Re: BUG #3387: mod on non-integer returns bad result

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От Gregory Stark
Тема Re: BUG #3387: mod on non-integer returns bad result
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Msg-id 87r6odb1k9.fsf@oxford.xeocode.com
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Ответ на Re: BUG #3387: mod on non-integer returns bad result  (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы Re: BUG #3387: mod on non-integer returns bad result  (Tom Lane <tgl@sss.pgh.pa.us>)
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"Tom Lane" <tgl@sss.pgh.pa.us> writes:

> Gregory Stark <stark@enterprisedb.com> writes:
>> The source of the problem is the floating point arithmetic which is used to do
>> the individual steps in the long division.
>
> I don't think so.  The ultimate source of the problem is that div_var
> can only report a finite number of digits.

In the case reported div_var was getting 70/70 = 0.99999. Which is really just
wrong. The only reason was because 1.0/70 isn't representable so (1.0/70) * 70
is slightly more than 1 which ... div_var really ought not have any trouble
representing an integer even in its finite number of digits.

--
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com

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