std::swap(std::function)(3)

std::swap(std::function)(3) 💅

okay so this page is from the C++ Standard Libary manual — that's the manual name, spelling and all, no cap — and it's all about the std::swap overload for std::function. Bestie, it's literally a swap for your polymorphic function wrappers. 🫶

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✨ NAME ✨

std::swap(std::function) - std::swap(std::function)

(yes, the name section is giving minimalist icon behavior. we respect it. 💅)

🌸 Synopsis 🌸

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) — literally nothing, not a single value, it's giving void energy. 🫶

🎬 Example 🎬

// Run this code

#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)

💀 Defect reports 💀

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

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

👑 See also 👑

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

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source: http://cppreference.com · version/date: 2024.06.10 · page: std::swap(std::function)(3) 💖✨