Merge 2025-06 LWG Motion 11

P3480R6 std::simd is a range

Author: tkoeppe

source/numerics.tex

@@ -16509,6 +16509,10 @@
   template<size_t N> requires (has_single_bit(N))
     constexpr flags<@\exposid{overaligned-flag}<N>@> flag_overaligned{};
 
+  // \ref{simd.iterator}, Class template \exposid{simd-iterator}
+  template<class V>
+    class @\exposidnc{simd-iterator}@;                // \expos
+
   // \ref{simd.class}, Class template \tcode{basic_simd}
   template<class T, class Abi = @\exposid{native-abi}@<T>> class basic_simd;
   template<class T, @\exposid{simd-size-type}@ N = @\exposid{simd-size-v}@<T, @\exposid{native-abi}@<T>>>
@@ -17204,6 +17208,262 @@
   specialization \tcode{\exposid{overaligned-flag}<std::min(N1, N2)>}.
 \end{itemdescr}
 
+\rSec2[simd.iterator]{Class template \exposid{simd-iterator}}
+\begin{codeblock}
+namespace std::datapar {
+  template<class V>
+  class @\exposidnc{simd-iterator}@ {                                                 // \expos
+    V* @\exposid{data_}@ = nullptr;                                                 // \expos
+    @\exposid{simd-size-type}@ @\exposidnc{offset_}@ = 0;                                         // \expos
+
+    constexpr @\exposidnc{simd-iterator}@(V& d, @\exposidnc{simd-size-type}@ off) noexcept;         // \expos
+
+  public:
+    using value_type = typename V::value_type;
+    using iterator_category = input_iterator_tag;
+    using iterator_concept = random_access_iterator_tag;
+    using difference_type = @\exposid{simd-size-type}@;
+
+    constexpr @\exposid{simd-iterator}@() = default;
+
+    constexpr @\exposid{simd-iterator}@(const @\exposid{simd-iterator}@&) = default;
+    constexpr @\exposid{simd-iterator}@& operator=(const @\exposid{simd-iterator}@&) = default;
+
+    constexpr @\exposid{simd-iterator}@(const @\exposid{simd-iterator}@<remove_const_t<V>>&) requires is_const_v<V>;
+
+    constexpr value_type operator*() const;
+
+    constexpr @\exposid{simd-iterator}@& operator++();
+    constexpr @\exposid{simd-iterator}@ operator++(int);
+    constexpr @\exposid{simd-iterator}@& operator--();
+    constexpr @\exposid{simd-iterator}@ operator--(int);
+
+    constexpr @\exposid{simd-iterator}@& operator+=(difference_type n);
+    constexpr @\exposid{simd-iterator}@& operator-=(difference_type n);
+
+    constexpr value_type operator[](difference_type n) const;
+
+    friend constexpr bool operator==(@\exposid{simd-iterator}@ a, @\exposid{simd-iterator}@ b) = default;
+    friend constexpr bool operator==(@\exposid{simd-iterator}@ a, default_sentinel_t) noexcept;
+    friend constexpr auto operator<=>(@\exposid{simd-iterator}@ a, @\exposid{simd-iterator}@ b);
+
+    friend constexpr @\exposid{simd-iterator}@ operator+(@\exposid{simd-iterator}@ i, difference_type n);
+    friend constexpr @\exposid{simd-iterator}@ operator+(difference_type n, @\exposid{simd-iterator}@ i);
+    friend constexpr @\exposid{simd-iterator}@ operator-(@\exposid{simd-iterator}@ i, difference_type n);
+
+    friend constexpr difference_type operator-(@\exposid{simd-iterator}@ a, @\exposid{simd-iterator}@ b);
+    friend constexpr difference_type operator-(@\exposid{simd-iterator}@ i, default_sentinel_t) noexcept;
+    friend constexpr difference_type operator-(default_sentinel_t, @\exposid{simd-iterator}@ i) noexcept;
+  };
+}
+\end{codeblock}
+
+\begin{itemdecl}
+constexpr @\exposid{simd-iterator}@(V& d, @\exposid{simd-size-type}@ off) noexcept;
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Initializes \exposid{data_} with \tcode{addressof(d)} and \exposid{offset_} with \tcode{off}.
+\end{itemdescr}
+
+\begin{itemdecl}
+constexpr @\exposid{simd-iterator}@(const @\exposid{simd-iterator}@<remove_const_t<V>>& i) requires is_const_v<V>;
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Initializes \exposid{data_} with \tcode{i.\exposid{data_}} and \exposid{offset_} with \tcode{i.\exposid{offset_}}.
+\end{itemdescr}
+
+\begin{itemdecl}
+constexpr value_type operator*() const;
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to: \tcode{return (*\exposid{data_})[\exposid{offset_}];}
+\end{itemdescr}
+
+\begin{itemdecl}
+constexpr @\exposid{simd-iterator}@& operator++();
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to: \tcode{return *this += 1;}
+\end{itemdescr}
+
+\begin{itemdecl}
+constexpr @\exposid{simd-iterator}@ operator++(int);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to:
+\begin{codeblock}
+@\exposid{simd-iterator}@ tmp = *this;
+*this += 1;
+return tmp;
+\end{codeblock}
+\end{itemdescr}
+
+\begin{itemdecl}
+constexpr @\exposid{simd-iterator}@& operator--();
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to: \tcode{return *this -= 1;}
+\end{itemdescr}
+
+\begin{itemdecl}
+constexpr @\exposid{simd-iterator}@ operator--(int);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to:
+\begin{codeblock}
+@\exposid{simd-iterator}@ tmp = *this;
+*this -= 1;
+return tmp;
+\end{codeblock}
+\end{itemdescr}
+
+\begin{itemdecl}
+constexpr @\exposid{simd-iterator}@& operator+=(difference_type n);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\expects
+\tcode{\exposid{offset_} + n} is in the range \crange{0}{V::size()}.
+
+\pnum
+\effects
+Equivalent to:
+\begin{codeblock}
+@\exposid{offset_}@ += n;
+return *this;
+\end{codeblock}
+\end{itemdescr}
+
+\begin{itemdecl}
+constexpr @\exposid{simd-iterator}@& operator-=(difference_type n);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\expects
+\tcode{\exposid{offset_} - n} is in the range \crange{0}{V::size()}.
+
+\pnum
+\effects
+Equivalent to:
+\begin{codeblock}
+@\exposid{offset_}@ -= n;
+return *this;
+\end{codeblock}
+\end{itemdescr}
+
+\begin{itemdecl}
+constexpr value_type operator[](difference_type n) const;
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to: \tcode{return (*\exposid{data_})[\exposid{offset_} + n];}
+\end{itemdescr}
+
+\begin{itemdecl}
+friend constexpr bool operator==(@\exposid{simd-iterator}@ i, default_sentinel_t) noexcept;
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to: \tcode{return i.\exposid{offset_} == V::size();}
+\end{itemdescr}
+
+\begin{itemdecl}
+friend constexpr auto operator<=>(@\exposid{simd-iterator}@ a, @\exposid{simd-iterator}@ b);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\expects
+\tcode{a.\exposid{data_} == b.\exposid{data_}} is \tcode{true}.
+
+\pnum
+\effects
+Equivalent to: \tcode{return a.\exposid{offset_} <=> b.\exposid{offset_};}
+\end{itemdescr}
+
+\begin{itemdecl}
+friend constexpr @\exposid{simd-iterator}@ operator+(@\exposid{simd-iterator}@ i, difference_type n);
+friend constexpr @\exposid{simd-iterator}@ operator+(difference_type n, @\exposid{simd-iterator}@ i);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to: \tcode{return i += n;}
+\end{itemdescr}
+
+\begin{itemdecl}
+friend constexpr @\exposid{simd-iterator}@ operator-(@\exposid{simd-iterator}@ i, difference_type n);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to: \tcode{return i -= n;}
+\end{itemdescr}
+
+\begin{itemdecl}
+friend constexpr difference_type operator-(@\exposid{simd-iterator}@ a, @\exposid{simd-iterator}@ b);
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\expects
+\tcode{a.\exposid{data_} == b.\exposid{data_}} is \tcode{true}.
+
+\pnum
+\effects
+Equivalent to: \tcode{return a.\exposid{offset_} - b.\exposid{offset_};}
+\end{itemdescr}
+
+\begin{itemdecl}
+friend constexpr difference_type operator-(@\exposid{simd-iterator}@ i, default_sentinel_t) noexcept;
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to: \tcode{return i.\exposid{offset_} - V::size();}
+\end{itemdescr}
+
+
+\begin{itemdecl}
+friend constexpr difference_type operator-(default_sentinel_t, @\exposid{simd-iterator}@ i) noexcept;
+\end{itemdecl}
+
+\begin{itemdescr}
+\pnum
+\effects
+Equivalent to: \tcode{return V::size() - i.\exposid{offset_};}
+\end{itemdescr}
+
 \rSec2[simd.class]{Class template \tcode{basic_simd}}
 
