Re: version specific enum members

[Phil Deets]

On Fri, 30 Oct 2009 00:03:23 -0500, Daniel Keep  
<daniel.keep.li...@gmail.com> wrote:



Phil Deets wrote:
Hi, is there a way to add members to an enum based on conditional
compilation symbols. I tried

enum Tag {
   A, B,
   version (symbol) {
      C, D,
   }
   E,
}

but it doesn't work. I know I could do

version (symbol) {
   enum Tag { A, B, C, D, E }
} else {
   enum Tag { A, B, E }
}

but I don't want to do that since in my case, there can be quite a few
elements outside of the version, and I don't want to repeat them all.

template Version(char[] ident)
{
    mixin(`version(`~ident~`) const Version = true;
           else const Version = false;`);
}

char[] genEnum(bool flag1, bool flag2)
{
    return "A, B, "
         ~ (flag1 ? "C, D, " : "")
         ~ "E, F, "
         ~ (flag2 ? "G, H, " : "")
         ~ "G, ";
}

mixin(genEnum( Version!(`symbol`), Version!(`somethingElse`) ));

... is about the best you can do, I think.

Hey, thanks for the idea. I worked with it a little bit to remove the  
generator function and use multiline strings. This is what I came up with.

mixin(q"ENUM
enum Tag
{
   A, B,
ENUM"~(Version!("symbol")?q"ENUM
   C, D,
ENUM":"")~q"ENUM
   E,
}
ENUM");

That's not pretty, but it's good enough for me.