Anonymous structure

[Adam D. Ruppe via Digitalmars-d-learn]

On Monday, 18 April 2016 at 02:12:24 UTC, Tofu Ninja wrote:
> Just out of curiosity, what is the point of the following?
>
> struct a{
> 	struct{
> 		int x;
> 		int y;
> 		int z;
> 	}
> }


The grouping matters when it is nested inside a union. Here's a 
real world example:

https://github.com/adamdruppe/arsd/blob/master/color.d#L128

The anonymous struct inside the union allows me to say that 
r,g,b, and a are NOT supposed to share memory, but rather give 
structure to the shared uint or ubyte[4] in the other union 
members.


My documentation generator also uses the grouping to add shared 
docs for the innards:

http://dpldocs.info/experimental-docs/arsd.color.Color.__anonymous.html

(I'm not terribly happy with giving it the name `__anonymous` in 
the docs but I didn't have any better idea yet.)

Though that isn't a feature of D itself, I do find it nice to be 
able to group documentation.


The struct inside union is the main pure-language use case I know 
of though.