Add merge for sequence senders

include/exec/__detail/__basic_sequence.hpp

@@ -71,35 +71,36 @@ namespace exec {
       return {};
     }
 
-    template <stdexec::__decays_to<__seqexpr> _Self, class _Env>
-    STDEXEC_MEMFN_DECL(auto get_item_types)(this _Self&& __self, _Env&& __env)
-      -> decltype(__self.__tag()
-                    .get_item_types(static_cast<_Self&&>(__self), static_cast<_Env&&>(__env))) {
+    template <stdexec::__decays_to<__seqexpr> _Self, class... _Env>
+    static auto get_item_types(_Self&& __self, _Env&&... __env)
+      -> decltype(__self.__tag().get_item_types(
+        static_cast<_Self&&>(__self),
+        static_cast<_Env&&>(__env)...)) {
       return {};
     }
 
     template <stdexec::__decays_to<__seqexpr> _Self, stdexec::receiver _Receiver>
-    STDEXEC_MEMFN_DECL(auto subscribe)(this _Self&& __self, _Receiver&& __rcvr) noexcept(noexcept(
+    static auto subscribe(_Self&& __self, _Receiver&& __rcvr) noexcept(noexcept(
       __self.__tag().subscribe(static_cast<_Self&&>(__self), static_cast<_Receiver&&>(__rcvr))))
       -> decltype(__self.__tag()
                     .subscribe(static_cast<_Self&&>(__self), static_cast<_Receiver&&>(__rcvr))) {
       return __tag_t::subscribe(static_cast<_Self&&>(__self), static_cast<_Receiver&&>(__rcvr));
     }
 
-    template <class _Sender, class _ApplyFn>
+    template <class _Sequence, class _ApplyFn>
     static auto
-      apply(_Sender&& __sndr, _ApplyFn&& __fun) noexcept(stdexec::__nothrow_callable<
-                                                         stdexec::__detail::__impl_of<_Sender>,
-                                                         stdexec::__copy_cvref_fn<_Sender>,
+      apply(_Sequence&& __sequence, _ApplyFn&& __fun) noexcept(stdexec::__nothrow_callable<
+                                                         stdexec::__detail::__impl_of<_Sequence>,
+                                                         stdexec::__copy_cvref_fn<_Sequence>,
                                                          _ApplyFn
       >)
         -> stdexec::__call_result_t<
-          stdexec::__detail::__impl_of<_Sender>,
-          stdexec::__copy_cvref_fn<_Sender>,
+          stdexec::__detail::__impl_of<_Sequence>,
+          stdexec::__copy_cvref_fn<_Sequence>,
           _ApplyFn
         > {
-      return static_cast<_Sender&&>(__sndr)
-        .__impl_(stdexec::__copy_cvref_fn<_Sender>(), static_cast<_ApplyFn&&>(__fun));
+      return static_cast<_Sequence&&>(__sequence)
+        .__impl_(stdexec::__copy_cvref_fn<_Sequence>(), static_cast<_ApplyFn&&>(__fun));
     }
   };
 

include/exec/sequence/ignore_all_values.hpp

@@ -276,8 +276,6 @@ namespace exec {
       using __completion_sigs = __sequence_completion_signatures_of_t<_Child, _Env>;
 
       template <class _Child>
-        requires receiver_of<_Receiver, __completion_sigs<_Child>>
-              && sequence_sender_to<_Child, __receiver_t<_Child>>
       auto operator()(__ignore, __ignore, _Child&& __child)
         noexcept(__nothrow_constructible_from<__operation_t<_Child>, _Child, _Receiver>)
           -> __operation_t<_Child> {
@@ -287,7 +285,7 @@ namespace exec {
 
     struct ignore_all_values_t {
       template <sender _Sender>
-      auto operator()(_Sender&& __sndr) const {
+      auto operator()(_Sender&& __sndr) const -> __well_formed_sender auto {
         auto __domain = __get_early_domain(static_cast<_Sender&&>(__sndr));
         return transform_sender(
           __domain, __make_sexpr<ignore_all_values_t>(__(), static_cast<_Sender&&>(__sndr)));
@@ -320,11 +318,6 @@ namespace exec {
         []<class _Sender, receiver _Receiver>(_Sender&& __sndr, _Receiver __rcvr) noexcept(
           __nothrow_callable<__sexpr_apply_t, _Sender, __connect_fn<_Receiver>>)
         -> __call_result_t<__sexpr_apply_t, _Sender, __connect_fn<_Receiver>>
-        requires receiver_of<_Receiver, __completion_sigs<__child_of<_Sender>, env_of_t<_Receiver>>>
-              && sequence_sender_to<
-                   __child_of<_Sender>,
-                   __receiver_t<__child_of<_Sender>, _Receiver>
-              >
       {
         static_assert(sender_expr_for<_Sender, ignore_all_values_t>);
         return __sexpr_apply(static_cast<_Sender&&>(__sndr), __connect_fn<_Receiver>{__rcvr});
@@ -340,4 +333,4 @@ namespace stdexec {
   template <>
   struct __sexpr_impl<exec::ignore_all_values_t>
     : exec::__ignore_all_values::__ignore_all_values_impl { };
-} // namespace stdexec
+} // namespace stdexec

