[2026-06 LWG Motion 2] P3319R6 Add an iota object for simd (and more)

source/numerics.tex

@@ -17020,6 +17020,8 @@
     constexpr resize_t<(basic_mask<Bytes, Abis>::size() + ...),
       basic_mask<Bytes, Abis...[0]>> cat(const basic_mask<Bytes, Abis>&...) noexcept;
 
+  template<class T> constexpr T iota = @\seebelow@;
+
   // \ref{simd.alg}, algorithms
   template<class T, class Abi>
     constexpr basic_vec<T, Abi>
@@ -19785,6 +19787,29 @@
 pack.
 \end{itemdescr}
 
+\indexlibrarymember{iota}{simd}
+\begin{itemdecl}
+template<class T> constexpr T iota = @\seebelow@;
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\mandates
+Either \tcode{T} is vectorizable and \tcode{is_arithmetic_v<T>} is \tcode{true}, or
+\begin{itemize}
+\item \tcode{T} is an enabled specialization of basic_vec,
+\item \tcode{is_arithmetic_v<typename T::value_type>} is \tcode{true}, and
+\item $\tcode{T::size() - 1} \lt \tcode{numeric_limits<typename T::value_type>::max()}$.
+\end{itemize}
+
+\pnum
+\remarks
+If \tcode{is_arithmetic_v<T>} is \tcode{true},
+the value of \tcode{iota<T>} is equal to \tcode{T()}.
+Otherwise, the value of \tcode{iota<T>} is equal to
+\tcode{T([](typename T::value_type i) { return i; })}.
+\end{itemdescr}
+
 \rSec3[simd.alg]{Algorithms}
 
 \indexlibrarymember{min}{simd}

source/support.tex

@@ -837,7 +837,7 @@
 #define @\defnlibxname{cpp_lib_shared_ptr_weak_type}@              201606L // also in \libheader{memory}
 #define @\defnlibxname{cpp_lib_shared_timed_mutex}@                201402L // also in \libheader{shared_mutex}
 #define @\defnlibxname{cpp_lib_shift}@                             202202L // also in \libheader{algorithm}
-#define @\defnlibxname{cpp_lib_simd}@                              202603L // also in \libheader{simd}
+#define @\defnlibxname{cpp_lib_simd}@                              202606L // also in \libheader{simd}
 #define @\defnlibxname{cpp_lib_simd_complex}@                      202502L // also in \libheader{simd}
 #define @\defnlibxname{cpp_lib_simd_permutations}@                 202506L // also in \libheader{simd}
 #define @\defnlibxname{cpp_lib_smart_ptr_for_overwrite}@           202002L // also in \libheader{memory}