Name

       lua-uri-urn-isbn - ISBN URN support for Lua URI library

Description

       The class "uri.urn.isbn" is used for URNs with the NID 'isbn', that is, URIs which begin "urn:isbn:".  It
       inherits from the uri.urn class.

       Some of the functionality of this class depends on the lua-isbn(3) module being installed, although it
       can be used without that.  In particular, if the module is installed then full checksum validation of the
       ISBN is performed, whereas without it the ISBN is only checked for invalid characters.  The ISBN value is
       normalized to include hyphens in the conventional places if the lua-isbn module is installed (the exact
       hyphen positions depend on the number), but without it all hyphens are removed instead.  If the ISBN ends
       in a checksum of 'x', then it folded to uppercase.

Methods

       All the methods defined in lua-uri(3) and lua-uri-urn(3) are supported, as well as the following:

       uri:isbn(...)
           Get or set the ISBN value as an object of the type provided by the "isbn" class in the lua-isbn(3)
           library.  This method will throw an exception if this library is not installed, or if the object
           supplied is not a valid ISBN object (it will currently accept a string, but you shouldn't rely on
           this).

       uri:isbn_digits(...)
           Get or set the ISBN value as a string containing just the numbers (and possibly an 'X' as the last
           digit).  There will be no hyphens in this value, and it should be exactly 10 or 13 characters long.

           If a new value is provided then it must not be nil, and will be validated in the normal way, causing
           an exception if it is invalid.

References

       This implements the 'isbn' NID defined in "RFC 3187", and is consistent with the same NID suggested in
       "RFC 2288".