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

["kevin cline" <kevin.cline@gmail.com>]

adaworks@sbcglobal.net wrote:
> "kevin cline" <kevin.cline@gmail.com> wrote in message
> news:1110830710.027630.241160@g14g2000cwa.googlegroups.com...

> Ada is every bit as expressive as C++.  There is not likely to be
> any improvement in the number of KSLOC using C++.  Oh, yes,
> if we choose to use a cryptic form of C++, with all the little
> shortcuts that make the code less readable, we might achieve
> some reduction in the KSLOC, but at what cost in understandability?
>
> Richard Riehle

C++ is more expressive because of implicit generic/template function
instantiation.  The limitations of Ada's explicit instantiation have
been shown to be a major impediment to creating advanced type systems,
e.g. modeling physical units.

Christopher Grein writes at
http://www.adapower.com/index.php?Command=Class&ClassID=Advanced&CID=215:

[Attempting to model physical units in Ada]
"Our attempt leads us to a plethora of overloaded functions. The number
of function definitions afforded runs into the hundreds...

...One could object that this definition has to be made only once and
for all in a reusable package, and later-on the package can simply be
withed and used without any need for the user to care about the
package's complexity, but unfortunately the argument is not fully
correct. Apart from the most probable compile time explosion, it takes
into account only simple multiplication and division. Operations like
exponentiation an and root extraction root (n, a) are not representable
at all.

So we have to confess that our attempt to let the compiler check
equations at compile time has miserably failed. The only proper way to
deal with dimensions in full generality is either to handle them as
attributes of the numeric values that are calculated and checked at
run-time or to use preprocessors. Also for these methods, there are
many examples to be found in literature."

Grein again, at
http://home.t-online.de/home/Christ-Usch.Grein/Ada/Dimension.html:

"A C++ solution, which is very similar to the Ada one presented here -
it does however not include fractional powers - can be found at
http://www.fnal.gov/docs/working-groups/fpcltf/html/SIunits-summary.html.
The big difference is that C++ templates allow type checking during
compile-time, so that no overhead neither in memory space nor in
runtime is incurred. In this respect, C++ templates ARE MORE POWERFUL
than Ada generics."   [Emphasis mine]

In my experience, C++ templates have allowed me to write fully
type-safe programs at a very high level, an ability which Ada generics
simply can not match.