On Sunday, 24 August 2014 at 23:42:51 UTC, Aerolite wrote:
Hey all,
I was surprised to learn yesterday that D does not actually
support Multiple-Dispatch, also known as Multimethods. Why is
this? Support for this feature is already present in Scala, C#
4.0, Groovy, Clojure, etc... Would it not make sense for D to
remain competitive in this regard?
While I think many of us are aware that problems of the nature
that require Multiple-Dispatch can be approached with the
Visitor
Pattern, there seems to be a general consensus that the Visitor
Pattern is pretty cumbersome and boilerplate-heavy, and thus
should be avoided.
The common response from my searching around seems to be that a
template-based, static implementation of Multiple-Dispatch is
the
go-to solution in D, but considering the existing template-bloat
issues we have, I can't help but wonder if language support for
this feature might be a better path to go down. Seems like it
wouldn't be too difficult to implement, although I've not looked
very deeply into dmd's source-code.
So what seems to be the situation here?
At this point, if something can be implemented in a library
rather than in the language, the odds are low that it will be
solved in the language. The language is very powerful and already
a bit complicated, so usually the response for questions like
this is that we'll take advantage of D's existing features to
implement the new feature rather than complicating the language
further. If you could come up with a very good reason why it had
to be in the language, then maybe it would happen, but my guess
is that that's not likely to happen.
- Jonathan M Davis
