C++ :: Synthesized Default Constructor

Dec 25, 2013

A compiler auto created default constructor is called a synthesized default constructor. It will initialize the built-in members to 0 or not depends on where the class object is defined? if I define a class

class point{
public:
double x, y;
};

if I define point point1; in global scope then point1.x and point1.y will be initialized to 0, if I define point point2; in a local scope, then its x and y won't be initialized? If it is like this, then I believe if there are built-in type members in a class, then the synthesized default constructor is almost useless!

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C++ :: No Appropriate Default Constructor Available?

Oct 12, 2014

First I wrote a Binary-tree class to draw a binary tree on the window. The nodes were small circles. Then I become wanted to change the shape of the nodes from circles to triangles by another class, Binary-tree-derived which is derived from Binary-tree class. I wrote the below code to do the job but I get two errors about constructors. First, code:

/* The binary-tree class, one of the topics that has been said in Programming Principles and Practice using C++ book by Biarne Stroustrup.
This code is written by R Abbasi (s.rabbasi@yahoo.com) */
#include <Simple_window.h>

[Code].....

Errors are:

Error12error C2512: 'Binary_tree' : no appropriate default constructor availablec:userscsdocumentsvisual studio 2012projects est_1 est_1 est_1.cpp91

13IntelliSense: no default constructor exists for class "Binary_tree"c:UsersCSDocumentsVisual Studio 2012Projects est_1 est_1 est_1.cpp91

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C++ ::  How To Write A Default Constructor

Sep 27, 2013

How do you write a default constructor?I need to use a default constructor that will initialize the data members:
- salesPerson to “Unknown”
- noOfWeek to 13
- amount to point to an array of thirteen 0.00s.

This is my weeklysales class

class WeeklySales {
char* salesPerson;
double* amount; // Pointer to an array
int noOfWeek; // Size of the array
};

Here's my attempted code:

//default constructor
WeeklySales (){
salesPerson="Unknown";
noOfWeek = 13;
amount = 0.00;
}

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C++ :: Creating Object Without Default Constructor

Jun 24, 2013

I have a question about the default constructor.

To my best understanding, the compiler will provide me with a deafult constructor only if there are no any user defined constructors, at all. Now consider the following code:

Code: class MyClass
{
private:
int m_data;
public:
MyClass(int init):m_data(init){cout<<"Ctr called"<<endl;}

[Code] ....

How is it that suddenly, there is a default constructor?

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C++ :: Undefined Reference To Default Constructor?

Jul 28, 2013

trying to practice the object-oriented part of it by converting my java programs into c++. I believe I understand the concepts of a header file and declaring the functions in the .cpp files. I keep getting this "Undefined reference to NamedStorm::NamedStorm()" error.

NamedStorm.h
#ifndef NAMEDSTORM_H
#define NAMEDSTORM_H
#include <string>
#include <iostream>
// NEVER use using namespce in header, use std instead.
using std::string;

[code]....

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C++ :: Create Two Box In Program Using Default Constructor

Apr 6, 2014

Im trying to create two box in this program using the default constructor. When i call to try and display the info, it says that x, y, and z are not declared in this scope. i wanted to have the user cin the length, height, and width using the void setBox function.

#include<iostream>
#include<string>
#include<cstdlib>
using namespace std;
class Box{
public:

[code]....

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C/C++ :: Use Of Implicit Default Constructor Provided By Compiler?

Sep 21, 2014

In C++ if no user defined constructor is provided for a class the compiler automatically provides a implicit default constructor.

An implicit default constructor is equivalent to a default constructor with no parameters and no body ?

So what is the use of a implicit default constructor provided by the compiler, if it is not going to do anything ?

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C++ :: Call To Implicitly - Deleted Default Constructor Of Node

Oct 26, 2014

i tried running my code and i keep getting the error "call to implicitly-deleted default constructor of 'node'. My code is as follows

//.h file
typedef struct node * point
struct node{
string data;
node *next
}

[code]....

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.

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C++ :: Make A Default Constructor Having Other Class Member Objects

Nov 7, 2014

class Date
Date(int=1, int=1, int=1990);
class Person
Person(string="", string="", Date=NULL);
class RealEstateAgent:Public Person
RealEstateAgent(string="",string="",Date=NULL,Date=NULL,int=NULL, double=0.0);
}

[code]....

how can I assign default values with Customer object and RealEstateAgent?

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C/C++ :: How To Define Default Constructor For A Template List Class

Apr 18, 2012

I was making a template list class, and using it to make list of objects of my own class.It works fine with integers, but not with other classses.

template <typename T>
class CList {
public:
    struct Node {
        T data;
        Node* next;

[code]....

While in AddElement(), it gives error - Default constructor not available.

template<typename T>
bool CList<T>::AddElement(T t) {
    bool result = true;  
    if (head == NULL) {

[code]....

what is wrong here.

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C++ :: Default Constructor - Set Array Of Strings To Null And Size Variable To 0

Dec 7, 2013

For my default constructor I need to set an array of strings to null and the size variable to 0. Here is my code for that

DynamicStringArray::DynamicStringArray() {
*DynamicArray[]=NULL;
size=0;
}

When I try and compile it I get an "expected primary expression before ']' token" error.

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C++ :: No Constructor Could Take Source Type Or Constructor Overload Resolution Was Ambiguous

Mar 1, 2014

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{

[code]....

