命名数组元素或联合中的结构和数组

struct Vector4D
{
   union
   {
      double components[4];
      struct { double x, y, z, t; } Endpoint;
   };
};

Vector4D v;
v.components[2] = 3.0;
ASSERT(v.Endpoint.z == 3.0) //let\'s ignore precision issues for now

x

y

y

z

.z()

#include <iostream>
using namespace std;

struct Vector4D
{
    Vector4D() : components(), x(components[0]), y(components[1]), z(components[2]), t(components[3]) { }

    double components[4];

    double& x;
    double& y;
    double& z;
    double& t;
};

int main()
{
    Vector4D v;

    v.components[0] = 3.0;
    v.components[1] = 1.0;
    v.components[2] = 4.0;
    v.components[3] = 15.0;

    cout << v.x << endl;
    cout << v.y << endl;
    cout << v.z << endl;
    cout << v.t << endl;
}

v.Endpoint.z

v[2]