Calcul du chiffre-clé, modulo 10, récursif BVR Suisse

modulo10.rb

# Calcul du chiffre-clé, modulo 10, récursif BVR Suisse
# Berechnung der Prüfziffer nach Modulo 10, rekursiv BESR Schweiz
# Calculating the Check Digits Using Module 10, Recursively

def modulo10_checksum(number) # Best to send a string, an integer with leading 0's will be interpreted as octal...
  # table from https://www.credit-suisse.com/media/production/pb/docs/unternehmen/kmugrossunternehmen/besr_technische_dokumentation_fr.pdf
  
  table = [
            [0,9,4,6,8,2,7,1,3,5],
            [9,4,6,8,2,7,1,3,5,0],
            [4,6,8,2,7,1,3,5,0,9],
            [6,8,2,7,1,3,5,0,9,4],
            [8,2,7,1,3,5,0,9,4,6],
            [2,7,1,3,5,0,9,4,6,8],
            [7,1,3,5,0,9,4,6,8,2],
            [1,3,5,0,9,4,6,8,2,7],
            [3,5,0,9,4,6,8,2,7,1],
            [5,0,9,4,6,8,2,7,1,3]
          ]
          
  numbers = number.to_s.chars.map(&:to_i) # Map integer to array of digits
  report = 0 # Start at row 0
  
  numbers.each do |n|
    report = table[report][n] # Traverse table for each digit
  end
  
  return (10-report)
end

La ligne 28 doit être modulo aussi:

return (10 - report) % 10

Est-ce que vous savez pourquoi on a choisi cette table particulière ?

Merci pour ces informations très utiles :)
Il est alors encore possible de simplifier un peu avec un tableau à une seule dimension:

def modulo10_checksum(number) # Best to send a string, an integer with leading 0's will be interpreted as octal

table = [0,9,4,6,8,2,7,1,3,5]

numbers = number.to_s.chars.map(&:to_i) # Map integer to array of digits
report = 0 # Start at row 0
numbers.each do |n|
report = table[(report+n)%10] # Traverse table for each digit
end

return (10-report)%10
end