PackedAliasSeq?

[Petar]

On Saturday, 24 February 2018 at 06:14:52 UTC, deadalnix wrote:
> On Thursday, 22 February 2018 at 19:26:54 UTC, Andrei 
> Alexandrescu wrote:
>> After coding https://github.com/dlang/phobos/pull/6192 with 
>> AliasSeq, the experience has been quite pleasurable. However, 
>> in places the AliasSeq tends to expand too eagerly, leading to 
>> a need to "keep it together" e.g. when you need to pass two of 
>> those to a template.
>>
>> I worked around the issue by nesting templates like this:
>>
>> template Merge(T...)
>> {
>>     template With(U...)
>>     {
>>         static if (T.length == 0)
>>             alias With = U;
>>         else static if (U.length == 0)
>>             alias With = T;
>>         else static if (T[0] < U[0]
>>                  || T[0] == U[0] && T[1].stringof <= 
>> U[1].stringof)
>>             alias With =
>>                 AliasSeq!(T[0], T[1], Merge!(T[2 .. 
>> $]).With!U);
>>        else
>>             alias With =
>>                 AliasSeq!(U[0], U[1], Merge!T.With!(U[2 .. 
>> $]));
>>     }
>> }
>>
>> So instead of the unworkable Merge!(AliasSeq!(...), 
>> AliasSeq!(...)), one would write 
>> Merge!(AliasSeq!(...)).With!(AliasSeq!(...)).
>>
>> The problem remains for other use cases, so I was thinking of 
>> adding to std.meta this simple artifact:
>>
>> template PackedAliasSeq!(T...)
>> {
>>     alias expand = AliasSeq!T;
>> }
>>
>> That way, everything stays together and can be expanded on 
>> demand.
>>
>>
>> Andrei
>
> Isn't a packed AliasSeq just a tuple ?

It is not a tuple (in the `std.typecons.Tuple` sense) if it can 
contain values, types and other kinds of symbols. I think a more 
appropriate name would be AliasTuple - an AliasSeq that doesn't 
auto-expand.