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  • Unresolved External Symbol linker error (C++)

    - by Niranjan
    Hi, I am trying to develop abstract design pattern code for one of my project as below.. But, I am not able to compile the code ..giving some compile errors(like "unresolved external symbol "public: virtual void __thiscall Xsecs::draw_lines(double,double)" (?draw_lines@Xsecs@@UAEXNN@Z)" ).. Can any one please help me out in this... #include "stdafx.h" #include <iostream> #include <vector> #include "Xsecs.h" using namespace std; //Product class class Xsecs { public: virtual void draw_lines(double pt1, double pt2); virtual void draw_curves(double pt1, double rad); }; class polyline: public Xsecs { public: virtual void draw_lines(double pt1,double pt2) { cout<<"draw_line in polygon"<<endl; } virtual void draw_curves(double pt1, double rad) { cout<<"Draw_curve in circle"<<endl; } /*void create_polygons() { cout<<"create_polygon_thru_draw_lines"<<endl; }*/ }; class circle: public Xsecs { public: virtual void draw_lines(double pt1,double pt2) { cout<<"draw_line in polygon"<<endl; } virtual void draw_curves(double pt1, double rad) { cout<<"Draw_curve in circle"<<endl; } /*void create_circles() { cout<<"Create circle"<<endl; }*/ }; //Factory class class Factory { public: virtual polyline* create_polyline()=0; virtual circle* create_circle()=0; }; class Factory1: public Factory { public: polyline* create_polyline() { return new polyline(); } circle* create_circle() { return new circle(); } }; class Factory2: public Factory { public: circle* create_circle() { return new circle(); } polyline* create_polyline() { return new polyline(); } }; int _tmain(int argc, _TCHAR* argv[]) { Factory1 f1; Factory * fp=&f1; return 0; }

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  • Java init method

    - by Johan Sjöberg
    What's a good way to make sure an init method is invoked in java? The alternatives I see are Don't test it, let the method fail by itself, likely by a NullPointerException Test if method was initialized or throw public void foo() { if (!inited) { throw new IllegalArgumentException("not initalized"); } ... } Delagate public void foo() { if (!inited) { throw new IllegalArgumentException("not initalized"); } fooInternal(); } private void fooInternal(){ ... }; Always init, and make init a noop otherwise public void foo() { init(); ... } public void init() { if(!inited) { ... } } Silently init public void foo() { if (!inited) { init(); } ... } Most of these approaches are very verbose and decreases overall readability.

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  • calling c function from assembly

    - by void
    I'm trying to use a function in assembly in a C project, the function is supposed to call a libc function let's say printf() but I keep getting a segmentation fault. In the .c file I have the declaration of the function let's say int do_shit_in_asm() In the .asm file I have .extern printf .section .data printtext: .ascii "test" .section .text .global do_shit_in_asm .type do_shit_in_asm, @function do_shit_in_asm: pushl %ebp movl %esp, %ebp push printtext call printf movl %ebp, %esp pop %ebp ret Any pointers would be appreciated. as func.asm -o func.o gcc prog.c func.o -o prog

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  • String Vector program exits before input

    - by kylepayne
    So, I have a project that must add, delete, and print the contents of a vector... the problem is that, when run the program exits before I can type in the string to add to the vector. I commented the function that that portion is in. Thanks! #include <iostream> #include <cstdlib> #include <vector> #include <string> using namespace std; void menu(); void addvector(vector<string>& vec); void subvector(vector<string>& vec); void vectorsize(const vector<string>& vec); void printvec(const vector<string>& vec); void printvec_bw(const vector<string>& vec); int main() { vector<string> svector; menu(); return 0; } //functions definitions void menu() { vector<string> svector; int choice = 0; cout << "Thanks for using this program! \n" << "Enter 1 to add a string to the vector \n" << "Enter 2 to remove the last string from the vector \n" << "Enter 3 to print the vector size \n" << "Enter 4 to print the contents of the vector \n" << "Enter 5 ----------------------------------- backwards \n" << "Enter 6 to end the program \n"; cin >> choice; switch(choice) { case 1: addvector(svector); break; case 2: subvector(svector); break; case 3: vectorsize(svector); break; case 4: printvec(svector); break; case 5: printvec_bw(svector); break; case 6: exit(1); default: cout << "not a valid choice \n"; // menu is structured so that all other functions are called from it. } } void addvector(vector<string>& vec) { string line; int i = 0; cout << "Enter the string please \n"; getline(cin, line); // doesn't prompt for input! vec.push_back(line); } void subvector(vector<string>& vec) { vec.pop_back(); return; } void vectorsize(const vector<string>& vec) { if (vec.empty()) { cout << "vector is empty"; } else { cout << vec.size() << endl; } return; } void printvec(const vector<string>& vec) { for(int i = 0; i < vec.size(); i++) { cout << vec[i] << endl; } return; } void printvec_bw(const vector<string>& vec) { for(int i = vec.size(); i > 0; i--) { cout << vec[i] << endl; } return; }

