locale Class

 

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

class locale;  

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>  
codecvt<char16_t, char, mbstate_t>  
codecvt<char32_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.

Constructors

localeCreates a locale, or a copy of a locale, or a copy of locale where a facet or a category has been replaced by a facet or category from another locale.

Typedefs

categoryAn integer type that provides bitmask values to denote standard facet families.

Member Functions

combineInserts a facet from a specified locale into a target locale.
nameReturns the stored locale name.

Static Functions

classicThe static member function returns a locale object that represents the classic C locale.
globalResets the default local for the program.

Operators

operator!=Tests two locales for inequality.
operator( )Compares two basic_string objects.
operator==Tests two locales for equality.

Classes

facetA class that serves as the base class for all locale facets.
idThe member class provides a unique facet identification used as an index for looking up facets in a locale.

Header: <locale>

Namespace: std

An integer type that provides bitmask values to denote standard facet families.

typedef int category;  
static const int collate = LC_COLLATE;  
static const int ctype = LC_CTYPE;  
static const int monetary = LC_MONETARY;  
static const int numeric = LC_NUMERIC;  
static const int time = LC_TIME;  
static const int messages = LC_MESSAGES;  
static const int all = LC_ALL;  
static const int none = 0;  

Remarks

The type is a synonym for an int type that can represent a group of distinct elements of a bitmask type local to class locale or can be used to represent any of the corresponding C locale categories. The elements are:

  • collate, corresponding to the C category LC_COLLATE

  • ctype, corresponding to the C category LC_CTYPE

  • monetary, corresponding to the C category LC_MONETARY

  • numeric, corresponding to the C category LC_NUMERIC

  • time, corresponding to the C category LC_TIME

  • messages, corresponding to the Posix category LC_MESSAGES

In addition, two useful values are:

  • none, corresponding to none of the C categories

  • all, corresponding to the C union of all categories LC_ALL

You can represent an arbitrary group of categories by using OR with these constants, as in monetary | time.

The static member function returns a locale object that represents the classic C locale.

static const locale& classic();

Return Value

A reference to the C locale.

Remarks

The classic C locale is the U.S. English ASCII locale within the Standard C Library that is implicitly used in programs that are not internationalized.

Example

// locale_classic.cpp  
// compile with: /EHsc  
#include <iostream>  
#include <string>  
#include <locale>  
  
using namespace std;  
  
int main( )   
{  
   locale loc1( "german" );  
   locale loc2 = locale::global( loc1 );  
   cout << "The name of the previous locale is: " << loc2.name( )  
        << "." << endl;  
   cout << "The name of the current locale is: " << loc1.name( )   
        << "." << endl;  
  
   if (loc2 == locale::classic( ) )  
      cout << "The previous locale was classic." << endl;  
   else  
      cout << "The previous locale was not classic." << endl;  
  
   if (loc1 == locale::classic( ) )  
      cout << "The current locale is classic." << endl;  
   else  
      cout << "The current locale is not classic." << endl;  
}  

The name of the previous locale is: C.  
The name of the current locale is: German_Germany.1252.  
The previous locale was classic.  
The current locale is not classic.  

Inserts a facet from a specified locale into a target locale.

template <class Facet>  
locale combine(const locale& _Loc) const;

Parameters

_Loc
The locale containing the facet to be inserted into the target locale.

Return Value

The member function returns a locale object that replaces in or adds to *this the facet Facet listed in _Loc.

