Re: APQ

["Warren W. Gay VE3WWG" <ve3wwg@NoSpam.cogeco.ca>]

Brian May wrote:
>>>>>>"Randy" == Randy Brukardt <randy@rrsoftware.com> writes:
>     Randy> I haven't looked at the code in question, but it certainly
>     Randy> is possible to have concrete operations and components on
>     Randy> an abstract type (the type has be abstract - if it is
>     Randy> tagged - to have abstract subprograms). We do it all the
>     Randy> time in Claw and its related programs. That's the big
>     Randy> difference between an abstract type and an Ada 2005
>     Randy> interface (which can't have any data or concrete
>     Randy> subprograms).
> 
> I tried to get it working, but couldn't:
> ...
>    type Root_Connection_Type is abstract new Ada.Finalization.Limited_Controlled with private;
> ...
>    procedure Connect(C : in out Root_Connection_Type) is abstract;
>    procedure Connect(C : in out Root_Connection_Type; Same_As : Root_Connection_Type'Class) is abstract;
> ...
> gcc-3.4 -c -gnata -gnatf -gnato -gnatwp -O0 comp_mysql.adb
> apq.ads:126:14: abstract subprogram not allowed for type "Root_Connection_Type"
> apq.ads:127:14: abstract subprogram not allowed for type "Root_Connection_Type"
> apq.ads:584:09: nonabstract type has abstract subprogram "Connect"
> gnatmake: "comp_mysql.adb" compilation error
> make: *** [mysql1] Error 4
> 
> What did I do wrong? How do I create a abstract type that is derived
> from Ada.Finalization.Limited_Controlled?

The error looks familiar, though I don't understand the reason
for the "limitation" that the compiler is imposing.

Warren.