std::swap(std::function)

 

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std::function

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function::function

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function::swap

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function::operator bool

function::operator()

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function::target

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operator==operator!= (until C++20)

swap(std::function)

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uses_allocator<std::function> (until C++17)

Deduction guides(C++17)

 

Defined in header <functional>
template<class R, class... Args> void swap(std::function<R(Args...)>& lhs, std::function<R(Args...)>& rhs )noexcept;		(since C++11)

Overloads the std::swap algorithm for std::function. Exchanges the state of lhs with that of rhs. Effectively calls lhs.swap(rhs).

Parameters

lhs, rhs

-

polymorphic function wrappers whose states to swap

Return value

(none)

Example

Run this code

#include <functional>#include <iostream>   void foo(constchar* str, int x){std::cout<<"foo(\""<< str <<"\", "<< x <<")\n";}   void bar(constchar* str, int x){std::cout<<"bar(\""<< str <<"\", "<< x <<")\n";}   int main(){std::function<void(constchar*, int)> f1{foo};std::function<void(constchar*, int)> f2{bar};   f1("f1", 1); f2("f2", 2);   std::cout<<"std::swap(f1, f2);\n";std::swap(f1, f2);   f1("f1", 1); f2("f2", 2);}

Output:

foo("f1", 1) bar("f2", 2) std::swap(f1, f2); bar("f1", 1) foo("f2", 2)

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 2062	C++11	overload of swap for function was not required to be noexcept	required

See also

swap	swaps the contents (public member function)
swap(std::move_only_function) (C++23)	specializes the std::swap algorithm (function)