Talk:Null object: Difference between revisions

The C anc C++ examples don't really fit the task description (and it's not possible to do so, because C and C++ don't know a generic null object). What you can have is a null ''pointer'', which is a pointer which doesn't point to any object (and that is indeed what <code>NULL</code> is for). The closest to a null object in C++ would be an empty <code>boost::optional</code> from the boost library.

 

::: Please stop changing task names and descriptions; we want to avoid accidentally making implementations of tasks wrong. Well, unless you're prepared to go through all the implementations and ''fix'' anything invalidated yourself. (Not all languages have a type system that admits nulls — i.e., a bottom to the pointer/reference type system — but where that's the case, there's typically other mechanisms for saying the broader statement of “there's nothing here”.) –[[User:Dkf|Donal Fellows]] 09:30, 11 November 2011 (UTC)

:::: as has been said above, the title was wrong, the solutions are right. i went over them, and below is a listing of the issues i found. i'd appreciate if someone could verify those findings.--[[User:EMBee|eMBee]] 13:54, 11 November 2011 (UTC)

 

== solutions that need review ==

* 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.