Isbn Verifier
The ISBN10 verification process is used to validate book identification
numbers. These normally contain dashes and look like: 3598215088
ISBN
The ISBN10 format is 9 digits (0 to 9) plus one check character (either a digit or an X only). In the case the check character is an X, this represents the value '10'. These may be communicated with or without hyphens, and can be checked for their validity by the following formula:
(x1 * 10 + x2 * 9 + x3 * 8 + x4 * 7 + x5 * 6 + x6 * 5 + x7 * 4 + x8 * 3 + x9 * 2 + x10 * 1) mod 11 == 0
If the result is 0, then it is a valid ISBN10, otherwise it is invalid.
Example
Let's take the ISBN10 3598215088
. We plug it in to the formula, and get:
(3 * 10 + 5 * 9 + 9 * 8 + 8 * 7 + 2 * 6 + 1 * 5 + 5 * 4 + 0 * 3 + 8 * 2 + 8 * 1) mod 11 == 0
Since the result is 0, this proves that our ISBN is valid.
Task
Given a string the program should check if the provided string is a valid ISBN10.
Putting this into place requires some thinking about preprocessing/parsing of the string prior to calculating the check digit for the ISBN.
The program should be able to verify ISBN10 both with and without separating dashes.
Caveats
Converting from strings to numbers can be tricky in certain languages.
Now, it's even trickier since the check digit of an ISBN10 may be 'X' (representing '10'). For instance 359821507X
is a valid ISBN10.
Bonus tasks

Generate a valid ISBN13 from the input ISBN10 (and maybe verify it again with a derived verifier).

Generate valid ISBN, maybe even from a given starting ISBN.