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std::functi...operatorbool(3)  C++ Standard Libary std::functi...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)

http://cppreference.com 	   2024.06.10	   std::functi...operatorbool(3)
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