Can you use RTTI to determine a union member?

[Kirk McDonald]

Janice Caron wrote:
> Suppose I have
> 
> union U
> {
>     A a;
>     B b;
>     C c;
> }
> 
> and a function f(U u)
> 
> is there any way to determine at runtime, which union member has been
> assigned? I guess I want to do something like
> 
> void f(U u)
> {
>     if (is(u.a.typeof == A)) /* stuff */
>     else if (is(u.a.typeof == B)) /* stuff */
>     else if (is(u.a.typeof == C)) /* stuff */
> }
> 
> except obviously that won't work because typeof is a compile time
> thing, not a run time thing, and so it will always return A.
> 
> I don't suppose there's a runtime solution? If not, I guess I'll just
> do what I've been doing all along (that is, store the choice in an
> enum outside the union).

enum + union is the age-old solution to this. D doesn't store this 
information for you (which I think is a good thing).

-- 
Kirk McDonald
http://kirkmcdonald.blogspot.com
Pyd: Connecting D and Python
http://pyd.dsource.org