std::atomic_ref<T>::exchange
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                    < cpp | atomic | atomic ref
                    
                                                            
                    |   T exchange( T desired, std::memory_order order = std::memory_order_seq_cst ) const noexcept;  | 
(since C++20) | |
Atomically replaces the value of the referenced object with desired. The operation is a read-modify-write operation. Memory is affected according to the value of order.
Parameters
| desired | - | value to assign | 
| order | - | memory order constraints to enforce | 
Return value
The value of the referenced object before the call.