NotImplementedException(); } public override MembershipUserCollection FindUsersByEmail(string emailToMatch, int pageIndex, int pageSize, out int totalRecords) { throw new NotImplementedException(); } public override MembershipUserCollection FindUsersByName(string usernameToMatch, int pageIndex, int pageSize, out int totalRecords) { throw new NotImplementedException(); } public override MembershipUserCollection GetAllUsers(int pageIndex, int pageSize, out int totalRecords) { throw new NotImplementedException(); } public override int GetNumberOfUsersOnline() { throw new NotImplementedException(); } public override string GetPassword(string username, string answer) { throw new NotImplementedException(); } public override MembershipUser GetUser(object providerUserKey, bool userIsOnline) { throw new NotImplementedException(); } public override MembershipUser GetUser(string username, bool userIsOnline) { throw new NotImplementedException(); } public override string GetUserNameByEmail(string email) { throw new NotImplementedException(); } protected override void OnValidatingPassword(ValidatePasswordEventArgs e) { base.OnValidatingPassword(e); } public override string ResetPassword(string username, string answer) { throw new NotImplementedException(); } public override bool UnlockUser(string userName) { throw new NotImplementedException(); } public override void UpdateUser(MembershipUser user) { throw new NotImplementedException(); } public override bool ValidateUser(string username, string password) { AccountRepository accountRepository = new AccountRepository(); var user = accountRepository.GetUser(username); if (string.IsNullOrEmpty(password.Trim())) return false; if (user == null) return false; //string hash = EncryptPassword(password); var email = user.Email; var pass = user.Password; if (user == null) return false; if (pass == password) { //User = user; return true; } return false; } #endregion protected string EncryptPassword(string password) { //we use codepage 1252 because that is what sql server uses byte[] pwdBytes = Encoding.GetEncoding(1252).GetBytes(password); byte[] hashBytes = System.Security.Cryptography.MD5.Create().ComputeHash(pwdBytes); return Encoding.GetEncoding(1252).GetString(hashBytes); } } SARoleProvider.cs public class SARoleProvider : RoleProvider { AccountRepository accountRepository = new AccountRepository(); public override bool IsUserInRole(string username, string roleName) { return true; } public override string ApplicationName { get { throw new NotImplementedException(); } set { throw new NotImplementedException(); } } public override void AddUsersToRoles(string[] usernames, string[] roleNames) { throw new NotImplementedException(); } public override void RemoveUsersFromRoles(string[] usernames, string[] roleNames) { throw new NotImplementedException(); } public override void CreateRole(string roleName) { throw new NotImplementedException(); } public override bool DeleteRole(string roleName, bool throwOnPopulatedRole) { throw new NotImplementedException(); } public override bool RoleExists(string roleName) { throw new NotImplementedException(); } public override string[] GetRolesForUser(string username) { int rolesCount = 0; IQueryable<RoleViewModel> rolesNames; try { // get roles for this user from DB... rolesNames = accountRepository.GetRolesForUser(username); rolesCount = rolesNames.Count(); } catch (Exception ex) { throw ex; } string[] roles = new string[rolesCount]; int counter = 0; foreach (var item in rolesNames) { roles[counter] = item.RoleName.ToString(); counter++; } return roles; } public override string[] GetUsersInRole(string roleName) { throw new NotImplementedException(); } public override string[] FindUsersInRole(string roleName, string usernameToMatch) { throw new NotImplementedException(); } public override string[] GetAllRoles() { throw new NotImplementedException(); } } AccountRepository.cs public class RoleViewModel { public string RoleName { get; set; } } public class AccountRepository { private DB db = new DB(); public User GetUser(string email) { return db.Users.SingleOrDefault(d => d.Email == email); } public IQueryable<RoleViewModel> GetRolesForUser(string email) { var result = ( from role in db.Roles join user in db.Users on role.RoleID equals user.RoleID where user.Email == email select new RoleViewModel { RoleName = role.Name }); return result; } } webconfig <membership defaultProvider="SAMembershipProvider" userIsOnlineTimeWindow="15"> <providers> <clear/> <add name="SAMembershipProvider" type="SA_Contacts.Membership.SAMembershipProvider, SA_Contacts" connectionStringName ="ShinyAntConnectionString" /> </providers> </membership> <roleManager defaultProvider="SARoleProvider" enabled="true" cacheRolesInCookie="true"> <providers> <clear/> <add name="SARoleProvider" type="SA_Contacts.Membership.SARoleProvider" connectionStringName ="ShinyAntConnectionString" /> </providers> </roleManager> AccountController.cs: public class AccountController : Controller { SAMembershipProvider provider = new SAMembershipProvider(); AccountRepository accountRepository = new AccountRepository(); public AccountController() { } public ActionResult LogOn() { return View(); } [AcceptVerbs(HttpVerbs.Post)] public ActionResult LogOn(string userName, string password, string returnUrl) { if (!ValidateLogOn(userName, password)) { return View(); } var user = accountRepository.GetUser(userName); var userFullName = user.FirstName + " " + user.LastName; FormsAuthentication.SetAuthCookie(userFullName, false); if (!String.IsNullOrEmpty(returnUrl) && returnUrl != "/") { return Redirect(returnUrl); } else { return RedirectToAction("Index", "Home"); } } public ActionResult LogOff() { FormsAuthentication.SignOut(); return RedirectToAction("Index", "Home"); } private bool ValidateLogOn(string userName, string password) { if (String.IsNullOrEmpty(userName)) { ModelState.AddModelError("username", "You must specify a username."); } if (String.IsNullOrEmpty(password)) { ModelState.AddModelError("password", "You must specify a password."); } if (!provider.ValidateUser(userName, password)) { ModelState.AddModelError("_FORM", "The username or password provided is incorrect."); } return ModelState.IsValid; } } In some testing controller I have following: [Authorize] public class ContactsController : Controller { SAMembershipProvider saMembershipProvider = new SAMembershipProvider(); SARoleProvider saRoleProvider = new SARoleProvider(); // // GET: /Contact/ public ActionResult Index() { string[] roleNames = Roles.GetRolesForUser("[email protected]"); // Outputs admin ViewData["r1"] = roleNames[0].ToString(); // Outputs True // I'm not even sure if this method is the same as the one below ViewData["r2"] = Roles.IsUserInRole("[email protected]", roleNames[0].ToString()); // Outputs True ViewData["r3"] = saRoleProvider.IsUserInRole("[email protected]", "admin"); return View(); } If I use attribute [Authorize] then everything works ok, but if I use [Authorize(Roles="admin")] then user is always rejected, like he is not in role. Any idea of what could be wrong here? Thanks in advance, Ile

