______________________________________________________________________
22 Localization library [lib.localization]
______________________________________________________________________
1 This clause describes components that C++ programs may use to encapsu
late (and therefore be more portable when confronting) cultural dif
ferences. The locale facility includes internationalization support
for character classification and string collation, numeric, monetary,
and date/time formatting and parsing, and message retrieval.
2 The following subclauses describe components for locales themselves,
the standard facets, and facilities from the ISO C library, as summa
rized in Table 1:
Table 1--Localization library summary
+---------------------------------------------------------------+
| Subclause Header(s) |
+---------------------------------------------------------------+
|_lib.locales_ Locales <locale> |
|_lib.locale.categories_ Standard locale Categories |
+---------------------------------------------------------------+
|_lib.c.locales_ C library locales <clocale> |
+---------------------------------------------------------------+
22.1 Locales [lib.locales]
Header <locale> synopsis
#include <limits>
#include <string>
#include <iosfwd>
#include <stdexcept> // for runtime_error
namespace std {
// subclause _lib.locale_, locale:
class locale;
template <class Facet> const Facet& use_facet(const locale&);
template <class Facet> bool has_facet(const locale&) throw();
template <class charT, class Traits>
basic_ostream<charT,Traits>&
operator<<(basic_ostream<charT,Traits>& s, const locale& loc);
template <class charT, class Traits>
basic_istream<charT,Traits>&
operator>>(basic_istream<charT,Traits>& s, locale& loc);
// subclause _lib.locale.convenience_, convenience interfaces:
template <class charT> bool isspace (charT c, const locale& loc) const;
template <class charT> bool isprint (charT c, const locale& loc) const;
template <class charT> bool iscntrl (charT c, const locale& loc) const;
template <class charT> bool isupper (charT c, const locale& loc) const;
template <class charT> bool islower (charT c, const locale& loc) const;
template <class charT> bool isalpha (charT c, const locale& loc) const;
template <class charT> bool isdigit (charT c, const locale& loc) const;
template <class charT> bool ispunct (charT c, const locale& loc) const;
template <class charT> bool isxdigit(charT c, const locale& loc) const;
template <class charT> bool isalnum (charT c, const locale& loc) const;
template <class charT> bool isgraph (charT c, const locale& loc) const;
template <class charT> charT toupper(charT c, const locale& loc) const;
template <class charT> charT tolower(charT c, const locale& loc) const;
// subclauses _lib.category.ctype_ and _lib.facet.ctype.special_, ctype:
class ctype_base;
template <class charT> class ctype;
class ctype<char>; // specialization
template <class charT> class ctype_byname;
class ctype_byname<char>; // specialization
class codecvt_base;
template <class fromT, class toT, class stateT> class codecvt;
template <class fromT, class toT, class stateT> class codecvt_byname;
// subclauses _lib.category.numeric_ and _lib.facet.numpunct_, numeric:
template <class charT, class InputIterator> class num_get;
template <class charT, class OutputIterator> class num_put;
template <class charT> class numpunct;
template <class charT> class numpunct_byname;
// subclause _lib.category.collate_, collation:
template <class charT> class collate;
template <class charT> class collate_byname;
// subclause _lib.category.time_, date and time:
class time_base;
template <class charT, class InputIterator> class time_get;
template <class charT, class InputIterator> class time_get_byname;
template <class charT, class OutputIterator> class time_put;
template <class charT, class OutputIterator> class time_put_byname;
// subclauses _lib.category.monetary_, money:
class money_base;
template <class charT, class InputIterator, bool Intl> class money_get;
template <class charT, class OutputIterator, bool Intl> class money_put;
template <class charT, bool Intl> class moneypunct;
template <class charT, bool Intl> class moneypunct_byname;
// subclause _lib.category.messages_, message retrieval:
class messages_base;
template <class charT> class messages;
template <class charT> class messages_byname;
}
1 The header <locale> defines classes and declares functions that encap
sulate and manipulate the information peculiar to a locale.1)
_________________________
1) In this subclause, the type name struct tm is an incomplete type
that is defined in <ctime>.
22.1.1 Class locale [lib.locale]
namespace std {
class locale {
public:
// types:
class facet;
class id;
typedef int category;
static const category // values assigned here are for exposition only
none = 0,
collate = 0x010, ctype = 0x020,
monetary = 0x040, numeric = 0x080,
time = 0x100, messages = 0x200,
all = collate | ctype | monetary | numeric | time | messages;
// construct/copy/destroy:
locale() throw()
locale(const locale& other) throw()
explicit locale(const char* std_name);
locale(const locale& other, const char* std_name, category);
template <class Facet> locale(const locale& other, Facet* f);
template <class Facet> locale(const locale& other,
const locale& one);
locale(const locale& other, const locale& one, category);
~locale() throw(); // non-virtual
const locale& operator=(const locale& other) throw();
// locale operations:
basic_string<char> name() const;
bool operator==(const locale& other) const;
bool operator!=(const locale& other) const;
template <class charT,Traits>
bool operator()(const basic_string<charT,Traits>& s1,
const basic_string<charT,Traits>& s2) const;
// global locale objects:
static locale global(const locale&);
static const locale& classic();
static locale transparent();
};
}
1 Class locale implements a type-safe polymorphic set of facets, indexed
by facet type. In other words, a facet has a dual role: in one sense,
it's just a class interface; at the same time, it's an index into a
locale's set of facets.
2 Access to the facets of a locale is via two member function templates,
use_facet<> and has_facet<>.
3 [Example: An iostream operator<< might be implemented as:2)
_________________________
2) Notice that, in the call to put, the stream is implicitly converted
to an ostreambuf_iterator<charT,traits>.
template <class charT, class traits>
basic_ostream<charT,traits>&
operator<< (basic_ostream<charT,traits>& s, Date d)
{
typename basic_ostream<charT,traits>::sentry cerberos;
if (cerberos) {
ios_base::iostate err = 0;
tm tmbuf; d.extract(tmbuf);
use_facet< time_put<charT,ostreambuf_iterator<charT,traits> > >(
s.getloc()).put(s, s, s.fill(), err, &tmbuf, 'x');
s.setstate(err); // might throw
}
return s;
}
--end example]
4 In the call to use_facet<Facet>(loc), the type argument chooses a
facet, making available all members of the named type. If Facet is not
present in a locale (or, failing that, in the global locale), it
throws the standard exception bad_cast. A C++ program can check if a
locale implements a particular facet with the template function
has_facet<Facet>(). User-defined facets may be installed in a locale,
and used identically as may standard facets (_lib.facets.examples_).
5 [Note: All locale semantics are accessed via use_facet<> and
has_facet<>, except that:
--A member operator template operator()(basic_string<C,T>&,
basic_string<C,T>&) is provided so that a locale may be used as a
predicate argument to the standard collections, to collate strings.
--Convenient global interfaces are provided for traditional ctype
functions such as isdigit() and isspace(), so that given a locale
object loc a C++ program can call isspace(c,loc). (This eases
upgrading existing extractors (_lib.istream.formatted_).) --end
note]
6 A locale which does not implement a facet delegates to the global
locale in effect at the time that instantiation of use_facet<> is
first called on that facet (_lib.locale.statics_).
7 An instance of locale is immutable; once a facet reference is obtained
from it, that reference remains usable as long as the locale value
itself exists. The effect of imbuing on a stream (_lib.ios.base_,
_lib.ios_), or installing as the global locale, the result of static
member locale::transparent() (or any locale with similar behavior) is
unspecified.
8 Caching results from calls to locale facet member functions during
calls to iostream inserters and extractors, and in streambufs between
calls to basic_streambuf::imbue, is explicitly supported
(_lib.streambuf_).3)
_________________________
3) This implies that member functions of iostream classes cannot safe
9 A locale constructed from a name string (such as "POSIX"), or from
parts of two named locales, or read from a stream, has a name; all
others do not. Named locales may be compared for equality; an unnamed
locale is equal only to (copies of) itself. For an unnamed locale,
locale::name() returns the string *".
22.1.1.1 locale types [lib.locale.types]
22.1.1.1.1 Type locale::category [lib.locale.category]
typedef int category;
1 Valid category values include the locale member bitmask elements none,
collate, ctype, monetary, numeric, time, and messages. In addition,
locale member all is defined such that the expression
(collate | ctype | monetary | numeric | time | messages | all) == all
is true. Further, the result of applying operators | and & to any two
valid values is valid, and results in the setwise union and intersec
tion, respectively, of the argument categories.
