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.
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 [tab:localization.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,char,mbstate_t> | |
| codecvt<char32_t,char,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> |
For any locale loc either constructed, or returned by locale::classic(), and any facet Facet shown in Table [tab:localization.category.facets], 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 [tab:localization.required.specializations].
| 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,char,mbstate_t> | |
| codecvt_byname<char32_t,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 formal parameter with name InputIterator or OutputIterator indicates the set of all possible specializations on parameters that satisfy the requirements of an Input Iterator or an Output Iterator, respectively ([iterator.requirements]). A template formal parameter with name C represents the set of types containing char, wchar_t, and any other implementation-defined character types that satisfy the requirements for a character on which any of the iostream components can be instantiated. A template formal parameter with name International represents the set of all possible specializations on a bool parameter.