Re: please help - access and inheritence

[Jeffrey Carter <spam@spam.com>]

Ratson Janiv wrote:
> type Vehicleptr is access Jr.Vehicle.Vehicle'Class;
> 
> type Vehiclesarr is array (1..Maxvehilces) of Vehicleptr;
> 
> Vp1,Vp2,Vp3,Vp4,Vp5: aliased Jr.Vehicle.Private_Car.Vehicle_Private;
> 
> Arr(1) := Vehicleptr(Vp1'access); -- failed, why? please ...

You could be a bit more clear about what the problem is. Does "failed" 
mean a run-time problem or a compiler error? In either case, more 
information about the "failure" would be helpful.

I note that Vehicleptr is not a general access type (access all 
<subtype>), but only allows access to values allocated on the heap 
(access <subtype>). Since Vp1'access does not designate a value 
allocated on the heap, it cannot be assigned to an object of type 
Vehicleptr. So if Arr (1) is a Vehicleptr [which seems likely, since 
you're trying to convert Vp1'access to Vehicleptr before assigning it to 
Arr (1)], the compiler should dissallow the assignment.

If you define Vehicleptr as access all ..., and Arr is declared as
Vehiclesarr, then you can write

Arr (1) := Vp1'access;

I guess saving the time to type an underline is more important than 
having code that is easy to read by using names such as Vehicle_Ptr.

-- 
Jeff Carter
"Every sperm is sacred."
Monty Python's the Meaning of Life
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