Null object: Difference between revisions
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Nothing -> "It's Nothing. Or null, whatever."
Just v -> "It's not Nothing; it is " ++ show v ++ "."</lang>
== Icon and Unicon ==
Icon/Unicon have a [[Icon%2BUnicon/Intro#null|null value/datatype]]. It isn't possible to undefine a variable.
==={{header|Icon}}===
<lang Icon>procedure main()
nulltest("a",a) # unassigned variables are null by default
nulltest("b",b := &null) # explicit assignment is possible
nulltest("c",c := "anything")
nulltest("c",c := &null) # varibables can't be undefined
end
procedure nulltest(name,var)
return write(name, if /var then " is" else " is not"," null.")
end</lang>
==={{header|Unicon}}===
This Icon solution works in Unicon.
=={{header|Io}}==
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