I am using sum to add-up 2 numbers in xsl. The numbers are 4412545665465445 and 8234567890123456. The sum of these should be 12647113555588901.
But the sum in xsl is returned as 12647113555588900. Even when those numbers are more than 16 digits, the sum returns 0s at the end. It means its not able to cater totals of greater than 16 digits and even when the result is more than 16 digits it returns 0s at the end.
I need to add numbers which could be of any length and their sum can be of any length. So how to solve this problem in xsl?

XSLT 1.0 numbers are double-precision floating point, so they are held accurately to about 16 decimal places.

If you want higher precision you could use XSLT 2.0 which offers integer and decimal data types. The precision of these is implementation-defined (ewith an 18 digit minimum) but you can choose an implementation such as Saxon which offers infinite precision.

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference

Thanks for reply.
But i am really new to XSL. So can you let me know how to move to xslt 2.0 or that Saxon ?

You can find information about the open source version of Saxon at http://saxon.sf.net/

How you move there depends entirely on where you are moving from!

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference