Build 4.0.0.18 of xlsgen includes a fix for the calculation engine. A more dynamic boolean for handling pseudo-expressions sometimes found in Excel formulas. For instance whenever a bool, instead of being the result of a logical expression such as A1 < 3, is just the coercion of whatever content in a cell as a bool. Hence what Excel does by making any number equivalent to a boolean with the following rules : any non-zero value is equivalent to a TRUE, and zero is equivalent to a FALSE. A logic by which -13,45 is equivalent to TRUE. This is precisely what xlsgen does beginning with this build, doing exactly what Excel does.