include/exec/sequence/iterate.hpp

@@ -167,7 +167,7 @@ namespace exec {
     struct iterate_t {
       template <std::ranges::forward_range _Range>
         requires __decay_copyable<_Range>
-      auto operator()(_Range&& __range) const {
+      auto operator()(_Range&& __range) const -> __well_formed_sequence_sender auto {
         return make_sequence_expr<iterate_t>(__decay_t<_Range>{static_cast<_Range&&>(__range)});
       }
 
@@ -219,4 +219,4 @@ namespace exec {
   inline constexpr iterate_t iterate;
 } // namespace exec
 
-#endif // STDEXEC_HAS_STD_RANGES()
+#endif // STDEXEC_HAS_STD_RANGES()

include/exec/sequence/merge.hpp

@@ -0,0 +1,216 @@
+/*
+ * Copyright (c) 2023 Maikel Nadolski
+ * Copyright (c) 2023 NVIDIA Corporation
+ *
+ * Licensed under the Apache License Version 2.0 with LLVM Exceptions
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *   https://llvm.org/LICENSE.txt
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include "../../stdexec/concepts.hpp"
+#include "../../stdexec/execution.hpp"
+#include "../sequence_senders.hpp"
+
+#include "../__detail/__basic_sequence.hpp"
+#include "./transform_each.hpp"
+#include "./ignore_all_values.hpp"
+#include "stdexec/__detail/__execution_fwd.hpp"
+#include "stdexec/__detail/__meta.hpp"
+#include "stdexec/__detail/__senders_core.hpp"
+#include "stdexec/__detail/__transform_completion_signatures.hpp"
+
+namespace exec {
+  namespace __merge {
+    using namespace stdexec;
+
+    template <class _Receiver>
+    struct __operation_base {
+      _Receiver __receiver_;
+    };
+
+    template <class _ReceiverId>
+    struct __result_receiver {
+      using _Receiver = stdexec::__t<_ReceiverId>;
+
+      struct __t {
+        using receiver_concept = stdexec::receiver_t;
+        using __id = __result_receiver;
+
+        __operation_base<_Receiver>* __op_;
+
+        void set_value() noexcept {
+          stdexec::set_value(static_cast<_Receiver&&>(__op_->__receiver_));
+        }
+
+        template <class _Error>
+        void set_error(_Error&& __error) noexcept {
+          stdexec::set_error(
+            static_cast<_Receiver&&>(__op_->__receiver_), static_cast<_Error&&>(__error));
+        }
+
+        void set_stopped() noexcept
+        {
+          stdexec::set_stopped(static_cast<_Receiver&&>(__op_->__receiver_));
+        }
+
+        auto get_env() const noexcept -> env_of_t<_Receiver> {
+          return stdexec::get_env(__op_->__receiver_);
+        }
+      };
+    };
+
+    template <class _ReceiverId>
+    struct __merge_each_fn {
+      using _Receiver = stdexec::__t<_ReceiverId>;
+
+      template <stdexec::sender _Item>
+      auto operator()(_Item&& __item, __operation_base<_Receiver>* __op) const noexcept(
+        __nothrow_callable<set_next_t, _Receiver&, _Item>)
+        -> next_sender_of_t<_Receiver, _Item> {
+        return exec::set_next(
+          __op->__receiver_, static_cast<_Item&&>(__item));
+      }
+    };
+
+    struct __combine {
+      template<class _ReceiverId>
+      using merge_each_fn_t = __binder_back<__merge_each_fn<_ReceiverId>, __operation_base<__t<_ReceiverId>>*>;
+
+      template<class _Sequence, class _ReceiverId>
+      using transform_sender_t = __call_result_t<exec::transform_each_t, _Sequence, merge_each_fn_t<_ReceiverId>>;
+      template<class _Sequence, class _ReceiverId>
+      using ignored_sender_t = __call_result_t<exec::ignore_all_values_t, transform_sender_t<_Sequence, _ReceiverId>>;
+
+      template<class _ReceiverId, class... _Sequences>
+      using result_sender_t = __call_result_t<when_all_t,
+                                                ignored_sender_t<_Sequences, _ReceiverId>...>;
+    };
+
+    template <class _ReceiverId, class... _Sequences>
+    struct __operation {
+      using _Receiver = stdexec::__t<_ReceiverId>;
+
+      using merge_each_fn_t = typename __combine::merge_each_fn_t<_ReceiverId>;
+
+      template<class _ReceiverIdDependent>
+      using result_sender_t = typename __combine::result_sender_t<_ReceiverIdDependent, _Sequences...>;
+