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  • Cheapest way of binding local variable to closure

    - by mmotorny
    I believe following to be a cheapest way of binding local variable to closure: void ByRValueReference(A&& a) { } std::function<void ()> CreateClosureByRValueReference() { A a; std::function<void ()> f = std::bind(&ByRValueReference, std::move(a)); // !!! return f; } However, it does not compile under Clang 3.1: error: no viable conversion from '__bind<void (*)(A &&), A>' to 'std::function<void ()>' and gcc 4.6.1: /usr/include/c++/4.6/functional:1778:2: error: no match for call to ‘(std::_Bind<void (*(A))(A&&)>) ()’ Am I violating the standard or it's just broken standard libraries?

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  • Referenced vector does not pass through functions

    - by kylepayne
    The referenced vector to functions does not hold the information in memory. Do I have to use pointers? Thanks. #include <iostream> #include <cstdlib> #include <vector> #include <string> using namespace std; void menu(); void addvector(vector<string>& vec); void subvector(vector<string>& vec); void vectorsize(const vector<string>& vec); void printvec(const vector<string>& vec); void printvec_bw(const vector<string>& vec); int main() { vector<string> svector; menu(); return 0; } //functions definitions void menu() { vector<string> svector; int choice = 0; cout << "Thanks for using this program! \n" << "Enter 1 to add a string to the vector \n" << "Enter 2 to remove the last string from the vector \n" << "Enter 3 to print the vector size \n" << "Enter 4 to print the contents of the vector \n" << "Enter 5 ----------------------------------- backwards \n" << "Enter 6 to end the program \n"; cin >> choice; switch(choice) { case 1: addvector(svector); menu(); break; case 2: subvector(svector); menu(); break; case 3: vectorsize(svector); menu(); break; case 4: printvec(svector); menu(); break; case 5: printvec_bw(svector); menu(); break; case 6: exit(1); default: cout << "not a valid choice \n"; // menu is structured so that all other functions are called from it. } } void addvector(vector<string>& vec) { //string line; //int i = 0; //cin.ignore(1, '\n'); //cout << "Enter the string please \n"; //getline(cin, line); vec.push_back("the police man's beard is half-constructed"); } void subvector(vector<string>& vec) { vec.pop_back(); return; } void vectorsize(const vector<string>& vec) { if (vec.empty()) { cout << "vector is empty"; } else { cout << vec.size() << endl; } return; } void printvec(const vector<string>& vec) { for(int i = 0; i < vec.size(); i++) { cout << vec[i] << endl; } return; } void printvec_bw(const vector<string>& vec) { for(int i = vec.size(); i > 0; i--) { cout << vec[i] << endl; } return; }

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  • [Ruby] How can I randomly iterate through a large Range?

    - by void
    I would like to randomly iterate through a range. Each value will be visited only once and all values will eventually be visited. For example: (0..9).sort_by{rand}.map{|x| f(x)} where f(x) is some function that operates on each value. A Fisher-Yates shuffle could be used to increase efficiency, but this code is sufficient for many purposes. My problem is that sort_by will transform the range into an array, which is not cool because I am working with astronomically large numbers. Ruby will quickly consume a large amount of RAM trying to create a monstrous array. This is also why the following code will not work: tried = {} # store previous attempts bigint = 99**99 bigint.times { x = rand(bigint) redo if tried[x] tried[x] = true f(x) # some function } This code is very naive and quickly runs out of memory as tried obtains more entries. What sort of algorithm can accomplish what I am trying to do?

