locale(3C++) - locale(3C++)
Standard C++ Library Copyright 1998, Rogue Wave Software, Inc.
NAMElocale
- A localization class containing a polymorphic set of facets.
SYNOPSIS
#include <locale>
class locale;
DESCRIPTIONlocale is a localization interface and a set of indexed facets, each of
which covers one particular localization issue. The default locale
object is constructed on the "C" locale. Locales can also be con‐
structed on named locales.
A calling program can determine whether a particular facet is contained
in a locale by using the has_facet function, and the program can obtain
a reference to that facet with the use_facet function. These are not
member functions, but instead take a locale object as an argument.
locale has several important characteristics.
First, successive calls to member functions always return the same
result. This allows a calling program to safely cache the results of a
call.
Only a locale constructed from a name, from parts of two named locales,
or from a stream, has a name. All other locales are unnamed. Only named
locales may be compared for equality. An unnamed locale is equal only
to itself.
INTERFACE
class locale {
public:
// types:
class facet;
class id;
typedef int category;
static const category none, collate, ctype, monetary,
numeric, time, messages,
all = collate | ctype | monetary |
numeric | time | messages;
// construct/copy/destroy:
locale()throw()
locale(const locale&) throw()
explicit locale(const char*);
locale(const locale&, const char*, category);
template <class Facet> locale(const locale&, Facet*);
locale(const locale&, const locale&, category);
~locale()throw(); // non-virtual
const locale& operator=(const locale&) throw();
template <class Facet> locale combine (const locale&);
// locale operations:
basic_string<char> name() const;
bool operator==(const locale&) const;
bool operator!=(const locale&) const;
template <class charT, class Traits, class Allocator>
bool operator()(const basic_string<charT,Traits,
Allocator>&,
const basic_string<charT,Traits,
Allocator>&)
const;
// global locale objects:
static locale global(const locale&);
static const locale& classic();
};
class locale::facet {
protected:
explicit facet(size_t refs = 0);
virtual ~facet();
private:
facet(const facet&); // not defined
void operator=(const facet&); // not defined
};
class locale::id {
public:id();
private:
void operator=(const id&); // not defined
id(const id&); // not defined
};
TYPES
category
Standard facets fall into eight broad categories. These are: none, collate,
ctype, monetary, numeric, time, messages, and all. all is a combination of
all the other categories except none. Bitwise operations may be applied to
combine or screen these categories. For instance, all is defined as:
(collate | ctype | monetary | numeric | time | messages)
locale member functions that take a category argument must be included with
one of the above values or with one of the constants from the old C locale
(for example, LC_CTYPE).
facet
Base class for facets. This class exists primarily to allow for reference
counting services to derived classes. All facets must derive from it,
either directly or indirectly (for example, facet -> ctype<char> ->
my_ctype).
If the refs argument to the constructor is 0, then destruction of the
object is delegated to the locale, or locales, containing it. This allows
the user to ignore lifetime management issues. On the other hand, if refs
is 1, then the object must be explicitly deleted; the locale does not do
so. In this case, the object can be maintained across the lifetime of mul‐
tiple locales.
Copy construction and assignment of this class are not allowed.
id
Type used to index facets in the locale container. Every facet must contain
a member of this type.
Copy construction and assignment of this type are not allowed.
CONSTRUCTORSlocale()throw()
Constructs a default locale object. This locale is the same as the last
argument passed to locale::global(), or, if that function has not been
called, the locale is the same as the classic "C" locale.
locale(const locale& other)throw()
Constructs a copy of the locale argument other.
explicit locale(const char* std_name);
Constructs a_locale object on the named locale indicated by std_name.
Throws a runtime_error exception if std_name is not a valid locale name.
locale(const locale& other, const char* std_name,
category cat);
Constructs a locale object that is a copy of other, except for the facets
that are in the category specified by cat. These facets are obtained from
the named locale identified by std_name. Throws a runtime_error exception
if std_name is not a valid locale name.
The resulting locale has a name only if other has a name.
template <class Facet>
locale(const locale& other, Facet* f);
Constructs a locale object that is a copy of other, except for the facet of
type Facet. Unless f is null, it is used to supply the missing facet. Oth‐
erwise the facet comes from other as well.
Note that the resulting locale does not have a name.
locale(const locale& other, const locale& one,
category cat);
Constructs a locale object that is a copy of other, except for facets that
are in the category specified by category argument cat. These missing
facets are obtained from the other locale argument, one.
Note that the resulting locale has a name only if both other and one have
names.
DESTRUCTORS
~locale();
Destroys the locale.
PUBLIC MEMBER OPERATORS
const locale&
operator=(const locale& other) throw();
Replaces *this with a copy of other. Returns *this.
template <class Facet>
locale combine(const locale& other);
Returns a locale object that is a copy of *this, except for the facet of
type Facet, which is taken from other. If other does not contain a facet of
type Facet, a runtime_error exception is thrown.
Note that the returned locale does not have a name.
booloperator==(const locale& other) const;
Returns true if both other and *this are the same object, if one is a copy
of another, or if both have the same name. Otherwise returns false.
booloperator!=(const locale& other) const;
Returns !(*this == other)
template <class charT,Traits>
booloperator()(const basic_string<charT,Traits>& s1,
const basic_string<charT,Traits>& s2) const;
This operator allows a locale object to be used as a comparison object for
comparing two strings. Returns the result of comparing the two strings
using the compare member function of the collate<charT> facet contained in
*this. Specifically, this function returns the following:
use_facet< collate<charT> >(*this).compare(s1.data(),
s1.data()+s1.size(), s2.data(),
s2.data()+s2.size()) < 0;
This allows a locale to be used with standard algorithms, such as sort, for
localized comparison of strings.
PUBLIC MEMBER FUNCTIONSbasic_string<char>
name() const;
Returns the name of this locale, if it has one; otherwise returns the
string "*".
STATIC PUBLIC MEMBER FUNCTIONS
static const locale&
classic();
Returns a locale with the semantics of the classic "C" locale.
static localeglobal(const locale& loc);
Sets the global locale to loc. This causes future uses of the default con‐
structor for locale to return a copy of loc. If loc has a name, this
function has the further effect of calling
std::setlocale(LC_ALL,loc.name().c_str());. Returns the previous
value of locale().
EXAMPLE
//
// locale.cpp
//
#include <string>
#include <vector>
#include <iostream>
#include "codecvte.h"
int main ()
{
using namespace std;
locale loc; // Default locale
// Construct new locale using default locale plus
// user defined codecvt facet
// This facet converts from ISO Latin
// Alphabet No. 1 (ISO 8859-1) to
// U.S. ASCII code page 437
// This facet replaces the default for
// codecvt<char,char,mbstate_t>
locale my_loc(loc,new ex_codecvt);
// imbue modified locale onto cout
locale old = cout.imbue(my_loc);
cout << "A \x93 jolly time was had by all" << endl;
cout.imbue(old);
cout << "A jolly time was had by all" << endl;
// Create a vector of strings
vector<string,allocator<void> > v;
v.insert(v.begin(),"antelope");
v.insert(v.begin(),"bison");
v.insert(v.begin(),"elk");
copy(v.begin(),v.end(),
ostream_iterator<string,char,
char_traits<char> >(cout," "));
cout << endl;
// Sort the strings using the locale as a comparitor
sort(v.begin(),v.end(),loc);
copy(v.begin(),v.end(),
ostream_iterator<string,char,
char_traits<char> >(cout," "));
cout << endl;
return 0;
}
SEE ALSO
facets, has_facet, use_facet, specific 'facet' reference_sections
Rogue Wave Software 02 Apr 1998 locale(3C++)