   Random Union Question
  I'm attempting to make a vector and matrix classes as similar to GLSL as possible and have had very little experience with what would be considered proper programming methods so I was curious what people thought of using unions like such:typedef struct _vec3 {union {float xyz[3];float rgb[3];float stp[3];struct {union {float xy[2];float rg[2];float st[2];struct {union {float x;float r;float s;};union {float y;float g;float t;};};};union {float z;float b;float p;};};struct {union {float x;float r;float s;};union {float yz[2];float ga[2];float tp[2];struct {union {float y;float g;float t;};union {float z;float b;float p;};};};};};} vec3;I know it looks hideous (as are all great sleep deprived ideas), but I'm more interested in compatibility and efficiency. I actually found it interesting that it compiles (using MS VS2008), since some variable names are the same. I tested it with a very simple case and it gave me correct results. I also made a vec2 struct similar to this one and used it instead of the float[2]s in this vec3 and it worked as well. Is it guaranteed that the results will be correct?   
  Using it like GLSL vectors would probably result in undefined behaviour as far as the standard is concerned.   