[Libreoffice-bugs] [Bug 80017] EDITING: Rounding error in simple calculation - no division or multipliction used

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=80017

--- Comment #8 from b. <newbie-02 at gmx.de> ---
just to clear out a few points ... 

rounding already happens on the source data, plenty 'decimal-exact' values do
not! have an exact floatung point representation, thus instead of 9425,03
something like 9425,0300000000006548 is stored, and thats probably not yet the
actual value but something calc can calculate and display, 

such imprecisions can add up in additions, throw away precision or even the
smaller value with summands of different magnitude, dramatically loose
precision on subtractions of similar values etc. 

quite often accumulated imprecisions throw a value across a border where calc
with it's 'approximate-equal' functionality (which is neccessary to circumvent
the imprecisions) stops to say 'different but similar enough to be equal' and
judges 'different', thus you get your errors, 

multiplikation and division are said to perform better, but are not totally
'safe' afaik, at least not in calc, 

'unavoidable' is not correct, we do have the input values, we do have math
rules about precision, we can round out - correctly - at least most of theese
artefacts, calc doesn't regarding 'performance' and too few developers who'd
like to enter this battle ...

we are not! talking about decimal numbers with few decimal digits, we are
talking to represent them with 'double precision binary float numbers', where
already dec 0,1 is an infinite fraction ... as the simple 1/3 is in decimal, 

calcs quality improved over the time, but this bug is still in, 

tdf#67026 is still live, i hope the problem will be solved sometime, because
only then one could use calc legally for financial calculations, 

'("Precision as shown" should be used with caution given its behaviour of
discarding all precision beneath that which is displayed)' yes!!!, be careful
with things like that, it's a silly brutal dump tool,

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