From acf66d8c7e98ab188010bcd74f428833f5e32724 Mon Sep 17 00:00:00 2001
From: Dawn Perchik <dawn@brightsidecomputing.com>
Date: Tue, 14 Nov 2023 20:24:55 -0800
Subject: [PATCH] P2819R2 Add tuple protocol to complex

---
 source/numerics.tex  | 57 ++++++++++++++++++++++++++++++++++++++++++++
 source/support.tex   |  2 +-
 source/utilities.tex |  2 +-
 3 files changed, 59 insertions(+), 2 deletions(-)

diff --git a/source/numerics.tex b/source/numerics.tex
index 50fbb0d68a..34e3ea944d 100644
--- a/source/numerics.tex
+++ b/source/numerics.tex
@@ -289,6 +289,20 @@
   template<class T> constexpr complex<T> tan  (const complex<T>&);
   template<class T> constexpr complex<T> tanh (const complex<T>&);
 
+  // \ref{complex.tuple}, tuple interface
+  template<class T> struct tuple_size;
+  template<size_t I, class T> struct tuple_element;
+  template<class T> struct tuple_size<complex<T>>;
+  template<size_t I, class T> struct tuple_element<I, complex<T>>;
+  template<size_t I, class T>
+    constexpr T& get(complex<T>&) noexcept;
+  template<size_t I, class T>
+    constexpr T&& get(complex<T>&&) noexcept;
+  template<size_t I, class T>
+    constexpr const T& get(const complex<T>&) noexcept;
+  template<size_t I, class T>
+    constexpr const T&& get(const complex<T>&&) noexcept;
+
   // \ref{complex.literals}, complex literals
   inline namespace literals {
   inline namespace complex_literals {
@@ -1121,6 +1135,49 @@
 The complex hyperbolic tangent of \tcode{x}.
 \end{itemdescr}
 
+\rSec2[complex.tuple]{Tuple interface}
+
+\indexlibraryglobal{tuple_size}%
+\indexlibraryglobal{tuple_element}%
+\begin{itemdecl}
+template<class T>
+struct tuple_size<complex<T>> : integral_constant<size_t, 2> {};
+
+template<size_t I, class T>
+struct tuple_element<I, complex<T>> {
+  using type = T;
+};
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\mandates
+\tcode{I < 2} is \tcode{true}.
+\end{itemdescr}
+
+\indexlibrarymember{get}{complex}%
+\begin{itemdecl}
+template<size_t I, class T>
+  constexpr T& get(complex<T>& z) noexcept;
+template<size_t I, class T>
+  constexpr T&& get(complex<T>&& z) noexcept;
+template<size_t I, class T>
+  constexpr const T& get(const complex<T>& z) noexcept;
+template<size_t I, class T>
+  constexpr const T&& get(const complex<T>&& z) noexcept;
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\mandates
+\tcode{I < 2} is \tcode{true}.
+
+\pnum
+\returns
+A reference to the real part of \tcode{z} if \tcode{I == 0} is \tcode{true},
+otherwise a reference to the imaginary part of \tcode{z}.
+\end{itemdescr}
+
 \rSec2[cmplx.over]{Additional overloads}
 
 \pnum
diff --git a/source/support.tex b/source/support.tex
index f867e7d5f9..3d4e9ac495 100644
--- a/source/support.tex
+++ b/source/support.tex
@@ -787,7 +787,7 @@
 #define @\defnlibxname{cpp_lib_transparent_operators}@             201510L
   // freestanding, also in \libheader{memory}, \libheader{functional}
 #define @\defnlibxname{cpp_lib_tuple_element_t}@                   201402L // freestanding, also in \libheader{tuple}
-#define @\defnlibxname{cpp_lib_tuple_like}@                        202207L
+#define @\defnlibxname{cpp_lib_tuple_like}@                        202311L
   // also in \libheader{utility}, \libheader{tuple}, \libheader{map}, \libheader{unordered_map}
 #define @\defnlibxname{cpp_lib_tuples_by_type}@                    201304L // freestanding, also in \libheader{utility}, \libheader{tuple}
 #define @\defnlibxname{cpp_lib_type_identity}@                     201806L // freestanding, also in \libheader{type_traits}
diff --git a/source/utilities.tex b/source/utilities.tex
index 60be15fec2..6e9c381be5 100644
--- a/source/utilities.tex
+++ b/source/utilities.tex
@@ -1612,7 +1612,7 @@
 A type \tcode{T} models and satisfies
 the exposition-only concept \exposconcept{tuple-like}
 if \tcode{remove_cvref_t<T>} is a specialization of
-\tcode{array}, \tcode{pair}, \tcode{tuple}, or \tcode{ranges::subrange}.
+\tcode{array}, \tcode{complex}, \tcode{pair}, \tcode{tuple}, or \tcode{ranges::subrange}.
 \end{itemdescr}
 
 \rSec2[tuple.tuple]{Class template \tcode{tuple}}