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  • Implementing Object Oriented: ansi-C approach

    - by No Money
    Hey there, I am an Intermediate programmer in Java and know some of the basics in C++. I recently started to scam over "C language" [please note that i emphasized on C language and want to stick with C as i found it to be a perfect tool, so no need for suggestions focusing on why should i move back to C++ or Java or any other crappy language (e.g: C#)]. Moving on, I code an Object Oriented approach in C but kindda scramble with the pointers part. Please understand that I am just a noob trying to extend my knowledge beyond what i learned in High School. Here is my code..... #include <stdio.h> typedef struct per{ int privateint; char *privateString; struct per (*New) (); void (*deleteperOBJ) (struct t_person *); void (*setperNumber) ((struct*) t_person,int); void (*setperString) ((struct*) t_person,char *); void (*dumpperState) ((struct*) t_person); }t_person; void setperNumber(t_person *const per,int num){ if(per==NULL) return; per->privateint=num; } void setperString(t_person *const per,char *string){ if(per==NULL) return; per->privateString=string; } void dumpperState(t_person *const per){ if(per==NULL) return; printf("value of private int==%d\n", per->privateint); printf("value of private string==%s\n", per->privateString); } void deleteperOBJ(struct t_person *const per){ free((void*)t_person->per); t_person ->per = NULL; } main(){ t_person *const per = (struct*) malloc(sizeof(t_person)); per = t_person -> struct per -> New(); per -> setperNumber (t_person *per, 123); per -> setperString(t_person *per, "No money"); dumpperState(t_person *per); deleteperOBJ(t_person *per); } Just to warn you, this program has several errors and since I am a beginner I couldn't help except to post this thread as a question. I am looking forward for assistance. Thanks in advance.

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  • Sprite not moving when using a function from another class SFML c++

    - by user2892932
    I have a Game.cpp, and I am calling a update function in my Player class. In my player update Function I have it to check for keyboard input, and it seems to work, but whenever I try to call the .move() function, it seems to not work. I get no errors either. I am new to sfml, and decent with c++. Help is appreciated! #include "Player.h" Player::Player(void): vel(0), maxvel(100) { Load("Assets/sss.png",true); } void Player::Update(sf::Sprite& p) { if (sf::Keyboard::isKeyPressed(sf::Keyboard::A)) { moveObject(-3,0, p); } if(sf::Keyboard::isKeyPressed(sf::Keyboard::D)) { moveObject(-3,0, p); } } Player::~Player(void) { } This is the GameObject cpp #include "GameObject.h" #include <iostream> GameObject::GameObject(void) { isLoaded = false; } void GameObject::Load(std::string flname, bool isPlayer) { if(!tex.loadFromFile(flname)) { EXIT_FAILURE; } else { if(isPlayer) { if(!tex.loadFromFile(flname, sf::IntRect(0,0,33,33))) { EXIT_FAILURE; } else { std::cout << "Loading image" << "\n"; filename = flname; spr.setTexture(tex); isLoaded = true; } } else { std::cout << "Loading image" << "\n"; filename = flname; spr.setTexture(tex); isLoaded = true; } } } void GameObject::Draw(sf::RenderWindow & window) { if(isLoaded) { window.draw(spr); window.display(); std::cout << "Sprite drew" << "\n"; } } void GameObject::setPos(float x, float y) { if(isLoaded) { spr.setPosition(x,y); } } sf::Vector2f GameObject::GetObjPos() { return spr.getPosition(); } sf::Sprite& GameObject::getSprite() { return spr; } void GameObject::moveObject(float x, float y, sf::Sprite& sp) { sp.move(x, y); } GameObject::~GameObject(void) { }

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  • How to use @BeforeClass and @AfterClass in JunitPerf?

    - by allenzzzxd
    Hi, I want to do some actions before the whole test suite (also after the suite). So I wrote like: public class PerformanceTest extends TestCase { @BeforeClass public static void suiteSetup() throws Exception { //do something } @AfterClass public static void suiteSetup() throws Exception { //do something } @Before public void setUp() throws Exception { //do something } @After public void tearDown() throws Exception { //do something } public PerformanceTest(String testName){ super(testName); } public static Test suite() { TestSuite suite = new TestSuite(); Test testcase1 = new PerformanceTest("DoTest1"); Test loadTest1 = new LoadTest(testcase1, n); Test testcase2 = new PerformanceTest("DoTest2"); Test loadTest2 = new LoadTest(testcase2, n); } public void DoTest1 throws Throwable{ //do something } public void DoTest2 throws Throwable{ //do something } } But I found that it never reach the code in @BeforeClass and @AfterClass. So how could I do to solve this problem? Or is there other way to realize this? Thank you for your help.

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  • Why is this std::bind not converted to std::function?

