如何声明操作符/重载函数来操作const变量和非const变量？

Question

I have the following code

#pragma once

#include "material.h"
#include "../Math/vector.h"
#include <cmath>

class LambertianMaterial : public Material
{
public:
    LambertianMaterial(Vector rho);
    Vector brdf(Vector wi) const
    {
        return mRho / M_PI; // Error here
    }

private:
    Vector mRho;
};

In the line corresponding to the return statement of brdf I am getting the following error

Invalid operands to binary expression ('const Vector' and 'double')

In the class vector I have declared the operator/ like

Vector operator/(const float a);

I was thinking of redefining the method to

friend Vector operator/(const Vector& v, const float& a);

Is this a good way of doing it or is there a way so that the current definition of the operator accounts for the const Vector case?

Answer 1

You could make it a const member function, which could be applied for const and non-const object, if it won't (and it shouldn't) modify any non-static member variables.

Vector operator/(const float a) const;

As you thought, making it non-member function (and declared as friend if necessary) could do the work too. IMO I prefer to it for operator/ . See Operator overloading : member function vs. non-member function? for more informations.