Null object: Difference between revisions

Just v -> "It's not Nothing; it is " ++ show v ++ "."</lang>

 

Icon/Unicon have a [[Icon%2BUnicon/Intro#null|null value/datatype]]. It isn't possible to undefine a variable.

 

<lang Icon>procedure main()

nulltest("a",a) # unassigned variables are null by default

return write(name, if /var then " is" else " is not"," null.")

end</lang>

 

=={{header|Io}}==