2 locale member functions expecting a category argument require either a
valid category value or one of the constants LC_CTYPE etc., defined in
<cctype>. Such a category value identifies a set of locale cate
gories. Each locale category, in turn, identifies a set of locale
facets, including at least those shown in Table 2:
_________________________
ly call imbue() themselves, except as specified elsewhere.
Table 2--Locale Category Facets
+------------------------------------------------------------+
|Category Includes Facets |
+------------------------------------------------------------+
|collate collate<char>, collate<wchar_t> |
+------------------------------------------------------------+
|ctype ctype<char>, ctype<wchar_t> |
| codecvt<char,char,mbstate_t>, |
| codecvt<char,wchar_t,mbstate_t>, |
| codecvt<wchar_t,char,mbstate_t> |
+------------------------------------------------------------+
|monetary moneypunct<char>, moneypunct<wchar_t> |
| moneypunct<char,true>, moneypunct<wchar_t,true>, |
| money_get<char>, money_get<wchar_t> |
| money_get<char,true>, money_get<wchar_t,true> |
| money_put<char>, money_put<wchar_t> |
| money_put<char,true>, money_put<wchar_t,true> |
+------------------------------------------------------------+
|numeric numpunct<char>, numpunct<wchar_t>, |
| num_get<char>, num_get<wchar_t> |
| num_put<char>, num_put<wchar_t> |
+------------------------------------------------------------+
|time time_get<char>, time_put<wchar_t>, |
| time_put<char>, time_put<wchar_t> |
+------------------------------------------------------------+
|messages messages<char>, messages<wchar_t> |
+------------------------------------------------------------+
+------- BEGIN BOX 1 -------+
Change: Added money_get<char,true>, money_get<wchar_t,true>,
money_put<char,true>, and money_put<wchar_t,true>. (The WG has
elected not to change the signatures of the money_get and money_put
facets and member functions.)
+------- END BOX 1 -------+
3 For any locale loc either constructed, or returned by
locale::classic(), and any facet Facet that is a member of a standard
category, has_facet<Facet>(loc) is true. Each locale member function
which takes a locale::category argument operates on the corresponding
set of facets.
4 An implementation is required to provide those instantiations for
facet templates identified as members of a category, and for those
shown in Table 3:
Table 3--Required Instantiations
+---------------------------------------------------------------+
|Category Includes Facets |
+---------------------------------------------------------------+
|collate collate_byname<char>, collate_byname<wchar_t> |
+---------------------------------------------------------------+
|ctype ctype_byname<char>, ctype_byname<wchar_t> |
+---------------------------------------------------------------+
|monetary moneypunct_byname<char,International>, |
| moneypunct_byname<wchar_t,International>, |
| money_get<char,International,InputIterator>, |
| money_get<wchar_t,International,InputIterator>, |
| money_put<char,International,OutputIterator>, |
| money_put<wchar_t,International,OutputIterator> |
+---------------------------------------------------------------+
|numeric numpunct_byname<char>, numpunct_byname<wchar_t> |
| num_get<C,InputIterator>, num_put<C,OutputIterator> |
+---------------------------------------------------------------+
|time time_get<char,InputIterator>, |
| time_get_byname<char,InputIterator>, |
| time_get<wchar_t,OutputIterator>, |
| time_get_byname<wchar_t,OutputIterator>, |
| time_put<char,OutputIterator>, |
| time_put_byname<char,OutputIterator>, |
| time_put<wchar_t,OutputIterator> |
| time_put_byname<wchar_t,OutputIterator> |
+---------------------------------------------------------------+
5 For the facets num_get<> and num_put<> the implementation provided
must depend only on the corresponding facets numpunct<> and ctype<>,
instantiated on the same character type. Other facets are allowed to
depend on any other facet that is part of a standard category.
6 In declarations of facets, a template formal parameter with name
InputIterator or OutputIterator indicates the set of all possible
instantiations on parameters that satisfy the requirements of an Input
Iterator or an Output Iterator, respectively
(_lib.iterator.requirements_). A template formal parameter with name
C represents the set of all possible instantiations on a parameter
that satisfies the requirements for a character on which any of the
iostream components can be instantiated.
22.1.1.1.2 Class locale::facet [lib.locale.facet]
namespace std {
class locale::facet {
protected:
explicit facet(size_t refs = 0);
virtual ~facet();
private:
facet(const facet&); // not defined
void operator=(const facet&); // not defined
};
}
1 Class facet is the base class for locale feature sets. A class is a
facet if it is publicly derived from another facet, or if it is a
class derived from locale::facet and containing a declaration as fol
lows:
static ::std::locale::id id;
Template parameters in this Clause which must be facets are those
named Facet in declarations. A program that passes a type that is not
a facet, as an (explicit or deduced) template parameter to a locale
function expecting a facet, is ill-formed.
2 The refs argument to the constructor is used for lifetime management.
--If (refs == 0) the facet's lifetime is managed by the locale or
locales it is incorporated into;
--if (refs == 1) its lifetime is until explicitly deleted.
3 Constructors of all facets defined in this Clause take such an argu
ment and pass it along to their facet base class constructor. All
one-argument constructors defined in this clause are explicit, pre
venting their participation in automatic conversions.
4 For some standard facets a standard _byname" class, derived from it,
implements the virtual function semantics equivalent to that facet of
the locale constructed by locale(const char*) with the same name.
Each such facet provides a constructor that takes a const char* argu
ment, which names the locale, and a refs argument, which is passed to
the base class constructor. If there is no _byname" version of a
facet, the base class implements named locale semantics itself by ref
erence to other facets.
22.1.1.1.3 Class locale::id [lib.locale.id]
namespace std {
class locale::id {
public:
id();
private:
void operator=(const id&); // not defined
id(const id&); // not defined
};
}
1 The class locale::id provides identification of a locale facet inter
faces, used as an index for lookup and to encapsulate initialization.
2 [Note: Because facets are used by iostreams, potentially while static
constructors are running, their initialization cannot depend on pro
grammed static initialization. One initialization strategy is for
locale to initialize each facet's id member the first time an instance
of the facet is installed into a locale. This depends only on static
storage being zero before constructors run (_basic.start.init_).
--end note]
22.1.1.2 locale constructors and destructor [lib.locale.cons]
locale() throw();
1 Default constructor: a snapshot of the current global locale.
Effects:
Constructs a copy of the argument last passed to
locale::global(locale&), if it has been called; else, the resulting
facets have virtual function semantics identical to those of
locale::classic(). [Note: This constructor is commonly used as the
default value for arguments of functions that take a const locale&
argument. --end note]
locale(const locale& other) throw();
Effects:
Constructs a locale which is a copy of other.
const locale& operator=(const locale& other) throw();
Effects:
Creates a copy of other, replacing the current value.
Returns:
*this
explicit locale(const char* std_name);
Effects:
Constructs a locale using standard C locale names, e.g. "POSIX".
The resulting locale implements semantics defined to be associated
with that name. Throws runtime_error if the argument is not valid.
Notes:
The set of valid string argument values is "C", "", and any imple
mentation-defined values.
locale(const locale& other, const char* std_name, category);
Effects:
Constructs a locale as a copy of other except for the facets identi
fied by the category argument, which instead implement the same
semantics as locale(std_name).
Notes:
The locale has a name if and only if other has a name.
template <class Facet> locale(const locale& other, Facet* f);
Effects:
Constructs a locale incorporating all facets from the first argument
except that of type Facet, and installs the second argument as the
remaining facet.
Notes:
The resulting locale has no name.
+------- BEGIN BOX 2 -------+
Editorial proposal: What if the pointer parameter is 0? Recommend:
Throw runtime_error.
+------- END BOX 2 -------+
template <class Facet> locale(const locale& other, const locale& one);
Effects:
Constructs a locale incorporating all facets from the first argument
except that identified by Facet, and that facet from the second
argument instead.
Throws:
runtime_error if has_facet<Facet>(one) is false.
Notes:
The resulting locale has no name.
locale(const locale& other, const locale& one, category cats);
Effects:
Constructs a locale incorporating all facets from the first argument
except those that implement cats, which are instead incorporated
from the second argument.
Notes:
The resulting locale has a name if and only if the first two argu
ments have names.
~locale() throw();
2 A non-virtual destructor that throws no exceptions.
22.1.1.3 locale members [lib.locale.members]
basic_string<char> name() const;
Returns:
The name of *this, if it has one; otherwise, the string "*".
