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  • Why would you precede the main() function in C with a data type?

    - by Milktrader
    Many are familiar with the hello world program in C #include <stdio.h> main () { printf ("hello world"); return 0; } Why do some precede the main () function with int as in: int main() Also, I've seen the word 'void' entered inside the () as in: int main(void) It seems like extra typing for nothing, but maybe it's a best practice that pays dividends in other situations? Also, why precede main() with an int if you're returning a character string? If anything, one would expect: char main(void) I'm also foggy about why we return 0 at the end of the function.

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  • Why this function overloading is not working?

    - by Jack
    class CConfFile { public: CConfFile(const std::string &FileName); ~CConfFile(); ... std::string GetString(const std::string &Section, const std::string &Key); void GetString(const std::string &Section, const std::string &Key, char *Buffer, unsigned int BufferSize); ... } string CConfFile::GetString(const string &Section, const string &Key) { return GetKeyValue(Section, Key); } void GetString(const string &Section, const string &Key, char *Buffer, unsigned int BufferSize) { string Str = GetString(Section, Key); // *** ERROR *** strncpy(Buffer, Str.c_str(), Str.size()); } Why do I get an error too few arguments to function ‘void GetString(const std::string&, const std::string&, char*, unsigned int)' at the second function ? Thanks

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  • C - Call a function

    - by Pedro
    Hello. I want to get a value from a function in other function i think i have to call a function in other function, then call it on main, but how? void funcA(PEOPLE people[], int *total){ FILE *fp; char line[100]; fp=fopen("example.txt","r"); if(fp==NULL){ exit(1); } else{ fgets(line, 100, fp);//get a number from the txt total=atoi(linha);//convert to int } } void funcB(PEOPLE people[], int *total){ int i; for(i=0;i<total;i++){ printf("%s\n",people[i].name); } funcA(people,&total); } void main(){ PERSON person[100]; int *total; funcB(people,&total); } What i'm doing wrong?

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  • C++ performance, optimizing compiler, empty function in .cpp

    - by Dodo
    I've a very basic class, name it Basic, used in nearly all other files in a bigger project. In some cases, there needs to be debug output, but in release mode, this should not be enabled and be a NOOP. Currently there is a define in the header, which switches a makro on or off, depending on the setting. So this is definetely a NOOP, when switched off. I'm wondering, if I have the following code, if a compiler (MSVS / gcc) is able to optimize out the function call, so that it is again a NOOP. (By doing that, the switch could be in the .cpp and switching will be much faster, compile/link time wise). --Header-- void printDebug(const Basic* p); class Basic { Basic() { simpleSetupCode; // this should be a NOOP in release, // but constructor could be inlined printDebug(this); } }; --Source-- // PRINT_DEBUG defined somewhere else or here #if PRINT_DEBUG void printDebug(const Basic* p) { // Lengthy debug print } #else void printDebug(const Basic* p) {} #endif

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  • ASP.NET null reference exception

    - by nanek
    Please help me to figure out what is wrong with this code: I have ASP.NET page with one button visible. When user clicks it - it instances MyClass (its implementation is in AppCode directory) and turns invisible (button2 becomes visible). When I click button2 it raises "Object reference not set to an instance of an object" Exception. What seems to be the problem? { public MyClass noviTest; protected void Page_Load(object sender, EventArgs e) { } protected void Button1_Click(object sender, EventArgs e) { noviTest = new MyClass(TextBox1.Text); Button1.Visible = false; Button2.Visible = true; } protected void Button2_Click(object sender, EventArgs e) { Label1.Text=noviTest.getID; //this is the critical line } } Thank You in advance, Regards

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  • XAML-based applications - Event Naming Conventions for C#

    - by user118190
    For event handling, I am starting to see many coders doing this: XButton.Click += OnXButtonClicked() ... void OnXButtonClicked() { ... } Where did this On_ convention come from? It just doesn't feel right in terms of methods. I am starting to see this as well and am wondering what others thought: XButton.Click += HandleXButtonClick() ... void HandleXButtonClick() { ... } When using intellisense, Visual Studio handles these like so: XButton.Click += XButton_Click; ... void XButton_Click(object sender, RoutedEventArgs e) { ... } I am seeking some advice on these naming conventions and would greatly appreciate some advice.

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  • What does this recursive function do?

