[libc++][c++23] P2374: views::cartesian_product

[PaulXiCao]

Closes #105209 .
WIP !!

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff 1a9521565019edc8589f234c95477ab0a6b164d5 150eed31fbe65730b989bf02cb1e62fbb99f340d --extensions cpp,,h -- libcxx/include/__ranges/cartesian_product_view.h libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/begin.pass.cpp libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/ctad.compile.pass.cpp libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/ctor.default.pass.cpp libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/ctor.pass.cpp libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/ctor.views.pass.cpp libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/end.pass.cpp libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/example_from_std.pass.cpp libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/size.pass.cpp libcxx/include/ranges libcxx/test/std/ranges/range.adaptors/range.zip/types.h

View the diff from clang-format here.

diff --git a/libcxx/include/__ranges/cartesian_product_view.h b/libcxx/include/__ranges/cartesian_product_view.h
index 4d95de846b..b413ebbb05 100644
--- a/libcxx/include/__ranges/cartesian_product_view.h
+++ b/libcxx/include/__ranges/cartesian_product_view.h
@@ -138,7 +138,7 @@ private:
         return ranges::begin(rng);
       };
 
-      return std::make_tuple(begin_or_first_end(std::bool_constant<I == 0>{}, std::get<I>(b))...);
+      return std::make_tuple(begin_or_first_end(std::bool_constant < I == 0 > {}, std::get<I>(b))...);
     };
     iterator<is_const> it(*this, ranges_to_iterators(std::make_index_sequence<1 + sizeof...(Vs)>{}));
     return it;
diff --git a/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/begin.pass.cpp b/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/begin.pass.cpp
index fac0d39b9f..586d757e0c 100644
--- a/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/begin.pass.cpp
+++ b/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/begin.pass.cpp
@@ -47,9 +47,8 @@ constexpr bool test() {
   { // all underlying iterators should be at the begin position
     std::ranges::cartesian_product_view v(
         SizedRandomAccessView{buffer}, std::views::iota(0), std::ranges::single_view(2.0));
-    std::same_as<std::tuple<int&, int, double&>> decltype(auto) mutVal = *v.begin();
-    std::same_as<std::tuple<int&, int, const double&>> decltype(auto) constVal =
-        *std::as_const(v).begin();
+    std::same_as<std::tuple<int&, int, double&>> decltype(auto) mutVal         = *v.begin();
+    std::same_as<std::tuple<int&, int, const double&>> decltype(auto) constVal = *std::as_const(v).begin();
     assert(mutVal == std::make_tuple(1, 0, 2.0));
     assert(constVal == std::make_tuple(1, 0, 2.0));
     assert(&(std::get<0>(mutVal)) == &buffer[0]);
diff --git a/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/ctor.views.pass.cpp b/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/ctor.views.pass.cpp
index 0c424acaf3..99391a8d5d 100644
--- a/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/ctor.views.pass.cpp
+++ b/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/ctor.views.pass.cpp
@@ -25,16 +25,19 @@ concept implicitly_constructible_from = requires(Args&&... args) { conversion_te
 static_assert(std::constructible_from<std::ranges::cartesian_product_view<SimpleCommon>, SimpleCommon>);
 static_assert(!implicitly_constructible_from<std::ranges::cartesian_product_view<SimpleCommon>, SimpleCommon>);
 
-static_assert(std::constructible_from<std::ranges::cartesian_product_view<SimpleCommon, SimpleCommon>, SimpleCommon, SimpleCommon>);
-static_assert(
-    !implicitly_constructible_from<std::ranges::cartesian_product_view<SimpleCommon, SimpleCommon>, SimpleCommon, SimpleCommon>);
+static_assert(std::constructible_from<std::ranges::cartesian_product_view<SimpleCommon, SimpleCommon>,
+                                      SimpleCommon,
+                                      SimpleCommon>);
+static_assert(!implicitly_constructible_from<std::ranges::cartesian_product_view<SimpleCommon, SimpleCommon>,
+                                             SimpleCommon,
+                                             SimpleCommon>);
 
 struct MoveAwareView : std::ranges::view_base {
-  int moves = 0;
+  int moves                 = 0;
   constexpr MoveAwareView() = default;
   constexpr MoveAwareView(MoveAwareView&& other) : moves(other.moves + 1) { other.moves = 1; }
   constexpr MoveAwareView& operator=(MoveAwareView&& other) {
-    moves = other.moves + 1;
+    moves       = other.moves + 1;
     other.moves = 0;
     return *this;
   }
@@ -51,12 +54,12 @@ constexpr void constructorTest(auto&& buffer1, auto&& buffer2) {
 }
 
 constexpr bool test() {
-
-  int buffer[] = {1, 2, 3, 4, 5, 6, 7, 8};
+  int buffer[]  = {1, 2, 3, 4, 5, 6, 7, 8};
   int buffer2[] = {9, 8, 7, 6};
 
