This Ruby file includes Ruby functions that Luhn algorithm is implemented. checkLuhn1 returns value if current barcode(including check digit) validates. checkLuhn2 returns value that current barcode join its checkdigit as suffix.

calcChecksum.rb

def sumLuhn (barcode, nParity)
  checksum = 0
	for i in 0..barcode.length - 1
		nDigit = barcode[i].to_i
		if nParity == i % 2
			nDigit = nDigit * 2
		end
		checksum = checksum + nDigit / 10 + nDigit % 10
	end
	return checksum % 10
end

#return turn if current barcode( including checkdigit ) validates, false if not.

def checkLuhn1(barcode)
	nParity = barcode.length % 2
	return sumLuhn(barcode, nParity) == 0
end

#return string if current barcode joined checkdigit as suffix.

def checkLuhn2(barcode)
	nParity = 1 - barcode.length % 2
	checksum = sumLuhn(barcode, nParity)
	return barcode + "#{( 10 - checksum % 10 ) % 10}"
end



puts checkLuhn1("79927398713") # return ture if valid barcode, return false if invalid barcode
puts checkLuhn2("7992739871") # return checkcode