a function returns a temporary object like
int myfun(){
int x = 0;
return x;
}
this function will return a temporary integer now void fun1(const int & num); this function can receive from myfun().BUT void fun2(int & num); this function cannot receive from myfun() Why is that, Moreover what is lifetime of a temporary object like one returned in myfun() ???
#include <iostream>
#include <cstdlib>
#include <time.h>
#include <conio.h>
using namespace std;
class Dice {
[Code] ....
Every time the roll_dice function get call twice for the same object, i receive the same dice values.
I'm having to do a little c++ (coming from java) and don't understand the syntax of the following declaration
Code:
SensorBase* const sensor(mSensors[i]);
It looks like it's declaring a const pointer to a SensorBase object but I don't understand how that applies to sensor(mSensors[i]) which looks like a function??
i want to store reference to a const object in my class as a member variable, as follow:
I basically want a readonly reference to |Data| in Device object.
Code:
class Device {
Device(const QList<QSharedPointer<Data>> & dataList) : _listRef(dataList) {
} protected:
const QList<QSharedPointer<Data>> & _listRef;
}
This does not allow me to initialize _listRef as something like NULL when it is not applicable.Also, i must change all my constructors and its child class to include an initialization of _listRef!!
What is the alternative? Is pointer the nearest? which of the following should be used?
Code:
const QList<QSharedPointer<Data>> * _listRef;
or
const QList<QSharedPointer<Data>> *const _listRef;
or
const QSharedPointer<QList<QSharedPointer<Data>>> _listRef; ????
will copy constructor does object initialization using another already created object? I understand that it can be applied for object initialization and not for assignment.Is it correct?
View 10 Replies View RelatedI have a method to take a Tile object and make an instances of it based on some data from the original object. Than it is suppose to manipulate the a specific instance and save the results. The first loop through it works but it changes all instance as well as the base.
public static int recurse(int count, Tile[,] b,Huristic h,int check) {
if (check==1) {
boardState.Add(B)/>;
return check;
} if (check == 0)
[Code] .....
#include "B.h"
class A {
public :
A()
{
s_b = new B();
b = new B();
[Code] ....
In my project i have seen static object as above . But not able to know what is the exact use of it and how they are different from general object .
I am trying to use web api in order to return custom json response keys. For this i have return a custom class to return json response
Custom Class:
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
[Code].....
I have a combobox with Items 1024
2048
4096
8192
String cach = form.comboCache.SelectedItem.ToString();
I am using the above code to retrive an item selected by user,But this line is giving an exception "Null Reference Exception, Object reference not set to an instance of an object"
I am using session to pass object from controller to custom class in MVC Web API. here is my code, i am getting error at session.
public HttpResponseMessage Get()
{
var person = db.Persons.ToList();
[Code]....
In Visual Studio 2010 C++
I have a series of existing text objects
The text properties names are
item1_lbl,
item2_lbl,
item3_lbl,
….
Based on a selection I want to change an object. I generate the name of the object I want to change in a string so from this string is there a way to get a pointer to the correct text object that is same name?
I'm trying to figure out how I can create a vertex array object at offset of a vertex buffer object.I've created the buffer object. I'd like the "texs" idnex data to start at the texture coordinate content of the vertex_t structure.
Type definitions:
struct vertex_t {
vector3d_t position;
float s; // Texture coordinate s
float t; // Texture coordinate t
};
Code so far:
// How do I make this start at a certain spot of the VBO?!
glVertexAttribPointer(texs, 2, GL_FLOAT, GL_FALSE, sizeof(vector3d_t), nullptr;
//...
The case is like
class B{
public:
somedata;
somefunction();
}
class A{
public:
data;
function();
}
in somefunction i want a pointer to current object of class A m new to c++
What rvalue references are? How are they useful? What are temporary objects?
View 1 Replies View RelatedIs it possible to create a temporary
std::list of pointers
I would like to pass a temporary
std::list
to the constructor of a class to initialize its own one.
For example, using a
std::vector
:
#include <iostream>
#include <vector>
void func(const std::vector<int*>& myVec) {
for(int i=0; i<myVec.size(); ++i){
[code]....
Can we do this? What are other possible problems in addition the ones I have just mentioned above?
Are there other ways of calling a const/non-const override? I want to defined some functions in terms of others, particularly accessors which might or might not require constness- in order to not copy & paste code. This is my current solution:
struct dumbArray {
dumbArray(unsigned int size):
m_array(new int[size]){
}
~dumbArray(){
delete m_array;
[Code] .....
difference between const and static const, more effectively. I know the basic concept of const and static but I need clear explanation of declaring "const" and "static const"
Ex:
const int a;
static const int a;
Is there any way to cast a non-const variable to const one?
