Re: ada and robots

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

>OBAda: I have some (small) sympathy with Joe Gwinn's position that some
>combinations of Ada83 compilers may have produced very different
>results. Imagine that you used a generic-sharing compiler orginally for a
>memory limited system, and then tried to port that code to a similar target
>that used expansion instead. Or tasking that mapped tasks to OS processes
>vs. run-time scheduling (and you want to do blocking IO in the tasks.)  One
>of the phrases I remember least fondly when trying to explain why some
>particular code was ill suited to a particular embedded
>compiler/runtime/target.
>        "But it runs just fine on our Vax using DEC Ada!"
>
    This may well be true, but I don't know how it could possibly be
    avoided. Whenever a language specifies a feature beyond a certain
    complexity, you're going to get a variety of different
    implementations which have inherent portability limits (especially
    in real-time where memory and/or time are limited resources.)

    For example: If Ada and C both specify some basic mathematical
    capability (C++ vs Integer'Succ(C)) you'd expect both statements
    to consume nearly the same amount of space/time on virtually any
    implementation (target hardware remaining the same). But the
    minute a language gives you something like "accept X do...", you
    can expect semantic behavior to be consistent, but space/time is
    going to be entirely dependent on what sort of tasking model
    underlies the support for the accept statement.

    I guess you could say that C solves the problem by never giving
    you anything very complex to use. So if you need the complex
    features, you've got to "roll your own" and in some cases this is
    going to be difficult to near impossible.

    I'd fault a compiler vendor for not selling semantically correct
    behavior, but I couldn't fault the vendor or the language just
    because a given feature may have multiple possible
    implementations, each with their own advantages and drawbacks.

    MDC

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
===============================================================================
    "You spend a billion here and a billion there. Sooner or later it
    adds up to real money."

        --  Everett Dirksen
===============================================================================