// fig15_21.cpp
// Adding and removing type attributes with type metafunctions.
#include <fmt/format.h>
#include <iostream>
#include <type_traits>

// add const to a type T
template <typename T>
struct my_add_const {
   using type = const T;
};

// general case: no pointer in type, so set nested type variable to T
template <typename T>
struct my_remove_ptr {
   using type = T;
};

// partial template specialization: T is a pointer type, so remove *
template <typename T>
struct my_remove_ptr<T*> {
   using type = T;
};

int main() {
   std::cout << fmt::format("{}\n{}{}\n{}{}\n\n",
      "ADD CONST TO A TYPE VIA A CUSTOM TYPE METAFUNCTION",
      "std::is_same_v<const int, my_add_const<int>::type>: ",
      std::is_same_v<const int, my_add_const<int>::type>,
      "std::is_same_v<int* const, my_add_const<int*>::type>: ",
      std::is_same_v<int* const, my_add_const<int*>::type>);

   std::cout << fmt::format("{}\n{}{}\n{}{}\n\n",
      "REMOVE POINTER FROM TYPES VIA A CUSTOM TYPE METAFUNCTION",
      "std::is_same_v<int, my_remove_ptr<int>::type>: ",
      std::is_same_v<int, my_remove_ptr<int>::type>,
      "std::is_same_v<int, my_remove_ptr<int*>::type>: ",
      std::is_same_v<int, my_remove_ptr<int*>::type>);

   std::cout << fmt::format("{}\n{}{}\n{}{}\n\n",
      "ADD REFERENCES TO TYPES USING STANDARD TYPE TRAITS",
      "std::is_same_v<int&, std::add_lvalue_reference<int>::type>: ",
      std::is_same_v<int&, std::add_lvalue_reference<int>::type>,
      "std::is_same_v<int&&, std::add_rvalue_reference<int>::type>: ",
      std::is_same_v<int&&, std::add_rvalue_reference<int>::type>);

   std::cout << fmt::format("{}\n{}{}\n{}{}\n{}{}\n",
      "REMOVE REFERENCES FROM TYPES USING STANDARD TYPE TRAITS",
      "std::is_same_v<int, std::remove_reference<int>::type>: ",
      std::is_same_v<int, std::remove_reference<int>::type>,
      "std::is_same_v<int, std::remove_reference<int&>::type>: ",
      std::is_same_v<int, std::remove_reference<int&>::type>,
      "std::is_same_v<int, std::remove_reference<int&&>::type>: ",
      std::is_same_v<int, std::remove_reference<int&&>::type>);
}


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