Does D support anonymous structs?

[Derek Parnell]

On Wed, 22 Feb 2006 20:58:35 -0800, Sean Kelly wrote:

> C:\code\d>type test.d
> void main()
> {
>      struct { int i; } s;
>      s.i = 1;
> }
> 
> C:\code\d>dmd test
> test.d(3): anonymous struct can only be a part of an aggregate

Yes. This is the rule "can only be a part of an aggregate". 


> ------------------------------------
> 
> C:\code\d>type test.d
> void main()
> {
>      struct S
>      {
>          union
>          {
>              struct
>              {
>                  int i1;
>              } s1;
>          } u;
>      }
> 
>      S s;
> }

The above doesn't work because if you have an anonymous struct/union is
*must not* have a name - that's why its anonymous. Consequently, you can
only have one anonymous aggregate per parent aggregate.

void main()
{
     struct S
     {
         union
         {
             struct
             {
                 int i1;
             };
         };
     }

     S s;
     s.i1 = 42; // You refer to anonymous struct members 
                // by the member id directly.
}

With named stucts, you have to separate the definition and the declaration. 

struct S  // Definition
{
  int i1;
}

S s;  // Declaration
s.i1 = 42;


With anonymous structs, the definition *is* the declaration.

struct S
{
  int i1;
  struct { int i2; } // Both definition and declaration.
}

S s;
s.i1 = 86;
s.i2 = 99;

-- 
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocracy!"
23/02/2006 5:19:12 PM