Class Template unordered_node_set

:idprefix: unordered_node_set_

`boost::unordered_node_set` — A node-based, open-addressing unordered associative container that stores unique values.

`boost::unordered_node_set` uses an open-addressing layout like `boost::unordered_flat_set`, but, being node-based, it provides pointer stability and node handling functionalities. Its performance lies between those of `boost::unordered_set` and `boost::unordered_flat_set`.

As a result of its using open addressing, the interface of `boost::unordered_node_set` deviates in a number of aspects from that of `boost::unordered_set`/`std::unordered_set`:

- `begin()` is not constant-time. - There is no API for bucket handling (except `bucket_count`). - The maximum load factor of the container is managed internally and can't be set by the user.

Other than this, `boost::unordered_node_set` is mostly a drop-in replacement of standard unordered associative containers.

Synopsis

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Description

*Template Parameters*

_Key_

`Key` must be https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^] from the container.

_Hash_

A unary function object type that acts a hash function for a `Key`. It takes a single argument of type `Key` and returns a value of type `std::size_t`.

_Pred_

A binary function object that induces an equivalence relation on values of type `Key`. It takes two arguments of type `Key` and returns a value of type `bool`.

_Allocator_

An allocator whose value type is the same as the container's value type.

Allocators using https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[fancy pointers] are supported.