I proposed as alternative to Luhn check. In special to validation problems like credit card number validation.
El jue., 30 abr. 2020 11:11, Richard O'Keefe <rao...@gmail.com> escribió: > I'm sure you could fit regular expressions into the Luhn check, > but I am rather mystified as to what one could possibly gain by doing so. > How do you do the equivalent of > #(0 2 4 6 8 1 3 5 7 9) at: char digitValue + 1 > in a regular expression and why would you want to? > > On Fri, 1 May 2020 at 01:31, Pablo Navarro <pablo...@gmail.com> wrote: > > > > Hello!. For this problem is possible to use Regular Expressions too. > > > > > https://ci.inria.fr/pharo-contribution/job/UpdatedPharoByExample/lastSuccessfulBuild/artifact/book-result/Regex/Regex.html > > > > Saludos, Pablo. > > El 30 de abr. de 2020 10:11 -0300, Stéphane Ducasse < > stephane.duca...@inria.fr>, escribió: > > > > It looks like a cool problem > > from where did you take it? > > > > I hope I can discuss my approch to this problem : > > > > Given a number determine whether or not it is valid per the Luhn formula. > > > > The Luhn algorithm is a simple checksum formula used to validate a > variety of identification numbers, such as credit card numbers and Canadian > Social Insurance Numbers. > > > > The task is to check if a given string is valid. > > > > > > > > I like people that are always thinking in string as if a collection of > number would not make it :) > > > > Validating a Number > > > > Strings of length 1 or less are not valid. Spaces are allowed in the > input, but they should be stripped before checking. All other non-digit > characters are disallowed. > > > > Example 1: valid credit card number > > > > 4539 1488 0343 6467 > > > > The first step of the Luhn algorithm is to double every second digit, > starting from the right. We will be doubling > > > > 4_3_ 1_8_ 0_4_ 6_6_ > > > > If doubling the number results in a number greater than 9 then subtract > 9 from the product. The results of our doubling: > > > > 8569 2478 0383 3437 > > > > Then sum all of the digits: > > > > 8+5+6+9+2+4+7+8+0+3+8+3+3+4+3+7 = 80 > > > > If the sum is evenly divisible by 10, then the number is valid. This > number is valid! > > > > > > my idea was to do these steps > > > > 1) reverse the input. > > > > 2) use this to double every second digit and calculate the sum of all > the numbers : > > > > checkNumber := (collection reverse selectwith index: [:item :index | > (index % 2 == 0) . IfTrue: [item *2]] ) sumNumbers > > > > > > > > you can also > > 1 to: xx by: 2 do: > > > > 3) check if its a valid number by doing this : > > > > > > ^ (checkNumber % 10 == 0) > > > > > > is this a good game plan or has it flaws or can I do it better ? > > > > Regards, > > > > > > Roelof > > > > > > > > > > > > -------------------------------------------- > > Stéphane Ducasse > > http://stephane.ducasse.free.fr / http://www.pharo.org > > 03 59 35 87 52 > > Assistant: Julie Jonas > > FAX 03 59 57 78 50 > > TEL 03 59 35 86 16 > > S. Ducasse - Inria > > 40, avenue Halley, > > Parc Scientifique de la Haute Borne, Bât.A, Park Plaza > > Villeneuve d'Ascq 59650 > > France > > > >
