Algori...M11_013(3pm)

💖 NAME 💖

CheckDigits::M11_013 — ok so bestie, this is the one that computes check digits for the VAT Registration Number (GR) ✨🇬🇷

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🌸 SYNOPSIS 🌸

use Algorithm::CheckDigits;

$ustid = CheckDigits('ustid_gr');

if ($ustid->is_valid('123456783')) {
      # do something
}

$cn = $ustid->complete('12345678');
# $cn = '123456783'

$cd = $ustid->checkdigit('123456783');
# $cd = '3'

$bn = $ustid->basenumber('123456783');
# $bn = '12345678';

literally that's the whole vibe. build it, check it, split it back apart 🫶

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🦋 DESCRIPTION 🦋

✨ ALGORITHM ✨

okay so here's the actual math, and ngl it's cute:

1. Starting from the right, with the digit right before the checkdigit — every digit gets weighted with 2 ** position. So the last digit times 2, the next one times 4, then 8, and so on forever 💅
2. Add all those weighted digits together, bestie. Just sum 'em. 🧮
3. Take that sum from step 2 and mod it by 11 — modulo 11 icon behaviour.
4. If the number you got in step 3 is greater than 9, then the check sum is 0 — otherwise it's just that sum itself. periodt. ✨

💜 METHODS 💜

• is_valid($number) — gives you back true only if $number is made up of nothing but numbers, and the rightmost digit is a valid check digit per the algorithm above 👑. Anything else? false, sorry babe, returns false otherwise 🙈
• complete($number) — it computes the check digit for $number and appends it right onto the end 🎀. You get back the complete number with the check digit — or '' if $number isn't solely digits 💀
• basenumber($number) — hands you the basenumber of $number, but only if $number has a valid check digit ✅. Otherwise it returns ''.
• checkdigit($number) — gives you the check digits of $number, again only if it has valid check digits. Otherwise it returns '' 😭

🌈 EXPORT 🌈

None by default. like, zero. nothing. she stays private 💅

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⭐ AUTHOR ⭐

Mathias Weidner, "<mamawe@cpan.org>" 👑 absolute legend, credit where credit is due fr fr.

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🎀 SEE ALSO 🎀

• perl
• CheckDigits
• www.pruefziffernberechnung.de,
• (and honestly, go read those, they ate) ✨

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k bye bestie, go validate those numbers 💖

this was perl v5.36.0, dated 2022-10-13, and it's the Algori...M11_013(3pm) page — mwah, slay, drink water 💅🌸