On 30/12/2019 01:34, Tatsuo Ishii wrote: > Hi, > > Can you please someone elaborate what's the meaning of "even" in > datatype.sgml? > > <para> > By default, floating point values are output in text form in their > shortest precise decimal representation; the decimal value produced is > closer to the true stored binary value than to any other value > representable in the same binary precision. (However, the output value is > currently never <emphasis>exactly</emphasis> midway between two > representable values, in order to avoid a widespread bug where input > routines do not properly respect the round-to-even rule.) This value will > ~~~~~~~~~~~~~~~~~~~ > use at most 17 significant decimal digits for <type>float8</type> > values, and at most 9 digits for <type>float4</type> values. > </para> > > I think "even" means "equality" here, not "even" of "even and odd".
It does actually mean "even and odd". This kind of rounding is also called "Banker's Rounding". https://en.wikipedia.org/wiki/Rounding#Round_half_to_even -- Vik Fearing
