Enumerating structs?

Heywood Floyd soul8o8 at gmail.com
Tue Jan 3 07:35:29 PST 2012


I have some structs

  struct A { int a; }
  struct B { int b, c; }

and I'd like to be able to enumerate them (preferrably as integers) based on their names. I've no idea how this would look, but
some pseudo code that would use this feature:

  // pseudo
  int type = stream.read!int();
    case A.enumof:
      auto data = stream.read!A();
      // ...
    case B.enumof:
      // ...
    // ...

The idea here is to enable stuff like static if's etc and to enforce the connection between the struct and the enumeration. Right now
I have a separate enums, like so:

  enum {A_ENUM = 1, B_ENUM = 2};
  // ...
    case A_ENUM:
       auto data = stream.read!A();
       // ...

But this means the idea that struct A has the enumeration "1" is only by convention. So when I, for instance, refactor struct A to "C",
all code still compiles. It would be cool if it didn't, somehow. With this small example it's of course not a problem, but for larger
more complex code perhaps.

A naive idea I had was to let each struct have an enum:

  struct A{
    enum TYPE_ENUM = 1;
    int a;

That would be refactor-friendly and be a strong connection, but then there's no guarantee two structs don't have the same enum,
of course. Another idea was to maybe use mixin to somehow construct the enum declaration:

  mixin enumByType!(A,B);

That could generate code like:

  enum {A_ENUM = 1, ...}

and then couple it with a

   // ...
   case typeEnumFor!A():
   // ...

but now it's starting to maybe feel a bit overkill?
Is there an easier/correct/other way?


I usually end up feeling like this a lot with D, I just realized. It's like, yes, with mixins I can more or less do anything, but where
does one stop? You know what I mean? I like it though. Mixin-paralysis : )


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