99 lines
3.8 KiB
Markdown
99 lines
3.8 KiB
Markdown
[locale.facet]
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# 28 Text processing library [[text]](./#text)
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## 28.3 Localization library [[localization]](localization#locale.facet)
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### 28.3.3 Locales [[locales]](locales#locale.facet)
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#### 28.3.3.1 Class locale [[locale]](locale#facet)
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#### 28.3.3.1.2 Types [[locale.types]](locale.types#locale.facet)
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#### 28.3.3.1.2.2 Class locale::facet [locale.facet]
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[ð](#lib:locale,facet)
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namespace std {class locale::facet {protected:explicit facet(size_t refs = 0); virtual ~facet();
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facet(const facet&) = delete; void operator=(const facet&) = delete; };}
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/text.tex#L766)
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Class facet is the base class for locale feature sets[.](#1.sentence-1)
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A class is a [*facet*](#def:facet "28.3.3.1.2.2 Class locale::facet [locale.facet]") if it is publicly derived from another facet, or
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if it is a class derived from locale::facet and
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contains a publicly accessible declaration as follows:[215](#footnote-215 "This is a complete list of requirements; there are no other requirements. Thus, a facet class need not have a public copy constructor, assignment, default constructor, destructor, etc.")static ::std::locale::id id;
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/text.tex#L781)
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Template parameters in this Clause
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which are required to be facets
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are those named Facet in declarations[.](#2.sentence-1)
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A program that passes
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a type that is *not* a facet, or
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a type that refers to a volatile-qualified facet,
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as an (explicit or deduced) template parameter to
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a locale function expecting a facet,
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is ill-formed[.](#2.sentence-2)
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A const-qualified facet is a valid template argument to
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any locale function that expects a Facet template parameter[.](#2.sentence-3)
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/text.tex#L794)
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The refs argument to the constructor is used for lifetime management[.](#3.sentence-1)
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For refs == 0,
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the implementation performs delete static_cast<locale::facet*>(f) (where f is a pointer to the facet)
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when the last locale object containing the facet is destroyed;
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for refs == 1, the implementation never destroys the facet[.](#3.sentence-2)
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/text.tex#L802)
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Constructors of all facets defined in this Clause
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take such an argument and pass it along to
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their facet base class constructor[.](#4.sentence-1)
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All one-argument constructors defined in this Clause are explicit,
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preventing their participation in implicit conversions[.](#4.sentence-2)
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[5](#5)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/text.tex#L809)
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For some standard facets a standard â…_bynameâ class,
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derived from it, implements the virtual function semantics
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equivalent to that facet of the locale
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constructed by locale(const char*) with the same name[.](#5.sentence-1)
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Each such facet provides a constructor that takes
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a const char* argument, which names the locale, and
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a refs argument, which is passed to the base class constructor[.](#5.sentence-2)
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Each such facet also provides a constructor that takes
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a string argument str and
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a refs argument,
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which has the same effect as calling the first constructor
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with the two arguments str.c_str() and refs[.](#5.sentence-3)
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If there is no â…_bynameâ version of a facet,
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the base class implements named locale semantics itself
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by reference to other facets[.](#5.sentence-4)
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[215)](#footnote-215)[215)](#footnoteref-215)
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This is a complete list of requirements; there are no other requirements[.](#footnote-215.sentence-1)
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Thus, a facet class need not have a public
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copy constructor, assignment, default constructor, destructor, etc[.](#footnote-215.sentence-2)
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