On Saturday, 10 November 2012 at 05:34:32 UTC, Jonathan M Davis
wrote:
...
The language is more complicated if you can explicitly choose
whether a
particular function is virtual or not. It also causes a number
of bugs. C++
has issues with it all the time. It certainly _can_ be done,
but the language
designers chose to go the Java route of making virtuality
implicit. On the
whole, it's exactly what you want.
Generally, public functions need to be virtual. If they don't,
you can mark
them as final. And it makes no sense for a protected function
to be non-
virtual. So, both of them are virtual.
I think that it is unsuccessful decision by the language
designers, because object oriented code use virtual functions not
much in most cases, thence it is useless and bad for performance
or it causes developer to set public and protected functions as
final explicitly very much.
It doesn't really make sense for private functions to be
virtual. If you want
them to be virtual, just use protected. And if private were
virtual, then that
would really hurt performance, and everyone would be forced to
mark all of
their private functions as final to avoid it. So, it just makes
more sense to
make them non-virtual.
package is more debatable, and some people have argued that it
should be
virtual, but Walter Bright and Andrei Alexandrescu don't think
that it really
makes sense to. I'd have to go digging through the archives for
the main
newsgroup though to find a post where they discuss it to tell
you exactly what
they said.
- Jonathan M Davis
I agree with everything that you say about private functions and
i agree with people who have argued that package functions should
can be virtual.=)
Thanks for help and interesting discussion.
PS: Sorry for my bad English.
