- minus unary operator overloading in c++
#include <iostream>
#include<conio.h>
using namespace std;
class Distance {
private:
int feet; // 0 to infinite
int inches; // 0 to 12
public:
// required constructors
Distance(){
feet = 0;
inches = 0;
}
Distance(int f, int i){
feet = f;
inches = i;
}
// method to display distance
void displayDistance() {
cout << "F: " << feet << " I:" << inches <<endl;
}
// overloaded minus (-) operator
Distance operator- () {
feet = -feet;
inches = -inches;
// return Distance(feet, inches);
}
};
int main() {
Distance D1(11, 10), D2(-5, 11);
-D1; // apply negation
D1.displayDistance(); // display D1
-D2; // apply negation
D2.displayDistance(); // display D2
return 0;
}
I am a beginner learning C++ overloading operator function. This code is actually working fine but at one step I am little confused about
// return Distance(feet, inches);
if I run program without making it comment the program also works fine than in what purpose is this statement is using
From [stmt.return]:
Flowing off the end of a constructor, a destructor, or a function with a cv void return type is equivalent to a return with no operand. Otherwise, flowing off the end of a function other than main ([basic.start.main]) results in undefined behavior.
Your program is resulting an undefined behavior, anything can happen as you can see here
Second, is it constructor function returning values?
I think you meant this line:
return Distance(feet, inches);
That line return a prvalue of Distance which is constructed from feet and inches. That value should be eligible to copy-elision and is guaranteed to be elided in copy from C++17
Third, how it is returning values I mean it is not a variable I always heard we can return values from variable?
From the said [stmt.return], emphasis is mine:
The expr-or-braced-init-list of a return statement is called its operand. A return statement with no operand shall be used only in a function whose return type is cv void, a constructor ([class.ctor]), or a destructor ([class.dtor]). A return statement with an operand of type void shall be used only in a function whose return type is cv void. A return statement with any other operand shall be used only in a function whose return type is not cv void; the return statement initializes the glvalue result or prvalue result object of the (explicit or implicit) function call by copy-initialization ([dcl.init]) from the operand. [ Note: A return statement can involve an invocation of a constructor to perform a copy or move of the operand if it is not a prvalue or if its type differs from the return type of the function. A copy operation associated with a return statement may be elided or converted to a move operation if an automatic storage duration variable is returned ([class.copy]). — end note ] [ Example:
std::pair<std::string,int> f(const char* p, int x) { return {p,x}; }
The return statement should go in those form:
return; // for void and constructor, destructor
or
return expression-or-braced-init-list;
Anyway, I think your minus operator should look like this:
Distance operator- () {
return Distance(-feet, -inches);
}