C++ Functional Library - operator()

Description

It invokes the stored callable function target with the parameters args.

Declaration

Following is the declaration for std::function::function::operator()

R operator()( Args... args ) const;

C++11

R operator()( Args... args ) const;

Parameters

args − parameters to pass to the stored callable function target.

Return Value

It returns none if R is void. Otherwise the return value of the invocation of the stored callable object.

Exceptions

noexcept: It doesnot throw any exceptions.

Example

In below example for std::function::operator().

#include <iostream>
#include <functional>
 
void call(std::function<int()> f) {
   std::cout << f() << '\n';
}

int normal_function() {
   return 50;
}

int main() {
   int n = 4;
   std::function<int()> f = [&n](){ return n; };
   call(f);

   n = 5;
   call(f);

   f = normal_function;
   call(f);
}

The output should be like this −

4
5
50

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