Question

So I have a vec4 class that uses members x,y,z,w which you can access using

point.x point.y etc.

However I want to reuse this vec4 class to be my color class (it already supports scalar multiplication, operator overloading lots of other nice stuff)
I just want to be able to refer to the members using another notation:

color.r
color.g
color.b

etc.

Is there anyway I can do this using a macro or other syntactic sugar?

Answer 1

If you are using Visual Studio (and are sure that it is the only target IDE…) you can use the following:

#include <cassert>

union vec4
{
    struct 
    {
        float x;
        float y;
        float z;
        float w;
    };
    struct
    {
        float r;
        float g;
        float b;
        float a;
    };
};

int main()
{
    vec4 vec = { 0 };
    vec.y = 10.0f;
    assert(vec.g == 10.0f);
    return 0;
}

It will yield warnings warning C4201: nonstandard extension used : nameless struct/union, though you can disable it.

EDIT: as it turns out gcc supports this extension as well.