Re: Backward compatibility between Ada 95 and Ada 83

["Marin David Condic, 561.796.8997, M/S 731-96" <condicma@PWFL.COM>]

 "James H. Robinson, III" <jr3uva90@EROLS.COM> writes:
>
>I'm using an Ada 95 compiler, but my class is teaching Ada 83.  How
>backwardly compatible is Ada 95 with Ada 83?
>
    I have ported a fairly significant body of Ada83 code across to a
    different target using Ada95. I have yet to encounter an issue
    where an incompatibility was due to differences between the two
    languages.

    Here's the scoop: I've got code that is compiled on a VAX,
    targeted to an MC68040(1) using an XD-Ada 83 compiler. It's
    getting moved to a Sun workstation and compiled (with some other
    code) using the GNAT Ada95 compiler. In tribute to Ada (and the
    luck of having similar hardware architectures!) I have had zero
    problems with any language features being incompatible, miniscule
    problems relating to representation clauses, a few problems
    relating to sizes of predefined entities (Developer's advice:
    *never* use the standard Integer, Float, etc. if you think you'll
    ever have to port or change the arithmetic behavior) and the bulk
    of my problems related to the architecture of the software itself.

    Explanation: I'm grabbing a chunk of an embedded control and
    building an environment for it to run on a Sun. My problem has
    been the design of the software involves many layers of "with"
    context clauses. Package A withs B, package B withs C, etc., etc.
    So if I just want one banana, I've got to take the whole gorilla.

    But I am *very* pleased with the fact that upward compatibility
    and porting to a different machine was this easy. Almost totally
    painless.

    MDC

    (1) BTW: Has anyone out there seen a decent MC680x0 software
    emulation to run on a VAX, Sun or PC? I need to propose a
    development/testing environment and I'm shopping around for
    software simulations. If you have one or know of one, please
    e-mail me directly. Thanks.


Marin David Condic, Senior Computer Engineer     ATT:        561.796.8997
Pratt & Whitney GESP, M/S 731-96, P.O.B. 109600  Fax:        561.796.4669
West Palm Beach, FL, 33410-9600                  Internet:   CONDICMA@PWFL.COM
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