Negative zero leading to unexpected issue in Rule Engine

[aworker]

Hi @ThomasLLN

I fully agree with you. May be the problem you have spotted is related to the way KNIME converts strings into doubles in some nodes. A similar problem is described in the post below when rounding integers:

Incorrect rounding in KNIME?

Maybe that won't help with the workaround but just to give a bit of background on why this is happening. We are using a library to do the parsing and evaluation of the expression. The round function is using something called 'rint' and citing the documentation ([1] and [2]): "If two double values that are mathematical integers are equally close, the result is the integer value that is even." and "This has better statistical properties." (I am not sure what properties that are, though.)

The problem may thus come from the fact that the numbers one enters in the Table Creator are originally strings that are converted into doubles. I guess the String to double conversion done by the -Table Creator- node is not handled in the same way for a 0.0 and a -0.0, most probably because of the rounding scheme used by KNIME to convert strings into doubles.

Best

Ael