Runtime heterogeneous collections?

[Jonathan M Davis]

On Thursday, January 17, 2019 1:21:41 AM MST Dukc via Digitalmars-d-learn 
wrote:
> On Thursday, 17 January 2019 at 02:27:20 UTC, Neia Neutuladh
>
> wrote:
> > 1. Make a wrapper class. Now you can store Object[], or you can
> > make a
> > base class or base interface and use that.
> > 2. Use Variant, which can wrap anything, or the related
> > Algebraic, which
> > can wrap a fixed collection of types.
>
> 3. Use an union. However, only do this if you always know from
> outside what type of data is stored in each node. If you need to
> memoize the type of data for each node, better resort to 1. or 2.

Variant types are really just user-friendly wrappers around unions. So,
pedantically, using a variant type such as Variant or Albegbraic and using a
union are fundamentally the same thing, though obviously, the actual usage
in terms of the code that you write is not the same, since if you use a
union directly, you have to deal with the union directly (including figuring
out how to know which type the union currently holds), whereas with a
Variant, you're using its API rather than dealing with the union directly.
In general, it's probably better to use Variant rather than union simply
because Variant deals with the type safety for you.

- Jonathan M Davis