Classes 2 problem...

[brianfast]

Hello I am reading the tutorial to try and learn c++ by myself. Today I move on to Classes II.

This is program

// vectors: overloading operators example
#include <iostream>
using namespace std;

class CVector {
public:
int x,y;
CVector () {};
CVector (int,int);
CVector operator + (CVector);
};

CVector::CVector (int a, int b) {
x = a;
y = b;
}

CVector CVector::operator+ (CVector param) {
CVector temp;
temp.x = x + param.x;
temp.y = y + param.y;
return (temp);
}

int main () {
CVector a (3,1);
CVector b (1,2);
CVector c;
c = a + b;
cout << c.x << "," << c.y;
return 0;
}

I do not understand:

CVector CVector::operator+ (CVector param) {
CVector temp;
temp.x = x + param.x;
temp.y = y + param.y;
return (temp);
}

How can you add thing with ONE parameter? It doesn't make sense!

[Scipio]

I don't completly understand your question, but if it is about the .x and .y:

Both temp and param are of class CVector, wich seems to have (at least) to membervariables: x and y. So one object (param) can have several values in it. By writing param.x you access the x-variable of param, by writing param.y you access the y-variable of param.

Hope this helps. If this isn't an answer to your question: what are you asking exactly?

[brianfast]

To me it seems like the parameter of the operator+ function is a single new CVector class called param. Then he makes a new Cvector class called temp. Then he says that temp.x is equivilant to x (where is this defined) + param.x (I think this is retained by the input of a Cvector class)...

Does the operator+ funtion work by taking the first CVector and getting the "x" and "y" values from there and then reading param.x and param.y from the second CVector class (the parameter)???

[Scipio]

x and y are membervariables. Take a look at this:

//...class declaration...

CVector firstObject;
CVector secondObject;
firstObject.x=1;
firstObject.y=2;
secondObject.x=3;
secondObject.y=4;
CVector thirdObject;
thirdObject=firstObject+secondObject;

Here the operator+ function from firstObject is called. As parameter, secondObject is used. It returns an object (temp) that has the added values from x (member of firstObject) + param.x (member of parameter) end y+param.y (same here) in it. This returnvalue is stored into thirdObject.