package checksum // https://en.m.wikibooks.org/wiki/Algorithm_Implementation/Checksums/Verhoeff_Algorithm#C var ( mult = [10][10]int{ {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, {1, 2, 3, 4, 0, 6, 7, 8, 9, 5}, {2, 3, 4, 0, 1, 7, 8, 9, 5, 6}, {3, 4, 0, 1, 2, 8, 9, 5, 6, 7}, {4, 0, 1, 2, 3, 9, 5, 6, 7, 8}, {5, 9, 8, 7, 6, 0, 4, 3, 2, 1}, {6, 5, 9, 8, 7, 1, 0, 4, 3, 2}, {7, 6, 5, 9, 8, 2, 1, 0, 4, 3}, {8, 7, 6, 5, 9, 3, 2, 1, 0, 4}, {9, 8, 7, 6, 5, 4, 3, 2, 1, 0}, } perm = [8][10]int{ {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, {1, 5, 7, 6, 2, 8, 3, 0, 9, 4}, {5, 8, 0, 3, 7, 9, 6, 1, 4, 2}, {8, 9, 1, 6, 0, 4, 3, 5, 2, 7}, {9, 4, 5, 3, 1, 2, 6, 8, 7, 0}, {4, 2, 8, 6, 5, 7, 3, 9, 0, 1}, {2, 7, 9, 3, 8, 0, 6, 4, 1, 5}, {7, 0, 4, 6, 9, 1, 3, 2, 5, 8}, } inv = [10]int{0, 4, 3, 2, 1, 5, 6, 7, 8, 9} ) func verhoeff(i, n, c int) int { return mult[c][perm[i%8][n]] } // Verhoeff checksum validation func Verhoeff(num int) bool { return IterInt(num, verhoeff) == 0 } // GetVerhoeff calculates the Verhoeff checksum digit for num. func GetVerhoeff(num int) int { return inv[IterInt(num*10, verhoeff)] }