    - by dauphic
    Why is the nested std::bind in the below code not implicitly converted to an std::function<void()> by any of the major compilers (VS2010/2012, gcc, clang)? Is this standard behavior, or a bug? #include <functional> void bar(int, std::function<void()>) { } void foo() { } int main() { std::function<void(int, std::function<void()>)> func; func = std::bind(bar, 5, std::bind(foo)); std::cin.get(); return 0; }

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  • Creating ActionEvent object for CustomButton in Java

    - by Crystal
    For a hw assignment, we were supposed to create a custom button to get familiar with swing and responding to events. We were also to make this button an event source which confuses me. I have an ArrayList to keep track of listeners that would register to listen to my CustomButton. What I am getting confused on is how to notify the listeners. My teacher hinted at having a notify and overriding actionPerformed which I tried doing, but then I wasn't sure how to create an ActionEvent object looking at the constructor documentation. The source, id, string all confuses me. Any help would be appreciated. Thanks! code: import java.awt.*; import java.awt.event.*; import javax.swing.*; import java.util.List; import java.util.ArrayList; public class CustomButton { public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { public void run() { CustomButtonFrame frame = new CustomButtonFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); } }); } public void addActionListener(ActionListener al) { listenerList.add(al); } public void removeActionListener(ActionListener al) { listenerList.remove(al); } public void actionPerformed(ActionEvent e) { System.out.println("Button Clicked!"); } private void notifyListeners() { ActionEvent event = new ActionEvent(CONFUSED HERE!!!!; for (ActionListener action : listenerList) { action.actionPerfomed(event); } } List<ActionListener> listenerList = new ArrayList<ActionListener>(); } class CustomButtonFrame extends JFrame { // constructor for CustomButtonFrame public CustomButtonFrame() { setTitle("Custom Button"); CustomButtonSetup buttonSetup = new CustomButtonSetup(); this.add(buttonSetup); this.pack(); } } class CustomButtonSetup extends JComponent { public CustomButtonSetup() { ButtonAction buttonClicked = new ButtonAction(); this.addMouseListener(buttonClicked); } // because frame includes borders and insets, use this method public Dimension getPreferredSize() { return new Dimension(200, 200); } public void paintComponent(Graphics g) { Graphics2D g2 = (Graphics2D) g; // first triangle coords int x[] = new int[TRIANGLE_SIDES]; int y[] = new int[TRIANGLE_SIDES]; x[0] = 0; y[0] = 0; x[1] = 200; y[1] = 0; x[2] = 0; y[2] = 200; Polygon firstTriangle = new Polygon(x, y, TRIANGLE_SIDES); // second triangle coords x[0] = 0; y[0] = 200; x[1] = 200; y[1] = 200; x[2] = 200; y[2] = 0; Polygon secondTriangle = new Polygon(x, y, TRIANGLE_SIDES); g2.drawPolygon(firstTriangle); g2.setColor(firstColor); g2.fillPolygon(firstTriangle); g2.drawPolygon(secondTriangle); g2.setColor(secondColor); g2.fillPolygon(secondTriangle); // draw rectangle 10 pixels off border int s1[] = new int[RECT_SIDES]; int s2[] = new int[RECT_SIDES]; s1[0] = 5; s2[0] = 5; s1[1] = 195; s2[1] = 5; s1[2] = 195; s2[2] = 195; s1[3] = 5; s2[3] = 195; Polygon rectangle = new Polygon(s1, s2, RECT_SIDES); g2.drawPolygon(rectangle); g2.setColor(thirdColor); g2.fillPolygon(rectangle); } private class ButtonAction implements MouseListener { public void mousePressed(MouseEvent e) { System.out.println("Click!"); firstColor = Color.GRAY; secondColor = Color.WHITE; repaint(); } public void mouseReleased(MouseEvent e) { System.out.println("Released!"); firstColor = Color.WHITE; secondColor = Color.GRAY; repaint(); } public void mouseEntered(MouseEvent e) {} public void mouseExited(MouseEvent e) {} public void mouseClicked(MouseEvent e) {} } public static final int TRIANGLE_SIDES = 3; public static final int RECT_SIDES = 4; private Color firstColor = Color.WHITE; private Color secondColor = Color.DARK_GRAY; private Color thirdColor = Color.LIGHT_GRAY; }

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  • Does dynamic_cast work inside overloaded operator delete ?

