union initalization

[Rufus Smith via Digitalmars-d-learn]

On Friday, 22 July 2016 at 02:08:06 UTC, Ali Çehreli wrote:
> On 07/21/2016 06:48 PM, Rufus Smith wrote:
> > I would like to combine two types
> >
> >
> > template Foo(A, B = 4)
> > {
> >      union
> >      {
> >         byte b = B;
> >         int a = A << 8;
> >      }
> > }
> >
> > This packs a and b together in to an int bytes, saving an
> int(rather
> > than storing a and b in an int each) and makes it easier to
> access.
>
> Bitfields may actually be useful in this case:
>
>   https://dlang.org/phobos/std_bitmanip.html#.bitfields
>

They don't allow default assignment though?

> > I get an error about overlapping default initialization. They
> don't
> > actually overlap in this case because of the shift.
>
> The following at least compiles:
>
> struct Foo(int A, byte B = 4)
> {
>     union
>     {
>         byte b = void;
>         int a = void;
>         uint __both = (A << 8) | B;
>     }
> }
>
> void main() {
>     auto f = Foo!(42)();
> }
>
> Ali

Maybe... I don't like extra member. Bitfields seem like it would 
be the best way but I require default initialization. I want to 
hide as details of the work on unpacking as possible.