>
> P.S.:
> One of the difficulties I had at first was in understanding the difference
> between super call and up-calls. A super call is a call to a super class
> (base class, lower down in the module hierarchy), an up-call is a call to a
> sub class (higher up in the module hierarchy). So: up-call = "sub call" (#
> super call).
> A framework like BlackBox heavily relies upon up-calls but tries to avoid
> super calls!
>
While the above statement may be technically correct, it mixes two
notions and thus confuses the issue even more.
A normal subroutine call is a "down call" since a procedure higher up
in the module chain is calling a procedure lower in the module chain.
With procedure variables and overridden methods, it becomes possible for
a module to invoke a procedure higher up in the module chain, or an "up
call". Such up calls are prevelant in framework systems, which are
unfinished by definition and comleted into a working system by
application specific procedures.
It is possible to discuss "up" and "down" calls without any reference to
object oriented programming.
Venkat Rao
GTE
Received on Mon Feb 15 1999 - 14:51:25 UTC