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locale Class

The class that describes a locale object that encapsulates culture-specific information as a set of facets that collectively define a specific localized environment.

For a list of all members of this type, see locale Members.

A facet is a pointer to an object of a class derived from class facet that has a public object of the form:

static locale::id id;

You can define an open-ended set of these facets. You can also construct a locale object that designates an arbitrary number of facets.

Predefined groups of these facets represent the locale categories traditionally managed in the Standard C Library by the function setlocale.

Category collate (LC_COLLATE) includes the facets:

collate<char>
collate<wchar_t>

Category ctype (LC_CTYPE) includes the facets:

ctype<char>
ctype<wchar_t>
codecvt<char, char, mbstate_t>
codecvt<wchar_t, char, mbstate_t>

Category monetary (LC_MONETARY) includes the facets:

moneypunct<char, false>
moneypunct<wchar_t, false>
moneypunct<char, true>
moneypunct<wchar_t, true>
money_get<char, istreambuf_iterator<char> >
money_get<wchar_t, istreambuf_iterator<wchar_t> >
money_put<char, ostreambuf_iterator<char> >
money_put<wchar_t, ostreambuf_iterator<wchar_t> >

Category numeric (LC_NUMERIC) includes the facets:

num_get<char, istreambuf_iterator<char> >
num_get<wchar_t, istreambuf_iterator<wchar_t> >
num_put<char, ostreambuf_iterator<char> >
num_put<wchar_t, ostreambuf_iterator<wchar_t> >
numpunct<char>
numpunct<wchar_t>

Category time (LC_TIME) includes the facets:

time_get<char, istreambuf_iterator<char> >
time_get<wchar_t, istreambuf_iterator<wchar_t> >
time_put<char, ostreambuf_iterator<char> >
time_put<wchar_t, ostreambuf_iterator<wchar_t> >

Category messages (LC_MESSAGES) includes the facets:

messages<char>
messages<wchar_t>

(The last category is required by Posix, but not the C Standard.)

Some of these predefined facets are used by the iostreams classes, to control the conversion of numeric values to and from text sequences.

An object of class locale also stores a locale name as an object of class string. Using an invalid locale name to construct a locale facet or a locale object throws an object of class runtime_error. The stored locale name is "*" if the locale object cannot be certain that a C-style locale corresponds exactly to that represented by the object. Otherwise, you can establish a matching locale within the Standard C Library, for the locale object loc, by calling setlocale(LC_ALL, loc.name().c_str()).

In this implementation, you can also call the static member function:

static locale empty( );

to construct a locale object that has no facets. It is also a transparent locale; if the template functions has_facet and use_facet cannot find the requested facet in a transparent locale, they consult first the global locale and then, if that is transparent, the classic locale. Thus, you can write:

cout.imbue(locale::empty( ));

Subsequent insertions to cout are mediated by the current state of the global locale. You can even write:

locale loc(locale::empty( ), locale::classic( ),
    locale::numeric);
cout.imbue(loc);

Numeric formatting rules for subsequent insertions to cout remain the same as in the C locale, even as the global locale supplies changing rules for inserting dates and monetary amounts.

Header: <locale>

Namespace: std

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