    - by iammilind
    I came across this: struct Base { void* operator new (size_t); void operator delete (void*); virtual ~Base () {} // <--- polymorphic }; struct Derived : Base {}; void Base::operator delete (void *p) { Base *pB = static_cast<Base*>(p); if(dynamic_cast<Derived*>(pB) != 0) { /* ... NOT reaching here ? ... */ } free(p); } Now if we do, Base *p = new Derived; delete p; Surprisingly, the condition inside the Base::delete is not satisfied Am I doing anything wrong ? Or casting from void* looses the information of Derived* ?

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  • How do I combine similar method calls into a delegate pattern?

    - by Daniel T.
    I have three methods: public void Save<T>(T entity) { using (new Transaction()) { Session.Save(entity); } } public void Create<T>(T entity) { using (new Transaction()) { Session.Create(entity); } } public void Delete<T>(T entity) { using (new Transaction()) { Session.Delete(entity); } } As you can see, the only thing that differs is the method call inside the using block. How can I rewrite this so it's something like this instead: public void Save<T>(T entity) { TransactionWrapper(Session.Save(entity)); } public void Create<T>(T entity) { TransactionWrapper(Session.Create(entity)); } public void Save<T>(T entity) { TransactionWrapper(Session.Save(entity)); } So in other words, I pass a method call as a parameter, and the TransactionWrapper method wraps a transaction around the method call.

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  • C errors - Cannot combine with previous 'struct' declaration specifier && Redefinition of 'MyMIDINotifyProc' as different kind of symbol

    - by user1905634
    I'm still new to C but trying to understand it better by working my way through a small MIDI audio unit (in Xcode 4.3.3). I've been searching for an answer to this all day and still don't even understand exactly what the problem is. Here's the code in question: //MyMIDINotifyProc.h #ifndef MIDIInstrumentUnit_CallbackProcs_h #define MIDIInstrumentUnit_CallbackProcs_h void MyMIDINotifyProc (const MIDINotification *message, void *refCon); #endif //MyMIDINotifyProc.c #include <CoreMIDI/CoreMIDI.h> #include "MyMIDINotifyProc.h" void MyMIDINotifyProc (const MIDINotification *message, void *refCon) { //manage notification } In the header definition I get this: ! Cannot combine with previous 'struct' declaration specifier I've made sure the definitions match and tried renaming them and I still get this in my .c file: ! Redefinition of 'MyMIDINotifyProc' as different kind of symbol Which points to the .h definition as the 'Previous definition'. I know that MIDIServices.h in the CoreMIDI framework defines: typedef void (*MIDINotifyProc)(const MIDINotification *message, void *refCon); But I don't understand if/why that would cause an error. I would be grateful if anyone could offer some help.

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  • C++Template in Java?

    - by RnMss
    I want something like this: public abstract class ListenerEx<LISTENER, PARENT> implements LISTENER { PARENT parent; public ListenerEx(PARENT p) { parent = p; } } But it doesn't compile. Is there a better solution? Is there something in Java like C++ template that would do check syntax after template deduction? The following explains why I need such a ListenerEX class, if you already know what it is, you don't need to read the following. I have a main window, and a button on it, and I want to get access to some method of the main window's within the listener: public class MainWindow extends JFrame { public void doSomething() { /* ... */ } public void doSomethingElse() { /* ... */ } private JButton button; public MainWindow() { button = new JButton(...); add(button); button.setActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { doSomething(); doSomethingElse(); } }); } } This would compile but does not work properly all the time. (Why would it compile when the ActionListener does not have doSomething() method?) Of course we can do it like this: public class MainWindow extends JFrame { public void doSomething() { } public void doSomethingElse() { } private JButton button; public MainWindow() { button = new JButton(...); add(button); class ActionListener1 implements ActionListener { MainWindow parent; public ActionListener(MainWindow p) { parent = p; } public void actionPerformed(ActionEvent e) { parent.doSomething(); parent.doSomethingElse(); } } button.setActionListener(new ActionListener1(this)); } } However I hate this style ... So I tried: public abstract class ActionListenerEx<P> implements ActionListener { P parent; public ActionListenerEx(P p) { parent = p; } } public class MainWindow extends JFrame { public void doSomething() { } public void doSomethingElse() { } private JButton button; public MainWindow() { button = new JButton(...); add(button); button.setActionListener(new ActionListenerEx<MainWindow>(this) { public void actionPerformed(ActionEvent e) { parent.doSomething(); parent.doSomethingElse(); } }); } } But there's lots of Listeners beside the ActionListener ... public abstract class ActionListenerEx<LISTENER, PARENT> implements LISTENER { PARENT parent; public ActionListenerEx(PARENT p) { parent = p; } } However, it won't compile ... I am fresh at Java, and I wonder if there's already better solution.

