28 Text processing library [text]

28.3 Localization library [localization]

28.3.3 Locales [locales]

28.3.3.1 Class locale [locale]

28.3.3.1.2 Types [locale.types]

28.3.3.1.2.1 Type locale::category [locale.category]

using category = int;

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.

Further, the expression (X | Y), where X and Y each represent a single category, represents the union of the two categories.

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 86 .

For any locale loc either constructed, or returned by locale::classic(), and any facet Facet shown in Table 86, has_facet<Facet>(loc) is true.

Each locale member function which takes a locale::category argument operates on the corresponding set of facets.

An implementation is required to provide those specializations for facet templates identified as members of a category, and for those shown in Table 87 .

Table 87: 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<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>

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.

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 container types ([defns.character.container]) 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.