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• What to Return? Error String, Bool with Error String Out, or Void with Exception

  - by Ranger Pretzel

  I spend most of my time in C# and am trying to figure out which is the best practice for handling an exception and cleanly return an error message from a called method back to the calling method. For example, here is some ActiveDirectory authentication code. Please imagine this Method as part of a Class (and not just a standalone function.) bool IsUserAuthenticated(string domain, string user, string pass, out errStr) { bool authentic = false; try { // Instantiate Directory Entry object DirectoryEntry entry = new DirectoryEntry("LDAP://" + domain, user, pass); // Force connection over network to authenticate object nativeObject = entry.NativeObject; // No exception thrown? We must be good, then. authentic = true; } catch (Exception e) { errStr = e.Message().ToString(); } return authentic; } The advantages of doing it this way are a clear YES or NO that you can embed right in your If-Then-Else statement. The downside is that it also requires the person using the method to supply a string to get the Error back (if any.) I guess I could overload this method with the same parameters minus the "out errStr", but ignoring the error seems like a bad idea since there can be many reasons for such a failure... Alternatively, I could write a method that returns an Error String (instead of using "out errStr") in which a returned empty string means that the user authenticated fine. string AuthenticateUser(string domain, string user, string pass) { string errStr = ""; try { // Instantiate Directory Entry object DirectoryEntry entry = new DirectoryEntry("LDAP://" + domain, user, pass); // Force connection over network to authenticate object nativeObject = entry.NativeObject; } catch (Exception e) { errStr = e.Message().ToString(); } return errStr; } But this seems like a "weak" way of doing things. Or should I just make my method "void" and just not handle the exception so that it gets passed back to the calling function? void AuthenticateUser(string domain, string user, string pass) { // Instantiate Directory Entry object DirectoryEntry entry = new DirectoryEntry("LDAP://" + domain, user, pass); // Force connection over network to authenticate object nativeObject = entry.NativeObject; } This seems the most sane to me (for some reason). Yet at the same time, the only real advantage of wrapping those 2 lines over just typing those 2 lines everywhere I need to authenticate is that I don't need to include the "LDAP://" string. The downside with this way of doing it is that the user has to put this method in a try-catch block. Thoughts? Is there another way of doing this that I'm not thinking of?