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  • Whats wrong with the following code, its not compiling

    - by Ganesh Kundapur
    #include <iostream> #include <vector> using namespace std; class Base { public: void Display( void ) { cout<<"Base display"<<endl; } int Display( int a ) { cout<<"Base int display"<<endl; return 0; } }; class Derived : public Base { public: void Display( void ) { cout<<"Derived display"<<endl; } }; void main() { Derived obj; obj.Display(); obj.Display( 10 ); } $test1.cpp: In function ‘int main()’: test1.cpp:35: error: no matching function for call to ‘Derived::Display(int)’ test1.cpp:24: note: candidates are: void Derived::Display() On commenting obj.Display(10), it works.

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  • C++ - checking if a class has a certain method at compile time

    - by jetwolf
    Here's a question for the C++ gurus out there. Is there a way to check at compile time where a type has a certain method, and do one thing if it does, and another thing if it doesn't? Basically, I have a template function template <typename T> void function(T t); and I it to behave a certain way if T has a method g(), and another way if it doesn't. Perhaps there is something that can be used together with boost's enable_if? Something like this: template <typename T> enable_if<has_method<T, g, void ()>, void>::type function(T t) { // Superior implementation calling t.g() } template <typename T> disable_if<has_method<T, g, void ()>, void>::type function(T t) { // Inferior implementation in the case where T doesn't have a method g() } "has_method" would be something that preferably checks both that T has a method named 'g', and that the method has the correct signature (in this case, void ()). Any ideas?

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  • Getting list of all existing vtables.

    - by Patrick
    In my application I have quite some void-pointers (this is because of historical reasons, application was originally written in pure C). In one of my modules I know that the void-pointers points to instances of classes that could inherit from a known base class, but I cannot be 100% sure of it. Therefore, doing a dynamic_cast on the void-pointer might give problems. Possibly, the void-pointer even points to a plain-struct (so no vptr in the struct). I would like to investigate the first 4 bytes of the memory the void-pointer is pointing to, to see if this is the address of the valid vtable. I know this is platform, maybe even compiler-version-specific, but it could help me in moving the application forward, and getting rid of all the void-pointers over a limited time period (let's say 3 years). Is there a way to get a list of all vtables in the application, or a way to check whether a pointer points to a valid vtable, and whether that instance pointing to the vtable inherits from a known base class?

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  • system crash after declaring global object of the class

    - by coming out of void
    hi, i am very new to c++. i am getting system crash (not compilation error) in doing following: i am declaring global pointer of class. BGiftConfigFile *bgiftConfig; class BGiftConfigFile : public EftBarclaysGiftConfig { } in this class i am reading tags from xml file. it is crashing system when this pointer is used to retrieve value. i am doing coding for verifone terminal. int referenceSetting = bgiftConfig->getreferencesetting(); //system error getreferencesetting() is member fuction of class EftBarclaysGiftConfig i am confused about behavior of pointer in this case. i know i am doing something wrong but couldn't rectify it. When i declare one object of class locally it retrieves the value properly. BGiftConfigFile bgiftConfig1; int referenceSetting = bgiftConfig1->getreferencesetting(); //working But if i declare this object global it also crashes the system. i need to fetch values at different location in my code so i forced to use someting global. please suggest me how to rectify this problem.

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  • Reordering Variadic Parameters