22.1.1.4 locale operators [lib.locale.operators]
bool operator==(const locale& other) const;
Returns:
true if both arguments are the same locale, or one is a copy of the
other, or each has a name and the names are identical; false other
wise.
bool operator!=(const locale& other) const;
Returns:
The result of the expression: !(*this == other)
template <class charT, class Traits>
bool operator()(const basic_string<charT,Traits>& s1,
const basic_string<charT,Traits>& s2) const;
Effects:
Compares two strings according to the collate<charT> facet.
Notes:
This member operator template (and therefore locale itself) satis
fies requirements for a comparator predicate template argument
(_lib.algorithms_) applied to strings.
Returns:
The result of the following expression:
use_facet< collate<charT> >(*this).compare(s1.data(), s1.data()+s1.size(),
s2.data(), s2.data()+s2.size()) < 0;
1 [Example: A vector of strings v can be collated according to collation
rules in locale loc simply by (_lib.alg.sort_, _lib.vector_):
std::sort(v.begin(), v.end(), loc);
--end example]
22.1.1.5 locale static members [lib.locale.statics]
static locale global(const locale& loc);
1 Sets the global locale to its argument.
Effects:
Causes future calls to the constructor locale() to return a copy of
the argument. If the argument has a name, does
std::setlocale(LC_ALL, loc.name().c_str());
otherwise, the effect on the C locale, if any, is implementation-
defined. If the argument is (a copy of) the value returned by
locale::transparent(), throws runtime_error.
Returns:
The previous value of locale().
static const locale& classic();
2 The "C" locale.
Returns:
A locale that implements the classic "C" locale semantics, equiva
lent to the value locale("C").
Notes:
This locale, its facets, and their member functions, do not change
with time.
static locale transparent();
3 The continuously updated global locale.
Returns:
A locale which implements semantics that vary dynamically as the
global locale is changed.
Notes:
The effect of imbuing this locale into an iostreams component is
unspecified (_lib.ios.members_).
22.1.2 locale globals [lib.locale.global.templates]
template <class Facet> const Facet& use_facet(const locale& loc);
1 Get a reference to a facet of a locale.
Effects:
If the requested Facet is not present in loc, but is present in the
current global locale, returns the global locale's instance of
Facet. Because locale objects are immutable, subsequent calls to
use_facet<Facet>(loc) return the same object, regardless of subse
quent calls to setlocale or locale::global.
Notes:
The only exception to this rule is for the locale returned by
locale::transparent(); it always returns the facet found in the
global locale at the time of each call.
Throws:
bad_cast if (has_facet<Facet>(*this) || has_facet<Facet>(locale()))
is false, or other unspecified objects catchable as exception.
Returns:
A reference to the requested facet.
Notes:
The result is guaranteed by locale's value semantics to last as long
as the value of loc.
+------- BEGIN BOX 3 -------+
Is bad_cast the best choice of exceptions to throw?
+------- END BOX 3 -------+
template <class Facet> bool has_facet(const locale& loc) throw();
Returns:
An indication whether the facet requested is present in loc. If
use_facet<Facet>(loc) has already been called successfully, returns
true.
Notes:
has_facet<Facet>(locale::transparent()) always returns false.
template <class charT, class Traits>
basic_ostream<charT,Traits>&
operator<<(basic_ostream<charT,Traits>& s, const locale& loc);
2 The regular stream output operator for locales
(_lib.ostream.formatted_).
Effects:
s << loc.name() << endl.
Returns:
The output stream argument s.
template <class charT, class Traits>
basic_istream<charT,Traits>&
operator>>(basic_istream<charT,Traits>& s, locale& loc);
3 The regular stream input operator for locales
(_lib.istream.formatted_).
Effects:
Read a line into a string and construct a locale from it. If either
operation fails, indicates a failure by calling
s.setstate(ios_base::failbit) (which may throw ios_base::failure
(_lib.iostate.flags_), otherwise, assigns the constructed locale
object into the argument loc.
Returns:
s.
22.1.3 Convenience interfaces [lib.locale.convenience]
22.1.3.1 Character classification [lib.classification]
template <class charT> bool isspace (charT c, const locale& loc) const;
template <class charT> bool isprint (charT c, const locale& loc) const;
template <class charT> bool iscntrl (charT c, const locale& loc) const;
template <class charT> bool isupper (charT c, const locale& loc) const;
template <class charT> bool islower (charT c, const locale& loc) const;
template <class charT> bool isalpha (charT c, const locale& loc) const;
template <class charT> bool isdigit (charT c, const locale& loc) const;
template <class charT> bool ispunct (charT c, const locale& loc) const;
template <class charT> bool isxdigit(charT c, const locale& loc) const;
template <class charT> bool isalnum (charT c, const locale& loc) const;
template <class charT> bool isgraph (charT c, const locale& loc) const;
1 Each of these functions isF returns the result of the expression:
use_facet< ctype<charT> >(loc).is(ctype_base::F, c)
where F is the ctype_base::mask value corresponding to that function
(_lib.category.ctype_).4)
22.1.3.2 Character conversions [lib.conversions]
template <class charT> charT toupper(charT c, const locale& loc) const;
Returns:
use_facet<ctype<charT> >(loc).toupper(c).
template <class charT> charT tolower(charT c, const locale& loc) const;
Returns:
use_facet<ctype<charT> >(loc).tolower(c).
22.2 Standard locale categories [lib.locale.categories]
1 Each of the standard categories includes a family of facets. Some of
these implement formatting or parsing of a datum, for use by standard
or users' iostream operators << and >>, as members put() and get(),
respectively. Each such member function takes an ios_base& argument
whose members flags(), precision(), and width(), specify the format of
the corresponding datum. (_lib.ios.base_). Those functions which
need to use other facets call its member getloc() to retrieve the
locale imbued there. Formatting facets use the character argument
fill to fill out the specified width where necessary.
_________________________
4) When used in a loop, it is faster to cache the ctype<> facet and
use it directly, or use the vector form of ctype<>::is.
2
+------- BEGIN BOX 4 -------+
Editorial Proposal: If clear() and setstate() are moved to ios_base,
we should add:
The put() and get() members do not use rdstate(), setstate(), or
related members of the ios_base& argument.
+------- END BOX 4 -------+
The put() members make no provision for error reporting. (Any fail
ures of the OutputIterator argument must be extracted from the
returned iterator.) The get() members take an ios_base::iostate&
argument whose value they ignore, but set to ios_base::failbit in case
of a parse error.
22.2.1 The ctype category [lib.category.ctype]
namespace std {
class ctype_base {
public:
enum mask { // numeric values are for exposition only.
space=1<<0, print=1<<1, cntrl=1<<2, upper=1<<3, lower=1<<4,
alpha=1<<5, digit=1<<6, punct=1<<7, xdigit=1<<8,
alnum=alpha|digit, graph=alnum|punct
};
};
}
1 The type mask is a bitmask type.
22.2.1.1 Template class ctype [lib.locale.ctype]
template <class charT>
class ctype : public locale::facet, public ctype_base {
public:
typedef charT char_type;
explicit ctype(size_t refs = 0);
bool is(mask m, charT c) const;
const charT* is(const charT* low, const charT* high, mask* vec) const;
const charT* scan_is(mask m,
const charT* low, const charT* high) const;
const charT* scan_not(mask m,
const charT* low, const charT* high) const;
charT toupper(charT) const;
const charT* toupper(charT* low, const charT* high) const;
charT tolower(charT c) const;
const charT* tolower(charT* low, const charT* high) const;
charT widen(char c) const;
const char* widen(const char* low, const char* high, charT* to) const;
char narrow(charT c, char dfault) const;
const charT* narrow(const charT* low, const charT*, char dfault,
char* to) const;
static locale::id id;
protected:
~ctype(); // virtual
virtual bool do_is(mask m, charT c) const;
virtual const charT* do_is(const charT* low, const charT* high,
mask* vec) const;
virtual const charT* do_scan_is(mask m,
const charT* low, const charT* high) const;
virtual const charT* do_scan_not(mask m,
const charT* low, const charT* high) const;
virtual charT do_toupper(charT) const;
virtual const charT* do_toupper(charT* low, const charT* high) const;
virtual charT do_tolower(charT) const;
virtual const charT* do_tolower(charT* low, const charT* high) const;
virtual charT do_widen(char) const;
virtual const char* do_widen(const char* low, const char* high,
charT* dest) const;
virtual char do_narrow(charT, char dfault) const;
virtual const charT* do_narrow(const charT* low, const charT* high,
char dfault, char* dest) const;
};
+------- BEGIN BOX 5 -------+
Change: Changed return type of do_scan_is and do_scan_not to const
charT* to match the semantic description of the function.