   { // constructor from views
-    std::ranges::cartesian_product_view v(SizedRandomAccessView{buffer}, std::views::iota(0), std::ranges::single_view(2.));
+    std::ranges::cartesian_product_view v(
+        SizedRandomAccessView{buffer}, std::views::iota(0), std::ranges::single_view(2.));
     assert(*v.begin() == std::make_tuple(1, 0, 2.0));
   }
 
diff --git a/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/end.pass.cpp b/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/end.pass.cpp
index 1d057d05bc..8ec3bc925c 100644
--- a/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/end.pass.cpp
+++ b/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/end.pass.cpp
@@ -34,13 +34,13 @@ constexpr bool test() {
     assert(c.end() == c.begin() + N0 * N1);
   }
 
-  { // (non-empty range)^3 
+  { // (non-empty range)^3
     constexpr size_t N0 = 5, N1 = 42, N2 = 7;
     std::array<int, N0> a0;
     std::array<int, N1> a1;
     std::array<int, N2> a2;
     std::ranges::cartesian_product_view c{a0, a1, a2};
-    assert(c.end() == c.begin() + N0*N1*N2);
+    assert(c.end() == c.begin() + N0 * N1 * N2);
   }
 
   { // empty range
@@ -85,7 +85,7 @@ constexpr bool test() {
     assert(c.end() == c.begin());
   }
 
-  { // empty range X common range X empty range 
+  { // empty range X common range X empty range
     std::ranges::empty_view<int> e;
     constexpr size_t N = 7;
     std::array<int, N> a;
@@ -93,7 +93,7 @@ constexpr bool test() {
     assert(c.end() == c.begin());
   }
 
-  { // common range X empty range X empty range 
+  { // common range X empty range X empty range
     std::ranges::empty_view<int> e;
     constexpr size_t N = 7;
     std::array<int, N> a;
@@ -101,7 +101,7 @@ constexpr bool test() {
     assert(c.end() == c.begin());
   }
 
-  { // empty range X common range X common range 
+  { // empty range X common range X common range
     std::ranges::empty_view<int> e;
     constexpr size_t N0 = 7, N1 = 42;
     std::array<int, N0> a0;
@@ -110,7 +110,7 @@ constexpr bool test() {
     assert(c.end() == c.begin());
   }
 
-  { // common range X empty range X common range 
+  { // common range X empty range X common range
     std::ranges::empty_view<int> e;
     constexpr size_t N0 = 7, N1 = 42;
     std::array<int, N0> a0;
@@ -119,7 +119,7 @@ constexpr bool test() {
     assert(c.end() == c.begin());
   }
 
-  { // common range X common range X empty range 
+  { // common range X common range X empty range
     std::ranges::empty_view<int> e;
     constexpr size_t N0 = 7, N1 = 42;
     std::array<int, N0> a0;
diff --git a/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/example_from_std.pass.cpp b/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/example_from_std.pass.cpp
index 4d505921b3..90384fa590 100644
--- a/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/example_from_std.pass.cpp
+++ b/libcxx/test/std/ranges/range.adaptors/range.cartesian.product.view/example_from_std.pass.cpp
@@ -17,9 +17,7 @@ constexpr bool test() {
   struct ConstexprStringStream {
     std::string str;
 
-    constexpr ConstexprStringStream& operator<<(int x) {
-      return *this << char(x + 48);
-    }
+    constexpr ConstexprStringStream& operator<<(int x) { return *this << char(x + 48); }
     constexpr ConstexprStringStream& operator<<(char c) {
       str += c;
       return *this;
@@ -61,7 +59,7 @@ constexpr bool test() {
       "2 2 1\n"
       "2 2 2\n";
   assert(out.str == expected);
-  
+
   return true;
 }