Bug on a custom C++ class

Question

I need help on finding the problem using a custom c++ class to manage 3D positions. Here is the relevant code from the class ``` Punto operator+(Punto p){ return Punto(this->x + p.x, this->y + p.y, this->z + p.z); } Punto operator+(Punto *p){ return Punto(this->x + p->x, this->y + p->y, this->z + p->z); } Punto operator-(Punto p){ return Punto(this->x - p.x, this->y - p.y, this->z - p.z); } Punto operator-(Punto *p){ return Punto(this->x - p->x, this->y - p->y, this->z - p->z); } Punto *operator=(Punto p){ this->x = p.x; this->y = p.y; this->z = p.z; return this; } Punto *operator=(Punto *p){ this->x = p->x; this->y = p->y; this->z = p->z; return this; } ``` I'm using it here like this: ``` p = fem->elementoFrontera[i]->nodo[0] - fem->elementoFrontera[i]->nodo[1]; ``` Where nodo[i] is a Punto*, and it compiles fine, but when I try to do: ``` p = fem->elementoFrontera[i]->nodo[0] + fem->elementoFrontera[i]->nodo[1]; ``` The compiler says: In member function `void mdTOT::pintarElementos…

Accepted Answer

The first one compiles fine because you can subtract pointers in C/C++, but not add pointers. But in any case it doesn't do what you need - it doesn't use your overloaded operator. Since your operators are defined in a class, you need to operate on class instances, not on pointers. So, change to something like

```
Punto p = *(fem->elementoFrontera[i]->nodo[0]) + *(fem->elementoFrontera[i]->nodo[1]);
```

Another thing - you should use class references, not values, in operator definition. E.g.

```
 Punto& operator+(const Punto& p) {
```

EDIT. To simplify the code, you can create an accessor function, like this:

```
const Punto& NodoRef(int i, int j) {
  return *(fem->elementoFronteria[i]->Nodo[j]);
}
```

and then your code becomes as clean as

```
p = NodoRef(i,0) + NodoRef(i,1);
```

The NodoRef may be defined in your fem class, or outside. Just make sure the object fem is alive in the scope where you use the NodoRef.

Bug on a custom C++ class

Solution

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