+------- END BOX 5 -------+
1 Class ctype encapsulates the C library <cctype> features. istream
members are required to use ctype<> for character classing during
input parsing.
2 The base class implementation implements character classing appropri
ate to the implementation's native character set.
22.2.1.1.1 ctype members [lib.locale.ctype.members]
bool is(mask m, charT c) const;
const charT* is(const charT* low, const charT* high,
mask* vec) const;
Returns:
do_is(m,c) or do_is(low,high,vec)
const charT* scan_is(mask m,
const charT* low, const charT* high) const;
Returns:
do_scan_is(m,low,high)
const charT* scan_not(mask m,
const charT* low, const charT* high) const;
Returns:
do_scan_not(m,low,high)
charT toupper(charT) const;
const charT* toupper(charT* low, const charT* high) const;
Returns:
do_toupper(c) or do_toupper(low,high)
charT tolower(charT c) const;
const charT* tolower(charT* low, const charT* high) const;
Returns:
do_tolower(c) or do_tolower(low,high)
charT widen(char c) const;
const char* widen(const char* low, const char* high, charT* to) const;
Returns:
do_widen(c) or do_widen(low,high,to)
char narrow(charT c, char dfault) const;
const charT* narrow(const charT* low, const charT*, char dfault,
char* to) const;
Returns:
do_narrow(c,dfault) or do_narrow(low,high,dfault,to)
22.2.1.1.2 ctype virtual functions [lib.locale.ctype.virtuals]
bool do_is(mask m, charT c) const;
const charT* do_is(const charT* low, const charT* high,
mask* vec) const;
Effects:
Classifies a character or sequence of characters. For each argument
character, identifies a value M of type ctype_base::mask. The sec
ond form places M for all *p where (low<=p && p<high), into vec[p-
low].
Returns:
The first form returns the result of the expression (M & m) != 0;
i.e., true if the character has the characteristics specified. The
second form returns high.
const charT* do_scan_is(mask m,
const charT* low, const charT* high) const;
Effects:
Locates a character in a buffer that conforms to a classification m.
Returns:
The smallest pointer p in the range [low, high) such that is(*p)
would return true; otherwise, returns high.
const charT* do_scan_not(mask m,
const charT* low, const charT* high) const;
Effects:
Locates a character in a buffer that fails to conform to a classifi
cation m.
Returns:
The smallest pointer p, if any, in the range [low, high) such that
is(*p) would return false; otherwise, returns high.
charT do_toupper(charT c) const;
const charT* do_toupper(charT* low, const charT* high) const;
Effects:
Converts a character or characters to upper case. The second form
replaces each character *p in the range [low, high) for which a cor
responding upper-case character exists, with that character.
Returns:
The first form returns the corresponding upper-case character if it
is known to exist, or its argument if not. The second form returns
high.
charT do_tolower(charT c) const;
const charT* do_tolower(charT* low, const charT* high) const;
Effects:
Converts a character or characters to upper case. The second form
replaces each character *p in the range [low, high) and for which a
corresponding lower-case character exists, with that character.
Returns:
The first form returns the corresponding lower-case character if it
is known to exist, or its argument if not. The second form returns
high.
charT do_widen(char c) const;
const char* do_widen(const char* low, const char* high,
charT* dest) const;
Effects:
Applies the simplest reasonable transformation from a char value or
sequence of char values to the corresponding charT value or values.
The only characters for which unique transformations are required
are the digits, alphabetic characters, '-', '+', newline, and space.
For any named ctype category with a ctype<charT> facet ctw and valid
ctype_base::mask value M (is(M, c) || !ctw.is(M, do_widen(c)) ) is
true.5)
The second form transforms each character *p in the range [low,
high), placing the result in dest[p-low].
Returns:
The first form returns the transformed value. The second form
returns high.
char do_narrow(charT c, char dfault) const;
const charT* do_narrow(const charT* low, const charT* high,
char dfault, char* dest) const;
Effects:
Applies the simplest reasonable transformation from a charT value or
sequence of charT values to the corresponding char value or values.
The only characters for which unique transformations are required
are the digits, alphabetic characters, '-', '+', newline, and space.
For any named ctype category with a ctype<char> facet ctc however,
and ctype_base::mask value M,
(is(M,c) || !ctc.is(M, do_narrow(c),dfault) )"
is true (unless do_narrow returns dfault). In addition, for any
digit character c, the expression (do_narrow(c,dfault)-'0') evalu
ates to the digit value of the character. The second form trans
forms each character *p in the range [low, high), placing the result
(or dfault if no simple transformation is readly available) in
dest[p-low].
Returns:
The first form returns the transformed value; or dfault if no map
ping is readily available. The second form returns high.
22.2.1.2 Template class ctype_byname [lib.locale.ctype.byname]
_________________________
5) In other words, the transformed character is not a member of any
character classification that c is not also a member of.
template <class charT>
class ctype_byname : public ctype<charT> {
public:
explicit ctype_byname(const char*, size_t refs = 0);
protected:
~ctype_byname(); // virtual
virtual bool do_is(mask m, charT c) const;
virtual const charT* do_is(const charT* low, const charT* high,
mask* vec) const;
virtual const char* do_scan_is(mask m,
const charT* low, const charT* high) const;
virtual const char* do_scan_not(mask m,
const charT* low, const charT* high) const;
virtual charT do_toupper(charT) const;
virtual const charT* do_toupper(charT* low, const charT* high) const;
virtual charT do_tolower(charT) const;
virtual const charT* do_tolower(charT* low, const charT* high) const;
virtual charT do_widen(char) const;
virtual const char* do_widen(const char* low, const char* high,
charT* dest) const;
virtual char do_narrow(charT, char dfault) const;
virtual const charT* do_narrow(const charT* low, const charT* high,
char dfault, char* dest) const;
};
}
22.2.1.3 ctype specializations [lib.facet.ctype.special]
namespace std {
class ctype<char> : public locale::facet, public ctype_base {
public:
typedef char char_type;
explicit ctype(const mask* tab = 0, bool del = false,
size_t refs = 0);
bool is(mask m, char c) const;
const char* is(const char* low, const char* high, mask* vec) const;
const char* scan_is (mask m,
const char* low, const char* high) const;
const char* scan_not(mask m,
const char* low, const char* high) const;
char toupper(char c) const;
const char* toupper(char* low, const char* high) const;
char tolower(char c) const;
const char* tolower(char* low, const char* high) const;
char widen(char c) const;
const char* widen(const char* low, const char* high, char* to) const;
char narrow(char c, char dfault) const;
const char* narrow(const char* low, const char* high, char dfault,
char* to) const;
static locale::id id;
protected:
const mask* table() const throw();
static const mask* classic_table() throw();
~ctype(); // virtual
virtual char do_toupper(char) const;
virtual const char* do_toupper(char* low, const char* high) const;
virtual char do_tolower(char) const;
virtual const char* do_tolower(char* low, const char* high) const;
};
}
1 A specialization ctype<char> is provided so that the member functions
on type char can be implemented inline.6)
22.2.1.3.1 ctype<char> destructor [lib.facet.ctype.char.dtor]
~ctype();
Effects:
If the constructor's first argument was nonzero, and its second
argument was true, does delete [] table().
22.2.1.3.2 ctype<char> members [lib.facet.ctype.char.members]
explicit ctype(const mask* tab = 0, bool del = false,
size_t refs = 0);
Effects:
Passes its refs argument to its base class constructor.
bool is(mask m, char c) const;
const char* is(const char* low, const char* high,
mask* vec) const;
Effects:
The second form, for all *p in the range [low, high), assigns vec[p-
low] to table()[(unsigned char)*p].
Returns:
The first form returns table()[(unsigned char)c] & m; the second
form returns high.
const char* scan_is(mask m,
const char* low, const char* high) const;
Returns:
The smallest p in the range [low, high) such that
_________________________
6) Only the char (not unsigned char and signed char) form is provided.
