# `order_statistics_node_updator` Interface

Functor updating ranks of entries.

1. `order_statistics_key.hpp`
2. Template parameters.
3. Public Types and Constants:
   1. Policy definitions.
   2. Key-type definitions.
4. Public Methods:
   1. Constructors, destructor, and related.

## Template parameters.

Parameter | Description | Default Value

    Key

Key type.

-

    Allocator

Allocator type.

The allocator is only used for definitions, e.g., size_type, pointer, and reference.

    std::allocator<char>

## Policy definitions.

Type | Definition | Description

    allocator

    Allocator

Allocator type.

## Key-type definitions.

Type | Definition | Description

    key_type

    order_statistics_key<
        Key,
        Allocator>

Key-type on which this functor operates.

    const_key_pointer

    typename Allocator::template rebind<
        key_type>::other::const_pointer

Key pointer-type on which this functor operates.

## Constructors, destructor, and related.

Method | Description

    inline void
      swap
      (order_statistics_node_updator &r_other)

Swaps content.

    inline void
      operator()
      (const_key_pointer p_key,
        const_key_pointer p_l_child_key,
        const_key_pointer p_r_child_key)

Updates the rank of a key given its child keys.