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C++ :: Calling Constructor From Constructor Set Pointer To Null

Jan 25, 2014

VS 2012 / Windows 7 64 bit

class
class myclass {
public:
myclass(){/*stuff here*/}
myclass(int* p) {MyPointer = p; myclass()}

[Code] ....

it works until the myclass(int* p) calls myclass()

then the MyPointer will become CCCCCCCC (NULL value)!

is there a way to stop the second constructor from resetting the pointer value to null?

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C++ :: Using Constructor Within Constructor In Same Class

Feb 28, 2012

I am trying to use constructor within constructor in the same class. Is that possible. I have tried something and it shows me a error message:

error: type "mainClass" is not a direct base of "glavna"

This is the program I tried:

Code:
class mainClass {
private:
int x,y;

Code] ......

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C++ :: Derived Class Constructor Using Base Class Constructor?

Jan 1, 2013

Is this example correct? This example from a book

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?

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C :: Default Value Of Pointer

Feb 28, 2014

Following is the code snippet

Code:
[COLOR=white !important]?
1
2
3
4
5 char str1[]="Bombay";
char str2[]="Pune";
char *s1=str,*s2=str2;
while(*s1++=*s2=str2);
printf("%s",str1);

Output of this code comes out to be Pune

But according to me output should be puneay.

Pune should be copied in place of Bomb.and rest should be as it is.
[/COLOR]

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C++ :: Set Pointers To Default Value For Both 32 Bit And 64 Bit

Sep 6, 2013

I have a problem. I want to set pointers to a default value for both 32 bit and 64 bit compiles. The 32-bit version works as:

enum constants { UNDEFINED = 0xDeadBeef }
if ((unsigned long)ptr == UNDEFINED)

but I can't seem to extend this to 64-bits. I've tried
#if __SIZEOF_POINTER__ == 4
enum constants { UNDEFDATA = 0xDeadBeef };
}; // enum constants
#elif __SIZEOF_POINTER__ == 8
enum constants { UNDEFDATA = 0xDeadBeefDeadBeef };
#endif

with:
if (ptr == UNDEFINED)

but get a message saying the '==' is undefined (I understand this)

Is there any way to setup so that I can change the size of my constants so that the comparisons will always work correctly? I've tried a 'typedef' but the compiler complains at

'typedef unsigned long long ADDR' // won't accept, and
static const SlipCellBase * const TEMPORARY = (SlipCellBase&)0xFFFFFFFFFFFFFFFF; // illegal conversion

enum doesn't work (because it's an int?)

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C :: How To Create Default Arguments

Oct 20, 2013

How to create default arguments in C? Is there any way to make default arguments ( i mean any alternative for them).

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C++ :: Multiple Default Constructors Specified

Dec 16, 2014

I have an inherited class that essentially manages a Qt Window.

It is as follows (prototype below):

class QTMyOpenGLWindow : public QWindow, protected QOpenGLFunctions {
Q_OBJECT

[Code] ....

Now, I can understand the confusion of the compiler, but the functionality as I laid it out works for me (I can create the class with just specifying the parent and also have the option of preventing auto-initialization when creating). But, is there a better approach?

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C++ :: Default Arguments And Omitting Only Some Of Them?

Apr 7, 2014

I am trying to figure out what's the best way to accomplish something like this:

void function(t1 a=0,t2 b=0){/*...*/};
t2 value;
function(value);

That would throw a compile error, since the first argument that is being passed to the function (value) is considered the first argument in the declaration (a), which is of type t1. So, is there a way to force my function to consider value as the second argument instead of the first one? I am aware that this could be done using overloading, but the larger the amount of arguments, the larger amount of possibilities, so it might end up with a huge list of overloads. The best case scenario would be being able to set things like:

void function(t1 a=16,t1 b=0,t2 c=1){/*body*/};
function(b=3,a=0);
but I'm not aware of such feature in C++.

Would it be possible to design some sort of macro system to take care of this?

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C++ :: Where Is DirectX SDK Installed By Default

Feb 13, 2013

So a long time ago I messed around with DirectX but I don't remember where it gets placed by default. I want to just get rid of the SDK and get the up to date version of it.

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C++ :: Application Default Parameters?

Mar 16, 2013

I have developed an application in C++ that creates some text files in a directory chosen by the user.

How can I ask the user set a Default Directory Path (and some other default parameters) so that she doesn't have to enter the same data in the GUI everytime the application is run.

The application has been developed using Qt Creator.

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C++ :: Template Class With Default Value?

Mar 22, 2013

refer to the code below, the attribute class is created with the value type and default value, but why it doesn't work for std::string?

#include <string>
#include <iostream>
using namespace std;

[Code].....

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C++ :: What Is Default Size Of STL Vector

Jan 30, 2012

For example, I have an empty vector of integer. If I keep calling push_back on vector, is it going to be out of memory?

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C++ :: Implicit Default Ctor - What Is It For

Apr 16, 2013

Implicit default ctor does not initialize the built-in data members, so what is it needed for?

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C++ :: Custom Exceptions With Default Behaviour

May 24, 2013

I've been pondering which of these 2 approaches would make for the best interface for a library: Defining custom exceptions with specific names for different error scenarios but with standard behaviour, or simply using the predefined exceptions from the STL.

This is my current approach:
Code:
namespace rpp
{
class ConnectionError : public std::exception
{
public:
ConnectionError(const std::string &p_err);

[Code] .....

This seems to make for more descriptive code but it adds no functionality and the implementations are completely identical, which seems "off" to me, somehow.

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