Talk:Null object: Difference between revisions

* PARI/GP: can't tell if this example is about null or not.

* Perl: explains undef as a value but doesn't show how to tell the difference between the variable having a value and the variable actually being undefined. if that difference is not possible then this should be explained. i suppose it's the same as Perl 6, there it is explicitly stated that null objects can not be tested for.