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• Put indexes on a table with lots of BOOL/TINYINT?

  - by John Tyler

  An old mentor once told me to place indexes on most things you use a WHERE clause for. Should I put an index on BOOL/TINYINT's? There is a significant amount of them in the table I am working with, and often results are filtered by anywhere from 1-20 of these boolean conditions.

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• Some non-generic collections

  - by Simon Cooper

  Although the collections classes introduced in .NET 2, 3.5 and 4 cover most scenarios, there are still some .NET 1 collections that don't have generic counterparts. In this post, I'll be examining what they do, why you might use them, and some things you'll need to bear in mind when doing so. BitArray System.Collections.BitArray is conceptually the same as a List<bool>, but whereas List<bool> stores each boolean in a single byte (as that's what the backing bool[] does), BitArray uses a single bit to store each value, and uses various bitmasks to access each bit individually. This means that BitArray is eight times smaller than a List<bool>. Furthermore, BitArray has some useful functions for bitmasks, like And, Xor and Not, and it's not limited to 32 or 64 bits; a BitArray can hold as many bits as you need. However, it's not all roses and kittens. There are some fundamental limitations you have to bear in mind when using BitArray: It's a non-generic collection. The enumerator returns object (a boxed boolean), rather than an unboxed bool. This means that if you do this: foreach (bool b in bitArray) { ... } Every single boolean value will be boxed, then unboxed. And if you do this: foreach (var b in bitArray) { ... } you'll have to manually unbox b on every iteration, as it'll come out of the enumerator an object. Instead, you should manually iterate over the collection using a for loop: for (int i=0; i<bitArray.Length; i++) { bool b = bitArray[i]; ... } Following on from that, if you want to use BitArray in the context of an IEnumerable<bool>, ICollection<bool> or IList<bool>, you'll need to write a wrapper class, or use the Enumerable.Cast<bool> extension method (although Cast would box and unbox every value you get out of it). There is no Add or Remove method. You specify the number of bits you need in the constructor, and that's what you get. You can change the length yourself using the Length property setter though. It doesn't implement IList. Although not really important if you're writing a generic wrapper around it, it is something to bear in mind if you're using it with pre-generic code. However, if you use BitArray carefully, it can provide significant gains over a List<bool> for functionality and efficiency of space. OrderedDictionary System.Collections.Specialized.OrderedDictionary does exactly what you would expect - it's an IDictionary that maintains items in the order they are added. It does this by storing key/value pairs in a Hashtable (to get O(1) key lookup) and an ArrayList (to maintain the order). You can access values by key or index, and insert or remove items at a particular index. The enumerator returns items in index order. However, the Keys and Values properties return ICollection, not IList, as you might expect; CopyTo doesn't maintain the same ordering, as it copies from the backing Hashtable, not ArrayList; and any operations that insert or remove items from the middle of the collection are O(n), just like a normal list. In short; don't use this class. If you need some sort of ordered dictionary, it would be better to write your own generic dictionary combining a Dictionary<TKey, TValue> and List<KeyValuePair<TKey, TValue>> or List<TKey> for your specific situation. ListDictionary and HybridDictionary To look at why you might want to use ListDictionary or HybridDictionary, we need to examine the performance of these dictionaries compared to Hashtable and Dictionary<object, object>. For this test, I added n items to each collection, then randomly accessed n/2 items: So, what's going on here? Well, ListDictionary is implemented as a linked list of key/value pairs; all operations on the dictionary require an O(n) search through the list. However, for small n, the constant factor that big-o notation doesn't measure is much lower than the hashing overhead of Hashtable or Dictionary. HybridDictionary combines a Hashtable and ListDictionary; for small n, it uses a backing ListDictionary, but switches to a Hashtable when it gets to 9 items (you can see the point it switches from a ListDictionary to Hashtable in the graph). Apart from that, it's got very similar performance to Hashtable. So why would you want to use either of these? In short, you wouldn't. Any gain in performance by using ListDictionary over Dictionary<TKey, TValue> would be offset by the generic dictionary not having to cast or box the items you store, something the graphs above don't measure. Only if the performance of the dictionary is vital, the dictionary will hold less than 30 items, and you don't need type safety, would you use ListDictionary over the generic Dictionary. And even then, there's probably more useful performance gains you can make elsewhere.

