union initalization

[Ali Çehreli via Digitalmars-d-learn]

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

 > 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