How do I assign an alias to a function name in C++?

Question

It's easy to create a new name for a type, a variable or a namespace. But how do I assign a new name to a function? For example, I want to use the name holler for printf. #define is obvious... any other way?

Solutions:

1. #define holler printf
2. void (*p)() = fn; //function pointer
3. void (&r)() = fn; //function reference
4. inline void g(){ f(); }

Answer 1

There are different approaches:

• With C++11 with non-template non-overloaded functions you can simply use:

  const auto& new_fn_name = old_fn_name;
  

• If this function has multiple overloads you should use static_cast:

  const auto& new_fn_name = static_cast<OVERLOADED_FN_TYPE>(old_fn_name);
  

  Example: there are two overloads of function std::stoi

  int stoi (const string&, size_t*, int);
  int stoi (const wstring&, size_t*, int);
  

  If you want to make an alias to the first version you should use the following:

  const auto& new_fn_name = static_cast<int(*)(const string&, size_t*, int)>(std::stoi);
  

  Note: there is no way to make an alias to overloaded function such that all its overloaded versions work, so you should always specify which exact function overload you want.

• With C++14 you can go even further with constexpr template variables. That allows you to alias templated functions:

  template<typename T>
  constexpr void old_function(/* args */);
  
  template<typename T>
  constexpr auto alias_to_old = old_function<T>;
  

• Moreover, starting with C++11 you have a function called std::mem_fn that allows to alias member functions. See the following example:

  struct A {
     void f(int i) {
        std::cout << "Argument: " << i << '\n';
     }
  };
  
  
  A a;
  
  auto greet = std::mem_fn(&A::f); // alias to member function
  // prints "Argument: 5"
  greet(a, 5); // you should provide an object each time you use this alias
  
  // if you want to bind an object permanently use `std::bind`
  greet_a = std::bind(greet, a, std::placeholders::_1);
  greet_a(3); // equivalent to greet(a, 3) => a.f(3);