std::locale::locale(3)

NAME
std::locale::locale - std::locale::locale

Synopsis
   Defined in header <locale>
   locale() throw(); (until C++11)
   locale() noexcept; (since C++11)
   locale( const locale& other ) throw(); (until C++11)
   locale( const locale& other ) noexcept; (since C++11)
   explicit locale( const char* std_name ); (3)
   explicit locale( const std::string& std_name ); (4) (since C++11)
   locale( const locale& other, const char* (1) (5)
   std_name, category cat ); (2)
   locale( const locale& other, const std::string& (6) (since C++11)
   std_name, category cat );
   template< class Facet > (7)
   locale( const locale& other, Facet* f );
   locale( const locale& other, const locale& one, (8)
   category cat );
   Contstructs a new locale object.
   1) Default constructor. Constructs a copy of the global C++ locale, which is the
   locale most recently used as the argument to std::locale::global or a copy of
   std::locale::classic if no call to std::locale::global has been made.
   2) Copy constructor. Constructs a copy of other.
   3-4) Constructs a copy of the system locale with specified std_name (such as "C", or
   "POSIX", or "en_US.UTF-8", or "English_US.1251"), if such locale is supported by the
   operating system. The locale constructed in this manner has a name.
   5-6) Constructs a copy of other except for all the facets identified by the cat
   argument, which are copied from the system locale identified by its std_name. The
   locale constructed in this manner has a name if and only if other has a name.
   7) Constructs a copy of other except for the facet of type Facet (typically deduced
   from the type of the argument) which is installed from the argument facet. If facet
   is a null pointer, the constructed locale is a full copy of other. The locale
   constructed in this manner has no name.
   8) Constructs a copy of other except for all the facets identified by the cat
   argument, which are copied from one. If both other and one have names, then the
   resulting locale also has a name.

Parameters
   other - another locale to copy
   std_name - name of the system locale to use
   f - pointer to a facet to merge with other
   cat - the locale category used to identify the facets to merge with other
   one - another locale to take facets from

Exceptions
   3,5) std::runtime_error if the operating system has no locale named std_name or if
   std_name is a null pointer.
   4,6) std::runtime_error if the operating system has no locale named std_name.
   7,8) May throw implementation-defined exceptions.

Notes
   Overload 7 is typically called with its second argument, f, obtained directly from a
   new-expression: the locale is responsible for calling the matching delete from its
   own destructor.

Example
// Run this code
 #include <codecvt>
 #include <iostream>
 #include <locale>
 std::ostream& operator<< (std::ostream& os, std::locale const& loc)
 {
     if (loc.name().length() <= 80) { return os << loc.name() << '\n'; }
     for (const auto c : loc.name())
     {
         c != ';' ? os << c : os << "\n ";
     }
     return os << '\n';
 }
 int main()
 {
     std::locale l1;
         // l1 is a copy of the classic "C" locale
     std::locale l2("en_US.UTF-8");
         // l2 is a unicode locale
     std::locale l3(l1, l2, std::locale::ctype);
         // l3 is "C" except for ctype, which is unicode
     std::locale l4(l1, new std::codecvt_utf8<wchar_t>);
         // l4 is "C" except for codecvt
     std::cout
         << "Locale names:\n"
         << "l1: " << l1 << "l2: " << l2
         << "l3: " << l3 << "l4: " << l4;
 }

Possible output:
 Locale names:
 l1: C
 l2: en_US.UTF-8
 l3: LC_CTYPE=en_US.UTF-8
     LC_NUMERIC=C
     LC_TIME=C
     LC_COLLATE=C
     LC_MONETARY=C
     LC_MESSAGES=C
     LC_PAPER=C
     LC_NAME=C
     LC_ADDRESS=C
     LC_TELEPHONE=C
     LC_MEASUREMENT=C
     LC_IDENTIFICATION=C
 l4: *

See also
   destructor destructs the locale and the facets whose reference count becomes zero
                (public member function)