Re: Ariane 5 failure

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

robin <rav@GOANNA.CS.RMIT.EDU.AU> writes:
>---The issue was not the addition of a new exception handler.
>The issue was that a magnitude check should have been
>performed on a conversion from double precision floating
>point to 16-bit integer, but it wasn't.
>Of course, having an exceptin handler for this specific purpose
>would have helped, and should have been included as a fallback.
>
>        >Assuming that a new exception _handler_ had been added, then it _might
>made
>        >a difference.
>
>You can be absolutely certain that it would have helped.
>
    procedure ARIANE_FIVE_OPERATION is
        X   : FLOAT range -65536.0..65535.0 := 65535.0 ;
        Y   : INTEGER range -32768..32767 := 0 ;
    begin
        if (X not in -32768.0..32767.0) then
            SHUT_DOWN_THE_CHANNEL_AND_PASS_CONTROL_TO_THE_OTHER_SIDE ; --Boom!
        else
            Y := INTEGER (X) ;
        end if ;
    end ARIANE_FIVE_OPERATION ;

    *Absolutely* certain?

    Seems that the above algorithm *DOES* have runtime checks to
    constrain the assignment of a float to an integer, yet the
    accommodation is still a *BAD* engineering decision. We can polish
    and polish and polish the software all we want and perform all
    sorts of runtime checks, but if the accommodation remains wrong,
    we're polishing a turd.

    MDC

Marin David Condic, Senior Computer Engineer    ATT:        561.796.8997
M/S 731-96                                      Technet:    796.8997
Pratt & Whitney, GESP                           Fax:        561.796.4669
P.O. Box 109600                                 Internet:   CONDICMA@PWFL.COM
West Palm Beach, FL 33410-9600                  Internet:   CONDIC@FLINET.COM
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