std::variant::swap

 

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void swap( variant& rhs ) noexcept(/* see below */);	(1)	(since C++17)

Swaps two variant objects.

• if both *this and rhs are valueless by exception, does nothing
• otherwise, if both *this and rhs hold the same alternative, calls swap(std::get<i>(*this), std:get<i>(rhs)) where i is index(). If an exception is thrown, the state of the values depends on the exception safety of the swap function called.
• otherwise, exchanges values of rhs and *this. If an exception is thrown, the state of *this and rhs depends on exception safety of variant's move constructor.

The behavior is undefined unless lvalues of type T_i are Swappable and std::is_move_constructible_v<T_i> is true for all T_i in Types....

Parameters

rhs

-

a variant object to swap with

Return value

(none)

Exceptions

If this->index() == rhs.index(), may throw any exception thrown by swap(std::get<i>(*this), std::get<i>(rhs)) with i being index().

Otherwise, may throw any exception thrown by the move constructors of the alternatives currently held by *this and rhs.

noexcept specification:  

noexcept(((std::is_nothrow_move_constructible_v<Types> &&
           std::is_nothrow_swappable_v<Types>) && ...))