    - by null
    What does this function do? And how do you evaluate it? How to trace it? How to understand recursive method? I just can't understand the recursion, and the exam date is coming soon, and I know in order to understand recursion, I must first understand recursion. But I just can't write a slightly complex recursive method, can anyone help me out using the simplest English words. public class BalancedStrings { public static void printBalanced(String prefix, int a, int b) { if (a > 0) printBalanced(prefix + "a", a - 1, b); if (b > 0) printBalanced(prefix + "b", a, b - 1); if (a == 0 && b == 0) System.out.println(prefix); } public static void printBalanced(int n) { if (n % 2 == 0) { printBalanced("", n / 2, n / 2); } } public static void main(String[] args) { printBalanced(4); } }

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  • Event handling C# / Registering a callback

    - by Jeff Dahmer
    Events can only return void and recieve object sender/eventargs right? If so then craptastic.... how can I pass a function pointer to another obj, like: public bool ACallBackFunc(int n) { return n > 0; } public void RegisterCallback(Something s) { s.GiveCallBack(this.ACallBackFunc); } Something::GiveCallBack(Action? funcPtr) I tried using Action, but I need it to return some value and Actions can only return void. Also, we do not know what kind of a callback we will be recieving; it could return anything and have any params! Reflection will have to be used somehow I reckon.

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  • Java Thread Message Passing

    - by pkulak
    I'm writing an Android app. I have a main method, which creates and runs a new Thread using an anonymous inner Runnable class. The run() method, when it's done, calls a method on it's parent class (in the main thread) that calls notifyDataSetChanged() so that the main thread can redraw the new data. This is causing all kinds of trouble (ViewRoot$CalledFromWrongThreadException). The thing is, this method being called from the worker thread is on the class that's created in the UI thread. Shouldn't that be running on the UI thread? Or am I missing something? Here's some code about what I'm talking about: public class Mealfire extends Activity { @Override public void onCreate(Bundle icicle) { (new Thread() { public void run() { // Do a bunch of slow network stuff. update(); } }).start(); } private void update() { myAdapter.notifyDatasetChanged(); } }

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  • C++ Basic Class Layout

    - by Spencer
    Learning C++ and see the class laid out like this: class CRectangle { int x, y; public: void set_values (int,int); int area () {return (x*y);} }; void CRectangle::set_values (int a, int b) { x = a; y = b; } I know Java and methods(functions) in Java are written within the class. The class looks like a Java interface. I know I can write the class like this: class CRectangle { int x, y; public: void set_values (int a, int b) { x = a; y = b; }; int area () {return (x*y);} }; But is there a difference or standard?

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  • Debug.writeline locks

    - by Carra
    My program frequently stops with a deadlock. When I do a break-all and look at the threads I see that three threads are stuck in our logging function: public class Logging { public static void WriteClientLog(LogLevel logLevel, string message) { #if DEBUG System.Diagnostics.Debug.WriteLine(String.Format("{0} {1}", DateTime.Now.ToString("HH:mm:ss"), message)); //LOCK #endif //...Log4net logging } } If I let the program continue the threads are still stuck on that line. I can't see where this can lock. The debug class, string class & datetime class seem to be thread safe. The error goes away when I remove the "#if DEBUG System... #endif" code but I'm curious why this behavior happens. Thread one: public void CleanCache() { Logging.WriteClientLog(LogLevel.Debug, "Start clean cache.");//Stuck } Thread two: private void AliveThread() { Logging.WriteClientLog(LogLevel.Debug, "Check connection");//Stuck }

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  • Global variable in a recursive function how to keep it at zero?

    - by Grammin
    So if I have a recursive function with a global variable var_: int var_; void foo() { if(var_ == 3) return; else var_++; foo(); } and then I have a function that calls foo() so: void bar() { foo(); return; } what is the best way to set var_ =0 everytime foo is called thats not from within itself. I know I could just do: void bar() { var_ =0; foo(); return; } but I'm using the recursive function a lot and I don't want to call foo and forget to set var_=0 at a later date. Does anyone have any suggestions on how to solve this? Thanks, Josh

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  • Is there some way to assume @Nullable as default? (using FindBugs or any other free tool).

