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).
| lhs, rhs | - | polymorphic function wrappers whose states to swap |
(none).
#include <functional>
#include <iostream>
void foo(const char* str, int x) {
std::cout << "foo(\"" << str << "\", " << x << ")\n";
}
void bar(const char* str, int x) {
std::cout << "bar(\"" << str << "\", " << x << ")\n";
}
int main()
{
std::function<void(const char*, int)> f1{ foo };
std::function<void(const char*, 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)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 |
| swaps the contents (public member function) |
|
|
(C++23) | overloads the std::swap algorithm (function) |
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