PureBasic Forums - English

I am looking for an example that allows the calculation of a key from a modulo 10 example.
210000000003139471430009017
the result is 7 (position 27 of the figure)
Thank you in advance for helping me

What type of numbers do you have ?
Internal formats PB supports like Quad or Double aren't suitable for this kind of large integer values.
If they are strings, you can just take the last character.

If your numbers are already represented as decimal strings then just extract the last digit and there you go.

In all other cases: Please give us more information.

NicTheQuick wrote:just extract the last digit

Surely that's not always going to be the case? We're talking key calculations here. The 7 in the original post was just an example for that specific calculation, no?

What is a key calculation? Are we talking about private and public keys or signatures? I don't get it.

Nic, I suspect that he means a so called "check digit calculation" (in german "Prüfziffernberechnung").

@loulou2522:

This is a modulo 10 checksum calculation with weighting 2. You can get information about the check digit calculation methods here:
https://www.activebarcode.com/codes/che ... ulo10.html

Markus

kurzer wrote:Nic, I suspect that he means a so called "check digit calculation" (in german "Prüfziffernberechnung").

@loulou2522:

This is a modulo 10 checksum calculation with weighting 2.

Code: Select all

Procedure.s CalcChecksum(sNumber.s)
	Protected.i i, iDigit, iSum, iLen
	
	iLen = Len(sNumber)
		
		iSum = 0
		For i = 1 To iLen
			iDigit = Val(Mid(sNumber, i, 1))
			If i % 2 = 0 : iDigit * 2 : EndIf
			iSum + iDigit
		Next i
		ProcedureReturn Str((10 - iSum % 10) %10)
EndProcedure

Debug CalcChecksum("21000000000313947143000901")

You can get information about the check digit calculation methods here:
https://www.activebarcode.com/codes/che ... ulo10.html

Markus

Google "Luhn Formula" or "Luhn calculation"