Re: Unknown discriminants with nested records

[Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>]

On 06/16/2011 05:39 PM, Adam Beneschan wrote:
>
> The (<>) was intended to define types with unknown discriminants;

I thought it was initially created to fix the problem with generics, where in 
Ada 83 you could have

generic -- G
    type T is limited private;
    ...
package G is
    ...
end G;

package body G is
    ...
    V : T;
    ...
end G;

package I is new G (T => String, ...);

and it wasn't caught when you would like it. In Ada 95 and later, you have to 
have (<>) on the formal to have an indefinite actual, and the generic cannot 
have an uninitialized object of the type; without (<>), the actual must be 
definite; and the problem is caught when compiling the instantiation.

-- 
Jeff Carter
"Many times we're given rhymes that are quite unsingable."
Monty Python and the Holy Grail
57