simplied gather signatures (#116)

* simplied gather signatures

* clang-format

* revert CMakeList.txt change

* fixed formatting issue

Author: dietmarkuehl

include/beman/execution26/detail/gather_signatures.hpp

@@ -23,6 +23,7 @@ struct same_tag<Tag, R(A...)> {
 };
 template <typename Tag>
 struct bound_tag {
+    using type = Tag;
     template <typename T>
     using predicate = ::beman::execution26::detail::same_tag<Tag, T>;
 };
@@ -69,14 +70,12 @@ template <typename Tag,
           template <typename...> class Variant>
     requires requires {
         typename ::beman::execution26::detail::gather_signatures_helper<
-            ::beman::execution26::detail::meta::
-                filter<::beman::execution26::detail::bound_tag<Tag>::template predicate, signatures>,
+            ::beman::execution26::detail::meta::filter_tag<::beman::execution26::detail::same_tag, Tag, signatures>,
             Tuple,
             Variant>::type;
     }
 using gather_signatures = ::beman::execution26::detail::gather_signatures_helper<
-    ::beman::execution26::detail::meta::filter<::beman::execution26::detail::bound_tag<Tag>::template predicate,
-                                               signatures>,
+    ::beman::execution26::detail::meta::filter_tag<::beman::execution26::detail::same_tag, Tag, signatures>,
     Tuple,
     Variant>::type;
 } // namespace beman::execution26::detail

include/beman/execution26/detail/meta_filter.hpp

@@ -13,22 +13,44 @@ namespace beman::execution26::detail::meta::detail {
 template <template <typename> class, typename>
 struct filter;
 
+template <template <typename, typename> class, typename, typename>
+struct filter_tag;
+
 template <template <typename> class Predicate, template <typename...> class List>
 struct filter<Predicate, List<>> {
     using type = List<>;
 };
 
+template <template <typename, typename> class Predicate, typename Tag, template <typename...> class List>
+struct filter_tag<Predicate, Tag, List<>> {
+    using type = List<>;
+};
+
 template <template <typename> class Predicate, template <typename...> class List, typename H, typename... T>
 struct filter<Predicate, List<H, T...>> {
     using tail = typename beman::execution26::detail::meta::detail::filter<Predicate, List<T...>>::type;
     using type = ::std::conditional_t<Predicate<H>::value, ::beman::execution26::detail::meta::prepend<H, tail>, tail>;
 };
+
+template <template <typename, typename> class Predicate,
+          typename Tag,
+          template <typename...> class List,
+          typename H,
+          typename... T>
+struct filter_tag<Predicate, Tag, List<H, T...>> {
+    using tail = typename beman::execution26::detail::meta::detail::filter_tag<Predicate, Tag, List<T...>>::type;
+    using type =
+        ::std::conditional_t<Predicate<Tag, H>::value, ::beman::execution26::detail::meta::prepend<H, tail>, tail>;
+};
 } // namespace beman::execution26::detail::meta::detail
 
 namespace beman::execution26::detail::meta {
 template <template <typename> class Predicate, typename List>
 using filter = ::beman::execution26::detail::meta::detail::filter<Predicate, List>::type;
-}
+
+template <template <typename, typename> class Predicate, typename Tag, typename List>
+using filter_tag = ::beman::execution26::detail::meta::detail::filter_tag<Predicate, Tag, List>::type;
+} // namespace beman::execution26::detail::meta
 
 // ----------------------------------------------------------------------------