Using registered classes to realize specific type matching function template

Function templates allow different types to call code with the same function , It can reduce the redundancy of code , But what if you only want specific types to use function templates ？ It can be implemented by template specialization and registration classes .

The code is as follows ：

#include <iostream>

template <typename T>
struct Register{};

template <>
struct Register<int> {
  typedef int Type;
  constexpr static const char* TypeName = "int";
};

template <>
struct Register<float> {
  typedef float Type;
  constexpr static const char* TypeName = "float";
};

template <>
struct Register<long> {
  typedef long Type;
  constexpr static const char* TypeName = "long";
};

template <typename T, typename = typename Register<T>::Type>
void print(const T& x) {
  std::cout << Register<T>::TypeName << '\t' << x << std::endl;
}

int main() {
  print(-1);
  print(2147483650);
  print(12.11);  // double type , Mismatch 
  return 0;
}

All to Register Registered type , Can be matched successfully print function , Undirected Register The registered type will report an error when compiling , The error information is as follows ：