The “open” part means that the meeting is not a members-only affair, but that anybody interested in Ada is welcome, so feel free to invite whomever you might believe could be interested in spending an evening talking about Ada programming.

If you’re interested in participating, feel free to send us an email and we’ll inform you of the when and where. You can also ping me at Google+, identi.ca/thomaslocke or join the Freenode IRC #ada channel and look for ThomasLocke.

The meeting is of course free.

So next on the wiki-agenda is writing some new articles. It’s been a while since we’ve added anything new to our wiki, which is a bit of a shame. The last one I did was the GNATCOLL.JSON one, and that’s a good 2½ months ago! I’m considering doing one on the Ada.Task_Attributes package, but it’s not set in stone yet. Feel free to ping me if you’ve got any good ideas.

The library is provided for handling dimensioned values in Ada. The library supports irregular and shifted measurement units. String formatting and GTK+ widgets and cell renderers are provided.

New in version 3.2 is:

• The procedure Put in Measures_UTF8_Edit has additional parameters Field, Justify, Fill
• Fedora and Debian packages are provided for both 32- and 64-bit architectures.

You can read the full release announcement here.

Today’s gem is written by Emmanuel Briot and it deals with some of the new Ada 2012 features, specifically in relation to object oriented Ada programming. it’s called Gem #117: Design Pattern: Overridable Class Attributes in Ada 2012.

Most object-oriented programming languages provide a facility for declaring variables that are shared by all objects of a given class. In C++, these are called “static members” (and use the “static” keyword), and similarly Python has the notion of “class attributes”.

Let’s consider an example where this is useful. For instance, let’s say we want to define the notion of a block of text that is generated by expanding a template (perhaps after we replace some parameters in that template, as can be done with AWS’s templates parser, for instance). Once we have computed those parameters, we might want to generate multiple outputs (for instance HTML and CSV). Only the template needs to change, not the computation of the parameters.

I can’t say I’m a huge expert on object oriented Ada programming, but this little snippet actually made me hungry for playing around with some of the new Ada 2012 features, such as expression functions, where you can do stuff like this:

pragma Ada_2012;
 
type Text_Block is tagged null record;
function Template (Self : Text_Block) return String
   is ("filename.txt");
function Render (Self : Text_Block) return String;

Instead of the old more clunky method:

type Text_Block is tagged null record;
function Template (Self : Text_Block) return String;
function Render (Self : Text_Block) return String;
 
function Template (Self : Text_Block) return String is
   pragma Unreferenced (Self);
begin
   return "file_name.txt";
end Template;

Very nice indeed! The new Ada 2012 syntax allows for a much more simple and readable setup of the Text_Block type. But don’t take my word for it, go read the Gem instead. It is definitely worth it.

• GtkAda Contributions v. 2.11
• Ada Industrial Control Widget Library v. 1.1

GtkAda Contributions is the work of Dmitry Kazakov and Maxim Reznik. It is a package of proposed contributions to GtkAda, adding stuff like tasking support, embeddable images, spawning processes synchronously and asynchronously with pipes and a whole lot more. You can read the release announcement here.

Ada Industrial Control Widget Library enables you to create all sorts of graphical gauges, meters, clocks and oscilloscopes. If you need some sort of visual indication of load, pressure, speed or whatever, then this package will probably be able to get the work done. You can read Dmitry’s release announcement here.

With this one out of the way, we’re nearing completion. I think there’s only a few more pages missing from the old wiki, then we can shut it down completely. YAY!

I would very much like to hear from people using this new binding, or even better, from Kylix, the person who posted about to comp.lang.ada.

• Tables for Ada v1.11
• Strings edit v2.6
• Simple components v3.13

Tables for Ada provides a table that is searched using string keys. Strings edit implements and abundance of I/O facilities, and Simple components provides implementations of smart pointers, directed graphs, sets, maps, stacks, tables, string editing, unbounded arrays, expression analyzers, lock-free data structures, synchronization primitives (events, race condition free pulse events, arrays of events, reentrant mutexes, deadlock-free arrays of mutexes), pseudo-random non-repeating numbers, symmetric encoding and decoding, IEEE 754 representations support. Yea, I ripped that last wall of features directly from the website.

You can read the full release announcements for Tables for Ada, Strings edit and Simple components to get the full story on what exactly has been updated/fixed/changed in these packages.

The Ada program for FOSDEM 2012 is very interesting, with speakers such as Robert Dewar, Jean-Pierre Rosen, Jacob Sparre Andersen, José F. Ruiz, Xavier Grave, David Sauvage and Riccardo Bernardini. Yea, this is not an event to be missed.

You can read more about the event and the program here and here. Oh, and to top things off, here’s a FOSDEM interview with Robert Dewar.

Things were also stirring at the #ada Freenode IRC channel, and january the 17th. Marcelo Freitas put together a test, and actually found 46656 hash collisions simply by bruteforcing the Ada.Strings.Hash function, which is what AWS used at the time.

Those 46656 collision were enough to keep one core running at 100% for 3 minutes, using a simple “Hello World” AWS server.

Marcelo sent his findings to the AWS developers, and shortly thereafter these fixes were pushed to the AWS Git repository:

• Implement a secure string hash routine.
• Use AWS.Utils.Hash secure string hash routines.

The power of Open Source software is amazing. This fix went in the same day Marcelo had reported the issue. That is just plain awesome.

AWS now ranks proudly among the few web technologies where this problem has been fixed.