The specialization is specified in the standard, and not left as an
implementation detail, because it affects the derivation interface for
ctype<char>.
table()[(unsigned char) *p] & m
is true.
const char* scan_not(mask m,
const char* low, const char* high) const;
Returns:
The smallest p in the range [low, high) such that
table()[(unsigned char) *p] & m
is false.
char toupper(char c) const;
const char* toupper(char* low, const char* high) const;
Returns:
do_toupper(c) or do_toupper(low,high)
char tolower(char c) const;
const char* tolower(char* low, const char* high) const;
Returns:
do_tolower(c) or do_tolower(low,high)
char widen(char c) const;
const char* widen(const char* low, const char* high,
char* to) const;
Effects:
::memcpy(to, low, high-low)
Returns:
c or hi
char narrow(char c, char /*dfault*/) const;
const char* narrow(const char* low, const char* high,
char /*dfault*/, char* to) const;
Effects:
::memcpy(to, low, high-low)
Returns:
c or high.
const mask* table() const throw();
Returns:
The first constructor argument, if it was non-zero, otherwise clas
sic_table().
22.2.1.3.3 ctype<char> static [lib.facet.ctype.char.statics]
members
static const mask* classic_table() throw();
Returns:
A pointer the initial element of an array of size
numeric_limits<unsigned char>::max() + 1 which represents the clas
sifications of characters in the "C" locale.
22.2.1.3.4 ctype<char> virtual [lib.facet.ctype.char.virtuals]
functions
char do_toupper(char) const;
const char* do_toupper(char* low, const char* high) const;
char do_tolower(char) const;
const char* do_tolower(char* low, const char* high) const;
These functions are described identically as those members of the same
name in the ctype class template (_lib.locale.ctype.members_).
22.2.1.4 Class [lib.locale.ctype.byname.special]
ctype_byname<char>
class ctype_byname<char> : public ctype<charT> {
public:
explicit ctype_byname(const char*, size_t refs = 0);
protected:
~ctype_byname(); // virtual
virtual char do_toupper(char) const;
virtual const char* do_toupper(char* low, const char* high) const;
virtual char do_tolower(char) const;
virtual const char* do_tolower(char* low, const char* high) const;
};
}
1
22.2.1.5 Template class codecvt [lib.locale.codecvt]
namespace std {
class codecvt_base {
public:
enum result { ok, partial, error, noconv };
};
template <class fromT, class toT, class stateT>
class codecvt : public locale::facet, public codecvt_base {
public:
typedef fromT from_type;
typedef toT to_type;
typedef stateT state_type;
explicit codecvt(size_t refs = 0)
result convert(stateT& state,
const fromT* from, const fromT* from_end, const fromT*& from_next,
toT* to, toT* to_limit, toT*& to_next) const;
bool always_noconv() const throw();
int length(const stateT&, const fromT* from, const fromT* end,
size_t max) const;
int max_length() const throw();
static locale::id id;
protected:
~codecvt(); // virtual
virtual result do_convert(stateT& state,
const fromT* from, const fromT* from_end, const fromT*& from_next,
toT* to, toT* to_limit, toT*& to_next) const;
virtual bool do_always_noconv() const throw();
virtual int do_length(const stateT&, const fromT* from, const fromT* end,
size_t max) const;
virtual int do_max_length() const throw();
};
}
1 The class codecvt<fromT,toT,stateT> is for use when converting from
one codeset to another, such as from wide characters to multibyte
characters, or between wide character sets such as Unicode and EUC.
Instances of this facet are typically used in pairs instantiated oppo
sitely.
2 The stateT argument selects the pair of codesets being mapped between.
3 Implementations are required to provide instantiations for
<char,wchar_t,mbstate_t>, <wchar_t,char,mbstate_t>, and
<char,char,mbstate_t>. The last implements a degenerate conversion:
its member always_noconv() returns true and max_length() returns 1.
Instantiations on mbstate_t perform conversion between encodings known
to the library implementor. Other encodings can be converted by spe
cializing on a user-defined stateT type. The stateT object can con
tain any state that is useful to communicate to or from the special
ized do_convert member. The base class implementations convert the
implementation-defined native execution codeset.
22.2.1.5.1 codecvt members [lib.locale.codecvt.members]
result convert(stateT& state,
const fromT* from, const fromT* from_end, const fromT*& from_next,
toT* to, toT* to_limit, toT*& to_next) const;
Returns:
do_convert(state, from,from_end,from_next, to,to_limit,to_next);
bool always_noconv() const throw();
Returns:
do_always_noconv();
int length(stateT& state, const fromT* from, const fromT* from_end,
size_t max) const;
Returns:
do_length(state, from,from_end,max);
+------- BEGIN BOX 6 -------+
Change: Removed throw() from the declaration of length() for consis
tency with member convert().
+------- END BOX 6 -------+
int max_length() const throw();
Returns:
do_max_length();
22.2.1.5.2 codecvt virtual [lib.locale.codecvt.virtuals]
functions
result do_convert(stateT& state,
const fromT* from, const fromT* from_end, const fromT*& from_next,
toT* to, toT* to_limit, toT*& to_next) const;
Preconditions:
(from<=from_end && to<=to_end) well-defined and true; state initial
ized, if at the beginning of a sequence, or else equal to the result
of converting the preceding characters in the sequence.
Effects:
Translates characters in the range [from,from_end), placing the
results in sequential positions starting at to. Converts no more
than (from_end-from) fromT elements, and stores no more than
(to_limit-to) toT elements.
Stops if it encounters a character it cannot convert. It always
leaves the from_next and to_next pointers pointing one beyond the
last character successfully converted. [Note: If no translation is
needed (returns noconv), sets to_next equal to argument to, and
from_next equal to argument from. --end note]
Notes:
Its operations on state are unspecified.
[Note: This argument can be used, for example, to maintain shift
state, to specify conversion options (such as count only), or to
identify a cache of seek offsets. --end note]
Returns:
An enumeration value, as summarized in Table 4:
Table 4--convert result values
+-----------------------------------------------------------------+
| Value Meaning |
+-----------------------------------------------------------------+
|ok completed the conversion |
|partial not all source characters converted |
|error encountered a from_type character it could not convert |
|noconv no conversion was needed |
+-----------------------------------------------------------------+
A return value of partial, if (from_next==from_end), indicates that
either the destination sequence has not absorbed all the converted
toT values, or that additional fromT values are needed before
another toT value can be produced.
bool do_always_noconv() const throw();
Returns:
true if do_convert() returns noconv for all valid argument values.
The base class implementation for the instantiation
<char,char,mbstate_t> returns true, others return false.
+------- BEGIN BOX 7 -------+
Change: Clarified that the base class implementation of only the
<char,char,mbstate_t> instantiation returns true; it would make no
sense for the others to return true because they have actual conver
sion work to do.
+------- END BOX 7 -------+
int do_length(stateT& state, const fromT* from, const fromT* from_end,
size_t max) const;
Preconditions:
(from<=from_end) well-defined and true; state initialized, if at the
beginning of a sequence, or else equal to the result of converting
the preceding characters in the sequence.
Returns:
(from_next-from) where from_next is the largest value in the range
[from,from_end] such that the sequence of values in the range
[from,from_next) represents max or fewer valid complete characters
of type fromT. The base class implementation returns the lesser of
max and (from_end-from).
int do_max_length() const throw();
Returns:
The maximum value that do_length(state,from,from_end,1) can return
for any valid range [from,from_end) and stateT value state.
22.2.1.6 Template class [lib.locale.codecvt.byname]
codecvt_byname
namespace std {
template <class fromT, class toT, class stateT>
class codecvt_byname : public codecvt<fromT, toT, stateT> {
public:
explicit codecvt_byname(const char*, size_t refs = 0);
protected:
~codecvt_byname(); // virtual
virtual result do_convert(stateT& state,
const fromT* from, const fromT* from_end, const fromT*& from_next,
toT* to, toT* to_limit, toT*& to_next) const;
virtual bool do_always_noconv() const throw();
virtual int do_length(const stateT&, const fromT* from, const fromT* end,
size_t max) const;
virtual int do_max_length() const throw();
};
}
22.2.2 The numeric category [lib.category.numeric]
1 The classes num_get<> and num_put<> handle numeric formatting and
parsing. Virtual functions are provided for several numeric types.
Implementations may (but are not required to) delegate extraction of
smaller types to extractors for larger types.7)
2 The base class implementation refers to the ios_base& argument for
formatting specifications (_lib.locale.categories_), and to its imbued
locale for the numpunct<> facet to identify all numeric punctuation
preferences, and also for the ctype<> facet to perform character clas
sification.
3 Extractor and inserter members of the standard iostreams use num_get<>
and num_put<> member functions for formatting and parsing numeric val
ues (_lib.istream.formatted.reqmts_, _lib.ostream.formatted.reqmts_).
