Re: Ada OO Mechanism

[Samuel Mize <smize@imagin.net>]

Hyman Rosen <hymie@prolifics.com> wrote:
> Samuel Mize <smize@imagin.net> writes:
>> I hope you find this of some interest.
> 
> I'm trying to wrap my head around this class-wide type stuff.
> I'm still at that stage of pre-clarity confusion :-)
> 
> Here's some code I threw at gnat, based on Richard D. Riehle's example.
...
> Gnat complains about the assignment to z:
> ft.adb:8:14: ambiguous expression (cannot resolve "Get")
> ft.adb:8:14: possible interpretation at ft.ads:12
> ft.adb:8:14: possible interpretation at ft.ads:9
> ft.adb:8:14: possible interpretation at ft.ads:6

I did a direct cut and paste to files on my system here and it
worked fine.  One of us must have an old version of GNAT.  I'm
using GNAT 3.10 on Windows.

I can see an argument that, since a tag-indeterminate value is
going into a class-wide type variable, the tag is not determined:

> 	z: T'Class := GetC(a_f);
...
> begin
> 	z := Get(a_f);

But, like you, I believe the code is correct.  You can't have an
uninitialized (tag undetermined) class-wide variable, so it ought
to dispatch on that tag.

Best,
Sam Mize

-- 
Samuel Mize -- smize@imagin.net (home email) -- Team Ada
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