hello @all,
I tried to use '=value( text( x, "0.0" ) )' and similar to check results of my 'improved calculations' and control whether rounding worked correctly or went wrong.
That worked fine until i had to compare against 1.45 . the binary 'nearest' representation for 1.45 with IEEE doubles is 'undershot' as 1.449999999999999955591~, and thus the rounding performed by 'text' switches to '1.4' rather than '1.5'.
( same applies to plenty other values, I assume 50% of doubles for ~5 values have undershot representation )
That is! correct from a simple POV, but wrong when accounting that the value is the representant for decimal 1.45 .
( even pure 'C' calculates 'printf( " test: %.1f \n", 1.45 ) to '1.4' thus this question might be better suited in other forums ... ??? )
I could - and did - construct a workaround by evaluating a second string '=value( text( x, "0.000000000000000" ) )', and if i find a '5' there in the position after the rounding limit and the 'text' result is smaller than the origin add 0.1 to it ... but that's ... cumbersome.
'round' works better for this simple case, but fails for some other values ( from a decimal POV ), and that's just my task, find the critical values where round fails, thus round doesn't help.
Does anyone have a good idea for a 'elegant' way to achieve ... 'decimal correctly rounded results for double values'? It won't be a problem if slow or 'string-math', it's just needed for testing.
Best Regards,
b.
P.S. please be tolerant, I'm not a professional but just look, poke and try around, sometimes it results in good new things ... but not always ;-)