Example

// locale_combine.cpp  
// compile with: /EHsc  
#include <locale>  
#include <iostream>  
#include <tchar.h>  
using namespace std;  
  
int main() {  
   locale loc ( "German_germany" );  
   _TCHAR * s1 = _T("Das ist wei\x00dfzz."); // \x00df is the German sharp-s; it comes before z in the German alphabet  
   _TCHAR * s2 = _T("Das ist weizzz.");  
   int result1 = use_facet<collate<_TCHAR> > ( loc ).  
      compare (s1, &s1[_tcslen( s1 )-1 ],  s2, &s2[_tcslen( s2 )-1 ] );  
   cout << isalpha (_T ( '\x00df' ), loc ) << result1 << endl;  
  
   locale loc2 ( "C" );  
   int result2 = use_facet<collate<_TCHAR> > ( loc2 ).  
      compare (s1, &s1[_tcslen( s1 )-1 ],  s2, &s2[_tcslen( s2 )-1 ] );  
   cout << isalpha (_T ( '\x00df' ), loc2 )  << result2 << endl;  
  
   locale loc3 = loc2.combine<collate<_TCHAR> > (loc);  
   int result3 = use_facet<collate<_TCHAR> > ( loc3 ).  
      compare (s1, &s1[_tcslen( s1 )-1 ],  s2, &s2[_tcslen( s2 )-1 ] );  
   cout << isalpha (_T ( '\x00df' ), loc3 ) << result3 << endl;  
}  

A class that serves as the base class for all locale facets.

class facet { protected: explicit facet(size_t _Refs = 0); virtual ~facet(); private: facet(const facet&) // not defined void operator=(const facet&) // not defined };

Remarks

Note that you cannot copy or assign an object of class facet. You can construct and destroy objects derived from class locale::facet but not objects of the base class proper. Typically, you construct an object _Myfac derived from facet when you construct a locale, as in localeloc( locale::classic( ), new_Myfac);

In such cases, the constructor for the base class facet should have a zero _Refs argument. When the object is no longer needed, it is deleted. Thus, you supply a nonzero _ Refs argument only in those rare cases where you take responsibility for the lifetime of the object.

Resets the default locale for the program. This affects the global locale for both C and C++.

static locale global(const locale& _Loc);

Parameters

_Loc
The locale to be used as the default locale by the program.

Return Value

The previous locale before the default locale was reset.

Remarks

At program startup, the global locale is the same as the classic locale. The global() function calls setlocale( LC_ALL, loc.name. c_str()) to establish a matching locale in the Standard C library.

Example

// locale_global.cpp  
// compile by using: /EHsc  
#include <locale>  
#include <iostream>  
#include <tchar.h>  
using namespace std;  
  
int main( )  
{  
   locale loc ( "German_germany" );  
   locale loc1;  
   cout << "The initial locale is: " << loc1.name( ) << endl;  
   locale loc2 = locale::global ( loc );  
   locale loc3;  
   cout << "The current locale is: " << loc3.name( ) << endl;  
   cout << "The previous locale was: " << loc2.name( ) << endl;  
}  

The initial locale is: C  
The current locale is: German_Germany.1252  
The previous locale was: C  

The member class provides a unique facet identification used as an index for looking up facets in a locale.

class id { protected: id(); private: id(const id&) // not defined void operator=(const id&) // not defined };

Remarks

The member class describes the static member object required by each unique locale facet. Note that you cannot copy or assign an object of class id.

Creates a locale, or a copy of a locale, or a copy of locale where a facet or a category has been replaced by a facet or category from another locale.

locale();

explicit locale(
    const char* _Locname,  
    category _Cat = all);

explicit locale(
    const string& _Locname);

locale(
    const locale& _Loc);

locale(
    const locale& _Loc,   
    const locale& _Other,  
    category _Cat);

locale(
    const locale& _Loc,   
    const char* _Locname,  
    category _Cat);

template <class Facet>  
locale(
 const locale& _Loc,   
    const Facet* _Fac);

Parameters

_Locname
Name of a locale.

_Loc
A locale that is to be copied in constructing the new locale.

_Other
A locale from which to select a category.

_Cat
The category to be substituted into the constructed locale.

_Fac
The facet to be substituted into the constructed locale.

