Re: Suggestion for gnatstub

["Randy Brukardt" <randy@rrsoftware.com>]

Robert A Duff wrote in message ...
>"Marin David Condic" <mcondic.auntie.spam@acm.org> writes:
>
>> I can't think of too many other reasons to write a null procedure. If
it was
>> going to stay null forever, then why have it at all. Seems like the
>> mechanism is there so you can have a procedure waiting for the
programmer to
>> find the elusive Round Tuit. :-)
>
>I can't think of "too many", either, but I can think of some.  Just the
>other day I wrote a generic procedure to walk a tree.  The generic
takes
>two generic formal procedures, Pre_Action and Post_Action, which are
>called during the tree at the points you would guess.  They have
>defaults, "is Do_Nothing", so you can specify one or the other.
>Guess what procedure Do_Nothing looks like.  ;-)


Most action routines (callbacks) in Claw are defined as procedure
When_something (...) is null; end When_something;
These may be overridden in for a derived type, but the original routine
is likely to remain with a null body forever. I believe this is common
in object-oriented code.

            Randy.