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• Parsing "true" and "false" using Boost.Spirit.Lex and Boost.Spirit.Qi

  - by Andrew Ross

  As the first stage of a larger grammar using Boost.Spirit I'm trying to parse "true" and "false" to produce the corresponding bool values, true and false. I'm using Spirit.Lex to tokenize the input and have a working implementation for integer and floating point literals (including those expressed in a relaxed scientific notation), exposing int and float attributes. Token definitions #include <boost/spirit/include/lex_lexertl.hpp> namespace lex = boost::spirit::lex; typedef boost::mpl::vector<int, float, bool> token_value_type; template <typename Lexer> struct basic_literal_tokens : lex::lexer<Lexer> { basic_literal_tokens() { this->self.add_pattern("INT", "[-+]?[0-9]+"); int_literal = "{INT}"; // To be lexed as a float a numeric literal must have a decimal point // or include an exponent, otherwise it will be considered an integer. float_literal = "{INT}(((\\.[0-9]+)([eE]{INT})?)|([eE]{INT}))"; literal_true = "true"; literal_false = "false"; this->self = literal_true | literal_false | float_literal | int_literal; } lex::token_def<int> int_literal; lex::token_def<float> float_literal; lex::token_def<bool> literal_true, literal_false; }; Testing parsing of float literals My real implementation uses Boost.Test, but this is a self-contained example. #include <string> #include <iostream> #include <cmath> #include <cstdlib> #include <limits> bool parse_and_check_float(std::string const & input, float expected) { typedef std::string::const_iterator base_iterator_type; typedef lex::lexertl::token<base_iterator_type, token_value_type > token_type; typedef lex::lexertl::lexer<token_type> lexer_type; basic_literal_tokens<lexer_type> basic_literal_lexer; base_iterator_type input_iter(input.begin()); float actual; bool result = lex::tokenize_and_parse(input_iter, input.end(), basic_literal_lexer, basic_literal_lexer.float_literal, actual); return result && std::abs(expected - actual) < std::numeric_limits<float>::epsilon(); } int main(int argc, char *argv[]) { if (parse_and_check_float("+31.4e-1", 3.14)) { return EXIT_SUCCESS; } else { return EXIT_FAILURE; } } Parsing "true" and "false" My problem is when trying to parse "true" and "false". This is the test code I'm using (after removing the Boost.Test parts): bool parse_and_check_bool(std::string const & input, bool expected) { typedef std::string::const_iterator base_iterator_type; typedef lex::lexertl::token<base_iterator_type, token_value_type > token_type; typedef lex::lexertl::lexer<token_type> lexer_type; basic_literal_tokens<lexer_type> basic_literal_lexer; base_iterator_type input_iter(input.begin()); bool actual; lex::token_def<bool> parser = expected ? basic_literal_lexer.literal_true : basic_literal_lexer.literal_false; bool result = lex::tokenize_and_parse(input_iter, input.end(), basic_literal_lexer, parser, actual); return result && actual == expected; } but compilation fails with: boost/spirit/home/qi/detail/assign_to.hpp: In function ‘void boost::spirit::traits::assign_to(const Iterator&, const Iterator&, Attribute&) [with Iterator = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, Attribute = bool]’: boost/spirit/home/lex/lexer/lexertl/token.hpp:434: instantiated from ‘static void boost::spirit::traits::assign_to_attribute_from_value<Attribute, boost::spirit::lex::lexertl::token<Iterator, AttributeTypes, HasState>, void>::call(const boost::spirit::lex::lexertl::token<Iterator, AttributeTypes, HasState>&, Attribute&) [with Attribute = bool, Iterator = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, AttributeTypes = boost::mpl::vector<int, float, bool, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, HasState = mpl_::bool_<true>]’ ... backtrace of instantiation points .... boost/spirit/home/qi/detail/assign_to.hpp:79: error: no matching function for call to ‘boost::spirit::traits::assign_to_attribute_from_iterators<bool, __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, void>::call(const __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >&, const __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >&, bool&)’ boost/spirit/home/qi/detail/construct.hpp:64: note: candidates are: static void boost::spirit::traits::assign_to_attribute_from_iterators<bool, Iterator, void>::call(const Iterator&, const Iterator&, char&) [with Iterator = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >] My interpretation of this is that Spirit.Qi doesn't know how to convert a string to a bool - surely that's not the case? Has anyone else done this before? If so, how?

