Rounding in the price db.

[John Ralls]

> On Aug 11, 2015, at 8:29 AM, Geert Janssens <geert.gnucash at kobaltwit.be> wrote:
> 
> On Monday 10 August 2015 16:27:40 John Ralls wrote:
>>> On Aug 10, 2015, at 10:34 AM, Geert Janssens
>>> I seem to remember that banks here use 6 significant digits in
>>> exchange rates, which is not quite the same as 6 places after the
>>> decimal point. Your USD-Sao Tomean Dobra illustrates this: due to
>>> the extreme value difference between the two you need 10 digits
>>> after the decimal point, but only 6 of them are significant (ie not
>>> a leading zero).
>>> 
>>> Is this something our gnc_numeric code supports and can be used by
>>> the price db ?
>> 
>> We have “significant digits” rounding code, but IIRC it’s really six
>> decimal places. If we were to have real significant digits we’d need
>> to be careful to keep it away from the debits-and-credits code or it
>> could make a real mess.
>> 
> 
> I'm probably slow here. What mess would that create ?

Rounding errors leading to imbalances. Suppose the amount I paid for a car in June got rounded to six significant digits: The pennies would get rounded off (12,345.67). 

Regards,
John Ralls