DIP54 : revamp of Phobos tuple types

[monarch_dodra]

On Monday, 23 December 2013 at 13:31:36 UTC, Dicebot wrote:
> On Monday, 23 December 2013 at 13:23:39 UTC, monarch_dodra
>> eg:
>> staticIndexOf(int, TemplateArgumentList!(int, double), int);
>>
>> Produces 1? 2? 3?
>> I really don't know.
>
> Compile-time error, new `staticIndexOf` will strictly accept 2 
> template arguments - element and the list, similar to normal 
> `indexOf`:
>
> template staticIndexOf(T...)
>     if ((T.length == 2) && isTemplateArgumentList!(T[1]))

Ok... Then that'll break existing code that doesn't even *use* 
TypeTuple... Seems lose-lose to me :/

In any case, let me re-write my question it as:

staticIndexOf(int, 
TemplateArgumentList!(TemplateArgumentList!(int, double), int));

This time, its legal, right? What result does it create? Only the 
"outer" TAL gets auto-expanded, right? Expanding the inner one 
would seem wrong to me.

With that said, I can only image that the implementation of 
templates that simply recurse would become very hard to imlement.

I see value in having a packed type with explicit auto-expand, 
but I don't really see why it should replace the language's 
built-in variadic type list.