How to implement the Luhn alorithm in OCL

Question

I am trying to find the Luhn algorithm in OCL to check the validity of ISIN. Can anyone provide a code example would it be great!

I need it too, please write one! – Lars Jun 02 '20 at 14:50 — Lars, Jun 02 '20 at 14:50

score 1 · Answer 1 · answered Jun 02 '20 at 16:16

In pure OCL using the example from https://en.wikipedia.org/wiki/Luhn_algorithm

let s = Sequence{7,9,9,2,7,3,9,8,7,1} in
(Sequence{1..s->size()}
    ->collect(i | 
        let t = s->at(i) in
        if i.mod(2) = 1
        then t
        else let tt = 2 * t in tt.div(10) + tt.mod(10)
        endif)
    ->sum()*9)
.mod(10)

score 1 · Accepted Answer · answered Jun 03 '20 at 06:56

1

In the German Wikipedia article about the Luhns algorithm (https://de.wikipedia.org/wiki/Luhn-Algorithmus) you can find an example to calculate the value for an ident of 446-667-651. The algorithm below calculates the correct value of 40.

let list = '446667651'.ToCharArray.strToInt in 
Sequence{1..list->size}
->Collect(i|
    if (list->size-i).Mod(2)=0 then 
        list.at(i) 
    else 
        (list.at(i)*2).Mod(9) 
    endif)
->Sum

Maybe you need some adaptions for calculating the value for ISINs.

answered Jun 03 '20 at 06:56

Peter Buchmann

85
5

1

Yes, with some adaptations i got this to work. Thanx – Henrik Leijonhufvud Jun 04 '20 at 14:07
This answer is not OCL which requires parentheses on function calls and has no ToCharArray or strToInt functions. mod is not camelcase. The collection operation at() must be invoked using ->. – Ed Willink Jun 07 '20 at 07:22

score -1 · Answer 3 · answered Jun 02 '20 at 15:12

-1

Create a class:

   Attribute NextMult1Or2:Integer
   Method MultWith2Or1SumBiggerThan10(v:Integer):Integer
   Method GetCheckSum(input:String):Integer

The first method MultWith2Or1SumBiggerThan10:

let res=v*self.NextMult1Or2 in
(
  if self.NextMult1Or2=2 then
    self.NextMult1Or2:=1
  else
    self.NextMult1Or2:=2
  endif;
 if res>10 then
  res-9
 else
  res
 endif 
)

And the second method GetCheckSum(input:String):Integer

self.NextMult1Or2:=2;
input.ToCharArray->collect(c|
  let i=Integer.Parse(c) in (
    self.MultWith2Or1SumBiggerThan10(i)  
  )
)->sum

To calculate the checksum - send in all but check digit to GetCheckSum - the check digit is (((res+10) / 10).Truncate*10)-res (ie the diff from nearest 10:th above)

To check a sequence send in all including check digit to GetCheckSum - if res.Mod(10)= 0 it has passed

answered Jun 02 '20 at 15:12

Hans Karlsen

2,275
1
15
15

This answer is not OCL which has no ":=" operator, ";" terminator Attributes or Methods. – Ed Willink Jun 02 '20 at 16:18
In standard ocl there is no ":=" and no ";" operators that is correct - the answered used MDriven Action language that introduce these. But standard ocl does allow you to call functions that has no side effects @EdWillink – Hans Karlsen Jun 05 '20 at 14:06
Yes. And the question specifically requested an OCL answer. – Ed Willink Jun 07 '20 at 07:18

How to implement the Luhn alorithm in OCL

3 Answers3