# Difference between revisions of "Stanamic typing"

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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]] |

## Latest revision as of 15:19, 6 February 2021

"We describe a datatype of polymorphic balanced binary trees: AVL trees. The trees are polymorphic: the values in different nodes may have different type. The trees are balanced: for each non-leaf node, the heights of its two children can differ at most by one. Here, by definition the height of a node is 1 + max of the heights of its children. A leaf node has the height of 0.

The main feature of the present approach is a blended static and dynamic enforcement of the balancing constraint. The function make_node verifies the balancing constraint at compile time -- if it can. If the static check is not possible, the function delays the check till the run-time"