>On Sat, 5 Jul 2003, Beman Dawes wrote:
>
>> fpt_abs may do a unary "-" operation. I'm assuming, perhaps incorrectly,
>> that is essentially subtraction and subject to a possible rounding error.
>
>I don't think there is a system where the opposite of a representable
>number would not be a representable number. So there should be no rounding
>error when changing signs. At least not with IEEE-754 floating point
>numbers.
>
>Moreover, 0-x may lead to results different from -x. So changing sign is
>essantially "not" a subtraction :-).
So where does that leave us? There must be some reason Gennadiy's code is producing results one or two epsilons greater than expected.
--Beman
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