#includeIn the code above, we include the CallArgs header and define a function foo and a functor bar. We then use CallArgs hasDefined template to check whether these callable entities have defined return type and parameter list. We output the result to the console using std::cout. CallArgs belongs to the Boost library.#include void foo(int a, int b, int c) {} struct bar { void operator() (int d, int e) const {} }; int main() { std::cout << boost::callable_traits::has_defined ::value << std::endl; // Output: 1 std::cout << boost::callable_traits::has_defined ::value << std::endl; // Output: 1 std::cout << boost::callable_traits::has_defined ::value << std::endl; // Output: 0 std::cout << boost::callable_traits::has_defined ::value << std::endl; // Output: 1 std::cout << boost::callable_traits::has_defined ::value << std::endl; // Output: 1 return 0; }