Re: ada and robots

["Marin David Condic, 561.796.8997, M/S 731-93" <condicma@PWFL.COM>]

Joe Gwinn <gwinn@RES.RAY.COM> writes:
>In practice, C was much more successful than Ada83 at riding metal.
>Experience with Ada83 shows that it is very bad at direct control of
>hardware, especially I/O hardware, and simply does not handle shared
>memory correctly.  Ada95 is claimed to be better, but I don't have any
>direct experience with it.  Actually, not many people do just yet.  I
>suspect that most people are using C (perhaps called from Ada) for direct
>control of I/O hardware and the like.
>
    Maybe with some of the early generation compilers, but we've been
    "riding the metal" for years here in Ada and never had any trouble
    getting direct control over the hardware. Oh sure, once in a while
    you've got to dip into assembler to get at some real hardware
    specific feature, but that's true of *any* language and at least
    Ada specifies a way you can get at machine instructions without
    leaving the compiler.

    Not sure what the problem is you refer to with shared memory, but
    lots of embedded applications never use any shared memory.
    (Between processors? DMA devices? Shared between tasks?) If you
    mean shared between tasks, then Ada95 certainly did improve things
    with protected types, but I as yet have no practical real-time
    experience using protected types to point to as proof that it
    works well. I don't know why it wouldn't. But then, as I recall
    from my C programming days, C had neither any concept of tasks nor
    of shared memory between tasks, which left you "rolling your own"
    if you were multi-threading & sharing memory. If you had to "roll
    your own" in C, why would Ada be fundamentally any worse?

>Most "Ada systems" I have seen built recently are actually mixed-language
>systems, being a mix of C, C++, and Ada, with the Ada being in the
>minority (maybe 25%), if one counts all the purchased COTS code in the
>system.  Typically, the operating system, middleware, and GUI stuff are
>all in C, and the application code is mostly in Ada (with C bindings, and
>no Ada runtime).
>
    This might be true of someone developing under Motif or WindowsNT
    where you have a huge body of code someone else wrote in C that
    you're utilizing. But as I recall, the original post was about
    embedded microcontrollers for robotics and here there is no OS
    except what you build for yourself. (also very little GUI :-) Most
    of the Ada work I've done for either embedded systems or apps
    running under an OS have been 99% Ada and 1% other stuff. I may
    not be "typical" but my experience is that people usually pick a
    language for their app and build from there. The exception being
    if you've inherited some body of software you're trying to glue
    together with other stuff.

>I would also comment that DoD's recent recinding of the Ada Mandate will
>likely cause the Ada compiler and tools market to shrink to perhaps as
>little as one tenth of its prior size, and that significant added
>investment in Ada compilers and tools is therefore unlikely, at least
>until the size of the remaining market becomes clear.  A significant
>shrink is widely expected because the many DoD customers who chose Ada
>because of the mandate will now immediately vanish, and DoD's big push
>towards COTS is in effect a push to C/C++.  The Ada market used to be at
>most one tenth the size of the C market, and things took forever to get to
>the Ada world.  Now, it will be one hundredth.  So, if something Ada is
>not in hand today, don't wait.  It could be a long time coming.
>
    Mandate? We don' have no Mandate! We don' need no steenkin'
    Mandate!!! :-)

    I think this is a sort of self fulfilling prophecy. If Ada is
    technically better, it ought to get fair consideration. (I believe
    it is.) The availability of high quality compilers at reasonable
    cost for a large number of platforms tends to limit any business
    or practical objections to its use. The only case I can see for
    using C in a given app (especially embedded!) is that you can't
    find an adequate Ada environment for the target.

    I believe that if we go out and "Just Do It!" instead of having
    C++ envy, Ada can end up widely successful. Remember that C
    basically sat on the shelf for *years* as a niche language while
    people built stuff out of Fortran, Cobol, assembler, etc. It was
    only recently in its history that it gained any widespread
    popularity.

    MDC

Marin David Condic, Senior Computer Engineer    ATT:        561.796.8997
Pratt & Whitney, GESP                           Fax:        561.796.4669
West Palm Beach, FL                             Internet:   CONDICMA@PWFL.COM
===============================================================================
    "Having an open mind is nothing. The object of opening the mind, as
    of opening the mouth, is to shut it again on something solid."

        --  G.K. Chesterton
===============================================================================