Re: MI in Ada 200X

[Hyman Rosen <hyrosen@mail.com>]

Preben Randhol wrote:
 > Seriously what are the pros and cons of MI.

If SI is considered useful, I fail to see why MI would not be
considered useful. Implementing MI has its difficulties, related
to complicated memory layouts, casting, and so forth. You can get
an idea for the complexities by looking up the C++ ABI that gcc
implements.

Here's a particular example which is ever annoying in Java. A
common design pattern in Java is to have an interface, and then
make a companion class which implements the interface and provides
do-nothing implementations for all the methods. If you want a class
which implements both interfaces and does nothing for most of the
methods, you can't inherit from both companion classes. Instead,
you must reimplement at least one set of the dunsel methods.

C++ also has its stream classes, where istream and ostream inherit
from an ios_base, and then iostream inherits from istream and ostream.