Re: Limited_Controlled and constructor functions

[Maciej Sobczak <no.spam@no.spam.com>]

Robert A Duff wrote:

> It works in Ada 2005.

That's good news. :-)

> It's one of my favorite features of Ada 2005.

It's one of the many features that are essential for writing robust 
code, IMHO (from the C++ perspective).

> I'm not entirely sure what you're trying to accomplish, since the length
> of that array can't change, and there's nothing interesting for Finalize
> to do in this example.  Maybe you have other constructors?

Yes, there are other constructors that accept more parameters and that 
create longer arrays.

What I want to accomplish is the functional way of building lists of 
values of variant types:

P : constant Params := Make_Params(Param("Hello"),
                                    Param("Ada"),
                                    Param(12),
                                    Param(3.14)));

Make_Params is a constructor function that creates a list of 4 
parameters, each of them being a variant. I wanted to be able to store 
Strings in the variant without constraining their lengths (which is 
impossible), so I decided to use access variable that points to 
unconstrained String. I migh use Unbounded_String as well, but I don't 
yet see what would be the difference.
Everything should be nicely cleaned up after that - that's why Params is 
controlled, and since I don't want to bother with copy semantics, it is 
also limited.

It is part of the simple database binding that I wanted to write for the 
sake of exercise.
I will make the whole public once it's finished (but I need Ada2005 
compiler for that! :-) ).

-- 
Maciej Sobczak : http://www.msobczak.com/
Programming    : http://www.msobczak.com/prog/