    - by alex2k8
    Consider such code public void m1(String text) { if(text == null) text = "<empty>"; System.out.println(text.toLowerCase()); } And this is a buggy version: public void m1(String text) { System.out.println(text.toLowerCase()); } If null value passed, the NullPointerException may be thrown. I would like the static-analysis tool (e.g. FindBugs) to report this issue. Unsuccessfully the FindBugs (at least by default) requires me to specify @Nullable annotation explicitly. public void m1(@Nullable String text) { System.out.println(text.toLowerCase()); // FindBugs: text must be nonnull but is marked as nullable } The problem is that if I forget to annotate it, the bug will be missed!!! How can I make the FindBugs (or any other free tool) to assume @Nullable by default?

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  • Overriding vs Virtual

    - by anonymous
    What is the purpose of using the reserved word virtual in front of functions? If I want a child class to override a parent function, I just declare the same function such as "void draw(){}". class Parent{ public: void say(){ std::cout << "1"; }}; class Child : public Parent{public:void say(){ std::cout << "2"; } }; int main() { Child* a = new Child(); a->say(); return 0; } The output is 2. So again, why would the reserved word "virtual" be necessary in the header of say() ? Thanks a bunch.

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  • Please see following code and answer

    - by user323422
    template <class T> class _cExplicitInstation { public: void show1(T c) { double d =10.02 ; std::cout<<c; } void show2(T d) { std::cout<<d; } }; template _cExplicitInstation<char>; template void _cExplicitInstation<int>::show1(int c); int main() { _cExplicitInstation<char> abc; _cExplicitInstation<int>().show2(10);// it should show error as i have // explicitly declare for show1() function but its working // can u tell why? }

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  • [C] How I change a variable of a type to another one?

    - by drigoSkalWalker
    I want to do it: int main () { bla bla bla void *onetype; switch (USER_INPUT_TYPE) { CASE CONVERT_TO_CHAR: convert onetype VOID TO CHAR HOW??? CASE CONVERT_TO_INT: convert onetype VOID TO INT HOW??? LOT OF CASES... } } Yes, I know type casting, but type casting is a 'temporary' change... So...Is there any way to accomplish it in C? EDIT : Stop stop stop! Please, see, what are you doing is type casting, I KNOW THIS, you are creating another variable of the desirable type like int i = (int) onetype, I don't want this, I want something else like onetype = (int) onetype, without recreate them, without allocate another variable. Thanks a lot guys!

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  • Access WindowedApplication from package class.

    - by Senling
    Hi, I'm developing an AIR application, where i need to access WindowedApplication's function from the package class. This is the Main application (Partial code) import mx.events.CloseEvent; import messages.MessageWindow public function undock():void { stage.nativeWindow.visible = true; stage.nativeWindow.orderToFront(); //Clearing the bitmaps array also clears the applcation icon from the systray NativeApplication.nativeApplication .icon.bitmaps = []; } ]] Package: (Partial code) package messages { public class MessageWindow extends NativeWindow { public function MessageWindow():void { stage.addEventListener(MouseEvent.MOUSE_DOWN,onClick); } private function onClick(event:MouseEvent):void { ****** Need to call the undock method from here. ***** } } } Is it possible to call this way or suggest any other solution Thanks in advance Senling.

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  • Audio File continues to play even on leaving the view

    - by Swastik
    What I am doing is -(void)viewWillAppear:(BOOL)animated{ [NSTimer scheduledTimerWithTimeInterval:0.3 target:self selector:@selector(clickEvent:) userInfo:nil repeats:YES]; } -(void)clickEvent:(NSTimer *)aTimer{ NSDate* finishDate = [NSDate date]; if([finishDate timeIntervalSinceDate: self.startDate] 11 && touched == NO){ NSString *mp3Path = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"test.mp3"]; [self playMusicFile:mp3Path]; NSLog(@"Timer from First Page"); [aTimer invalidate]; //[touchCheckTimer release]; aTimer = nil; } else{ } -(void)playMusicFile:(NSString *)mp3Path{ NSURL *mp3Url = [NSURL fileURLWithPath:mp3Path]; NSError *err; AVAudioPlayer *audPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:mp3Url error:&err]; [self setAudioPlayer1:audPlayer]; if(audioPlayer1) [audioPlayer1 play]; [audPlayer release]; } Now, on pushing another view this audio file keeps playing in the background. Please help!

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  • Why does the compiler give an ambiguous invocation error when passing inherited types?

