[libcxx-commits] [libcxx] [libc++] Implement P2819: Add tuple protocol to complex (PR #72776)

[via libcxx-commits]

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@@ -1538,6 +1549,73 @@ inline namespace literals
 } // namespace literals
 #endif
 
+#if _LIBCPP_STD_VER >= 26
+// Tuple interface [complex.tuple]
+template<class _Tp>
+struct _LIBCPP_TEMPLATE_VIS tuple_size<complex<_Tp>>
+  : public integral_constant<size_t, 2> {};
+
+template<size_t _Ip, class _Tp>
+struct _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, complex<_Tp>>
+{
+  static_assert(_Ip < 2, "Index out of bounds in std::tuple_element<std::complex<T>>");
+
+  using type _LIBCPP_NODEBUG = _Tp;
+};
+
+template <size_t _Ip>
+struct __get_complex
+{
+  static_assert(_Ip < 2, "Index out of bounds in std::get<std::complex<T>>");
+
+  template <typename _Tp>
+  struct to_array_type;
+
+  template <typename _Tp>
+  struct to_array_type<complex<_Tp>>
+  {
+    using type _LIBCPP_NODEBUG = _Tp[2];
+  };
+
+  template <class _Tp>
+  static _LIBCPP_HIDE_FROM_ABI constexpr
+  decltype(auto)
+  get(_Tp&& __z) _NOEXCEPT
+  {
+    using _Array_type = typename __get_complex::to_array_type<std::remove_cvref_t<_Tp>>::type;
+    return reinterpret_cast<_ForwardLike<_Tp, _Array_type>>(__z)[_Ip];
----------------
PragmaTwice wrote:

Good catch! I've got your idea.

Since there are some template specializations of std::complex, maybe friend class is a more easy way.

Thank you!

https://github.com/llvm/llvm-project/pull/72776