146 lines
5.2 KiB
Markdown
146 lines
5.2 KiB
Markdown
[func.bind.bind]
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# 22 General utilities library [[utilities]](./#utilities)
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## 22.10 Function objects [[function.objects]](function.objects#func.bind.bind)
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### 22.10.15 Function object binders [[func.bind]](func.bind#bind)
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#### 22.10.15.4 Function template bind [func.bind.bind]
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L13401)
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In the text that follows:
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- [(1.1)](#1.1)
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g is a value of the result of a bind invocation,
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- [(1.2)](#1.2)
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FD is the type decay_t<F>,
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- [(1.3)](#1.3)
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fd is an lvalue that
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is a target object of g ([[func.def]](func.def "22.10.3 Definitions")) of type FD direct-non-list-initialized with std::forward<F>(f),
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- [(1.4)](#1.4)
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Ti is the ith type in the template parameter pack BoundArgs,
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- [(1.5)](#1.5)
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TDi is the type decay_t<Ti>,
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- [(1.6)](#1.6)
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ti is the ith argument in the function parameter pack bound_args,
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- [(1.7)](#1.7)
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tdi is a bound argument entity
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of g ([[func.def]](func.def "22.10.3 Definitions")) of type TDi direct-non-list-initialized with std::forward<Ti>(ti),
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- [(1.8)](#1.8)
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Uj is the jth deduced type of the UnBoundArgs&&... parameter
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of the argument forwarding call wrapper, and
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- [(1.9)](#1.9)
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uj is the jth argument associated with Uj[.](#1.sentence-1)
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[ð](#lib:bind_)
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`template<class F, class... BoundArgs>
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constexpr unspecified bind(F&& f, BoundArgs&&... bound_args);
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template<class R, class F, class... BoundArgs>
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constexpr unspecified bind(F&& f, BoundArgs&&... bound_args);
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`
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L13430)
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*Mandates*: is_constructible_v<FD, F> is true[.](#2.sentence-1)
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For each Ti in BoundArgs, is_constructible_v<TDi, Ti> is true[.](#2.sentence-2)
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L13435)
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*Preconditions*: FD and each TDi meet
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the [*Cpp17MoveConstructible*](utility.arg.requirements#:Cpp17MoveConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]") and [*Cpp17Destructible*](utility.arg.requirements#:Cpp17Destructible "16.4.4.2 Template argument requirements [utility.arg.requirements]") requirements[.](#3.sentence-1)
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*INVOKE*(fd, w1, w2, …,wN) ([[func.require]](func.require "22.10.4 Requirements")) is a valid expression for some
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values w1, w2, …, wN, whereN has the value sizeof...(bound_args)[.](#3.sentence-2)
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L13444)
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*Returns*: An argument forwarding call wrapper g ([[func.require]](func.require "22.10.4 Requirements"))[.](#4.sentence-1)
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A program that attempts to invoke a volatile-qualified g is ill-formed[.](#4.sentence-2)
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When g is not volatile-qualified, invocation ofg(u1, u2, …, uM) is expression-equivalent ([[defns.expression.equivalent]](defns.expression.equivalent "3.22 expression-equivalent")) to*INVOKE*(static_cast<Vfd>(vfd), static_cast<V1>(v1), static_cast<V2>(v2), …, static_cast<VN>(vN)) for the first overload, and*INVOKE*<R>(static_cast<Vfd>(vfd), static_cast<V1>(v1), static_cast<V2>(v2), …, static_cast<VN>(vN)) for the second overload,
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where the values and types of the target argument vfd and
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of the bound argumentsv1, v2, …, vN are determined as specified below[.](#4.sentence-3)
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[5](#5)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L13466)
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*Throws*: Any exception thrown by the initialization of
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the state entities of g[.](#5.sentence-1)
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[6](#6)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L13471)
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[*Note [1](#note-1)*:
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If all of FD and TDi meet
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the requirements of [*Cpp17CopyConstructible*](utility.arg.requirements#:Cpp17CopyConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]"), then
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the return type meets the requirements of [*Cpp17CopyConstructible*](utility.arg.requirements#:Cpp17CopyConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]")[.](#6.sentence-1)
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â *end note*]
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[7](#7)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L13479)
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The values of the [*bound arguments*](#def:bound_arguments) v1, v2, …, vN and their
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corresponding types V1, V2, …, VN depend on the
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types TDi derived from
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the call to bind and the
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cv-qualifiers cv of the call wrapper g as follows:
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- [(7.1)](#7.1)
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if TDi is reference_wrapper<T>, the
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argument is tdi.get() and its type Vi is T&;
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- [(7.2)](#7.2)
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if the value of is_bind_expression_v<TDi> is true, the argument isstatic_cast<cv TDi&>(tdi)(std::forward<Uj>(uj)...) and its type Vi isinvoke_result_t<cv TDi&, Uj...>&&;
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- [(7.3)](#7.3)
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if the value j of is_placeholder_v<TDi> is not zero, the argument is std::forward<Uj>(uj) and its type Vi is Uj&&;
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- [(7.4)](#7.4)
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otherwise, the value is tdi and its type Vi is cv TDi&[.](#7.sentence-1)
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[8](#8)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L13507)
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The value of the target argument vfd is fd and
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its corresponding type Vfd is cv FD&[.](#8.sentence-1)
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