I want to read variable n from file and then use it to declare array "int arr[n]", but because n is non-const, the compiler doesn't allow me to do that.
I have an assignment that asks me to implement a variant of the classic bouncing balls program.
'Each ball should start off at the top of the screen with a random speed in the x direction. Whenever a ball hits a screen boundary it should bounce off at an angle equal to the impact angle and lose some speed. Eventually each ball should come to a rest at the bottom of the screen. Five seconds after coming to a rest a ball should be removed from the screen.'
'Your code must keep track of objects (balls) by placing the object data structures in a linked list. You need to create your own linked list implementation. Below is a brief description of the object programming interface: CreateObject - Create a new object. The function accepts as input parameters a pointer to the SDL screen, a pointer to a model triangle array, and a variable telling the size of the model triangle array. The function returns a pointer to a new object data structure. The model triangle array specified as input parameter should not be shared across objects. (Not sharing the model triangle array allows e.g. objects to have different colors.)
Perform the necessary memory allocation and copying.DestroyObject - Free object. The function accepts as input parameters a pointer to an object data structure. The function should free all memory allocated to represent the object (memory allocated for the model triangle array and the object data structure itself).
Drawobject - Draw object on screen. The function accepts as input parameters a pointer to an object data structure. The function must draw the object on the screen by calling DrawTriangle on each of the model triangles. Remember to update scale, translation, etc., in each triangle data structure before invoking DrawTriangle.
Hint: Do not make the bouncing algorithm too complex. Bouncing a ball off a vertical or horizontal surface can be accomplished without resorting to calculating impact angles.'
The function I'm stuck at, is the first one - createobject.
My first aim is to get one ball on the screen.
Code:
// Create new object
object_t *CreateObject(SDL_Surface *screen, triangle_t *model, int numtriangles)
{
object_t *object = malloc(sizeof(object_t));
object->model = malloc(sizeof(sphere_model));
object->screen = SDL_Surface;
memcpy(*model, object->model, sizeof(object_t));
return object;
// Implement me
}
This is what I've done so far.
I have two classes one called Date and the other is University , Date class has two overloaded operators , ostream and istream to take in the data and print them out :
ostream & operator<<(ostream & out, Date & x) {
out<< x.month << "/" << x.day << "/" << x.year ;
return out;
[Code] ....
The University class has an object of type Date called establishDate and I must use this to print out the date along with the University name and location, here's University class :
University.h
class University {
public:
University (); // constructor
friend ostream & operator<<(ostream & out, University & x); // print the university data
friend istream & operator>>(istream & in, University & x); // to read university data
[Code] .....
so how do I use the establishDate object ?
it is not possible to get a type from an object, only from a type. Even with auto, you can only instantiate another type of the same type.I'd like to get a type from an object given another type, mainly because it is less typing and less error prone.
Some psudocode:
Type1 A<X, Y> a;
int b;
Type2 a.InnerType<b>::type c; // obviously won't work
A work around I thought of would be to use functions:
Type1 A<X, Y> a;
int b;
auto c = a.getInnerType(b);
Which is kinda interesting and looks like the way I'm going to go. However, I'm just wondering if there is any other ways of doing this as I don't really want to instantiate an object if I can avoid it (though the optimizer will probably just dump it anyway).
I have the following problem, I have an object of a class Subject, and I want that this object points to another object of class Classes, creating a kind of link. How can I do that?
View 4 Replies View RelatedSo I am trying to develop a sort of 2d spacesim engine for creating games in C++. The project uses SFML for graphics, and I am currently trying to compile it on Linux using g++.
The main issue that I am wrestling with is that of simulation objects having their position, velocity, and rotation variables constantly getting set to NaN for reasons that are beyond me. The behaviour is not consistent, and occasionally will occur or not occur without any discernible pattern.
The github repo for the code is here: [URL] ....
I understand that NaN values can spread easily by operations on one another, but I cant seem to figure out where the initial issue is occurring here.
is it possible to get object name in the constructor? I would like to initialize an object of circle class without any arguments and put some pretty lines in constructor to get and save as table of chars the name of creating object. Is it possible? I work with MSVS2012.
View 4 Replies View Relatedint NextPixel(int antIndex, int currentPixel , Ant *ant , IplImage *edgeImg) {
int left = currentPixel - 1 ;
int right = currentPixel + 1 ;
int up = currentPixel - edgeImg->widthStep ;
int down = currentPixel + edgeImg->widthStep ;
[[Code] ....
if those lines are uncommented , program gives heap error.Why?
why we use this object and what purpose we use it
View 2 Replies View Related