added meta::transform

Author: dietmarkuehl

include/beman/execution26/detail/meta_transform.hpp

@@ -0,0 +1,34 @@
+// include/beman/execution26/detail/meta_transform.hpp                -*-C++-*-
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifndef INCLUDED_BEMAN_EXECUTION26_DETAIL_META_TRANSFORM
+#define INCLUDED_BEMAN_EXECUTION26_DETAIL_META_TRANSFORM
+
+#include <beman/execution26/detail/meta_contains.hpp>
+
+// ----------------------------------------------------------------------------
+
+namespace beman::execution26::detail::meta::detail
+{
+    template <template <typename> class Transform, typename List> struct transform;
+
+    template <template <typename> class Transform,
+              template <typename... T> class List,
+              typename... T>
+    struct transform<Transform, List<T...>>
+    {
+        using type = List<Transform<T>...>;
+    };
+}
+
+namespace beman::execution26::detail::meta
+{
+    template <template <typename> class Transform, typename List>
+    using transform = typename
+        ::beman::execution26::detail::meta::detail::transform<Transform, List>
+        ::type;
+}
+
+// ----------------------------------------------------------------------------
+
+#endif

include/beman/execution26/detail/meta_unique.hpp

@@ -16,30 +16,6 @@ namespace beman::execution26::detail::meta::detail
     template <typename, typename> struct make_unique;
     template <typename> struct unique;
 
-#if 0
-
-    template <template <typename...> class List>
-    struct unique<List<>>
-    {
-        using type = List<>;
-    };
-    template <template <typename...> class List, typename T>
-    struct unique<List<T>>
-    {
-        using type = List<T>;
-    };
-
-    template <template <typename...> class List, typename H, typename... T>
-    struct unique<List<H, T...>>
-    {
-        using tail = ::beman::execution26::detail::meta::detail::unique<List<T...>>::type;
-        using type = ::std::conditional_t<
-            ::beman::execution26::detail::meta::contains<H, T...>,
-            tail,
-            ::beman::execution26::detail::meta::prepend<H, tail>
-            >;
-    };
-#else
     template <template <typename...> class List, typename... R>
     struct make_unique<List<R...>, List<>>
     {
@@ -67,7 +43,6 @@ namespace beman::execution26::detail::meta::detail
             List<T...>
         >::type;
     };
-#endif
 }
 
 namespace beman::execution26::detail::meta

src/beman/execution26/CMakeLists.txt

@@ -84,6 +84,7 @@ target_sources(${TARGET_LIBRARY}
     ${PROJECT_SOURCE_DIR}/include/beman/execution26/detail/meta_contains.hpp
     ${PROJECT_SOURCE_DIR}/include/beman/execution26/detail/meta_filter.hpp
     ${PROJECT_SOURCE_DIR}/include/beman/execution26/detail/meta_prepend.hpp
+    ${PROJECT_SOURCE_DIR}/include/beman/execution26/detail/meta_transform.hpp
     ${PROJECT_SOURCE_DIR}/include/beman/execution26/detail/meta_unique.hpp
     ${PROJECT_SOURCE_DIR}/include/beman/execution26/detail/movable_value.hpp
     ${PROJECT_SOURCE_DIR}/include/beman/execution26/detail/never_stop_token.hpp

src/beman/execution26/tests/CMakeLists.txt

@@ -2,6 +2,7 @@
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 list(APPEND execution_tests
+    meta-transform.pass
     exec-then.pass
     exec-read-env.pass
     exec-get-delegation-scheduler.pass

src/beman/execution26/tests/meta-transform.pass.cpp

@@ -0,0 +1,47 @@
+// src/beman/execution26/tests/meta-transform.pass.cpp                -*-C++-*-
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <beman/execution26/detail/meta_transform.hpp>
+#include <beman/execution26/detail/type_list.hpp>
+#include <test/execution.hpp>
+#include <concepts>
+#include <type_traits>
+
+// ----------------------------------------------------------------------------
+
+namespace
+{
+    template <typename>
+    struct foo {};
+    template <typename T>
+    using bar = foo<T>;
+
+    template <typename T>
+    struct baz { using type = foo<T>; };
+    template <typename T>
+    using baz_t = typename baz<T>::type;;
+}
+
+auto main() -> int
+{
+    static_assert(std::same_as<
+        test_detail::type_list<>,
+        test_detail::meta::transform<foo, test_detail::type_list<>>
+    >);
+    static_assert(std::same_as<
+        test_detail::type_list<foo<bool>, foo<char>>,
+        test_detail::meta::transform<foo, test_detail::type_list<bool, char>>
+    >);
+    static_assert(std::same_as<
+        test_detail::type_list<foo<bool>, foo<char>>,
+        test_detail::meta::transform<bar, test_detail::type_list<bool, char>>
+    >);
+    static_assert(std::same_as<
+        test_detail::type_list<foo<bool>, foo<char>>,
+        test_detail::meta::transform<baz_t, test_detail::type_list<bool, char>>
+    >);
+    static_assert(std::same_as<
+        test_detail::type_list<bool, char>,
+        test_detail::meta::transform<std::type_identity_t, test_detail::type_list<bool, char>>
+    >);
+}