 \rSec3[simd.overview]{Class template \tcode{basic_simd} overview}
@@ -17215,6 +17475,14 @@
     using value_type = T;
     using mask_type = basic_simd_mask<sizeof(T), Abi>;
     using abi_type = Abi;
+    using @\libmember{iterator}{basic_simd}@ = @\exposid{simd-iterator}@<basic_simd>;
+    using @\libmember{const_iterator}{basic_simd}@ = @\exposid{simd-iterator}@<const basic_simd>;
+
+    constexpr iterator @\libmember{begin}{basic_simd}@() noexcept { return {*this, 0}; }
+    constexpr const_iterator @\libmember{begin}{basic_simd}@() const noexcept { return {*this, 0}; }
+    constexpr const_iterator @\libmember{cbegin}{basic_simd}@() const noexcept { return {*this, 0}; }
+    constexpr default_sentinel_t @\libmember{end}{basic_simd}@() const noexcept { return {}; }
+    constexpr default_sentinel_t @\libmember{cend}{basic_simd}@() const noexcept { return {}; }
 
     static constexpr integral_constant<@\exposid{simd-size-type}@, @\exposid{simd-size-v}@<T, Abi>> size {};
 
@@ -19101,6 +19369,14 @@
   public:
     using value_type = bool;
     using abi_type = Abi;
+    using @\libmember{iterator}{basic_simd_mask}@ = @\exposid{simd-iterator}@<basic_simd_mask>;
+    using @\libmember{const_iterator}{basic_simd_mask}@ = @\exposid{simd-iterator}@<const basic_simd_mask>;
+
+    constexpr iterator @\libmember{begin}{basic_simd_mask}@() noexcept { return {*this, 0}; }
+    constexpr const_iterator @\libmember{begin}{basic_simd_mask}@() const noexcept { return {*this, 0}; }
+    constexpr const_iterator @\libmember{cbegin}{basic_simd_mask}@() const noexcept { return {*this, 0}; }
+    constexpr default_sentinel_t @\libmember{end}{basic_simd_mask}@() const noexcept { return {}; }
+    constexpr default_sentinel_t @\libmember{cend}{basic_simd_mask}@() const noexcept { return {}; }
 
     static constexpr integral_constant<@\exposid{simd-size-type}@, @\exposid{simd-size-v}@<@\exposid{integer-from}@<Bytes>, Abi>>
       size {};