W3cubDocs

/C++

std::locale::locale

Defined in header `<locale>`
	(1)
locale() throw();		(until C++11)
locale() noexcept;		(since C++11)
	(2)
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* std_name, category cats );	(5)
locale( const locale& other, const std::string& std_name, category cats );	(6)	(since C++11)
template< class Facet > locale( const locale& other, Facet* f );	(7)
locale( const locale& other, const locale& one, category cats );	(8)

Constructs 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.

4) Equivalent to locale(std_name.c_str()).

5) Constructs a copy of other except for all the facets identified by the cats 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.

6) Equivalent to locale(other, std_name.c_str(), cats).

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 f. If f is a null pointer, the constructed locale is a full copy of other. The program is ill-formed if Facet is not a facet or it is a volatile-qualified facet.

If f is null, the constructed locale has the same name as other. Otherwise, the constructed locale has no name.

8) Constructs a copy of other except for all the facets identified by the cats argument, which are copied from one.

If cats is equal to locale::none, the constructed locale has a name if and only if other has a name. Otherwise, the constructed locale has a name if and only if other and one both have names.

Parameters

other	-	another locale to copy
std_name	-	name of the system locale to use
f	-	pointer to a facet to merge with `other`
cats	-	the facet categories 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.

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

#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()
{
    // l1 is a copy of the classic "C" locale
    std::locale l1; 
    // l2 is a unicode locale
    std::locale l2("en_US.UTF-8");
    // l3 is "C" except for ctype, which is unicode
    std::locale l3(l1, l2, std::locale::ctype);
    // l4 is "C" except for codecvt
    std::locale l4(l1, new std::codecvt_utf8<wchar_t>);
 
    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: *

Defect reports

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