Sequence separation

[Engine Machine via Digitalmars-d-learn]

On Wednesday, 17 August 2016 at 18:38:48 UTC, Engine Machine 
wrote:
> On Wednesday, 17 August 2016 at 08:37:32 UTC, Lodovico Giaretta 
> wrote:
>> On Tuesday, 16 August 2016 at 23:18:28 UTC, Adam D. Ruppe 
>> wrote:
>>> [...]
>>
>> You mean something like:
>>
>> struct MySequence(Args...)
>> {
>>     enum length = Args.length;
>>     alias args = Args;
>> }
>>
>> alias x = MySequence!(a, b, MySequence!(c, d));
>>
>> static assert(x.length == 3)
>> static assert(x.args[2].length == 2);
>
> Thanks, basically works.
>
> How can I test, though, if a argument uses a MySequence? I 
> can't do if (Args[0] == MySequence) because MySequence is 
> templated. While I could test for a length, that doesn't work 
> because some types have a length. I could add another enum to 
> MySequence, but again, not safe.
>
> I could do some string tests, but that doesn't work.
>
> in your exmaple,
>
> if (x.args[2] == MySequence) ??
>
> I simply need to differentiate between a parameter/arg being a 
> MySequence and not.

I guess I'll go with something like

static if ((a.Args[2]).stringof[0..11] == "MySequence!")

Doesn't feel entirely safe but probably will work without issue.

Maybe there is a better way?