# Concurrent Operations

The following table provides additional information on the members of this template class.
Member | Description
--- | ---
reference local() | If there is no current element corresponding to the current thread, then this method constructs a new element. A new element is copy-constructed if an exemplar was provided to the constructor for `*this`, otherwise a new element is default constructed. Returns: A reference to the element of `*this` that corresponds to the current thread.
reference local( bool& exists ) | Similar to `local()`, except that `exists` is set to true if an element was already present for the current thread; false otherwise. Returns: Reference to thread-local element.
size_type size() const | Returns: The number of elements in `*this`. The value is equal to the number of distinct threads that have called local() after `*this` was constructed or most recently cleared.
bool empty() const | Returns: `size()==0`

Parent topic: enumerable_thread_specific Template Class