    - by void-pointer
    I have come across the need to reorder a variadic list of parameters that is supplied to the constructor of a struct. After being reordered based on their types, the parameters will be stored as a tuple. My question is how this can be done so that a modern C++ compiler (e.g. g++-4.7) will not generate unnecessary load or store instructions. That is, when the constructor is invoked with a list of parameters of variable size, it efficiently pushes each parameter into place based on an ordering over the parameters' types. Here is a concrete example. Assume that the base type of every parameter (without references, rvalue references, pointers, or qualifiers) is either char, int, or float. How can I make it so that all the parameters of base type char appear first, followed by all of those of base type int (which leaves the parameters of base type float last). The relative order in which the parameters were given should not be violated within sublists of homogeneous base type. Example: foo::foo() is called with arguments float a, char&& b, const float& c, int&& d, char e. The tuple tupe is std::tuple<char, char, int, float, float>, and it is constructed like so: tuple_type{std::move(b), e, std::move(d), a, c}. Consider the struct defined below, and assume that the metafunction deduce_reordered_tuple_type is already implemented. How would you write the constructor so that it works as intended? If you think that the code for deduce_reodered_tuple_type, would be useful to you, I can provide it; it's a little long. template <class... Args> struct foo { // Assume that the metafunction deduce_reordered_tuple_type is defined. typedef typename deduce_reordered_tuple_type<Args...>::type tuple_type; tuple_type t_; foo(Args&&... args) : t_{reorder_and_forward_parameters<Args>(args)...} {} }; Edit 1 The technique I describe above does have applications in mathematical frameworks that make heavy use of expression templates, variadic templates, and metaprogramming in order to perform aggressive inlining. Suppose that you wish to define an operator that takes the product of several expressions, each of which may be passed by reference, reference to const, or rvalue reference. (In my case, the expressions are conditional probability tables and the operation is the factor product, but something like matrix multiplication works suitably as well.) You need access to the data provided by each expression in order to evaluate the product. Consequently, you must move the expressions passed as rvalue references, copy the expressions passed by reference to const, and take the addresses of expressions passed by reference. Using the technique I describe above now poses several benefits. Other expressions can use uniform syntax to access data elements from this expression, since all of the heavy-lifting metaprogramming work is done beforehand, within the class. We can save stack space by grouping the pointers together and storing the larger expressions towards the end of the tuple. Implementing certain types of queries becomes much easier (e.g. check whether any of the pointers stored in the tuple aliases a given pointer). Thank you very much for your help!

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  • Clicking Elements in Android Doesn't Display the Correct Values

    - by Devin
    I apologize if this code looks a bit like a mess (considering the length); I figured I'd just include everything that goes on in my program at the moment. I'm attempting to create a fairly simple Tic Tac Toe app for Android. I've set up my UI nicely so far so that there are a "grid" of TextViews. As a sort of "debug" right now, I have it so that when one clicks on a TextView, it should display the value of buttonId in a message box. Right now, it displays the correct assigned value for the first element I click, but no matter what I click afterwards, it always just displays the first value buttonID had. I attempted to debug it but couldn't exactly find a point where it would pull the old value (to the best of my knowledge, it reassigned the value). There's a good possibility I'm missing something small, because this is my first Android project (of any note). Can someone help get different values of buttonId to appear or point out the error in my logic? The code: package com.TicTacToe.app; import com.TicTacToe.app.R; //Other import statements public class TicTacToe extends Activity { public String player = "X"; public int ALERT_ID; public int buttonId; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); //Sets up instances of UI elements final TextView playerText = (TextView)findViewById(R.id.CurrentPlayerDisp); final Button button = (Button) findViewById(R.id.SetPlayer); final TextView location1 = (TextView)findViewById(R.id.location1); final TextView location2 = (TextView)findViewById(R.id.location2); final TextView location3 = (TextView)findViewById(R.id.location3); final TextView location4 = (TextView)findViewById(R.id.location4); final TextView location5 = (TextView)findViewById(R.id.location5); final TextView location6 = (TextView)findViewById(R.id.location6); final TextView location7 = (TextView)findViewById(R.id.location7); final TextView location8 = (TextView)findViewById(R.id.location8); final TextView location9 = (TextView)findViewById(R.id.location9); playerText.setText(player); //Handlers for events button.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { // Perform action on click if (player.equals("X")){ player = "O"; playerText.setText(player); } else if(player.equals("O")){ player = "X"; playerText.setText(player); } //Sets up the dialog buttonId = 0; ALERT_ID = 0; onCreateDialog(ALERT_ID); showDialog(ALERT_ID); } }); location1.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //Sets up the dialog buttonId = 1; ALERT_ID = 0; onCreateDialog(ALERT_ID); showDialog(ALERT_ID); } }); location2.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //Sets up the dialog buttonId = 2; ALERT_ID = 0; onCreateDialog(ALERT_ID); showDialog(ALERT_ID); } }); location3.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //Sets up the dialog buttonId = 3; ALERT_ID = 0; onCreateDialog(ALERT_ID); showDialog(ALERT_ID); } }); location4.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //Sets up the dialog buttonId = 4; ALERT_ID = 0; onCreateDialog(ALERT_ID); showDialog(ALERT_ID); } }); location5.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //Sets up the dialog buttonId = 5; ALERT_ID = 0; onCreateDialog(ALERT_ID); showDialog(ALERT_ID); } }); location6.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //Sets up the dialog buttonId = 6; ALERT_ID = 0; onCreateDialog(ALERT_ID); showDialog(ALERT_ID); } }); location7.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //Sets up the dialog buttonId = 7; ALERT_ID = 0; onCreateDialog(ALERT_ID); showDialog(ALERT_ID); } }); location8.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //Sets up the dialog buttonId = 8; ALERT_ID = 0; onCreateDialog(ALERT_ID); showDialog(ALERT_ID); } }); location9.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //Sets up the dialog buttonId = 9; ALERT_ID = 0; onCreateDialog(ALERT_ID); showDialog(ALERT_ID); } }); } protected Dialog onCreateDialog(int id){ String msgString = "You are on spot " + buttonId; AlertDialog.Builder builder = new AlertDialog.Builder(this); builder.setMessage(msgString) .setCancelable(false) .setNeutralButton("Ok", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int id) { dialog.cancel(); } }); AlertDialog alert = builder.create(); return alert; } }