22.2.2.1 Template class num_get [lib.locale.num.get]
namespace std {
template <class charT, class InputIterator = istreambuf_iterator<charT> >
class num_get : public locale::facet {
public:
typedef charT char_type;
typedef InputIterator iter_type;
explicit num_get(size_t refs = 0);
_________________________
7) Parsing "-1" correctly into (e.g.) an unsigned short requires that
the corresponding member get() at least extract the sign before dele
gating.
iter_type get(iter_type in, iter_type end, ios_base&,
ios_base::iostate& err, bool& v) const;
iter_type get(iter_type in, iter_type end, ios_base& ,
ios_base::iostate& err, long& v) const;
iter_type get(iter_type in, iter_type end, ios_base&,
ios_base::iostate& err, unsigned short& v) const;
iter_type get(iter_type in, iter_type end, ios_base&,
ios_base::iostate& err, unsigned int& v) const;
iter_type get(iter_type in, iter_type end, ios_base&,
ios_base::iostate& err, unsigned long& v) const;
iter_type get(iter_type in, iter_type end, ios_base&,
ios_base::iostate& err, float& v) const;
iter_type get(iter_type in, iter_type end, ios_base&,
ios_base::iostate& err, double& v) const;
iter_type get(iter_type in, iter_type end, ios_base&,
ios_base::iostate& err, long double& v) const;
static locale::id id;
protected:
~num_get(); // virtual
virtual iter_type do_get(iter_type, iter_type, ios_base&,
ios_base::iostate& err, bool& v) const;
virtual iter_type do_get(iter_type, iter_type, ios_base&,
ios_base::iostate& err, long& v) const;
virtual iter_type do_get(iter_type, iter_type, ios_base&,
ios_base::iostate& err, unsigned short& v) const;
virtual iter_type do_get(iter_type, iter_type, ios_base&,
ios_base::iostate& err, unsigned int& v) const;
virtual iter_type do_get(iter_type, iter_type, ios_base&,
ios_base::iostate& err, unsigned long& v) const;
virtual iter_type do_get(iter_type, iter_type, ios_base&,
ios_base::iostate& err, float& v) const;
virtual iter_type do_get(iter_type, iter_type, ios_base&,
ios_base::iostate& err, double& v) const;
virtual iter_type do_get(iter_type, iter_type, ios_base&,
ios_base::iostate& err, long double& v) const;
};
}
1 The facet num_get is used to parse numeric values from an input
sequence such as an istream.
22.2.2.1.1 num_get members [lib.facet.num.get.members]
iter_type get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, bool& val) const;
iter_type get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, long& val) const;
iter_type get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, unsigned short& val) const;
iter_type get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, unsigned int& val) const;
iter_type get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, unsigned long& val) const;
iter_type get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, short& val) const;
iter_type get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, double& val) const;
iter_type get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, long double& val) const;
Returns:
do_get(in, end, str, err, val).
22.2.2.1.2 num_get virtual [lib.facet.num.get.virtuals]
functions
iter_type do_get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, bool& val) const;
iter_type do_get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, long& val) const;
iter_type do_get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, unsigned short& val) const;
iter_type do_get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, unsigned int& val) const;
iter_type do_get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, unsigned long& val) const;
iter_type do_get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, float& val) const;
iter_type do_get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, double& val) const;
iter_type do_get(iter_type in, iter_type end, ios_base& str,
ios_base::iostate& err, long double& val) const;
Effects:
Reads characters from in, interpreting them according to
str.flags(), use_facet< ctype<charT> >(loc), and use_facet<
numpunct<charT> >(loc). If an error occurs, val is unchanged; oth
erwise it is set to the resulting value.
Digit group separators are optional; if present, digit grouping is
checked after the entire number is read. If no grouping is speci
fied, any thousands separator characters encountered in the input
sequence are not considered part of the numeric format.
When reading a non-numeric boolean value, the names are compared
exactly.
Returns:
An iterator pointing one past the last character consumed as part of
the converted field.
22.2.2.2 Template class num_put [lib.locale.num.put]
namespace std {
template <class charT, class OutputIterator = ostreambuf_iterator<charT> >
class num_put : public locale::facet {
public:
typedef charT char_type;
typedef OutputIterator iter_type;
explicit num_put(size_t refs = 0);
iter_type put(iter_type s, ios_base& f, char_type fill, bool v) const;
iter_type put(iter_type s, ios_base& f, char_type fill, long v) const;
iter_type put(iter_type s, ios_base& f, char_type fill,
unsigned long v) const;
iter_type put(iter_type s, ios_base& f, char_type fill,
double v) const;
iter_type put(iter_type s, ios_base& f, char_type fill,
long double v) const;
static locale::id id;
protected:
~num_put(); // virtual
virtual iter_type do_put(iter_type, ios_base&, char_type fill,
bool v) const;
virtual iter_type do_put(iter_type, ios_base&, char_type fill,
long v) const;
virtual iter_type do_put(iter_type, ios_base&, char_type fill,
unsigned long) const;
virtual iter_type do_put(iter_type, ios_base&, char_type fill,
double v) const;
virtual iter_type do_put(iter_type, ios_base&, char_type fill,
long double v) const;
};
}
1 The facet num_put is used to format numeric values to a character
sequence such as an ostream.
22.2.2.2.1 num_put members [lib.facet.num.put.members]
iter_type put(iter_type out, ios_base& str, char_type fill,
bool val) const;
iter_type put(iter_type out, ios_base& str, char_type fill,
long val) const;
iter_type put(iter_type out, ios_base& str, char_type fill,
unsigned long val) const;
iter_type put(iter_type out, ios_base& str, char_type fill,
double val) const;
iter_type put(iter_type out, ios_base& str, char_type fill,
long double val) const;
Returns:
do_put(out, str, fill, val).
22.2.2.2.2 num_put virtual [lib.facet.num.put.virtuals]
functions
iter_type do_put(iter_type out, ios_base& str, char_type fill,
bool val) const;
iter_type do_put(iter_type out, ios_base& str, char_type fill,
long val) const;
iter_type do_put(iter_type out, ios_base& str, char_type fill,
unsigned long val) const;
iter_type do_put(iter_type out, ios_base& str, char_type fill,
double val) const;
iter_type do_put(iter_type out, ios_base& str, char_type fill,
long double val) const;
Effects:
Writes characters to the sequence out, formatting val according to
str.flags(), fill, use_facet< ctype<charT> >(str.getloc()), and
use_facet< numpunct<charT> >(str.getloc()). Inserts digit group
separators as specified by numpunct<charT>::do_grouping.
Returns:
An iterator pointing immediately after the last character produced.
22.2.3 The numeric punctuation facet [lib.facet.numpunct]
22.2.3.1 Template class numpunct [lib.locale.numpunct]
namespace std {
template <class charT>
class numpunct : public locale::facet {
public:
typedef charT char_type;
typedef basic_string<charT> string_type;
explicit numpunct(size_t refs = 0);
char_type decimal_point() const;
char_type thousands_sep() const;
string grouping() const;
string_type truename() const;
string_type falsename() const;
static locale::id id;
protected:
~numpunct(); // virtual
virtual char_type do_decimal_point() const;
virtual char_type do_thousands_sep() const;
virtual string do_grouping() const;
virtual string_type do_truename() const; // for bool
virtual string_type do_falsename() const; // for bool
};
}
1 numpunct<> specifies numeric punctuation. The base class provides
classic C" numeric formats, while the _byname" version supports named
locale (e.g. POSIX, X/Open) numeric formatting semantics.
2 The syntax for number formats is as follows, where digit represents
the radix set specified by the fmtflags argument value, whitespace is
as determined by the facet ctype<charT> (_lib.locale.ctype_), and
thousands-sep and decimal-point are the results of corresponding
numpunct<charT> members. Integer values have the format:
integer ::= [sign] units
sign ::= plusminus [whitespace]
plusminus ::= '+' | '-'
units ::= digits [thousands-sep units]
digits ::= digit [digits]
and floating-point values have:
floatval ::= [sign] units [decimal-point [digits]] [e [sign] digits] |
[sign] decimal-point digits [e [sign] digits]
e ::= 'e' | 'E'
where the number of digits between thousands-seps is as specified by
do_grouping(). For parsing, if the digits portion contains no thou
sands-separators, no grouping constraint is applied.
+------- BEGIN BOX 8 -------+
Note: The WG agreed that sequences such as "0xFF" are valid numbers,
and (editorially) need to be represented in the syntax spec above.
+------- END BOX 8 -------+
22.2.3.1.1 numpunct members [lib.facet.numpunct.members]
char_type decimal_point() const;
Returns:
do_decimal_point()
char_type thousands_sep() const;
Returns:
do_thousands_sep()
+------- BEGIN BOX 9 -------+
Change: The previous version said thousands_sep() returned thou
sands_sep() (itself). Changed to do_thousands_sep().
