I am confused for first call to push_back copy constructor is called for second call I am expecting it to move class instance to new memory location there by trigering move and then inserting second class instance expected call:
Copy constructor
Move constructor
Copy constructor
but its calling
Copy constructor
Copy constructor
Move constructor
I'm currently writing a chunk of code that will take inputs from the user and push them into a vector until 0 is entered, at which point it will break the loop and continue on with the rest of the program. This is nothing I haven't done before, but I have never encountered this error.
The code chunk looks like this:
typedef vector <int> ivec; int main() { ivec nums; int input; while (true) { cout << "Enter a positive integer, or 0 to quit" << endl;
[Code] ....
My standard testing input has been 3 5 6 3 8 (then 0 to quit), so one would expect my sequence to be 3 5 6 3 8...but instead after the 8 I get a random number value that is usually quite large and I cannot figure out where it comes from (ex. 3 5 6 3 8 201338847).
The following are the cases when copy constructor is called.
1)When instantiating one object and initializing it with values from another object. 2)When passing an object by value. 3)When an object is returned from a function by value.
I don't understand #2 How can and object be passed by value? when I think of passing object I think of passing by address or reference. explain
I don't understand #3 how can a function returned object by value I think of again passing by address or reference.
I am unable to understand how a move constructor works in this example of code. If someone could break down the process of what is taking place and explain to me on why to use a move constructor.
Code: class MyString { MyString(MyString&& MoveSource) { if( MoveSource.Buffer != NULL ) { Buffer = MoveSource.Buffer; // take ownership i.e. 'move' MoveSource.Buffer = NULL; // set the move source to NULL i.e. free it } } };
Example from "SamsTeachYourself: C++ in One Hour a Day"
I was wondering that why in the below code, the copy constructor is called 2 times.
Code: class A { private: static int count; int age; public: A()
[code].....
I think that when f(a) is called, since I am passing this as value, no copy constructor should be called. The copy constructor should called when the return object "x" is assigned to:
When the below is done, does it call the constroctor only, and if yes, constructors do not have return types so how does it work? is there anything behind the scene?
wxAddHandler(new wxPNG_HANDLER); and sf::RenderWindow(sf::VideoMode(...),...);
I can't get my 'Front End' view model's constructor to be called. If i remove my dependency from the mvvm-light framework and use MSDN mvvm paterns then the constructor is called. What am i doing wrong. It seem like there is a data context binding issue between my XMAL and my view model backing.
ViewModelLocator.cs using GalaSoft.MvvmLight.Ioc; using Microsoft.Practices.ServiceLocation; using Point_Of_Sale.Model; using System.Collections.Generic; namespace Point_Of_Sale.ViewModel { public class ViewModelLocator
#include<iostream> using namespace std; class Cents { public: int m_nCents; Cents(int nCents=0):m_nCents(nCents){ cout<<"Calling normal constructor with value:"; m_nCents = nCents; cout<<m_nCents<<endl;
[code].....
Question is :Why is the overloaded copy constructor that I have written not getting called here?Internally default copy constructor is getting called.Thats why we get value of obj2.m_nCents as 37.
I have the following classes and 'dreaded diamond':
A / / B C / / D | | E
Classes B & C both inherit from A using public virtual A.
E is the only concrete class. None of the classes are totally abstract.
Every class has a copy constructor.
All of the copy constructors are chained together through the initialization lists.
E correctly calls D's copy constructor.
D correctly calls B and C's copy constructors.
But neither B nor C call A's copy constructor, although A's default constructor is called. To reiterate B and C have a call to A's copy constructor in their initialization lists.
I guess A's default constructor is being called is because of virtual inheritence, but why isn't its copy constructor called (too)?
A's copy constructor includes some very important code and I could do with calling it. Should I call it from the concrete class' initialization list or is that considered bad form?
Ok so I am working on a game and I'm in the process of developing my Player class. Anyways, what I have is a keyboard function that is called in my main function to make a shape move.
void myKeyboardFunction(unsigned char key, int x, int y) { switch ( key ) {
[Code].....
But when I try to call it, trying to copy my previous method,
glutKeyboardFunc(Player1.playerControls);
I get an error
error C3867: 'Player::playerControls': function call missing argument list; use '&Player::playerControls' to create a pointer to member
I get an error saying it can't convert parameters. I would just like to understand why the arguments become a problem when I make the function a member of my class, when the first method I used is so easy.
Exercise 7.24: Give your Screen class three constructors: a defaultconstructor; a constructor that takes values for height and width and initializes the contents to hold the given number of blanks; and a constructor that takes values for height, width, and a character to use as the contents of the screen.
Giving the screen a default constructor was easy. The next part is probably easy aswell, I just dont understand what they mean when they say "and initalize the contents to hold the given number of blanks" and something in the 3rd part when they say "character to use as the contents of the screen".
