Re: constructor in abstract tagged types

[Jere <jhb.chat@gmail.com>]

On Wednesday, May 8, 2019 at 2:37:25 PM UTC-4, Daniel wrote:
> Hello, im trying to know how can i use abstract tagged types and constructors at the same time.
> 
> I have this
> 
> <SNIPPED>
> 
> Option 2:
> 
>   return Son'(Father with
>                Skate =>True);
> 
> Problem: i cannot initialize Father or call any kind of constructor of Father becouse compiler don't let me make any kind of function of a abstract tagged type.
> 
> Regards,
> Daniel.

GNAT accepts: 

   function F_Build(Years : Natural) return Son is
   begin
      return (Years => Years, Skate => True, others => <>);
   end F_Build;

I assume since it is abstract you don't have to lead with "Father with"
in the aggregate initialization.  If you need something more complex 
for the other fields you can optionally use extended returns:

   function F_Build(Years : Natural) return Son is
   begin
      return Result : Son := (Years => Years, Skate => True, others => <>) do
         Result.Field1 := -- Something complex;
         ***
      end return;
   end F_Build;

Tested this with GNAT 7.1.1