Re: Ada.Real_Time.Time_Last

[AdaMagica <christ-usch.grein@t-online.de>]

Am Samstag, 18. November 2017 14:18:44 UTC+1 schrieb Niklas Holsti:
> On 17-11-18 15:06 , AdaMagica wrote:
> > Am Freitag, 17. November 2017 22:39:51 UTC+1 schrieb Niklas Holsti:
> >
> >> Long ago, I suggested (on c.l.a) an Ada extension by which a package
> >> could declare private types using the same classes of types that can be
> >> used for generic formal types. That would IMO not only be useful for
> >> programmers, it could formalise some of the informal text in the Ada RM.
> >> For example, RM A.4.8 defines the type Ada.Direct_IO.Count as
> >>
> >>     type Count is range 0 .. implementation defined;
> >>
> >> With the suggested extension, this could be written in legal (extended)
> >> Ada as
> >>
> >>     type Count is private range <>;
> >>
> >> That form still does not show that Count'First = 0, but with a little
> >> further extension one could perhaps leave only the upper bound
> >> unspecified, as in:
> >>
> >>     type Count is private range 0 .. <>;
> >>
> >> Perhaps it is time for me to revive this proposal...
> >>
> > Problem with this is that private types have no predefined operators.
> 
> That is a problem with private types in *current* Ada, where a private 
> type is fully "opaque". This proposal is meant to remove this problem, 
> by letting the programmer provide more information about the private 
> type, in the same way as information can now be provided about generic 
> formal types, to equip those types with predefined operators that can be 
> used in the generic.

Yes - but what do we gain with this new syntax? Is it worth the effort? Which problem does it solve (to rephrase Randy)?