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• Erroneous/Incorrect C2248 error using Visual Studio 2010

  - by Dylan Bourque

  I'm seeing what I believe to be an erroneous/incorrect compiler error using the Visual Studio 2010 compiler. I'm in the process of up-porting our codebase from Visual Studio 2005 and I ran across a construct that was building correctly before but now generates a C2248 compiler error. Obviously, the code snippet below has been generic-ized, but it is a compilable example of the scenario. The ObjectPtr<T> C++ template comes from our codebase and is the source of the error in question. What appears to be happening is that the compiler is generating a call to the copy constructor for ObjectPtr<T> when it shouldn't (see my comment block in the SomeContainer::Foo() method below). For this code construct, there is a public cast operator for SomeUsefulData * on ObjectPtr<SomeUsefulData> but it is not being chosen inside the true expression if the ?: operator. Instead, I get the two errors in the block quote below. Based on my knowledge of C++, this code should compile. Has anyone else seen this behavior? If not, can someone point me to a clarification of the compiler resolution rules that would explain why it's attempting to generate a copy of the object in this case? Thanks in advance, Dylan Bourque Visual Studio build output: c:\projects\objectptrtest\objectptrtest.cpp(177): error C2248: 'ObjectPtr::ObjectPtr' : cannot access private member declared in class 'ObjectPtr' with [ T=SomeUsefulData ] c:\projects\objectptrtest\objectptrtest.cpp(25) : see declaration of 'ObjectPtr::ObjectPtr' with [ T=SomeUsefulData ] c:\projects\objectptrtest\objectptrtest.cpp(177): error C2248: 'ObjectPtr::ObjectPtr' : cannot access private member declared in class 'ObjectPtr' with [ T=SomeUsefulData ] c:\projects\objectptrtest\objectptrtest.cpp(25) : see declaration of 'ObjectPtr::ObjectPtr' with [ T=SomeUsefulData ] Below is a minimal, compilable example of the scenario: #include <stdio.h> #include <tchar.h> template<class T> class ObjectPtr { public: ObjectPtr<T> (T* pObj = NULL, bool bShared = false) : m_pObject(pObj), m_bObjectShared(bShared) {} ~ObjectPtr<T> () { Detach(); } private: // private, unimplemented copy constructor and assignment operator // to guarantee that ObjectPtr<T> objects are not copied ObjectPtr<T> (const ObjectPtr<T>&); ObjectPtr<T>& operator = (const ObjectPtr<T>&); public: T * GetObject () { return m_pObject; } const T * GetObject () const { return m_pObject; } bool HasObject () const { return (GetObject()!=NULL); } bool IsObjectShared () const { return m_bObjectShared; } void ObjectShared (bool bShared) { m_bObjectShared = bShared; } bool IsNull () const { return !HasObject(); } void Attach (T* pObj, bool bShared = false) { Detach(); if (pObj != NULL) { m_pObject = pObj; m_bObjectShared = bShared; } } void Detach (T** ppObject = NULL) { if (ppObject != NULL) { *ppObject = m_pObject; m_pObject = NULL; m_bObjectShared = false; } else { if (HasObject()) { if (!IsObjectShared()) delete m_pObject; m_pObject = NULL; m_bObjectShared = false; } } } void Detach (bool bDeleteIfNotShared) { if (HasObject()) { if (bDeleteIfNotShared && !IsObjectShared()) delete m_pObject; m_pObject = NULL; m_bObjectShared = false; } } bool IsEqualTo (const T * pOther) const { return (GetObject() == pOther); } public: T * operator -> () { ASSERT(HasObject()); return m_pObject; } const T * operator -> () const { ASSERT(HasObject()); return m_pObject; } T & operator * () { ASSERT(HasObject()); return *m_pObject; } const T & operator * () const { ASSERT(HasObject()); return (const C &)(*m_pObject); } operator T * () { return m_pObject; } operator const T * () const { return m_pObject; } operator bool() const { return (m_pObject!=NULL); } ObjectPtr<T>& operator = (T * pObj) { Attach(pObj, false); return *this; } bool operator == (const T * pOther) const { return IsEqualTo(pOther); } bool operator == (T * pOther) const { return IsEqualTo(pOther); } bool operator != (const T * pOther) const { return !IsEqualTo(pOther); } bool operator != (T * pOther) const { return !IsEqualTo(pOther); } bool operator == (const ObjectPtr<T>& other) const { return IsEqualTo(other.GetObject()); } bool operator != (const ObjectPtr<T>& other) const { return !IsEqualTo(other.GetObject()); } bool operator == (int pv) const { return (pv==NULL)? IsNull() : (LPVOID(m_pObject)==LPVOID(pv)); } bool operator != (int pv) const { return !(*this == pv); } private: T * m_pObject; bool m_bObjectShared; }; // Some concrete type that holds useful data class SomeUsefulData { public: SomeUsefulData () {} ~SomeUsefulData () {} }; // Some concrete type that holds a heap-allocated instance of // SomeUsefulData class SomeContainer { public: SomeContainer (SomeUsefulData* pUsefulData) { m_pData = pUsefulData; } ~SomeContainer () { // nothing to do here } public: bool EvaluateSomeCondition () { // fake condition check to give us an expression // to use in ?: operator below return true; } SomeUsefulData* Foo () { // this usage of the ?: operator generates a C2248 // error b/c it's attempting to call the copy // constructor on ObjectPtr<T> return EvaluateSomeCondition() ? m_pData : NULL; /**********[ DISCUSSION ]********** The following equivalent constructs compile w/out error and behave correctly: (1) explicit cast to SomeUsefulData* as a comiler hint return EvaluateSomeCondition() ? (SomeUsefulData *)m_pData : NULL; (2) if/else instead of ?: if (EvaluateSomeCondition()) return m_pData; else return NULL; (3) skip the condition check and return m_pData as a SomeUsefulData* directly return m_pData; **********[ END DISCUSSION ]**********/ } private: ObjectPtr<SomeUsefulData> m_pData; }; int _tmain(int argc, _TCHAR* argv[]) { return 0; }