Remarks

The first constructor initializes the object to match the global locale. The second and third constructors initialize all the locale categories to have behavior consistent with the locale name _Locname. The remaining constructors copy _Loc, with the exceptions noted:

locale(const locale& _Loc, const locale& _Other, category _Cat);

replaces from _Other those facets corresponding to a category C for which C & _Cat is nonzero.

locale(const locale& _Loc, const char* _Locname, category _Cat);

locale(const locale& _Loc, const string& _Locname, category _Cat);

replaces from locale(_Locname, _All) those facets corresponding to a category C for which C & _Catis nonzero.

template<class Facet> locale(const locale& _Loc, Facet* _Fac);

replaces in (or adds to) _Loc the facet _Fac, if _Fac is not a null pointer.

If a locale name _Locname is a null pointer or otherwise invalid, the function throws runtime_error.

Example

// locale_locale.cpp  
// compile with: /EHsc  
#include <locale>  
#include <iostream>  
#include <tchar.h>  
using namespace std;  
  
int main( ) {  
  
   // Second constructor  
   locale loc ( "German_germany" );  
   _TCHAR * s1 = _T("Das ist wei\x00dfzz."); // \x00df is the German sharp-s, it comes before z in the German alphabet  
   _TCHAR * s2 = _T("Das ist weizzz.");  
   int result1 = use_facet<collate<_TCHAR> > ( loc ).  
      compare (s1, &s1[_tcslen( s1 )-1 ],  s2, &s2[_tcslen( s2 )-1 ] );  
   cout << isalpha (_T ( '\x00df' ), loc ) << result1 << endl;  
  
   // The first (default) constructor  
   locale loc2;  
   int result2 = use_facet<collate<_TCHAR> > ( loc2 ).  
      compare (s1, &s1[_tcslen( s1 )-1 ],  s2, &s2[_tcslen( s2 )-1 ] );  
   cout << isalpha (_T ( '\x00df' ), loc2 )  << result2 << endl;  
  
   // Third constructor  
   locale loc3 (loc2,loc, _M_COLLATE );  
   int result3 = use_facet<collate<_TCHAR> > ( loc3 ).  
      compare (s1, &s1[_tcslen( s1 )-1 ],  s2, &s2[_tcslen( s2 )-1 ] );  
   cout << isalpha (_T ( '\x00df' ), loc3 ) << result3 << endl;  
  
   // Fourth constructor  
   locale loc4 (loc2, "German_Germany", _M_COLLATE );  
   int result4 = use_facet<collate<_TCHAR> > ( loc4 ).  
      compare (s1, &s1[_tcslen( s1 )-1 ],  s2, &s2[_tcslen( s2 )-1 ] );  
   cout << isalpha (_T ( '\x00df' ), loc4 ) << result4 << endl;  
}  

Returns the stored locale name.

string name() const;

Return Value

A string giving the name of the locale.

Example

// locale_name.cpp  
// compile with: /EHsc  
#include <iostream>  
#include <string>  
#include <locale>  
  
using namespace std;  
  
int main( )   
{  
   locale loc1( "german" );  
   locale loc2 = locale::global( loc1 );  
   cout << "The name of the previous locale is: "   
        << loc2.name( ) << "." << endl;  
   cout << "The name of the current locale is: "   
        << loc1.name( ) << "." << endl;  
}  

The name of the previous locale is: C.  
The name of the current locale is: German_Germany.1252.  

Tests two locales for inequality.

bool operator!=(const locale& right) const;

Parameters

right
One of the locales to be tested for inequality.

Return Value

A Boolean value that is true if the locales are not copies of the same locale; false if the locales are copies of the same locale.

Remarks

Two locales are equal if they are the same locale, if one is a copy of the other, or if they have identical names.

