C++ :: Operator Overloading And Mysterious Object Dereferencing?
May 7, 2015
This is the main header with three classes, in summary ADNodeInstance is a data holder, ADNode is encapsulating a pointer to ADNodeInstance, and ADGraphBuilder is a main class which holds all the ADNodeInstances and manages them.:
From this all I could infer is that in the funcreateGradientMessage on the switch for TANH the segfault occurs for the expression: directGradient * child * (1 - child). From the output I can see that this is what happens in order:
Unary negation on node 5 resulting in 15Addition of node 16 and 15 (e.g. the brackets) resulting in 17trying to multiply 14 and 5 - SEGFAULT something wrong with 5
So my question is what exactly is happening? I tried to understand but can't.
Try to implement overloading << operator. If I done it void then everything work fine (see comment out) if I make it class of ostream& then the operator return to me some memory address.
Code: #ifndef Point_HPP // anti multiply including gates #define Point_HPP #include <sstream> class Point { private:// declaration of private data members double x;// X coordinate double y;// Y coordinate
In that situation, << does not call the overloaded function, but rather calls the << method defined in the i/o library, which prints a message to the controlling terminal. So once it prints the message to the terminal, it then returns the out instance. Why return the out instance rather than a boolean like true? As you can see from the example, once the message is printed to terminal, out is not used anymore.
Code: #include <iostream>#include <iomanip> using namespace std; class Score { private: // Value at which we'll shift digits from million_counter to billion_counter static const int THRESHOLD = 1000000000;
[Code] ....
It gives the errors: line 105 error: million_counter was not declared in this scope line 106 error: normalizeScore was not declared in this scope line 110 error: million_counter was not declared in this scope and more of that until line 170 error: no match for 'operator<<' in 'std:perator<< <std::char_traits<char> >((* & std::cout), ((const char*)"a+b is ")) <<operator+((*c(const Score*) (& a)), (*(const Score*)(& b)))'
I thought that because i declared friend functions, they would be able to access the private variables of the class.
Well... I observed, as a non-professional programmer that "overloading operators" has some strict rules and some conventions... so any operator can differ from another. In order to have a clearest idea, I'd like to ask you to specify, for every operator, the correct (or best) way to overload it.
There are cases where you define &operator and cases where you define operator (without "&"). There are cases where operator are defined as "friend" inside class, and other cases where operator is declared externally.
example: ostream &operator<< (why it uses & ??)
So can we have a summary for all kind of operators?
I'm trying to overload operator<<, but I get an error saying 'ostream' does not name a type. Am I forgetting to declare something else? ostream& operator<< (ostream& out, Struct &b);I made sure to #include <iostream> too.
I am having a bit of an issue figuring out how to operator overload with chaining. I have this as my operator= function (Its for linked lists)
WORD & WORD::operator=(const WORD & Org){ cout << " operator= has been called WITH CHAINING "; character *p = front;
[Code] ....
I want to be able to do X = X = X where X is of class WORD, but it errors when that line is called. And by error, I dont mean a written error, it just compiles, then says 'MSVC has stopped working' on a new pop up.
How to finish these two remaining operator overloading functions
Also, "contents and NumItems are private"
Code: Bag operator+ (const Bag& b1, const Bag& b2); //Postcondition: the bag returned is the union of b1 and b2. ostream& operator<<(ostream&, const Bag&); //Overloading operator <<
I have a date class and i overloaded operator >> to accept input in dd/mm/yyyy format. if i enter the wrong date format my program will crash. How do i do exception handling for this? How should i do the try part? and for catch, I'll just catch a date class variable?
Code: void operator >> (istream &is, clsDate &date) { string inputDate; is >> inputDate; int mm = stringToNumber(inputDate.substr(3,2)); // read 2 characters from character number 3 start int dd = stringToNumber(inputDate.substr(0,2)); // read 2 characters from character number 0 start int yy = stringToNumber(inputDate.substr(6,4)); // read 4 characters from character number 6 start
these function works. but if i concat literal strings with '+', i must use '(string)'. so i'm trying overload the operator + for concat literal strings, but without sucess:(
I have a class A, from which three classes Aa Ab and Ac are inherited. In class A I have defined some functions by virtual foo()=0, which I implemented in each subclass. Each class is written in a separated .h and .cpp file.
However, now I think it is possible to overload the operator+ INSIDE each class (including pure virtual in class A), such that something like
int main() { A *value = new Aa(); A value2 = *value + 1.0f; }
This should be realizable, because the operator+ is part of the Aa class. Now, I would like to do something like
int main() { A *value = new Aa(); A value2 = 1.0f + *value; }
This time, I expect I cannot overwrite the operator+, because it is not part of either class A or class Aa.
