std::promise<R>::operator=

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atomic_flag_testatomic_flag_test_explicit (C++20)(C++20)
atomic_flag_waitatomic_flag_wait_explicit (C++20)(C++20)
atomic_flag_notify_one (C++20)
atomic_flag_notify_all (C++20)

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std::promise

Member functions
promise::promise
promise::~promise
promise::operator=
promise::swap
Getting the result
promise::get_future
Setting the result
promise::set_value
promise::set_value_at_thread_exit
promise::set_exception
promise::set_exception_at_thread_exit
Non-member Functions
swap(std::promise)
Helper Classes
uses_allocator<std::promise>

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promise& operator=( promise&& other)noexcept;	(1)	(since C++11)
promise& operator=(const promise& rhs)= delete;	(2)	(since C++11)

Assigns the contents.

1) Move assignment operator. First, abandons the shared state (as in~promise()), then assigns the shared state ofother as if by executingstd::promise(std::move(other)).swap(*this).

2)promise is not copy-assignable.