Class Template unordered_set

:idprefix: unordered_set_

`boost::unordered_set` — An unordered associative container that stores unique values.

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 (i.e. `allocator_traits` can destroy it).

_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 implements an equivalence relation on values of type `Key`. 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.

The elements are organized into buckets. Keys with the same hash code are stored in the same bucket.

The number of buckets can be automatically increased by a call to insert, or as the result of calling rehash.

Configuration macros

`BOOST_UNORDERED_ENABLE_SERIALIZATION_COMPATIBILITY_V0`