# Concurrently unsafe modifiers

All member functions in this section can only be performed serially. The behavior is undefined in case of concurrent execution of these member functions with other (either concurrently safe) methods.

## Clearing

>     void clear();

> Removes all elements from the container.

## Erasing elements

>     iterator unsafe_erase( const_iterator pos );

>     iterator unsafe_erase( iterator pos );

> Removes the element pointed to by `pos` from the container.

> Invalidates all iterators and references to the removed element.

> Returns: `iterator` that follows the removed element.

> Requirements: the iterator `pos` should be valid, dereferenceable and point to the element in `*this`.

>     size_type unsafe_erase( const key_type& key );

> Removes the element with the key equivalent to `key` if it exists in the container.

> Invalidates all iterators and references to the removed element.

> Returns: `1` if an element with the key equivalent to `key` exists; `0`, otherwise.

>     template <typename K>
>     size_type unsafe_erase( const K& key );

> Removes the element with the key equivalent to `key` if it exists in the container.

> Invalidates all iterators and references to the removed element.

> This overload only participates in overload resolution if all of the following conditions are met:

> - The qualified-id `hasher::transparent_key_equal` is valid and denotes a type.

> - `std::is_convertible<K, iterator>::value` is `false`.

> - `std::is_convertible<K, const_iterator>::value` is `false`.

> Returns: `1` if an element with the key equivalent to `key` exists; `0`, otherwise.

## Erasing sequences

>     iterator unsafe_erase( const_iterator first, const_iterator last );

> Removes all elements from the half-open interval `[first, last)` from the container.

> Returns: `iterator` that follows the last removed element.

> Requirements: the range `[first, last)` must be a valid subrange in `*this`.

## Extracting nodes

>     node_type unsafe_extract( iterator pos );

>     node_type unsafe_extract( const_iterator pos );

> Transfers ownership of the element pointed to by `pos` from the container to the node handle.

> No copy or move constructors of `value_type` are performed.

> Invalidates all iterators to the extracted element. Pointers and references to the extracted element remain valid.

> Returns: the node handle that owns the extracted element.

> Requirements: the iterator `pos` should be valid, dereferenceable and point to the element in `*this`.

>     node_type unsafe_extract( const key_type& key );

> If an element with the key equivalent to `key` exists, transfers ownership of this element from the container to the node handle.

> No copy or move constructors of `value_type` are performed.

> Invalidates all iterators to the extracted element. Pointers and references to the extracted element remain valid.

> Returns: the node handle that owns the extracted element or an empty node handle if an element with the key equivalent to `key` was not found.

>     template <typename K>
>     node_type unsafe_extract( const K& key );

> If an element with the key equivalent to `key` exists, transfers ownership of this element from the container to the node handle.

> No copy or move constructors of `value_type` are performed.

> Invalidates all iterators to the extracted element. Pointers and references to the extracted element remain valid.

> This overload only participates in overload resolution if all of the following conditions are met:

> - The qualified-id `hasher::transparent_key_equal` is valid and denotes a type.

> - `std::is_convertible<K, iterator>::value` is `false`.

> - `std::is_convertible<K, const_iterator>::value` is `false`.

> Returns: the node handle that owns the extracted element or an empty node handle if an element with the key equivalent to `key` was not found.

## swap

>     void swap( concurrent_unordered_map& other ) noexcept(/*See below*/);

> Swaps contents of `*this` and `other`.

> Swaps allocators if `std::allocator_traits<allocator_type>::propagate_on_container_swap::value` is `true`.

> Otherwise, if `get_allocator() != other.get_allocator()`, the behavior is undefined.

> Exceptions: `noexcept` specification:

> >     noexcept(std::allocator_traits<allocator_type>::is_always_equal::value &&
> >              std::is_nothrow_swappable<hasher>::value &&
> >              std::is_nothrow_swappable<key_equal>::value