> I think this definitely indicates a bug:
>
> regression=# select '9791020902573'::isbn;
> isbn
> ---------------
> 10-209-0257-4
> (1 row)
Yes, indeed, this one is definitely a bug.
> regression=# select '9791020902573'::isbn = '10-209-0257-4'::isbn;
> ?column?
> ----------
> f
> (1 row)
>
> so apparently the canonicalization conversion wasn't right to begin with.
I still do not get it, "False" is expected on this last one, as this is
not the same book.
> I have no idea which of these forms should be considered valid or
> canonical, but surely the two behaviors exhibited above are wrong.
I think that it is only the first one, i.e. converting the ISBN13 code
beginning with 979 to a ISBN10 should have raised an exception.
--
Fabien.