Re: Adding "()" operator to Ada 200X

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

Mário Amado Alves wrote:

>> IMO one should first add a new set of types: "index" types. (Dmitry)
> 
> Maybe *every* 'conceptual' type should be in the type system.
> A la Smalltalk.

Every conceptual type a programmer might imagine. That's the difference 
between ADT and non-ADT. Alas, there is no ADT for 2nd-order types (type 
sets like (<>), range (<>), mod (<>) etc) in Ada. That has to be changed. 

Another weakness is absense of supertypes. It is impossible to develop a 
type hierarchy before coding in a project of real size. Especially it is 
true for Ada as opposed to "run-once" languages. So if I want to mix String 
and Unbounded_String let me do it.

> This includes exceptions (cf. AE'2001) and,

I am not sure that exceptions should be of different types. To have classes 
of exceptions one just need them to be ordered in some way. Type hierarchy 
brings an order, but other, undesirable effects, as well. I would prefer an 
ordered set of exceptions of same (index) type. With index types one could 
do something like:

IO_Errors : exception'Set := End_Error..Use_Error;
...
exception
   when IO_Errors =>

> yes, ranges.
> It always bugged me what is the 'return type' of the Range attribute.
> I think it's the only attribute that does not return a type proper.
> Even exceptions and tags have their 'surrogates' in the type system.
> I can see "I .. J" as sugar for "Range (From => I, To => J)".
> ".." as an operator!

And "|" as an operator!

Then somebody (me?) whould ask for:

Prime_Numbers : Integer'Set := 1 | 3 | 5 | 7 | 11 | 13;
type Primes is Integer Prime_Numbers; -- (:-))

> But this be too much to prepare for Ada 200Y :-(
> Ada 20XX maybe, if we're still around :-)

--
Regards,
Dmitry A. Kazakov
www.dmitry-kazakov.de