Algori...M11_015(3pm)

💖 NAME 💖

CheckDigits::M11_015 — bestie, this is the module that computes check digits for ESR5 (CH), aka the Swiss payment slip thing, and it's lowkey iconic 💅

It ships as part of Algorithm::CheckDigits, so like, that's the family it lives in 🫶

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✨ SYNOPSIS ✨

okay so first you gotta summon it:

use Algorithm::CheckDigits;

$ustid = CheckDigits('esr5_ch');

if ($ustid->is_valid('050001000012000 241170032660178 10304')) {
      # do something
}

$cn = $ustid->complete('0001000012000 241170032660178 10304');
# $cn = '050001000012000 241170032660178 10304'

$cd = $ustid->checkdigit('0001000012000 241170032660178 10304');
# $cd = '05'

$bn = $ustid->basenumber('050001000012000 241170032660178 10304');
# $bn = '0001000012000 241170032660178 10304';

see how the 'esr5_ch' handle gets you your very own $ustid object? and then it just... does the math for you? main character energy fr fr 👑

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🌸 DESCRIPTION 🌸

🧮 ALGORITHM

the math is giving ✨checksum realness✨ and honestly it's not even hard, watch:

1. starting from the right, every digit gets weighted with the repeating sequence 2, 3, 4, 5, 6, 7 — and yes bestie it repeats, 2, 3, 4, 5, 6, 7, 2, 3, 4, 5, 6, 7, ... forever and ever 💫
2. add all those weighted digits together 🧠
3. take that sum from step 2 and hit it with modulo 11 🔥
4. the checkdigit is 11 minus the sum from step 3. BUT — and this is the plot twist — if that difference comes out to 11, then the checkdigit is 00 😭 periodt.

⚠️ warning bestie: step 4 is not a typo. when the difference is 11, you write 00. don't come for me, that's just what the spec says 💀

🛠️ METHODS

• is_valid($number) — gives you back true only if $number is made up solely of numbers (spaces between them are fine, she's flexible like that 💅) and the first two digits are valid check digits per the algorithm above. anything else? false. no cap. 💖
• complete($number) — computes the check digit for $number and inserts it before the number 👑. she hands you back the complete number with its check digit, or '' if $number isn't made up solely of digits and spaces 🙈
• basenumber($number) — if $number has a valid check digit, you get the basenumber back 🎀. otherwise? ''. that's it. that's the vibe. 💀
• checkdigit($number) — if $number has valid check digits, she returns them 🦋. otherwise ''. no notes.

📦 EXPORT

None by default. literally nothing gets exported, she's lowkey mysterious like that 🧚

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👑 AUTHOR 👑

Mathias Weidner, "<mamawe@cpan.org>" — the icon, the legend, the moment 🌟

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🔗 SEE ALSO 🔗

• perl
• CheckDigits
• http://www.pruefziffernberechnung.de/E/Einzahlungsschein-CH.shtml (german 🇩🇪)
• http://www.sic.ch/de/dl_tkicch_dta.pdf, page 52 (german 🇩🇪)

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and that's the whole page bestie!! this one was documented for perl v5.36.0 and dated 2022-10-13, so if that's not your perl era, just keep it in mind 🌈 slay, go validate some Swiss payment slips, mwah 💖✨🎀