I want to create my own Tuple type

[Paul Backus]

On Monday, 11 January 2021 at 09:42:39 UTC, Ola Fosheim Grøstad 
wrote:
> On Monday, 11 January 2021 at 05:59:03 UTC, Paul Backus wrote:
>> You can just fall back to `alias expand this` like Phobos's 
>> Tuple does in this case. No compiler modification needed.
>
> I though maybe it would be nice in general to be able to create 
> static indexed type by having a special field name pattern, but 
> I will have a another look at staticMap (I don't really want 
> the full staticMap into object.d though).

I have no idea why you're bringing up staticMap here. The 
simplest way to create a tuple's fields is to use type sequence 
instantiation [1], like Phobos does:

struct Tuple(Types...)
{
     Types expand;

     // ...
}

You can then access the individual fields with `expand[i]`, where 
`i` is any compile-time evaluable integer expression. Adding 
`alias expand this` (as Phobos does) allows the indexing to be 
performed directly on the tuple, without having to write 
`.expand` first.

To handle dynamic vs. static indexing you can use a simple static 
if:

static if (allSameTypes) {
     auto opIndex(size_t i) {
         // ...
     }
} else {
     alias expand this;
}

[1] 
https://dlang.org/articles/ctarguments.html#type-seq-instantiation