    - by Matt Mitchell
    What is happening in the C# compiler to cause the following ambiguous invocation compilation error? The same issue applies to extension methods, or when TestClass is generic and using instance rather than static methods. class Type1 { } class Type2 : Type1 {} class TestClass { public static void Do<T>(T something, object o) where T : Type1 {} public static void Do(Type1 something, string o) {} } void Main() { var firstInstance = new Type1(); TestClass.Do(firstInstance, new object()); // Calls Do(Type1, obj) TestClass.Do(firstInstance, "Test"); // Calls Do<T>(T, string) var secondInstance = new Type2(); TestClass.Do(secondInstance, new object()); // Calls Do(Type1, obj) TestClass.Do(secondInstance, "Test"); // "The call is ambiguous" compile error }

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  • c++ signatures, pointers

    - by coubeatczech
    Hello, what's the difference between these signatures? T * f(T & identifier); T & f(T & identifier); T f(T & identifier); void f(T * identifier); void f(T & identifier); void f(T identifier); I met pointers in c, but the amperstand in function signature is new for me. Can Anyone explain this?

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  • StructureMap: How can i unit test the registry class?

    - by Marius
    I have a registry class like this: public class StructureMapRegistry : Registry { public StructureMapRegistry() { For<IDateTimeProvider>().Singleton().Use<DateTimeProviderReturningDateTimeNow>(); } I want to test that the configuration is according to my intent, so i start writing a test: public class WhenConfiguringIOCContainer : Scenario { private TfsTimeMachine.Domain.StructureMapRegistry registry; private Container container; protected override void Given() { registry = new TfsTimeMachine.Domain.StructureMapRegistry(); container = new Container(); } protected override void When() { container.Configure(i => i.AddRegistry(registry)); } [Then] public void DateTimeProviderIsRegisteredAsSingleton() { // I want to say "verify that the container contains the expected type and that the expected type // is registered as a singleton } } How can verify that the registry is accoring to my expectations? Note: I introduced the container because I didn't see any sort of verification methods available on the Registry class. Idealy, I want to test on the registry class directly.

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  • Application_EndRequest Dosent Fire on a 404

    - by Shane
    I am using ASP MVC 2 and Nhibernate. I have created an HTTP Module as demonstrated in Summer of NHibernate 13 that looks like so: public void Init(HttpApplication context) { context.PreRequestHandlerExecute += new EventHandler(Application_BeginRequest); context.PostRequestHandlerExecute += new EventHandler(Application_EndRequest); } private void Application_BeginRequest(object sender, EventArgs e) { ISession session = StaticSessionManager.OpenSession(); session.BeginTransaction(); CurrentSessionContext.Bind(session); } private void Application_EndRequest(object sender, EventArgs e) { ISession session = CurrentSessionContext.Unbind(StaticSessionManager.SessionFactory); if (session != null) try { session.Transaction.Commit(); } catch (Exception) { session.Transaction.Rollback(); } finally { session.Flush(); session.Close(); } } web.config <add name="UnitOfWork" type="HttpModules.UnitOfWork"/> My problem is that Application_EndRequest never gets called on a 404 error so if my view does not render I completely block database access until my flush takes place. I am fairly new to NHibernate so I am not sure if I am missing something.

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  • c++ design question: Can i query the base classes to find the number of derived classes satisfying a

    - by vivekeviv
    I have a piece of code like this class Base { public: Base(bool _active) { active = _active; } void Configure(); void Set Active(bool _active); private: bool active; }; class Derived1 : public Base { public: Derived1(bool active):Base(active){} }; similarly Derived 2 and Derived 3 Now if i call derived1Object.Configure, i need to check how many of the derived1Obj, derived2Obj,derived3Obj is active. Should i add this in the "Base" class like a function say, GetNumberOfActive()? And If the implementation is like this: class Imp { public: void Configure() { //Code instantiating a particular Derived1/2/3 Object int GetNumberOfActiveDerivedObj(); baseRef.Configure(int numberOfActiveDerivedClasses); } prive: Derived1 dObj1(true); Derived2 dObj2(false); Derived3 dObj3(true); }; should i calculate the numberOfActive Derived Objects in Imp Class? THanks

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  • Why is the output like this?

    - by javatechi
    class another { public void method(Object o) { System.out.println("This is in method which takes object"); } public void method(String s) { System.out.println("This is method which takes string"); } } public class NewClass { public static void main(String args[]) { another an = new another(); an.method(null); } } When I try to execute this, I get This is method which takes string as the output. Why not "This is in method which takes object"? Object can also be null and string can also be null, why doesn't it invoke first method?

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