[C++ Template] NP decay

[C++ Template] NP decay.h

#pragma once
#include <type_traits>

template<class _Ty>
struct np_decay_impl {
  using _T0  = typename std::conditional_t<std::is_function_v<std::remove_pointer_t<_Ty>>, _Ty, std::remove_reference_t<_Ty>>;
  using _T1  = typename std::conditional_t<std::is_function_v<std::remove_pointer_t<_Ty>>, _T0, std::remove_pointer_t<_T0>>;
  using _T2  = typename std::conditional_t<std::is_array_v<_T1>, std::remove_extent_t<_T1>, _T1>;
  using type = typename std::conditional_t<std::is_function_v<std::remove_pointer_t<_Ty>>, _T2, std::remove_cv_t<_T2>>;
};

template<class _Ty, bool is_same = std::is_same_v<_Ty, typename np_decay_impl<_Ty>::type>>
struct np_decay;

template<class _Ty>
struct np_decay<_Ty, true> {
  using type = _Ty;
};

template<class _Ty>
struct np_decay<_Ty, false> : 
public np_decay<typename np_decay_impl<_Ty>::type> {};

template<class _Ty>
using np_decay_t = typename np_decay<_Ty>::type;