std::function::operator()(3)

✨ NAME ✨

std::function::operator() - std::function::operator() (yes bestie, the name is literally the name twice and it's giving main character energy 👑). This is the std::function::operator()(3) page from the C++ Standard Libary manual, folded in right here near the top like a little intro 🫶.

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🦋 Synopsis 🦋

R operator()( Args... args ) const;  (since C++11)

Okay so what this actually does: it invokes the stored callable function target with the parameters args. Effectively it does INVOKE<R>(f, std::forward<Args>(args)...), where f is the target object of *this. Periodt ✨.

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🌸 Parameters 🌸

• args — parameters to pass to the stored callable function target. That's the whole vibe 🎀.

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💖 Return value 💖

None if R is void. Otherwise, you get the return value of the invocation of the stored callable object. No cap.

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💀 Exceptions 💀

Throws std::bad_function_call if *this does not store a callable function target, i.e. !*this == true. So if it's empty, it's throwing hands — protect your vibe check, bestie 😭.

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🍓 Example 🍓

The following example shows how std::function can be passed to other functions by value. Also, it shows how std::function can store lambdas. Here's the exact code, including the // Run this code bit from the original:

// Run this code

#include <functional>
#include <iostream>

void call(std::function<int()> f) // can be passed by value
{
    std::cout << f() << '\n';
}

int normal_function()
{
    return 42;
}

int main()
{
    int n = 1;
    std::function<int()> f = [&n](){ return n; };
    call(f);

    n = 2;
    call(f);

    f = normal_function;
    call(f);
}

🍓 Output 🍓

1
2
42

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👀 See also 👀

Here's every reference from the original See also zone — yes, all of it, because we don't skip details in this group chat 💅:

• operator() — invokes the target
  • (C++23) — public member function of std::move_only_function
• operator() — calls the stored function
  • public member function of std::reference_wrapper<T>
• bad_function_call — the exception thrown when invoking an empty std::function
  • (C++11) — class
• invoke — invokes any Callable object with given arguments
• invoke_r — and possibility to specify return type
  • (C++17)
  • (since C++23)
  • (C++23)
  • (function template)

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okay bestie, that's the whole page — catch you later 💖 this little icon came from http://cppreference.com, dated 2024.06.10, and it's the std::function::operator()(3) page. mwah 💋✨