cppdraft_translate/cppdraft/exec/general.md

[exec.general]

33 Execution control library [exec]

33.1 General [exec.general]

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This Clause describes components supporting execution of function objects ([function.objects]).

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The following subclauses describe the requirements, concepts, and components for execution control primitives as summarized in Table 157.

Table 157 — Execution control library summary [tab:exec.summary]

🔗	Subclause	Header
🔗 [exec.sched]	Schedulers
🔗 [exec.recv]	Receivers
🔗 [exec.opstate]	Operation states
🔗 [exec.snd]	Senders

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Table 158 shows the types of customization point objects ([customization.point.object]) used in the execution control library.

Table 158 — Types of customization point objects in the execution control library [tab:exec.pos]

🔗 Customization point	Purpose	Examples
🔗 object type
🔗 core	provide core execution functionality, and connection between core components	e.g., connect, start
🔗 completion functions	called by senders to announce the completion of the work (success, error, or cancellation)	set_value, set_error, set_stopped
🔗 senders	allow the specialization of the provided sender algorithms	sender factories (e.g., schedule, just, read_env)sender adaptors (e.g., continues_on, then, let_value)sender consumers (e.g., sync_wait)
🔗 queries	allow querying different properties of objects	general queries (e.g., get_allocator, get_stop_token)environment queries (e.g., get_scheduler, get_delegation_scheduler)scheduler queries (e.g., get_forward_progress_guarantee)sender attribute queries (e.g., get_completion_scheduler)

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This clause makes use of the following exposition-only entities.

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For a subexpression expr, let MANDATE-NOTHROW(expr) be expression-equivalent to expr.

Mandates: noexcept(expr) is true.

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namespace std {templateconcept movable-value = // exposition onlymove_constructible<decay_t> &&constructible_from<decay_t, T> &&(!is_array_v<remove_reference_t>);}

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For function types F1 and F2 denotingR1(Args1...) and R2(Args2...), respectively,MATCHING-SIG(F1, F2) is true if and only ifsame_as<R1(Args1&&...), R2(Args2&&...)> is true.

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For a subexpression err, let Err be decltype((err)) and let AS-EXCEPT-PTR(err) be:

• (8.1)

  err if decay_t denotes the type exception_ptr. Preconditions: !err is false.

• (8.2)

  Otherwise,make_exception_ptr(system_error(err)) if decay_t denotes the type error_code.

• (8.3)

  Otherwise, make_exception_ptr(err).

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For a subexpression expr, let AS-CONST(expr) be expression-equivalent to[](const auto& x) noexcept -> const auto& { return x; }(expr)