Re: derived formal types and known discriminants

[sbelmont700@gmail.com]

On Friday, June 30, 2017 at 2:10:01 PM UTC-4, Randy Brukardt wrote:
> 
> Sure, but they're very inflexible in that usage (as bad or worse than the 
> original unconstrained types). So I tend to view these as an either/or 
> proposition: untagged, mutable types with discriminants, or tagged types 
> without discriminants. Again, YMMV.
> 


At the risk of having some of the other thread's shade thrown in here, aren't tagged discriminated records the de facto way of doing initialization?  That is, extending a Controlled type and then using discriminants in place of ctor arguments?  I can see that a "real" discriminated record (i.e. variant records) probably have little use in a tagged hierarchy, but access discriminants (et al) seem much closer to 'constant record elements' than a truly discriminated record.

After all, how else is one supposed to do construction for an abstract parent type?  In C++, for example, an abstract type still has a constructor (that all children would have to explicitly call with the required arguments), but in Ada 'constructing functions' are off the table since the type is abstract.  So apparently the only thing left is to use Initialize and then ferry any required arguments over as discriminants?  This is the method given in many texts and examples, so please set me straight if i'm way off base.

Thank you again to everyone for the helpful comments and continued support.

-sb