Editing Oz (programming language) (section)

=== State and objects ===

It is again possible to extend the declarative model to support state and object-oriented programming with very simple semantics. To create a new mutable data structure called Cells:
<syntaxhighlight lang="erlang">
local A X in
   A = {NewCell 0}
   A := 1  % changes the value of A to 1
   X = @A  % @ is used to access the value of A
end
</syntaxhighlight>

With these simple semantic changes, the whole object-oriented paradigm can be supported. With a little syntactic sugar, OOP becomes well integrated in Oz.
<syntaxhighlight lang="erlang">
class Counter
   attr val
   meth init(Value)
      val:=Value
   end
   meth browse
      {Browse @val}
   end
   meth inc(Value)
      val :=@val+Value
   end
end

local C in
   C = {New Counter init(0)}
   {C inc(6)}
   {C browse}
end
</syntaxhighlight>