+      struct __t : __operation_base<_Receiver> {
+        using __id = __operation;
+
+        connect_result_t<result_sender_t<_ReceiverId>, stdexec::__t<__result_receiver<_ReceiverId>>> __op_result_;
+
+        __t(_Receiver __rcvr, _Sequences... __sequences)
+          : __operation_base<
+              _Receiver
+            >{static_cast<_Receiver&&>(__rcvr)}
+          , __op_result_{stdexec::connect(
+            stdexec::when_all(
+              exec::ignore_all_values(
+                exec::transform_each(static_cast<_Sequences&&>(__sequences), merge_each_fn_t{{this}, {}, {}}))...),
+            stdexec::__t<__result_receiver<_ReceiverId>>{this})} {
+        }
+
+        void start() & noexcept {
+          stdexec::start(__op_result_);
+        }
+      };
+    };
+
+    template <class _Receiver>
+    struct __subscribe_fn {
+      _Receiver& __rcvr_;
+
+      template <class... _Sequences>
+      auto operator()(__ignore, __ignore, _Sequences... __sequences) noexcept(
+        (__nothrow_decay_copyable<_Sequences> && ...)
+        && __nothrow_move_constructible<_Receiver>)
+        -> __t<__operation<__id<_Receiver>, _Sequences...>> {
+        return {
+          static_cast<_Receiver&&>(__rcvr_),
+          static_cast<_Sequences&&>(__sequences)...};
+      }
+    };
+
+    struct merge_t {
+      template <class... _Sequences>
+      auto operator()(_Sequences&&... __sequences) const
+        noexcept((__nothrow_decay_copyable<_Sequences> && ...))
+        -> __well_formed_sequence_sender auto {
+        auto __domain = __common_domain_t<_Sequences...>();
+        return transform_sender(
+          __domain, make_sequence_expr<merge_t>(__(),
+              static_cast<_Sequences&&>(__sequences)...));
+      }
+
+      template <class _Error>
+      using __set_error_t = completion_signatures<set_error_t(__decay_t<_Error>)>;
+
+      struct _INVALID_ARGUMENTS_TO_MERGE_ { };
+
+      template <class _Self, class _Env>
+      using __error_t = __mexception<
+        _INVALID_ARGUMENTS_TO_MERGE_,
+        __children_of<_Self, __q<_WITH_SEQUENCES_>>,
+        _WITH_ENVIRONMENT_<_Env>
+      >;
+
+      template <class... _Env>
+      struct __completions_fn_t {
+
+        template <class... _Sequences>
+        using __f = __meval<
+          __concat_completion_signatures,
+          completion_signatures<set_stopped_t()>,
+          __sequence_completion_signatures_of_t<_Sequences, _Env...>...
+        >;
+      };
+
+      template <class _Self, class... _Env>
+      using __completions_t = __children_of<_Self, __completions_fn_t<_Env...>>;
+
+      template <sender_expr_for<merge_t> _Self, class... _Env>
+      static auto get_completion_signatures(_Self&&, _Env&&...) noexcept {
+          return __minvoke<__mtry_catch<__q<__completions_t>, __q<__error_t>>, _Self, _Env...>();
+      }
+
+      template <class... _Env>
+      struct __items_fn_t {
+
+        template <class... _Sequences>
+        using __f = stdexec::__mapply<
+        stdexec::__munique<stdexec::__q<exec::item_types>>,
+          stdexec::__minvoke<
+            stdexec::__mconcat<stdexec::__qq<exec::item_types>>,
+              __item_types_of_t<_Sequences, _Env...>...>>;
+      };
+
+      template <class _Self, class... _Env>
+      using __items_t = __children_of<_Self, __items_fn_t<_Env...>>;
+
+      template <sender_expr_for<merge_t> _Self, class... _Env>
+      static auto get_item_types(_Self&&, _Env&&...) noexcept {
+          return __minvoke<__mtry_catch<__q<__items_t>, __q<__error_t>>, _Self, _Env...>();
+      }
+
+      template <sender_expr_for<merge_t> _Self, receiver _Receiver>
+      static auto subscribe(_Self&& __self, _Receiver __rcvr)
+        noexcept(__nothrow_callable<__sexpr_apply_t, _Self, __subscribe_fn<_Receiver>>)
+          -> __sexpr_apply_result_t<_Self, __subscribe_fn<_Receiver>> {
+        return __sexpr_apply(static_cast<_Self&&>(__self), __subscribe_fn<_Receiver>{__rcvr});
+      }
+    };
+  } // namespace __merge
+
+  using __merge::merge_t;
+  inline constexpr merge_t merge{};
+} // namespace exec