Getting derived classes

[Jason House]

dsimcha wrote:

> == Quote from Andrei Alexandrescu (SeeWebsiteForEmail at erdani.org)'s
> article
>> dsimcha wrote:
>> > I know that, in std.traits, there's a template that spits out all base
>> > classes
>> > for a given class.  Based on reading the source, it seems to work based
>> > on a
>> > rather interesting use case for is expressions.  Is there any
>> > equivalent way
>> > to do the opposite:  For any given position in a class hierarchy, to
>> > get a tuple of all possible descendants?
>> That's not possible in general because in D the derived classes form an
>> open set. I guess it could be done at runtime via reflection (not
>> implemented afaik), but not at compile time.
>> Andrei
> 
> Not quite sure I understand why this has to be the case.  Somewhere in the
> docs, Walter explicitly says that, since D knows about the whole class
> tree, the compiler can figure out which functions in a hierarchy can be
> made non-virtual. If this is the case, why is the compiler not able to
> know about the whole class tree for purposes of creating lists of derived
> classes?

There are many things hiding somewhere in the docs are many things that are
not implemented :)