Check digit calculation functions

The StreamServer supports the Mod10, Mod10L, and Mod11 check digit calculation schemes. Please read the descriptions carefully before you use the functions. Relying only on the function names can sometimes be misleading. For example, Mod11 does not only do a modulo 11 calculation, but uses weight values as well.

Arguments and return values are strings. Arguments can consist of moderately long digit sequences and return values can consists of non-digit values. Currently, the functions do not check that the input string contains digits. Spaces are skipped.

If the input string contains many digits, you should consider using multiple check digits.

Check digit calculation functions

The table below contains a short description of each script function. For information about syntax, examples, etc., see the full description of each script function.

Function name	Description
Mod10	Performs a Pad 10-based check digit calculation with the alternating weights 2 and 1, starting at the end of the string. The digits of the values are summed. This check digit calculation method is known as Luhn’s algorithm.
Mod10L	Calculates a length check digit and a Luhn check digit. First the length check digit is calculated (length plus 2, mod 10). Then, to calculate the check digit, the length check digit is added at the end of the string and a pad 10-based check digit calculation (same as for Mod10) is performed. Both the length check digit (first) and the pad 10-based check digit are included in the returned result.
Mod11	Performs a Pad 11-based check digit calculation with the cycled weights 7, 9, 5, 3, 2, 4, 6, 8, starting at the end of the string. Weighted values are summed. A resulting 0 is replaced by a 5, and a resulting 10 is replaced by a 0.