RosettaCodeData/Task/Null-object/Icon/null-object.icon

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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