overloading operations for enums

[Rene Zwanenburg via Digitalmars-d-learn]

On Monday, 26 May 2014 at 16:54:02 UTC, Dominikus Dittes Scherkl 
wrote:
> Hello.
>
> I want to create some finite algebra, where the elements are 
> enumerated but operations on them are defined (with composition 
> tables).
>
> e.g.:
>
> enum color = { white, yellow, red, blue, orange, violet, green, 
> black };
>
> color a = blue;
> a += yellow;
> assert(a == green);
>
> is this possible in D?
>
> Because, if I define a struct, I can define operation 
> overloads, but then I have no enumeration of possible values. 
> But if I enumerate, I cannot
> overload operations.
> What have I missed?

You can make an enumeration of structs:

struct S
{
   int i;
}

enum E
{
   Something = S(1),
   SomethingElse = S(2)
}