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std::function::operatorbool(3) C++ Standard Libary std::function::operatorbool(3)

NAME

std::function::operatorbool - std::function::operatorbool

Synopsis


explicit operator bool() const noexcept; (since C++11)


Checks whether *this stores a callable function target, i.e. is not empty.

Parameters


(none)

Return value


true if *this stores a callable function target, false otherwise.

Example

// Run this code


#include <functional>
#include <iostream>


void sampleFunction()
{
std::cout << "This is the sample function!\n";
}


void checkFunc(std::function<void()> const& func)
{
// Use operator bool to determine if callable target is available.
if (func)
{
std::cout << "Function is not empty! Calling function.\n";
func();
}
else
std::cout << "Function is empty. Nothing to do.\n";
}


int main()
{
std::function<void()> f1;
std::function<void()> f2(sampleFunction);


std::cout << "f1: ";
checkFunc(f1);


std::cout << "f2: ";
checkFunc(f2);
}

Output:


f1: Function is empty. Nothing to do.
f2: Function is not empty! Calling function.
This is the sample function!

See also


operator bool checks if the std::move_only_function has a target
(C++23) (public member function of std::move_only_function)

2024.06.10 http://cppreference.com