Example

// locale_op_ne.cpp  
// compile with: /EHsc  
#include <iostream>  
#include <string>  
#include <locale>  
  
using namespace std;  
  
int main( )   
{  
   locale loc1( "German_Germany" );  
   locale loc2( "German_Germany" );  
   locale loc3( "English" );  
  
   if ( loc1 != loc2 )  
      cout << "locales loc1 (" << loc1.name( )  
      << ") and\n loc2 (" << loc2.name( ) << ") are not equal." << endl;  
   else  
      cout << "locales loc1 (" << loc1.name( )  
      << ") and\n loc2 (" << loc2.name( ) << ") are equal." << endl;  
  
   if ( loc1 != loc3 )  
      cout << "locales loc1 (" << loc1.name( )  
      << ") and\n loc3 (" << loc3.name( ) << ") are not equal." << endl;  
   else  
      cout << "locales loc1 (" << loc1.name( )  
      << ") and\n loc3 (" << loc3.name( ) << ") are equal." << endl;  
}  

locales loc1 (German_Germany.1252) and  
 loc2 (German_Germany.1252) are equal.  
locales loc1 (German_Germany.1252) and  
 loc3 (English_United States.1252) are not equal.  

Compares two basic_string objects.

template <class CharType, class Traits, class Allocator>  
bool operator()(
    const basic_string<CharType, Traits, Allocator>& left,  
    const basic_string<CharType, Traits, Allocator>& right) const;

Parameters

left
The left string.

right
The right string.

Return Value

The member function returns:

  • –1 if the first sequence compares less than the second sequence.

  • +1 if the second sequence compares less than the first sequence.

  • 0 if the sequences are equivalent.

Remarks

The member function effectively executes:

const collate<CharType>& fac = use_fac<collate<CharType>>(*this);

return (fac.compare(left.begin(), left.end(), right.begin(), right.end()) <0);

Thus, you can use a locale object as a function object.

Example

// locale_op_compare.cpp  
// compile with: /EHsc  
#include <iostream>  
#include <string>  
#include <locale>  
  
int main( )   
{  
   using namespace std;  
   wchar_t *sa = L"ztesting";  
   wchar_t *sb = L"\0x00DFtesting";  
   basic_string<wchar_t> a( sa );  
   basic_string<wchar_t> b( sb );  
  
   locale loc( "German_Germany" );  
   cout << loc( a,b ) << endl;  
  
   const collate<wchar_t>& fac = use_facet<collate<wchar_t> >( loc );  
   cout << ( fac.compare( sa, sa + a.length( ),  
       sb, sb + b.length( ) ) < 0) << endl;  
}  

0  
0  

Tests two locales for equality.

bool operator==(const locale& right) const;

Parameters

right
One of the locales to be tested for equality.

Return Value

A Boolean value that is true if the locales are copies of the same locale; false if the locales are not copies of the same locale.

Remarks

Two locales are equal if they are the same locale, if one is a copy of the other, or if they have identical names.

Example

// locale_op_eq.cpp  
// compile with: /EHsc  
#include <iostream>  
#include <string>  
#include <locale>  
  
using namespace std;  
  
int main( )   
{  
   locale loc1( "German_Germany" );  
   locale loc2( "German_Germany" );  
   locale loc3( "English" );  
  
   if ( loc1 == loc2 )  
      cout << "locales loc1 (" << loc1.name( )  
      << ")\n and loc2 (" << loc2.name( ) << ") are equal."   
      << endl;  
   else  
      cout << "locales loc1 (" << loc1.name( )  
      << ")\n and loc2 (" << loc2.name( ) << ") are not equal."   
      << endl;  
  
   if ( loc1 == loc3 )  
      cout << "locales loc1 (" << loc1.name( )  
      << ")\n and loc3 (" << loc3.name( ) << ") are equal."   
      << endl;  
   else  
      cout << "locales loc1 (" << loc1.name( )  
      << ")\n and loc3 (" << loc3.name( ) << ") are not equal."   
      << endl;  
}  

locales loc1 (German_Germany.1252)  
 and loc2 (German_Germany.1252) are equal.  
locales loc1 (German_Germany.1252)  
 and loc3 (English_United States.1252) are not equal.  

<locale>
Code Pages
Locale Names, Languages, and Country/Region Strings
Thread Safety in the C++ Standard Library

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