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!
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
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 };
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?
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;
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:
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.
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?
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?
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
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?
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?
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.
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.
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.
