Undefined values: Difference between revisions

In PARI, you can do the same but the function <code>is_entry()</code> is more appropriate:

<lang C>is_entry("v") == NULL;</lang>

 

=={{header|Perl}}==

Done

</pre>

=={{header|Perl 6}}==

Perl 6 has "interesting" values of undef, but unlike Perl 5, doesn't actually have a value named <tt>undef</tt>. Instead, several very different meanings of undefinedness are distinguished. First, <tt>Nil</tt> represents the absence of a value. The absence of a value cannot be stored. Instead, an attempt to assign <tt>Nil</tt> to a storage location causes that location to revert to its uninitialized state, however that is defined.