Re: Question on variant/discriminated records

["J-P. Rosen" <rosen@adalog.fr>]

Le 31/12/2020 à 11:38, reinert a écrit :
> Assume the following program and change "y1" to "y". 
> 
> procedure test3 is
>  type options1_Type is (a,b,c);
>  type rec1_Type(option1 : options1_Type) is
>    record
>       x : Float;
>       case option1 is
>         when a => null;
>         when b => y : float;
>         when c => y1,z : float;
>       end case;
>    end record;
> begin
>    null;
> end test3;
> 
> My compiler does not like this change.  I find it not natural to invent
> a new name "y1" instead of "y". What should I do?
> 
Yes, it is a rule that identifiers in parallel branches cannot be
identical. And there is a good reason for this: in Ada, when you access
a component, the compiler checks that the component exists, according to
the value of the discriminant. Assume that you write (if V is of type
rec1_type):
   V.Y := 1.0;

If both components are named Y, should the discriminant be B or C?
-- 
J-P. Rosen
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