ISBN13 check digit: Difference between revisions

</pre>

=={{header|Ring}}==

<lang ring>

load "stdlib.ring"

isbn = ["978-1734314502","978-1734314509", "978-1788399081", "978-1788399083","978-2-74839-908-0","978-2-74839-908-5","978 1 86197 876 9"]

for n = 1 to len(isbn)

sum = 0

isbnStr = isbn[n]

isbnStr = substr(isbnStr,"-","")

isbnStr = substr(isbnStr," ","")

for m = 1 to len(isbnStr)

if m%2 = 0

num = 3*number(substr(isbnStr,m,1))

sum = sum + num

else

num = number(substr(isbnStr,m,1))

sum = sum + num

ok

next

if sum%10 = 0

see "" + isbn[n] + ": true" + nl

else

see "" + isbn[n] + ": bad" + nl

ok

next

</lang>

Output:

<pre>

978-1734314502: true

978-1734314509: bad

978-1788399081: true

978-1788399083: bad

978-2-74839-908-0: true

978-2-74839-908-5: bad

978 1 86197 876 9: true