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.


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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.
> 
> 

Unfortunately, that's going to be about the best you can do, unless you're willing to play with string mixins and their ilk.

Ellery Newcomer 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.
>>
>>
> 
> Unfortunately, that's going to be about the best you can do, unless
> you're willing to play with string mixins and their ilk.

Or unless you create an enhancement request. That seems a very valid one.

On Thu, 29 Oct 2009 18:28:12 -0500, Ary Borenszweig <ary@esperanto.org.ar> wrote:

> Ellery Newcomer 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.
>>>
>>>
>>  Unfortunately, that's going to be about the best you can do, unless
>> you're willing to play with string mixins and their ilk.
>
> Or unless you create an enhancement request. That seems a very valid one.

Done (on the main D list).

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.

On Fri, 30 Oct 2009 00:03:23 -0500, Daniel Keep <daniel.keep.lists@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.

Phil Deets wrote:
> On Thu, 29 Oct 2009 18:28:12 -0500, Ary Borenszweig <ary@esperanto.org.ar> wrote:
> 
>> Ellery Newcomer 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.
>>>>
>>>>
>>>  Unfortunately, that's going to be about the best you can do, unless
>>> you're willing to play with string mixins and their ilk.
>>
>> Or unless you create an enhancement request. That seems a very valid one.
> 
> Done (on the main D list).

I meant a bugzilla enhancement, otherwise it'll get lost in the newsgroups.

On Fri, 30 Oct 2009 06:38:44 -0500, Ary Borenszweig <ary@esperanto.org.ar> wrote:

> Phil Deets wrote:
>> On Thu, 29 Oct 2009 18:28:12 -0500, Ary Borenszweig <ary@esperanto.org.ar> wrote:
>>
>>> Ellery Newcomer wrote:
>>>>  Unfortunately, that's going to be about the best you can do, unless
>>>> you're willing to play with string mixins and their ilk.
>>>
>>> Or unless you create an enhancement request. That seems a very valid one.
>>  Done (on the main D list).
>
> I meant a bugzilla enhancement, otherwise it'll get lost in the newsgroups.

Well, I wanted to gauge support for the idea. It turns out I found a string mixin workaround that works; so it isn't critical for me now.