CHECKSUM_ALGORITHMS.md

Check Digit Algorithms

This page defines the basic check digit algorithms used by couriers to verify that a tracking number is valid.

This reference page is useful for anyone wishing to use this repository to create a new tracking number library in your language. Keep in mind that the implementation in your language may already exist!

def mod7(arr: List[int], checkDigit: int):
    x: Long = parseLong(string(arr))
    return x % 7 == checkDigit;

def mod10(
        arr: List[int], checkDigit: int,
        evensMultiplier: int, oddsMultiplier: int):
    total = sum(
        idx % 2 == 0 and evensMultiplier * val or oddsMultiplier * val
        for idx, val in enumerate(arr))
    x = total % 10;
    if (x != 0) {
        x = 10 - x;
    }
    return x == checkDigit;

def s10(seq1: List[int], checkDigit: int):
    int[] weightings = {8,6,4,2,3,5,9,7};
    x = sum(x * y for x, y in zip(seq1, weightings))
    r = x % 11;
    if (r == 1) {
        r = 0;
    } else if (r == 0) {
        r = 5;
    } else {
        r = 11 - r;
    }
    return r == checkDigit;

def sumProductWithWeightingsAndModulo(
        arr: List[int], checkDigit: int, weightings: List[int],
        modulo1: int, modulo2: int):
    x = sum(x * y for x, y in zip(seq1, weightings))
    return x % modulo1 % modulo2 == checkDigit;

def dummy(arr: List[int], checkDigit: int):
    return True