Talk:Luhn algorithm: Difference between revisions

Revision as of 08:29, 11 May 2020

Revision as of 18:47, 11 May 2020

Line 158:

Both the C# implementation and the Scala implementation seems wrong to me. The algorithm states "Counting from the check digit, which is the rightmost, and moving left, double the value of every second digit". Then, shouldn't the example read:

<sourcesyntaxhighlight lang="csharp">

bool isLuhnValid(string s)

{

return s.Reverse().SelectMany((c, i) => ((c - '0') << (i & 1)).ToString()).Sum(c => (c - '0')) % 10 == 0;

}

</syntaxhighlight>

</source>

Similarly for Scala, shouldn't it be:

<sourcesyntaxhighlight lang="scala">

def isLuhnValid(s : String) =

s.reverse.zipWithIndex.map({ case (c, i) => ((c - '0') << (i & 1))}).mkString.map(_ - '0').sum % 10 == 0

</syntaxhighlight>

</source>

[[User:Rehno Lindeque|Rehno Lindeque]] ([[User talk:Rehno Lindeque|talk]]) 09:33, 1 June 2011 (UTC)

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I've also put up a gist on github with the code and tests showing correctness. https://gist.github.com/1773914

<sourcesyntaxhighlight lang="python">

def luhn_checksum(card_number):

def digits_of(n):

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def calculate_luhn(partial_card_number):

return 10 - luhn_checksum(int(partial_card_number) * 10)

</syntaxhighlight>

</source>

[[Special:Contributions/206.169.213.106|206.169.213.106]] ([[User talk:206.169.213.106|talk]]) 21:08, 8 February 2012 (UTC)

:It looks good. I've put this version up in the article. – [[User:Acdx|Acdx]] <small>(<i>[[User_talk:Acdx|talk]]</i>)</small> 11:55, 18 February 2012 (UTC)

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Here is a basic Ruby solution to luhn10 validation. I decided to place it here instead of the article.

<sourcesyntaxhighlight lang=ruby>

def luhn10?(number)

checksum = 0

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split_integer(number).inject(0){ |sum,digit| sum += digit.to_i}

end

</syntaxhighlight>

</source>

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