Re: GNAT GPL is not shareware

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

On Thu, 08 Jan 2015 11:55:09 +0100, G.B. wrote:

> On 08.01.15 09:14, Dmitry A. Kazakov wrote:
>> On Wed, 7 Jan 2015 16:47:25 -0600, Randy Brukardt wrote:
>>
>>> I have yet to use *anything* that used a DB that could not have been done
>>> better without the DB.
>>
>> True.
> 
> False, in general:
> 
> As soon as you start talking truly relational, you'll either
> use Prolog-ish programs, which are DB programs.

Prolog has nothing to do with DB, except that, Randy's statement fully
apply to Prolog: anything done in Prolog that could have been done better
without Prolog.

> Or, in Ada, you'll use pointers or cursors, or symbols in
> anything else, and start reinventing everything that the full
> relational model provides for free.

Relational algebra (RA) can be implemented in Ada. No problem, except
issues with generics.

You cannot easily do:

   generic
       type Tuple_Element_Array is (Positive range <>) of private;
   package Relational is

with

   Tuple_Element_Array'Element_Type (N)

to denote N'th type.

> Using the GNAT repertoire in the compiler sources,
> this question is typical of thinking "relational":
> 
> "List all Ada identifiers that are public in packages
>   that are children of P0, provided that they are not of
>   a pointer type."

This is not relational. Relational algebra does not deploy universally
qualified expression. You need a set (table) to search though.

Once you have it, it is a big question whether relational operations would
be useful or could be implemented at all. There are quite few things which
are good mapped onto relations and the corresponding data structures
backing them, e.g. B-trees.

A simple counterexample is spatial neighbour search (kD-tree).
 
> A standard RDBMS solution, while obvious, is perhaps
> inadequate for reasons of performance, specialization,
> Ada fanatism, etc. But it takes a political argument
> to deny that compilers do actually include those data
> structures and algorithms that the relational model
> has as built-ins.

There are many bad-to-destructive technologies used everywhere. E.g.
AdaCore's GNAT uses XML, Python. At least RA could have some application
areas. XML and Python have none.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de