A "null" node updater, indicating that no node updates are required.
Interface::Concepts::Null Policy Classes explains the concept of a null policy.
Defined in: trie_policy.hpp
| Parameter | Description | Default Value | 
| class Const_Node_Iterator | Const node iterator type. | - | 
| class Node_Iterator | Node iterator type. | - | 
| class E_Access_Traits | Comparison functor. | - | 
| class Allocator | Allocator type. | - |