+------- END BOX 9 -------+
string grouping() const;
Returns:
do_grouping()
string_type truename() const;
string_type falsename() const;
Returns:
do_truename() or do_falsename(), respectively.
22.2.3.1.2 numpunct virtual [lib.facet.numpunct.virtuals]
functions
char_type do_decimal_point() const;
Returns:
A character for use as the decimal radix separator. The base class
implementation returns '.'.
string_type do_thousands_sep() const;
Returns:
A character for use as the digit group separator. The base class
implementation returns ','.
string do_grouping() const;
Returns:
A basic_string<char> vec used as a vector of integer values, in
which each element vec[i] represents the number of digits8) in the
group at position i, starting with position 0 as the rightmost
group. If vec.size() <= i, the number is the same as group (i-1);
if (i<0 || vec[i]<=0 || vec[i]==CHAR_MAX), the size of the digit
group is unlimited.
The base class implementation returns the empty string, indicating
no grouping.
string_type do_truename() const;
string_type do_falsename() const;
Returns:
A string representing the name of the boolean value true or false,
respectively.
In the base class implementation these names are "true" and "false".
_________________________
8) Thus, the string " 03" specifies groups of 3 digits each, and "3"
probably indicates groups of 51 (!) digits each.
22.2.3.2 Template class [lib.locale.numpunct.byname]
numpunct_byname
namespace std {
template <class charT>
class numpunct_byname : public numpunct<charT> {
// this class is specialized for char and wchar_t.
public:
explicit numpunct_byname(const char*, size_t refs = 0);
protected:
~numpunct_byname(); // virtual
virtual char_type do_decimal_point() const;
virtual char_type do_thousands_sep() const;
virtual string do_grouping() const;
virtual string_type do_truename() const; // for bool
virtual string_type do_falsename() const; // for bool
};
}
22.2.4 The collate category [lib.category.collate]
22.2.4.1 Template class collate [lib.locale.collate]
namespace std {
template <class charT>
class collate : public locale::facet {
public:
typedef charT char_type;
typedef basic_string<charT> string_type;
explicit collate(size_t refs = 0);
int compare(const charT* low1, const charT* high1,
const charT* low2, const charT* high2) const;
string_type transform(const charT* low, const charT* high) const;
long hash(const charT* low, const charT* high) const;
static locale::id id;
protected:
~collate(); // virtual
virtual int do_compare(const charT* low1, const charT* high1,
const charT* low2, const charT* high2) const;
virtual string_type do_transform(const charT* low, const charT* high) const;
virtual long do_hash (const charT* low, const charT* high) const;
};
}
1 The class collate<charT> provides features for use in the collation
(comparison) and hashing of strings. A locale member function tem
plate, operator(), uses the collate facet to allow a locale to act
directly as the predicate argument for standard algorithms
(_lib.algorithms_) and containers operating on strings. The base
class implementation applies lexicographic ordering
(_lib.alg.lex.comparison_).
2 Each function compares a string of characters *p in the range
[low,high).
22.2.4.1.1 collate members [lib.locale.collate.members]
int compare(const charT* low1, const charT* high1,
const charT* low2, const charT* high2) const;
Returns:
do_compare(low1, high1, low2, high2)
string_type transform(const charT* low, const charT* high) const;
Returns:
do_transform(low, high)
long hash(const charT* low, const charT* high) const;
Returns:
do_hash(low, high)
22.2.4.1.2 collate virtual [lib.locale.collate.virtuals]
functions
int do_compare(const charT* low1, const charT* high1,
const charT* low2, const charT* high2) const;
Returns:
1 if the first string is greater than the second, -1 if less, zero
otherwise. The base class implementation implements a lexicographi
cal comparison (_lib.alg.lex.comparison_).
string_type do_transform(const charT* low, const charT* high) const;
Returns:
A basic_string<charT> value that, compared lexicographically with
the result of calling transform() on another string, yields the same
result as calling do_compare() on the same two strings.9)
long do_hash(const charT* low, const charT* high) const;
Returns:
An integer value equal to the result of calling hash() on any other
string for which do_compare() returns 0 (equal) when passed the two
strings. [Note: The probability that the result equals that for
another string which does not compare equal should be very small,
_________________________
9) This function is useful when one string is being compared to many
other strings.
approaching (1.0/numeric_limits<unsigned long>::max()). --end
note]
22.2.4.2 Template class [lib.locale.collate.byname]
collate_byname
namespace std {
template <class charT>
class collate_byname : public collate<charT> {
public:
explicit collate_byname(const char*, size_t refs = 0);
protected:
~collate_byname(); // virtual
virtual int do_compare(const charT* low1, const charT* high1,
const charT* low2, const charT* high2) const;
virtual string_type do_transform(const charT* low, const charT* high) const;
virtual long do_hash( const charT* low, const charT* high) const;
};
22.2.5 The time category [lib.category.time]
1 The templates time_get<charT,InputIterator> and
time_put<charT,OutputIterator> provide date and time formatting and
parsing. Their members use their ios_base&, ios_base::iostate&, and
fill arguments as described in (_lib.locale.categories_), and the
ctype<> facet, to determine formatting details.
22.2.5.1 Template class time_get [lib.locale.time.get]
namespace std {
class time_base {
public:
enum dateorder { no_order, dmy, mdy, ymd, ydm };
};
template <class charT, class InputIterator = istreambuf_iterator<charT> >
class time_get : public locale::facet, public time_base {
public:
typedef charT char_type;
typedef InputIterator iter_type;
explicit time_get(size_t refs = 0);
dateorder date_order() const { return do_date_order(); }
iter_type get_time(iter_type s, iter_type end, ios_base& f,
ios_base::iostate& err, tm* t) const;
iter_type get_date(iter_type s, iter_type end, ios_base& f,
ios_base::iostate& err, tm* t) const;
iter_type get_weekday(iter_type s, iter_type end, ios_base& f,
ios_base::iostate& err, tm* t) const;
iter_type get_monthname(iter_type s, iter_type end, ios_base& f,
ios_base::iostate& err, tm* t) const;
iter_type get_year(iter_type s, iter_type end, ios_base& f,
ios_base::iostate& err, tm* t\fP) const;
static locale::id id;
protected:
~time_get(); // virtual
virtual dateorder do_date_order() const;
virtual iter_type do_get_time(iter_type s, iter_type end, ios_base&,
ios_base::iostate& err, tm* t) const;
virtual iter_type do_get_date(iter_type s, iter_type end, ios_base&,
ios_base::iostate& err, tm* t) const;
virtual iter_type do_get_weekday(iter_type s, iter_type end, ios_base&,
ios_base::iostate& err, tm* t) const;
virtual iter_type do_get_monthname(iter_type s, ios_base&,
ios_base::iostate& err, tm* t) const;
virtual iter_type do_get_year(iter_type s, iter_type end, ios_base&,
ios_base::iostate& err, tm* t) const;
};
}
1 time_get is used to parse a character sequence, extracting components
of a time or date into a struct tm record. Each get member parses a
format as produced by a corresponding format specifier to
time_put<>::put. If the sequence being parsed matches the correct
format, the corresponding members of the struct tm argument are set to
the values used to produce the sequence; otherwise either an error is
reported or unspecified values are assigned.10)
22.2.5.1.1 time_get members [lib.locale.time.get.members]
dateorder date_order() const;
Returns:
do_date_order()
iter_type get_time(iter_type s, iter_type end, ios_base& str,
ios_base::iostate& err, tm* t) const;
Returns:
do_get_time(s, end, str, err, t)
iter_type get_date(iter_type s, iter_type end, ios_base& str,
ios_base::iostate& err, tm* t) const;
Returns:
do_get_date(s, end, str, err, t)
_________________________
10) In other words, user confirmation is required for reliable parsing
of user-entered dates and times, but machine-generated formats can be
parsed reliably. This allows parsers to be aggressive about inter
preting user variations on standard formats.
iter_type get_weekday(iter_type s, iter_type end, ios_base& str,
ios_base::iostate& err, tm* t) const;
iter_type get_monthname(iter_type s, iter_type end, ios_base& str,
ios_base::iostate& err, tm* t) const;
Returns:
do_get_weekday(s, end, str, err, t) or do_get_monthname(s, end, str,
err, t
iter_type get_year(iter_type s, iter_type end, ios_base& str,
ios_base::iostate& err, tm* t) const;
Returns:
do_get_year(s, end, str, err, t)
22.2.5.1.2 time_get virtual [lib.locale.time.get.virtuals]
functions
dateorder do_date_order() const;
Returns:
An enumeration value indicating the preferred order of components
for those date formats that are composed of day, month, and year.11)
Returns no_order if the date format specified by 'x' contains other
variable components (e.g. Julian day, week number, week day).
