Re: overloading the [] operator in a vector child class

Hi,

I am creating a child class of the vector, which contains a couple of
functions to make the work with carthesian coordinate vectors easier.
To make things work more easily, I would like to be able to access the
vector through a string which is either x, y or z. So that I can use:

---xyzvec.hh--
#ifndef XYZVEC_HH
#define XYZVEC_HH

#include <vector>
#include <iostream>

xyzvec vec ;
vec["x"] = 3;
double testing = vec["x"].

My class is now:

class xyzvec : public vector<double> {

public:
  xyzvec( void ) : vector<double>(3) { }

  xyzvec(double x, double y, double z) : vector<double>(3) {
    (*this)[0] = x;
    (*this)[1] = y;
    (*this)[2] = z;
  }

  double x() { return (*this)[0] ; }
  double y() { return (*this)[1] ; }
  double z() { return (*this)[2] ; }

  double length( void ) {
    double n = pow(pow((*this)[0],2) + pow((*this)[1],2) + pow((*this)
[2],2),0.5) ;
    return n;
  }
double& operator[] (const string&) {
     if(string=="x") return &(*this)[0] ;
     if(string=="y") return &(*this)[0] ;
     if(string=="z") return &(*this)[0] ;}

private:

} ;

#endif
---

Probably I am doing something horribly wrong with the pointers, but
this yields a big heap of errors.