Re: Root_String'Class? (Was: Is this expected behavior or not)

["Randy Brukardt" <randy@rrsoftware.com>]

"Jacob Sparre Andersen" <sparre@nbi.dk> wrote in message 
news:8761zuizmq.fsf_-_@adaheads.sparre-andersen.dk...
> Randy Brukardt wrote:
>
> [ many interesting things about string types ]
>
> You mention creating an abstract tagged Root_String type and deriving
> actual string types from it.  Do you have some concrete ideas for how
> you would do it?  Could it be done with what we have in Ada 2012?  Or
> would it require some extensions to the language?

There is a rough proposal in the body of AI12-0021-1/01. Please note that 
this is completely my invention which has not be vetted by anyone.

The only needed magic is to allow string literals for the root type. 
Everything else needed is already provided by Ada 2012. (Note that I turned 
slices into functions, we'd need an extra facility to support the slice 
syntax. I don't find that important enough to bother with, but perhaps 
others will disagree.) Most of the less-primitive operations would primarily 
be supported via Ada.Strings.General (which would be similar in contents to 
Ada.Strings.Fixed). One imagines that types similar to Unbounded_String and 
Bounded_Striing would also be provided as members of Root_String'Class, so 
they would have much smaller packages and would be much more interoperable.

The downside is that elements would be accessed as Wide_Wide_Characters, 
which in some cases (16-bit processors, for instance) would make things more 
expensive than currently. And of course, a lot more dispatching.

                                    Randy.