Entrypoint crossdiff compatible with UTF-8
Input INTEGER natural number Output INTEGER cross diff from input
The alternate cross sum (also called cross diff) is to alternate addition and subtraction the digits of a number starting right. i.e. 12345: 5-4+3-2+1 = 3 Test-SQL SELECT 3 AS ISCORRECT, F_CROSSDIFF(12345) FROM RDB$DATABASE; SELECT NULL AS ISCORRECT, F_CROSSDIFF(NULL) FROM RDB$DATABASE;