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• Best way to check for nullable bool in a condition expression (if ...)

  - by FireSnake

  I was wondering what was the most clean and understandable syntax for doing condition checks on nullable bools. Is the following good or bad coding style? Is there a way to express the condition better/more cleanly? bool? nullableBool = true; if (nullableBool ?? false) { ... } else { ... } especially the if (nullableBool ?? false) part. I don't like the if (x.HasValue && x.Value) style ... (not sure whether the question has been asked before ... couldn't find something similar with the search)

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• Is it good practice to avoid declaring a pointer to BOOL type in objective C?

  - by Krishnan

  I read this question in stackoverflow. The excerpt answer provided by bbum is below: The problem isn't the assignment, it is much more likely that you declared your instance variable to be BOOL *initialBroadcast;. There is no reason to declare the instance variable to be a pointer (at least not unless you really do need a C array of BOOLs).. Remove the * from the declaration. 1.Is there anything wrong in using a pointer variable even when I do not have to maintain an array of BOOLs? 2.I think even if avoiding them a good practice, it is not specific to objective-C and applies to all programming languages which has pointers. Please answer my questions.

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• C++ volatile required when spinning on boost::shared_ptr operator bool()?

  - by JaredC

  I have two threads referencing the same boost::shared_ptr: boost::shared_ptr<Widget> shared; On thread is spinning, waiting for the other thread to reset the boost::shared_ptr: while(shared) boost::thread::yield(); And at some point the other thread will call: shared.reset(); My question is whether or not I need to declare the shared pointer as volatile to prevent the compiler from optimizing the call to shared.operator bool() out of the loop and never detecting the change? I know that if I were simply looping on a variable, waiting for it to reach 0 I would need volatile, but I'm not sure if boost::shared_ptr is implemented in such a way that it is not necessary here.

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