1st Question: I have three different classes A, B, and C; and correspondingly overloaded the insertion stream operator(<<) for all three classes. Classes A and B each have objects of class C as private data members. I am seeking a scheme whereby the << operator behaves differently for class C objects when an object of class A is to be printed from when an object of class B is to be printed. In other words, I want to have one << operator function invoked for class C when the object in question is of class A and another << operator function called for class C when the object in question is of class B. Is this realizable?
2nd Question: I have a derived class that uses a search function defined in an 'inaccessible' linked-list base class. By inaccessible, I mean I cannot change the contents of any of the member functions of this base class. The search function has three cout statements that print string literals showing results of the search operation if:
a. list is empty b. search item is found in the list c. search item is not found in the list upon searching
I am seeking a scheme whereby, instead of displaying the results of the search operation on the standard output (i.e. screen), a function I write can capture these string literals as input parameters, and process them for a Boolean value return. Is it possible to preclude the printing of the literals on the screen in this manner?
I wrote a class that can display fractions ex. 1/4 and I cannot figure out how to get >> to process 1/4 and separate them into variables numerator and denominator.
my program just constantly creates RationalNumber Objects when it reaches cin >> A .
To get a value I would always use setter and getter. Would it be much better (performance) to use vector subscript operator overloading? And does vector subscription operator overloading require a size for the vector?
I'm working on a project and I'm not quite sure how to implement the Copy constructor and Overloaded assignment operator.
This is what the instructions say if that matters at all: Since you have dynamic variables in your class, you should make sure that the big three are implements. You already have the destructor, but you will need to add a copy constructor and the overloaded assignment operator. This is simpler than it sounds, but it requires some thinking. You need to make sure that both the copy constructor and the assignment operator create new containers.
#include <iostream> using namespace std; class Date { private: int month, day, year; public: // class constructors can be overloaded Date(int m, int d, int y) {
[Code] ....
Actually ,I'm not sure whether my understanding of operator>> function is correct. Here is my understanding of operator>> function.....
operator>> function takes Date object as argument from main function and it reads data from the console using istream(This is all I know about istream) into the new Date object which is created by operator>> function..
This is all I know about operator>> function...I really don't know why it has to return istream reference(I know the return type is istream, but other than that ? I want to know why operator>> function creates new Date object ? It already has a reference to Date object ....why not simply set the values of the already existing Date object instead of creating one..?
So i am having troubles with operator overloading in inherited class. Basically, it doesnt work. Consider this:
Code:
class A { public: A() { x=0; z= new int;
[Code] ....
Some how the copy constructor of a is improperly executed - the pointer is copied over, not re-created. As a result, the destructors crashes due to double-free.
*/ B bb = b; //doesnt work B bbb(b); //doesnt work B bbbb(b, 0); //works }
Above code shows the problem well. The "official" copy-constructor wont work - it copies over the pointer directly, and doesnt create a new one as it should. However, if i provide my own pseudo-copy-constructor that works. But ofcourse it's just a cheap work around - and wont actually work in real code (STL).
Recently, i successfully overloaded postfix operator to class counter by using Object and Class. Now, i want to overload same postfix operator to Inheritance. I created my code and generated in compiler. But, my compiler signaled me uncommon error(saw first time) and i couldn't generate any idea where my actually mistake is.
Here is my Code which objective is to count the number increasingly or decreasingly as per object created of CountDn class.
Code: #include <iostream> using namespace std; class Counter // base class { protected : // NOTE : Not Private unsigned int count;
[Code] ....
Error :|41|error: no 'operator++(int)' declared for postfix '++', trying prefix operator instead| |42|error: no 'operator++(int)' declared for postfix '++', trying prefix operator instead| |42|error: no match for 'operator=' in 'c2 = c1.CountDn::<anonymous>.Counter:perator++()'| |44|error: no 'operator--(int)' declared for postfix '--', trying prefix operator instead|
class Var { public: Var(); ~Var(); private: QMap<QString, QSharedPointer<Data>> _mapVars; }; QDataStream &operator<<(QDataStream &stream, const QSharedPointer<Data> p_data); QDataStream &operator>>(QDataStream &stream, Data &p_data)
I want to serialize _mapVars into a file. However, I have many other classes that are derived from Data, do i need to check for Data type inside the overloaded << functions like below in order to serialize ??? This doesn';t seem to be very correct ...
