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| − | "We describe a datatype of polymorphic balanced binary trees: AVL trees.
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| − | The trees are polymorphic: the values in different nodes may have
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| − | different type. The trees are balanced: for each non-leaf node, the
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| − | heights of its two children can differ at most by one. Here, by
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| − | definition the height of a node is 1 + max of the heights of its
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| − | children. A leaf node has the height of 0.
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| − | The main feature of the present approach is a blended static and dynamic
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| − | enforcement of the balancing constraint. The function make_node
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| − | verifies the balancing constraint at compile time -- if it can. If the
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| − | static check is not possible, the function delays the check till the
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| − | run-time"
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| − | [http://okmij.org/ftp/Haskell/types.html#stanamic-AVL Polymorphic stanamically balanced AVL trees]
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| − | [[Category:Idioms]]
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