From 6d40405e7a8e63455281444c531b63806c933dc6 Mon Sep 17 00:00:00 2001
From: Maarten Arnst <maarten.arnst@uliege.be>
Date: Mon, 2 Sep 2024 14:10:45 +0200
Subject: [PATCH] add utilities that extend Kokkos::Impl::type_list

---
 CMakeLists.txt                            |  1 +
 include/kokkos-utils/impl/type_list.hpp   | 78 +++++++++++++++++++++++
 include/kokkos-utils/impl/type_traits.hpp |  5 +-
 tests/impl/CMakeLists.txt                 |  5 ++
 tests/impl/test_type_list.cpp             | 70 ++++++++++++++++++++
 5 files changed, 158 insertions(+), 1 deletion(-)
 create mode 100644 include/kokkos-utils/impl/type_list.hpp
 create mode 100644 tests/impl/test_type_list.cpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 19c9c7b..8e7e455 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -61,6 +61,7 @@ target_sources(
         include/kokkos-utils/concepts/Space.hpp
         include/kokkos-utils/concepts/View.hpp
 
+        include/kokkos-utils/impl/type_list.hpp
         include/kokkos-utils/impl/type_traits.hpp
 
         include/kokkos-utils/view/extents.hpp
diff --git a/include/kokkos-utils/impl/type_list.hpp b/include/kokkos-utils/impl/type_list.hpp
new file mode 100644
index 0000000..8ba4aef
--- /dev/null
+++ b/include/kokkos-utils/impl/type_list.hpp
@@ -0,0 +1,78 @@
+#ifndef KOKKOS_UTILS_IMPL_TYPE_LIST_HPP
+#define KOKKOS_UTILS_IMPL_TYPE_LIST_HPP
+
+#include "impl/Kokkos_Utilities.hpp"
+
+/**
+ * @file
+ *
+ * This file provides extensions to the @c Kokkos::Impl::type_list struct in @c Kokkos_Utilities.hpp.
+ */
+
+namespace Kokkos::utils::impl
+{
+
+//! @name Get the number of types in a @c Kokkos::Impl::type_list.
+///@{
+template <typename>
+struct TypeListSize;
+
+template <typename... Ts>
+struct TypeListSize<Kokkos::Impl::type_list<Ts...>> : std::integral_constant<size_t, sizeof...(Ts)> {};
+
+template <typename T>
+inline constexpr size_t type_list_size_v = TypeListSize<T>::value;
+///@}
+
+//! @name Get the @p I th type in a @c Kokkos::Impl::type_list.
+///@{
+template <size_t, typename>
+struct TypeListAt;
+
+template <size_t I, typename Head, typename... Tail>
+struct TypeListAt<I, Kokkos::Impl::type_list<Head, Tail...>>
+  : TypeListAt<I - 1, Kokkos::Impl::type_list<Tail...>> {};
+
+template <class Head, class... Tail>
+struct TypeListAt<0, Kokkos::Impl::type_list<Head, Tail...>>
+{
+    using type = Head;
+};
+
+template <size_t I, typename T>
+using type_list_at_t = typename TypeListAt<I, T>::type;
+///@}
+
+//! @name Transform a @c Kokkos::Impl::type_list.
+///@{
+template <template <typename> typename, typename>
+struct TransformTypeList;
+
+template <template <typename> typename TransformerType, typename... Ts>
+struct TransformTypeList<TransformerType, Kokkos::Impl::type_list<Ts...>>
+{
+    using type = Kokkos::Impl::concat_type_list_t<Kokkos::Impl::type_list<typename TransformerType<Ts>::type...>>;
+};
+
+template <template <typename> typename TransformerType, typename T>
+using transform_type_list_t = typename TransformTypeList<TransformerType, T>::type;
+///@}
+
+//! @name Convert a @c Kokkos::Impl::type_list into a @c std::tuple.
+///@{
+template <typename>
+struct TypeListToTuple;
+
+template <typename... Ts>
+struct TypeListToTuple<Kokkos::Impl::type_list<Ts...>>
+{
+    using type = std::tuple<Ts...>;
+};
+
+template <typename T>
+using type_list_to_tuple_t = typename TypeListToTuple<T>::type;
+///@}
+
+} // namespace Kokkos::utils::impl
+
+#endif // KOKKOS_UTILS_IMPL_TYPE_LIST_HPP
diff --git a/include/kokkos-utils/impl/type_traits.hpp b/include/kokkos-utils/impl/type_traits.hpp
index 3382284..b3c24f5 100644
--- a/include/kokkos-utils/impl/type_traits.hpp
+++ b/include/kokkos-utils/impl/type_traits.hpp
@@ -4,11 +4,14 @@
 #include <type_traits>
 
