9784774133416 → 978[477413341]6 → 477413341
4×10 + 7×9 + 7×8 + 4×7 + 1×6 + 3×5 + 3×4 + 4×3 + 1×2 = 234それを11で割った余りを11から引く。
234÷11=29 余り3 → 11 - 3 = 8
"477413341" + "8" → 4774133418
asin = isbn13.substr(3,9); var ck = 0; for (var i = 0; i < 9; i++) { ck += asin.substr(i,1) * (10 - i); } ck = (11 - ck % 11) % 11; asin = asin + ((ck == 10) ? 'X' : ck);
$asin =~ s/^\d{3}(\d{9})\d$/$1/; my $ck; for (my $i = 0; $i < 9; $i++) { $ck += substr($asin, $i, 1) * (10 - $i); } my $cs = (11 - $ck % 11) % 11; $asin .= ($cs == 10) ? "X" : $cs;