Think I have made a breakthrough... Would the constructor for the second part look like this:
I get the error at the line "ptr1 = new node;" I tried putting a default constructor for my node struct and that fixed the problem but a new problem arises. It states that i have a linker error after i compile it with a default constructor.
I am creating a Matrix class, and one of the constructors parses a string into a matrix. However, printing the result of the constructor (this->Print()) prints what I expect, and an <object_just_created>.Print() call returns bogus data. How is this even possible?
Snippets below:
Matrix::Matrix(const string &str) { // Parse a new matrix from the given string Matrix r = Matrix::Parse(str); nRows= r.nRows; nCols= r.nCols;
[Code] ....
in the driver program, here are the two successive calls
Matrix mm6("[1 2 3.8 4 5; 6 7 8 9 10; 20.4 68.2 1341.2 -15135 -80.9999]"); mm6.Print(); // mm6.Print() calls bogus data, -2.65698e+303 at each location. The matrix's // underlying array is valid, because printing the addresses yields a block // of memory 8 bits apart for each location
I am currently trying to implement a 2d vector to store x and y of type int.
I have successfully passed it to the function, however i am unable to store the values in it. It always returns with a segmentation fault and my program terminates from there. May i know how do i store them properly and call them out?
Below is my code snippet
int reconstructSecret(int x, int y, vector< vector<int> > &inVec ,int constructSecret) { int getX,getY,formula,accum,count,getSecret,startPosition,nextPosition,numerator,denominator; getX=x; getY=y; int result;
[Code] .....
The main method
vector< vector<int> > inVec; for(int i=0;i<constructSecret;i++) { cout<<"please key in the "<<i<< "share of x value:"; cin>>x;
// Creates a generic entity in the entity pool void EntityManager::CreateEntity() {
[Code] .....
In this case it checks the entity pool for an entity, if one exists it moves it to the active entities and then returns the unique id, if one doesn't exist it creates one then calls itself to run the check again to verify and move the new entity.
My question is, is this a valid form of recursion since it only incurs a single loop of recursion, or should I reform the entire system to work differently? If so, how do you set this up in a way that does not cause recursion?
And came across the following error during link stage: "/usr/include/c++/4.6/bits/stl_vector.h:1080:4: error: no matching function for call to ‘std::vector<cv::Point_<int> >::_M_fill_initialize(std::vector<cv::Point_<int> >::size_type, int&)’ "
i am writing this bank accounts program using structures. i haven't implemented the function before that i want to check if the data is being read and printed. When i build and run the program in visual studio it gives me the following error. "No constructor could take the source type, or constructor overload resolution was ambiguous". Now whats wrong in this program?
/* Bank Accounts Program */ #include <iostream> #include <string> #include <fstream> #include <cstdlib>//needed to use system() function using namespace std; const int MAX_NUM = 50; struct Name{
Constructor of the Base Class Person::Person(char* n="", char* nat="U.S.A", int s=1) { name = n; nationality = nat; sex = s; }
Constructor of the Derived Class (inherited from the base class)
Student(char* n, int s=0, char* i=""): Person(n, s)
Why the initialized list of the base class constructor doesn't match the initialized list of the derived class constructor? I know this book is a little bit old, I'm not sure if this wrong in VC++ 2010?
How can I move a character around a 2D map? After some research and a bunch of work I made a function for movement:
unsigned int gamespeed = 100; unsigned int stage = 1; void controls() {
[Code]....
Maps are stored in a different .cpp file
So this code works, but is complicated, ugly and evil (I have to make a pointer to the first map and change the pointer to the next map every time the user reaches the exit, without the pointer this code is, of course, incompatible). How can I reduce this code to be less evil/ugly or at least smaller?
Also it would be nice if the user could move around with arrows as well as with WASD
I want to move a character in a 2D array This Character should move vertically in a 2D Array To exemplify it for Exam in Snake Game A character automatically moves Please Write a example code that works
Having trouble getting my square to move to the left my code and instructions of what i am suppose to do is below. No sure how to move my square or if I am even going in the right direction as to writing code to do so. Note that it is only part of my code ( part 2 of project)
Part 2:
Write a graphical application that draws a square and then moves it.
Get the x and y coordinates for the top left corner of the square from the user using the get_int() member function of cwin. Get the length of a side of the square from the user using get_int() as well. Now draw the square to cwin according to the user input.Ask the user how many units to the left they want to move it using get_int() again. Then move the square, clear the screen, and draw it again.
// Part 2 // /* command output to declare the x,y value and 1 side length of a square through user interaction( Has user input intergers) */ int x_value = cwin.get_int("What is the x_value of the top left of the square?"); int y_value = cwin.get_int("What is the y_value of the top left of the square?"); int side_length = cwin.get_int("Input the length for one side of the square:"); /* Data type for the 4 corners of the square */ Point e; Point f;
