Re: errata/273: LRM does not specify result of real division by 0

From: Steven Sharp (sharp@cadence.com)
Date: Wed Jan 29 2003 - 18:40:01 PST

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    The following reply was made to PR errata/273; it has been noted by GNATS.

    From: Steven Sharp <sharp@cadence.com>
    To: etf-bugs@boyd.com
    Cc:
    Subject: Re: errata/273: LRM does not specify result of real division by 0
    Date: Wed, 29 Jan 2003 21:38:19 -0500 (EST)

    >The LRM references IEEE 754 only with respect to floating point representation,
    >but not with respect to floating point arithmetic.
    >
    >Also, you can not assume that the processor is 100% IEEE 754-compliant.
    >I have known processors that were not.
     
     That is a valid point. I have known such processors also, including the x86.
     
     But this argues against the LRM specifying these things. The only
     practical way for the software to do floating point calculations is to
     use the hardware it is running on. If the behavior of that hardware for
     exception cases is not going to be consistent across platforms, then the
     LRM should not try to specify it.
     
    >Also, some conversion questions that come to mind:
    >
    >- How is Infinity (+ or -) converted to an integer?
    >- How is NaN converted to an integer?
     
     However the floating point unit does it. These cases just aren't worth
     any special treatment by the software.
     
    >- How is a negative number converted to an unsigned integer?
     
     This is actually specified, in the first paragraph of 4.1.6.
     
     Steven Sharp
     sharp@cadence.com
     

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