Refer to class members with aliases

  alias, c++, member, vector

I have a vector class

class vec3
    FLOAT x, y, z;

    vec3(FLOAT X = 0, FLOAT Y = 0, FLOAT Z = 0)
        x = X;
        y = Y;
        z = Z;

And I need to be able to use this vector as either spacial dimension using x, y, z, or as color using r, g, b or as measure dimensions using w, h, l.

It would be a waste of memory to have this vector class containing 9 members. Instead I want it to contain x, y and z and refer to them as stated above.

I already searched online and found almost fitting solutions, see C++ member variable aliases?

But the thing is, if I use something like

struct Vertex {
    float& r() { return values[0]; }
    float& g() { return values[1]; }
    float& b() { return values[2]; }

    float& x() { return values[0]; }
    float& y() { return values[1]; }
    float& z() { return values[2]; }

    float  operator [] (unsigned i) const { return this->values_[i]; }
    float& operator [] (unsigned i)       { return this->values_[i]; }
    operator float*() const { return this->values_; }

    float[3] values_;

then I can only read the struct members, not set them, and if I use

struct vertex
    float data[3];
    float &x, &y, &z;
    float &r, &g, &b;

    vertex() : x(data[0]), y(data[1]), z(data[2]), r(data[0]), g(data[1]), b(data[2]) {

    float& operator [](int i) { 
        return data[i];

then the struct increases in memory because each reference takes up space.

Source: Windows Questions C++