Re: Teaching new tricks to an old dog (C++ -->Ada)

["Jerry Coffin" <jcoffin@taeus.com>]

Chad  R. Meiners wrote:
> Jerry Coffin wrote
> > I was talking specifically about Airbus' use, and looking at:
> >http://www.esil.univ-mrs.fr/~spc/rcs02/slides/Baufreton.pdf
> >and:
>
>http://www.systemes-critiques.org/jslc2001_slides/FrancoisXavier_Dorm...
> >indicates that they're consistently using C, not Ada.
>
> No the slides do not indicate this.  For all we know the project that
> the slides are talking about has to target hardware for which there
> is only a C compiler.  It could be that Airbus only uses such tools
> on such hardware.

First of all, at least in my dictionary, "indicate" is defined with
words like "points to" and "suggests", NOT "proves" or anything very
similar.

Second, I have to wonder whether you really have a good idea of the
size of project we're talking about. Just for example, Airbus is
currently working on the A350, which is fairly based fairly closely on
the A340, to the point that it's expected to share a common type rating
with the 340 (meaning as far as flying them goes, they're considered
the same plane).

Despite that derivation, the A350 is expected to take about 6 years and
cost (at least) 3,500,000,000 Euros to develop. Developing an entirely
new plane runs in the vicinity of twice that.

This leads to two points: first of all, neither Airbus nor anybody else
is designing hundreds or even dozens of these at a time -- IOW, knowing
what they're doing in only one or two projects really _does_ tell you a
lot about what the company as a whole is doing, and for an extended
period of time at that.

Second, unless porting Ada compilers is a LOT more expensive than
porting C++ compilers, pre-existing availability of a particular
compiler is NOT much of a consideration for this size of project. Just
for the sake of argument, let's assume a compiler port costs a half
million US dollars. If you figure that up in terms of how time spent on
the project, it comes to a matter of hours -- i.e. the compiler port
would only have to save them a couple of hours overall to pay for
itself.

Now, it's certainly true that software alone doesn't account for nearly
all the expenditure -- but it's significant enough to figure in the
same basic terms. The compiler might have to save a whole day to pay
for itself, but almost certainly would not have to save (say) a whole
month to pay off.

> Using presentation slides as such an indicator is usually a bad idea.
> Presentation slides are made for a specific context, and time frame.
> They often lack full and complete information.  The slides don't
> explicitly support your claim.

I'll openly admit that the slides don't absolutely _prove_ nearly as
much as we'd like to know. They're generally vague, lacking detail,
definition or rigor -- but despite that they still constitute roughly
95% of the hard evidence presented so far in this entire thread!

--
    Later,
    Jerry.

The universe is a figment of its own imagination.