28 Localization library [localization]

28.3 Locales [locales]

28.3.1 Class locale [locale]

28.3.1.1 Types [locale.types]

28.3.1.1.1 Type locale​::​category [locale.category]

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using category = int;
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Valid category values include the locale member bitmask elements collate, ctype, monetary, numeric, time, and messages, each of which represents a single locale category.
In addition, locale member bitmask constant none is defined as zero and represents no category.
And locale member bitmask constant all is defined such that the expression 
(collate | ctype | monetary | numeric | time | messages | all) == all
is true, and represents the union of all categories.
Further, the expression (X | Y), where X and Y each represent a single category, represents the union of the two categories.
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locale member functions expecting a category argument require one of the category values defined above, or the union of two or more such values.
Such a category value identifies a set of locale categories.
Each locale category, in turn, identifies a set of locale facets, including at least those shown in Table 102.
Table 102: Locale category facets   [tab:locale.category.facets]
Category
Includes facets
collate
collate<char>, collate<wchar_­t>
ctype
ctype<char>, ctype<wchar_­t>
codecvt<char, char, mbstate_­t>
codecvt<char16_­t, char8_­t, mbstate_­t>
codecvt<char32_­t, char8_­t, mbstate_­t>
codecvt<wchar_­t, char, mbstate_­t>
monetary
moneypunct<char>, moneypunct<wchar_­t>
moneypunct<char, true>, moneypunct<wchar_­t, true>
money_­get<char>, money_­get<wchar_­t>
money_­put<char>, money_­put<wchar_­t>
numeric
numpunct<char>, numpunct<wchar_­t>
num_­get<char>, num_­get<wchar_­t>
num_­put<char>, num_­put<wchar_­t>
time
time_­get<char>, time_­get<wchar_­t>
time_­put<char>, time_­put<wchar_­t>
messages
messages<char>, messages<wchar_­t>
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For any locale loc either constructed, or returned by locale​::​classic(), and any facet Facet shown in Table 102, has_­facet<Facet>(loc) is true.
Each locale member function which takes a locale​::​category argument operates on the corresponding set of facets.
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An implementation is required to provide those specializations for facet templates identified as members of a category, and for those shown in Table 103.
Table 103: Required specializations   [tab:locale.spec]
Category
Includes facets
collate
collate_­byname<char>, collate_­byname<wchar_­t>
ctype
ctype_­byname<char>, ctype_­byname<wchar_­t>
codecvt_­byname<char, char, mbstate_­t>
codecvt_­byname<char16_­t, char8_­t, mbstate_­t>
codecvt_­byname<char32_­t, char8_­t, mbstate_­t>
codecvt_­byname<wchar_­t, char, mbstate_­t>
monetary
moneypunct_­byname<char, International>
moneypunct_­byname<wchar_­t, International>
money_­get<C, InputIterator>
money_­put<C, OutputIterator>
numeric
numpunct_­byname<char>, numpunct_­byname<wchar_­t>
num_­get<C, InputIterator>, num_­put<C, OutputIterator>
time
time_­get<char, InputIterator>
time_­get_­byname<char, InputIterator>
time_­get<wchar_­t, InputIterator>
time_­get_­byname<wchar_­t, InputIterator>
time_­put<char, OutputIterator>
time_­put_­byname<char, OutputIterator>
time_­put<wchar_­t, OutputIterator>
time_­put_­byname<wchar_­t, OutputIterator>
messages
messages_­byname<char>, messages_­byname<wchar_­t>
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The provided implementation of members of facets num_­get<charT> and num_­put<charT> calls use_­facet<F>(l) only for facet F of types numpunct<charT> and ctype<charT>, and for locale l the value obtained by calling member getloc() on the ios_­base& argument to these functions.
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In declarations of facets, a template parameter with name InputIterator or OutputIterator indicates the set of all possible specializations on parameters that meet the Cpp17InputIterator requirements or Cpp17OutputIterator requirements, respectively ([iterator.requirements]).
A template parameter with name C represents the set of types containing char, wchar_­t, and any other implementation-defined character types that meet the requirements for a character on which any of the iostream components can be instantiated.
A template parameter with name International represents the set of all possible specializations on a bool parameter.