 /**
- * @brief This namespace provides extensions to the @c type_traits standard header.
+ * @file
+ *
+ * This file provides extensions to the @c type_traits standard header.
  *
  * References:
  *      * https://en.cppreference.com/w/cpp/header/type_traits
  */
+
 namespace Kokkos::utils::impl
 {
 
diff --git a/tests/impl/CMakeLists.txt b/tests/impl/CMakeLists.txt
index bcdee61..1fc813b 100644
--- a/tests/impl/CMakeLists.txt
+++ b/tests/impl/CMakeLists.txt
@@ -1,3 +1,8 @@
+### TEST : type_list ###
+add_one_test(
+    TEST_NAME type_list
+)
+
 ### TEST : type_traits ###
 add_one_test(
     TEST_NAME type_traits
diff --git a/tests/impl/test_type_list.cpp b/tests/impl/test_type_list.cpp
new file mode 100644
index 0000000..38ed493
--- /dev/null
+++ b/tests/impl/test_type_list.cpp
@@ -0,0 +1,70 @@
+#include "gtest/gtest.h"
+
+#include "kokkos-utils/impl/type_list.hpp"
+
+/**
+ * @file
+ *
+ * @addtogroup unittests
+ *
+ * **Type list**
+ *
+ * This group of tests check the behavior of our utilities extending @c Kokkos::Impl::type_list.
+ */
+
+namespace Kokkos::utils::tests::impl
+{
+
+using type_list_t = Kokkos::Impl::type_list<char, short, int>;
+
+//! @test Check @ref Kokkos::utils::impl::type_list_size_v.
+TEST(impl, type_list_size_v)
+{
+    using Kokkos::utils::impl::type_list_size_v;
+
+    using type_list_empty_t = Kokkos::Impl::type_list<>;
+    static_assert(type_list_size_v<type_list_empty_t> == 0);
+
+    static_assert(type_list_size_v<type_list_t> == 3);
+}
+
+//! @test Check @ref Kokkos::utils::impl::type_list_at_t.
+TEST(impl, type_list_at_t)
+{
+    using Kokkos::utils::impl::type_list_at_t;
+
+    static_assert(std::same_as<type_list_at_t<0, type_list_t>, char>);
+    static_assert(std::same_as<type_list_at_t<1, type_list_t>, short>);
+    static_assert(std::same_as<type_list_at_t<2, type_list_t>, int>);
+}
+
+//! Helper struct for the test of @ref Kokkos::utils::impl::transform_type_list_t.
+template <typename T>
+struct VectorOfTransformer
+{
+    using type = std::vector<T>;
+};
+
+//! @test Check @ref Kokkos::utils::impl::transform_type_list_t.
+TEST(impl, transform_type_list_t)
+{
+    using Kokkos::utils::impl::transform_type_list_t;
+
+    using transformed_type_list_t = transform_type_list_t<VectorOfTransformer, type_list_t>;
+
+    using expt_transformed_type_list_t = Kokkos::Impl::type_list<std::vector<char>, std::vector<short>, std::vector<int>>;
+
+    static_assert(std::same_as<transformed_type_list_t, expt_transformed_type_list_t>);
+}
+
+//! @test Check @ref Kokkos::utils::impl::type_list_to_tuple_t.
+TEST(impl, type_list_to_tuple)
+{
+    using Kokkos::utils::impl::type_list_to_tuple_t;
+
+    using expt_tuple_t = std::tuple<char, short, int>;
+
+    static_assert(std::same_as<type_list_to_tuple_t<type_list_t>, expt_tuple_t>);
+}
+
+} // namespace Kokkos::utils::tests::impl