How do I call operator function to add two objects? [duplicate] - c++

Question

This question already has an answer here:
Overloaded Addition assignment operator in C++ for two /more than two objects?
(1 answer)
Closed 5 years ago.
Trying to develop operator == to compare two balls where two balls are considered equal if they have the same radius and operator > to compare two balls. To see if one ball has a bigger radius than another one, for let's say ball x is > than another ball y. += to add the volume of the right-side-operand to the volume of the left-side-operand. It is like to melt two metal balls to make one metal ball. The new ball's radius is cube root of (r1^3 + r2^3). Wish to use pow() function to calculate the cube value and cube root value. operator + to add the two balls together and return a new ball. The size of the new ball is the sum of the size of the two operands connected by the +.
In the main() function, couldn't add ball m(10) with ball n(20) to create another ball d, like d = m+n.
int main()
{
//use ball
ball x; float re;
//radius of ball y is set to 10
ball y(10);
//asks for radius of x?
cout << "Enter radius for ball x: ";
cin >> re;
//sets the radius of x
x.set_radius(re);
ball m(10);
ball n(20);
ball d;
d = m + n;
//cout << "The radius of ball d is " << m.;
system("pause");
return 0;
}
//ball.h
{
class ball
{
public:
//sets the intial raduis to 0
ball() {
radius = 0;
}
ball(float radii) {
radius = radii;
}
float get_radius() {
return radius;
}
void set_radius(float redly) {
radius = redly;
}
bool operator == (ball x) {
if (radius == x.radius)
return true;
else
return false;
}
bool operator > (ball x) {
if (radius > x.radius)
return true;
else
return false;
}
bool operator += (ball x) {
radius += x.radius;
}
ball operator + (ball a, ball b) {
ball d;
d += a;
d += b;
return d;
}
private:
float radius;
};
}
#endif

Answer 1

If you are only looking for (x_volume/ y_volume)% and (x_surfacearea/y_surfacearea)%
I suggest doing :
float vol_over_y() {
float v;
v = ((radius * radius * radius)/(10*10*10));
return v;
}
float sa_over_y() {
float a;
a = (radius * radius /(10*10));
return a;
}
because other constants like (4.0/3.0)* 3.14 in volume and 3.14 in surface area cancel out.
If in case y changes,
float vol_over_y(float y_rad) {
float v;
v = ((radius * radius * radius)/(y_rad*y_rad*y_rad));
return v;
}
float sa_over_y(float y_rad) {
float a;
a = (radius * radius /(y_rad*y_rad));
return a;
}

Answer 2

You thought too much. It is simply a little tweak in your main logic:
ball x;
ball y(10);
// your code to construct x
cout << "The volume of x is " << ( x.volume() / y.volume() )<< "% of the volume of y."<< endl;
// similar for surface area, try it out yourself
If in case you really need to do it in a method(which is quite ridiculous imho), you should just pass the other ball in and calculate:
float volume_ratio_to(const ball& base) {
return volume() / base.volume();
}
And your main logic become
cout << "The volume of x is " << x.volume_ratio_to(y) << "% of the volume of y."<< endl;
Edited for your updated question:
The reason why + operator does not work for you is because you didn't overloaded the operator right.
If you want it to be member of ball, the + operator should only takes one argument.
i.e. looks like:
class ball {
//....
ball operator + (ball another);
}
Or, don't make it member of ball:
// outside ball class
ball operator + (ball a, ball b) {....}
Refer to Overloaded Addition assignment operator in C++ for two /more than two objects? for more detailed description on how to overload addition operator.
There are quite a lot of other problems in your code too
You should have passed balls to methods by reference instead of by value
You should have considered adding const in various places
You += logic is totally wrong. Pay attention to what you quoted:
+= to add the volume of the right-side-operand to the volume of the
left-side-operand. It is like to melt two metal balls to make one
metal ball. The new ball's radius is cube root of (r1^3 + r2^3)

Answer 3

//This helps
int main()
{
//use ball
ball x; float re;
ball y(10);
cout << "Enter radius for ball x: " << endl;
cin >> re;
x.setl(re);
cout << "The volume of x is " << (x.volume()/y.volume())*100 << "%
of the volume of y."<< endl;
cout << "The surfacearea of x box is " <<
(x.surface_area()/y.surface_area())*100 << "% of
the surfacearea of y." << endl;
system("pause");
return 0;
}
//ball.h
#pragma once
#ifndef Ball
#define Ball
namespace bsize
{
class ball
{
public:
ball(){
radius = 0;
}
ball(float radii) {
radius = radii;
}
float volume() {
float v;
v = ((4.0/3.0)* 3.14 * (radius * radius * radius));
return v;
}
float surface_area() {
float a;
a = (4 * 3.14 * radius * radius);
return a;
}
float get_radius(){
return radius;
}
void set_radius(float redly) {
radius = redly;
}
private:
float radius;
};
}
#endif