33 Execution control library [exec]

33.16 Namespace parallel_scheduler_replacement [exec.parschedrepl]

33.16.2 Receiver proxies [exec.parschedrepl.recvproxy]

namespace std::execution::parallel_scheduler_replacement { struct receiver_proxy { protected: virtual bool query-env(unspecified) noexcept = 0; // exposition only public: virtual void set_value() noexcept = 0; virtual void set_error(exception_ptr) noexcept = 0; virtual void set_stopped() noexcept = 0; template<class P, class-type Query> optional<P> try_query(Query q) const noexcept; }; struct bulk_item_receiver_proxy : receiver_proxy { virtual void execute(size_t, size_t) noexcept = 0; }; }
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receiver_proxy represents a receiver that will be notified by the implementations of parallel_scheduler_backend to trigger the completion operations.
bulk_item_receiver_proxy is derived from receiver_proxy and is used for bulk_chunked and bulk_unchunked customizations that will also receive notifications from implementations of parallel_scheduler_backend corresponding to different iterations.
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template<class P, class-type Query> optional<P> try_query(Query q) const noexcept;
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Mandates: P is a cv-unqualified non-array object type.
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Returns: Let env be the environment of the receiver represented by *this.
If
  • (3.1)
    Query is not a member of an implementation-defined set of supported queries; or
  • (3.2)
    P is not a member of an implementation-defined set of supported result types for Query; or
  • (3.3)
    the expression q(env) is not well-formed,
then returns nullopt.
Otherwise, if q(env) has type cv P, then returns q(env).
Otherwise, returns an implementation-defined value of type optional<P>.
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Remarks: get_stop_token_t is in the implementation-defined set of supported queries, and inplace_stop_token is a member of the implementation-defined set of supported result types for get_stop_token_t.
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Recommended practice: If P is inplace_stop_token and T is a type other than inplace_stop_token that models stoppable_token, try_query should return an object of type inplace_stop_token such that until one of set_value, set_error or set_stopped is called on *this, all calls to try_query return equivalent inplace_stop_token objects.