Having trouble calling two functions from a structure, no logic error.

Question

#include <iostream>
#include <cmath>
using namespace std;
struct Point3D {
    int x;
    int y;
    int z;
};

Point3D AddTwoPoints(Point3D a, Point3D b)
{
float c2.x = b.x + a.x;    /*outputs error expected initializer before '.' token
float c2.y = b.y + a.y;
float c2.z = b.z + a.z;      */
return;
}
Point3D SubtractTwoPoints(Point3D a, Point3D b) {
float d2.x = b.x - a.x;    /*outputs error expected initializer before '.' token
float d2.y = b.y - a.y;
float d2.z = b.z - a.z;      */
return;
}

int main()
{
    Point3D a2, b2;
    a2.x = 4;
    a2.y = 7;
    a2.z = -14;
    b2.x = 5;
    b2.y = 5;
    b2.z = 10;

Point3D c2 = AddTwoPoints(a2, b2);
    cout << "Add a2 and b2: (" << c2.x << "," << c2.y << "," << c2.z << ")" << endl;  
    Point3D d2 = SubtractTwoPoints(a2, b2);
    cout << "Subtract b2 from a2: (" << d2.x << "," << d2.y << "," << d2.z << ")" << endl;  
    return 0;
}

Answer 1

You're using c2.x for a variable name. Variable names cannot contain a dot (.). You can use underscore (_) or just call your variables x, y, z instead. :)

Another solution is to return a new Point3D and initialize it while you return it:

Point3D AddTwoPoints(Point3D a, Point3D b)
{
    return Point3D { a.x + b.x, a.y + b.y, a.z + b.z };
}

Point3D SubtractTwoPoints(Point3D a, Point3D b)
{
    return Point3D { a.x - b.x, a.y - b.y, a.z - b.z };
}