Re: [Caml-list] Just how slow are classes?

[Leo White <leo@lpw25.net>]

> > While I am also curious why "nice cases" of objects/classes couldn't
> > be optimized (perhaps some link time check), when most of the objects
> > adhere to a nice hierarchy, I would like to defer that discussion
> > until another time.
> 
> Oh, this is quickly explained. There is no hierarchy at runtime you can
> exploit. Remember that object X can be a subtype of object Y even if
> there is no inheritance relationship. This is very different from other
> OO languages.
> 

It is worth noting that you get similar issues with things like Java interfaces
(you can think of every method in an OCaml object type as a Java interface
containing a single method), and there are some effective mechanisms for
optimising them. The most important of these is inline method caching, which
is implemented for OCaml objects. Others, such as perfect hashing[1] are not
implemented for OCaml, so there is probably room for improvement, but they
would require significant amounts of work.

Regards,

Leo

[1] http://www.lirmm.fr/~ducour/Publis/RD-TOPLAS-08.pdf