Re: Renaming an abstract function

[Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov>]

"Nick Roberts" <nickroberts@adaos.worldonline.co.uk> writes:

> "Stephen Leake" <stephen.a.leake.1@gsfc.nasa.gov> wrote in message
> > ...
> > Well, the full text of the AI talks about renaming an _inherited_
> > subprogram, not the abstract subprogram itself. It does not discuss
> > exactly what should happen for this case.
> 
> Precisely my point (in parallel post).
> 
> > Simply following the rules for inheriting abstract subprograms, you
> > are required to give an overriding subprogram for any derived type.
> > Thus, if the renaming is valid, you'd have to override both P and "*",
> 
> This is correct.
> 
> > which is surely not the intent.
> 
> Yes it is the intent. The Rationale (8.3) makes this clear.

Well, I meant the "intent of the programmer". If I rename a function,
I "intend" to have two names for one function. If, when deriving the
type, I must provide _two_ functions, that is not two names for _one_
function. Of course, I can provide the same function, but I'd prefer
the language to enforce it.

Rationale 8.3 does say the behavior of renamed primitive operations
"may be considered surprising". I guess that's all I'm saying; I find
the behavior of inherited renamed primitive operations surprising. But
having read the Rationale (something I should do more often), I can
see why it has to be this way.

> > So it seems reasonable to conclude that the renaming itself is
> > invalid.
> 
> No, I don't think so.

Right, this is pretty close to the example in the rationale.

> > We could propose a "renaming inheritance" rule that says an
> > equivalent renaming is applied to the overriding subprogram; that
> > is the intent of this renaming.
> 
> Intriguing idea, but it is already laid down: the renaming creates a new
> 'slot', thus both (the original and renamed) subprograms can be (and, in the
> case of an asbtract subprogram, would need to be) overridden separately.

Yes, but the Rationale doesn't specifically address inheriting a
renamed function. It would be good if it did.

-- 
-- Stephe