Re: Ada and QNX

[mark_lundquist@my-deja.com]

In article <8sfm52$f4$1@nnrp1.deja.com>,
  mjsilva@my-deja.com wrote:
> In article <39EB42B1.A14BDCB6@motorola.com>,
>   Igor Kovalenko <Igor.Kovalenko@motorola.com> wrote:
> > mjsilva@my-deja.com wrote:
> > >
> > > In article <39EA9161.6469DDE2@home.com>,
> > >   Igor Kovalenko <kovalenko@home.com> wrote:
> > > > Ada is way too high and abstract to be good for system level
> > > programming
> > >
> > > What low-level system-programming functionality is missing in Ada?
> In
> > > fact Ada has more low-level functionality than C or C++.  It was,
> after
> > > all, originally designed for -embedded- applications.
> > >
> >
> > I did not say anything is missing. I said that it is 'too high'
which
> > should mean there is just too much stuff to bear along with what you
> > really need in most cases.
>
> OK, what 'too high' stuff must you bear in order to do system-level
> programming in Ada?

I've written device drivers, bootloader and debug monitor code, and a
full TCP/IP stack in Ada, and I have to say I really like Ada for
system-level programming.  Even in a "system level" project you are
going to have some bits that are really down on the bare iron, and then
the rest which is really your logic or whatever and is not
particularly "system-level", except by virtue of being part of
something bigger (like an OS) that you do consider to be "system-
level"!  And for all the rest of those bits, being able to program at
an appropriate level of abstraction is quite nice.  For the "bare iron"
bits, on the other hand, I really find nothing in Ada that gets in the
way or is "too abstract".  It's just not there.  This is from my
experience of actually using it.  The language will, however, tend to
get in your way if you insist on a C-style way of doing things, so you
have to learn how to do it the Ada way.  It's also true that the Ada
locutions are less cryptic and more verbose, which until you get the
feel of it may make it feel "too abstract" -- but really it's not.

I haven't really done any system-level programming in C or C++, but to
be fair I think a fair bit of any programming project in C (and even
C++) becomes indistinguishable from system-level progamming.  An
example would be whenever you have to deal with char [] strings (and
you do have to deal with them, even in C++, because while you might
prefer to use String objects instead, at some point you usually have to
interface w/ pieces of code that did *not* use String!)  Another
example is when application code has to call an OS for which C is the
natural binding.  In Ada the virtually-system-level bits are still
there where you have to deal with the OS, but if you're using a thick
binding (like POSIX) then the low-level bits are hidden for you in the
binding.

Mark Lundquist
Rational Software


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