Using signum() Function in RTF-Template

Hello,

I'm using an RTF-Template, because my customer needs a text based file. Inside the RTF-Template is a lot of logic based on XSLT.

My Problem:

I have to use the signum() function out of the java.lang.Math class

<?namespace:math=http://www.oracle.com/XSL/Transform/java/java.lang.Math?>

<?math:ceil('12.34')?>

<?math:signum('12.34')?>

The ceil-result is correct: 13

The sigmun-result is an Error: class overloaded

The signum()-function is declared as double or float inside java.lang.Math.

But if I use <?math:signum(double,'12.34')?> the result is:       (yes you see right, it's only a blank piece of pixels)