std::locale

An object of class std::locale is an immutable indexed set of immutable facets. Each stream object of the C++ input/output library is associated with an std::locale object and uses its facets for parsing and formatting of all data. In addition, a locale object is associated with each std::basic_regex object. (since C++11)

Each locale constructed in a C++ program holds at least the following standard facets (i.e. std::has_facet returns true

Internally, a locale object is implemented as if it is a reference-counted pointer to an array (indexed by std::locale::id ) of reference-counted pointers to facets: copying a locale only copies one pointer and increments several reference counts. To maintain the standard C++ library thread safety guarantees (operations on different objects are always thread-safe), both the locale reference count and each facet reference count are updated in a thread-safe manner, similar to std::shared_ptr

Member types

Member constants

std::locale member functions expecting a category argument require one of the category values defined above, or the union of two or more such values. The LC constants

Member functions

Example

#include <iostream>
#include <locale>
 
int main()
{
    std::wcout << L"User-preferred locale setting is "
               << std::locale("").name().c_str() << L'\n';
    // on startup, the global locale is the "C" locale
    std::wcout << 1000.01 << L'\n';
 
    // replace the C++ global locale and the "C" locale with the user-preferred locale
    std::locale::global(std::locale(""));
    // use the new global locale for future wide character output
    std::wcout.imbue(std::locale());
 
    // output the same number again
    std::wcout << 1000.01 << L'\n';
}

User-preferred locale setting is en_US.UTF8
1000.01
1,000.01

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also