Implement std::function in C++

First, I introduce you to the std::function and then proceed to the implementation

Class template std::function is a general-purpose polymorphic function wrapper. Instances of std::function can store, copy, and invoke any CopyConstructible Callable target:

functionslambda expressionsbind expressionspointers to member functionspointers to data members.or other function objects

std::function is introduced in C++ 17
The stored callable object is called the target of std::function. If a std::...