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Difference between revisions of "cpp/locale/locale/locale"

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< cpp‎ | locale‎ | locale
m (→‎Example: fmt)
m (→‎Example: "")
 
Line 102: Line 102:
  
 
     std::locale l3(l1, new std::codecvt_utf8<wchar_t>);
 
     std::locale l3(l1, new std::codecvt_utf8<wchar_t>);
−
     std::cout << "Name of 'C' locale except for codecvt: " << l3;
+
     std::cout << "Name of \"C\" locale except for codecvt: " << l3;
  
 
     std::locale l4(l1, l2, std::locale::ctype);
 
     std::locale l4(l1, l2, std::locale::ctype);
−
     std::cout << "Name of 'C' locale except for ctype, which is unicode:\n  " << l4;
+
     std::cout << "Name of \"C\" locale except for ctype, which is unicode:\n  " << l4;
 
}
 
}
 
|p=true
 
|p=true
Line 111: Line 111:
 
Name of a copy of the classic "C" locale: C
 
Name of a copy of the classic "C" locale: C
 
Name of unicode locale: en_US.UTF-8
 
Name of unicode locale: en_US.UTF-8
−
Name of 'C' locale except for codecvt: *
+
Name of "C" locale except for codecvt: *
−
Name of 'C' locale except for ctype, which is unicode:
+
Name of "C" locale except for ctype, which is unicode:
 
   LC_CTYPE=en_US.UTF-8;
 
   LC_CTYPE=en_US.UTF-8;
 
   LC_NUMERIC=C;
 
   LC_NUMERIC=C;

Latest revision as of 17:51, 21 October 2024

 
C++
 
Localization library
 
std::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.

Contents

[edit] 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

[edit] 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.

[edit] 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.

[edit] Example

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

Possible output: 

Name of a copy of the classic "C" locale: C
Name of unicode locale: en_US.UTF-8
Name of "C" locale except for codecvt: *
Name of "C" locale except for ctype, which is unicode:
  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

[edit] Defect reports

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

DR Applied to Behavior as published Correct behavior
LWG 436 C++98 for overload (7), it was unclear
whether Facet can be cv-qualified 		it can be const-qualified,
but not volatile-qualified
LWG 2295 C++98 for overload (7), the constructed locale had no name even if f is null it has the name of other

[edit] See also

 destructs the locale and the facets whose reference count becomes zero
(public member function) [edit]

[edit] External links

1.  List of Windows locale names.
2.  List of Linux locale names.
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