Accessing operator inside struct itself

Question

I'm trying to access an operator inside the struct itself, is this possible?

struct st{
    float vd;
    float val(){
      return this[3]; //this dont work, is there a some way?
    }
    float operator[](size_t idx){
        return  vd*idx;
    }
};

Answer 1

this is a pointer to the object not the object itself. If you want to call a member function you can call the function directly

float val(){
  return operator[](3);
}

or you can dereference this and call [] on the actual object.

float val(){
  return (*this)[3];
}

Since this is a pointer return this[3]; translated to return (this + 3); which means give me the object that resides address of this + sizeof(st)*3 which is an invalid object since this is not an array. This is UB and will also cause a compiler error as the type of this[3] is a st and your function is supposed to return a float.