See: <a href="/doc/reference/classes/ucalc/isdefault-=-[bool]/">IsDefault = [bool]</a>, <a href="/doc/reference/classes/ucalc.item/valuebool/valuebool-void/">ValueBool()</a>, <a href="/doc/reference/classes/ucalc.item/valuebool/valuebool-bool/">ValueBool(bool)</a>