Re: Q: Endless loop by dispatching

["Robert I. Eachus" <rieachus@attbi.com>]

Chad R. Meiners wrote:

> Well one problem is that some people (as in me) think that Tucker's behavior
> is common sense. Although either way, it is best to have the compilers agree
> ;)

On most every issue debated in the ARG, the actual decision made is 
almost a detail.  The important parts are to make sure that everyone 
understands the issue, that we don't create new issues when fixing a 
current one, and to cover all cases.

I personally think that the effort needed to allow support two 
dispatching operations of the same name, and which one gets called 
depends on the place in the text of the call is unnecessary overhead. 
(Note that having several dispatching operations with the same name, and 
determining which is called by a view conversion is clearly necessary. 
The surprise in this case is that there is no view conversion needed.)

But again, any case where this comes up is expected to be one where the 
user is unintentionally shooting himself in the foot.  The intent of 
adding pragma Overriding or the overriding keyword is to allow the user 
to detect such cases at compile time.  THAT is the important part of the 
AI.  This particular example arose when I was demonstrating that there 
are cases of overriding where there would be no reasonable place to put 
the pragma or keyword.  It turned out that in this particular case, I 
was right to be wrong.  I understood the rules the way GNAT implements 
them, while others compilers do it differently.

I think that the final resolution will be to read things the way Tuck 
was arguing, with possibly a few "extra" words to insure that the only 
cases where the dual meanings arise are in package specs. I don't think 
we want a Beaujolais-like effect, where adding a with clause can change 
which version gets called.

-- 

                                                        Robert I. Eachus

�In an ally, considerations of house, clan, planet, race are 
insignificant beside two prime questions, which are: 1. Can he shoot? 2. 
Will he aim at your enemy?� -- from the Laiden novels by Sharon Lee and 
Steve Miller.