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  • Issue when rotating a UIScrollView

    - by leachianus.gecko
    I am having issues trying to get the pageControl sample code to work with rotation. I managed to get it to rotate but it does not visually load correctly until I start to scroll (then it works fine). Any Idea on how I can fix this problem? Here is a link to the project if you want to see it in action. This code is based off the PageControl example apple has provided. here is the code: #import "ScrollingViewController.h" #import "MyViewController.h" @interface ScrollingViewController (PrivateMethods) - (void)loadScrollViewWithPage:(int)page; @end @implementation ScrollingViewController @synthesize scrollView; @synthesize viewControllers; - (void)viewDidLoad { amount = 5; [super viewDidLoad]; [self setupPage]; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; } - (void)viewDidUnload { [scrollView release]; } - (void)dealloc { [super dealloc]; } - (void)setupPage { NSMutableArray *controllers = [[NSMutableArray alloc] init]; for (unsigned i = 0; i < amount; i++) { [controllers addObject:[NSNull null]]; } self.viewControllers = controllers; [controllers release]; // a page is the width of the scroll view scrollView.pagingEnabled = YES; scrollView.contentSize = CGSizeMake(scrollView.frame.size.width * amount, 200); scrollView.showsHorizontalScrollIndicator = NO; scrollView.showsVerticalScrollIndicator = NO; scrollView.scrollsToTop = NO; scrollView.delegate = self; [self loadScrollViewWithPage:0]; [self loadScrollViewWithPage:1]; } #pragma mark - #pragma mark UIScrollViewDelegate stuff - (void)scrollViewDidScroll:(UIScrollView *)_scrollView { if (pageControlIsChangingPage) { return; } /* * We switch page at 50% across */ CGFloat pageWidth = _scrollView.frame.size.width; int dog = floor((_scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1; // pageControl.currentPage = page; [self loadScrollViewWithPage:dog - 1]; [self loadScrollViewWithPage:dog]; [self loadScrollViewWithPage:dog + 1]; } - (void)loadScrollViewWithPage:(int)page { if (page < 0) return; if (page >= amount) return; MyViewController *controller = [viewControllers objectAtIndex:page]; if ((NSNull *)controller == [NSNull null]) { controller = [[MyViewController alloc] initWithPageNumber:page]; [viewControllers replaceObjectAtIndex:page withObject:controller]; [controller release]; } if (nil == controller.view.superview) { CGRect frame = scrollView.frame; frame.origin.x = frame.size.width * page; frame.origin.y = 0; controller.view.frame = frame; [scrollView addSubview:controller.view]; } } - (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation { [self setupPage]; } - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { // Return YES for supported orientations return YES; } @end

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  • Define thread in C++

    - by Vsevywniy
    How do I start a thread using _beginthreadex(), making it execute void myFunction(wchar_t *param);? I try to use this: _beginthread(NULL, 0, myFunction, L"someParam", 0, &ThreadID); but there is compilation error: error C2664: 'beginthreadex' : cannot convert parameter 3 from 'void (_cdecl *)(wchar_t *)' to 'unsigned int (__stdcall *)(void *)'. How I can resolve this error? I seem able to do _beginthread((void(*)(void*))myFunction, 0 , (void *)L"someParam");. But for _beginthreadex() these casts don't seem to work. What do I need to do?

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