[GAP] old attribute

[Robert Dewar]

On 10/28/2011 11:35 AM, Dick Gayler wrote:
> I am using ada in an upper division course covering design by contract.
> Specifically, I am using the precondition and postcondition pragmas.  As
> is typical in academia, I am "going overboard" to emphasize the
> concepts.  The problem that I have run across is that is seems that the
> implementation of the old attribute makes a shallow copy of the object
> leading to the obvious problems with linked structures.  Has anyone
> looked at what has to be done so that the old attribute when make a deep
> copy?  I am trying to avoid explicitly putting the "deep copy" code in
> the subprograms.

Interesting, obviously this cannot be done automatically since what
a "deep copy" means is very data structure dependent, I guess what
you would need is a user defined attribute function something like

   for typ'Old use subprogram

where subprogram has the profile

   function typ'Old (Arg : typ) return typ;

Definitely an interesting suggestion.
>
> Thank you.
>