+------- BEGIN BOX 10 -------+
Change: Changed X to x above; the C strftime format %X does not spec
ify any date components.
+------- END BOX 10 -------+
iter_type do_get_time(iter_type s, iter_type end, ios_base& str,
ios_base::iostate& err, tm* t) const;
Effects:
Reads characters starting at s until it has extracted those struct
tm members, and remaining format characters, used by time_put<>::put
to produce the format specified by 'X', or until it encounters an
error or end of sequence.
Returns:
An iterator pointing immediately beyond the last character recog
nized as possibly part of a valid time.
_________________________
11) This function is intended as a convenience only, for common for
mats, and may return no_order in valid locales.
iter_type do_get_date(iter_type s, iter_type end, ios_base& str,
ios_base::iostate& err, tm* t) const;
Effects:
Reads characters starting at s until it has extracted those struct
tm members, and remaining format characters, used by time_put<>::put
to produce the format specified by 'x', or until it encounters an
error.
Returns:
An iterator pointing immediately beyond the last character recog
nized as possibly part of a valid date.
iter_type do_get_weekday(iter_type s, iter_type end, ios_base& str,
ios_base::iostate& err, tm* t) const;
iter_type do_get_monthname(iter_type s, iter_type end, ios_base& str,
ios_base::iostate& err, tm* t) const;
Effects:
Reads characters starting at s until it has extracted the (perhaps
abbreviated) name of a weekday or month. If it finds an abbrevia
tion that is followed by characters that could match a full name, it
continues reading until it matches the full name or fails. It sets
the appropriate struct tm member accordingly.
Returns:
An iterator pointing immediately beyond the last character recog
nized as part of a valid name.
iter_type do_get_year(iter_type s, iter_type end, ios_base& str,
ios_base::iostate& err, tm* t) const;
Effects:
Reads characters starting at s until it has extracted an unambiguous
year identifier. It is implementation-defined whether two-digit
year numbers are accepted, and (if so) what century they are assumed
to lie in. Sets the t->tm_year member accordingly.
Returns:
An iterator pointing immediately beyond the last character recog
nized as part of a valid year identifier.
22.2.5.2 Template class [lib.locale.time.get.byname]
time_get_byname
namespace std {
template <class charT, class InputIterator = istreambuf_iterator<charT> >
class time_get_byname : public time_get<charT, InputIterator> {
public:
explicit time_get_byname(const char*, size_t refs = 0);
protected:
~time_get_byname(); // virtual
virtual dateorder do_date_order() const;
virtual iter_type do_get_time(iter_type s, iter_type end, ios_base&,
ios_base::iostate& err, tm* t) const;
virtual iter_type do_get_date(iter_type s, iter_type end, ios_base&,
ios_base::iostate& err, tm* t) const;
virtual iter_type do_get_weekday(iter_type s, iter_type end, ios_base&,
ios_base::iostate& err, tm* t) const;
virtual iter_type do_get_monthname(iter_type s, iter_type end, ios_base&,
ios_base::iostate& err, tm* t) const;
virtual iter_type do_get_year(iter_type s, iter_type end, ios_base&,
ios_base::iostate& err, tm* t) const;
};
}
22.2.5.3 Template class time_put [lib.locale.time.put]
namespace std {
template <class charT, class OutputIterator = ostreambuf_iterator<charT> >
class time_put : public locale::facet {
public:
typedef charT char_type;
typedef OutputIterator iter_type;
explicit time_put(size_t refs = 0);
// the following is implemented in terms of other member functions.
iter_type put(iter_type s, ios_base& f, char_type fill, const tm* tmb,
const charT* pattern, const charT* pat_end) const;
iter_type put(iter_type s, ios_base& f, char_type fill,
const tm* tmb, char format, char modifier = 0) const;
static locale::id id;
protected:
~time_put(); // virtual
virtual iter_type do_put(iter_type s, ios_base&, char_type, const tm* t,
char format, char modifier) const;
};
}
22.2.5.3.1 time_put members [lib.locale.time.put.members]
iter_type put(iter_type s, ios_base&, char_type fill, const tm* t,
const charT* pattern, const charT* pat_end) const;
iter_type put(iter_type s, ios_base&, char_type fill, const tm* t,
char format, char modifier = 0) const;
Effects:
The first form interprets the characters immediately following a %
in the sequence between pattern and pat_end as format specifiers,
according to the mapping used by the function strftime() Characters
are converted using ctype<>::narrow() to identify format specifiers.
[Note: This implies that if narrow() has no mapping for the charac
ter %, no format specifiers are identified. --end note]
The second form calls do_put() once, simply passing along its argu
ments.
Returns:
An iterator pointing immediately after the last character produced.
22.2.5.3.2 time_put virtual [lib.locale.time.put.virtuals]
functions
iter_type do_put(iter_type s, ios_base&, char_type fill, const tm* t,
char format, char modifier) const;
Effects:
Formats the contents of the parameter t into characters placed on
the output sequence s. Formatting is controlled by the parameters
format and modifier, interpreted identically as the format speci
fiers in the string argument to the standard library function
strftime().12)
Returns:
An iterator pointing immediately after the last character produced.
22.2.5.4 Template class [lib.locale.time.put.byname]
time_put_byname
namespace std {
template <class charT, class OutputIterator = ostreambuf_iterator<charT> >
class time_put_byname : public time_put<charT, OutputIterator>
{
public:
explicit time_put_byname(const char*, size_t refs = 0);
protected:
~time_put_byname(); // virtual
virtual iter_type do_put(iter_type s, ios_base&, char_type, const tm* t,
char format, char modifier) const;
};
}
22.2.6 The monetary category [lib.category.monetary]
1 These templates handle monetary formats. A template parameter indi
cates whether local or international monetary formats are to be used.
2 money_get<> and money_put<> members use their ios_base&,
ios_base::iostate&, and fill arguments as described in
(_lib.locale.categories_), and the moneypunct<> and ctype<> facets, to
determine formatting details.
_________________________
12) Interpretation of the modifier argument is implementation-defined,
but should follow POSIX conventions.
22.2.6.1 Template class money_get [lib.locale.money.get]
namespace std {
template <class charT, bool Intl = false,
class InputIterator = istreambuf_iterator<charT> >
class money_get : public locale::facet {
public:
typedef charT char_type;
typedef InputIterator iter_type;
typedef basic_string<charT> string_type;
explicit money_get(size_t refs = 0);
iter_type get(iter_type s, iter_type end, ios_base& f,
ios_base::iostate& err, long double& units) const;
iter_type get(iter_type s, iter_type end, ios_base& f,
ios_base::iostate& err, string_type& digits) const;
static const bool intl = Intl;
static locale::id id;
protected:
~money_get(); // virtual
virtual iter_type do_get(iter_type, iter_type, ios_base&,
ios_base::iostate& err, long double& units) const;
virtual iter_type do_get(iter_type, iter_type, ios_base&,
ios_base::iostate& err, string_type& digits) const;
};
}
22.2.6.1.1 money_get members [lib.locale.money.get.members]
iter_type get(iter_type s, iter_type end, ios_base& f,
ios_base::iostate& err, long double& quant) const;
iter_type get(s, iter_type end, ios_base&f,
ios_base::iostate& err, string_type& quant) const;
Returns:
do_get(s, end, f, err, quant)
22.2.6.1.2 money_get virtual [lib.locale.money.get.virtuals]
functions
iter_type do_get(iter_type s, iter_type end, ios_base& str,
ios_base::iostate& err, long double& units) const;
iter_type do_get(iter_type s, iter_type end, ios_base& strfP,
ios_base::iostate& err, string_type& digits) const;
Effects:
Reads characters from s until it has constructed a monetary value,
as specified in str.flags() and the moneypunct<charT> facet of
str.getloc(), or until it encounters an error or runs out of charac
ters. It parses the format sequence specified by money
punct<>::neg_format() for all monetary values. The result is a pure
sequence of digits, representing a count of the smallest unit of
currency representable.13)
_________________________
13) For example, the sequence $1,056.23 in a common U.S. locale would
Digit group separators are optional; if present, digit grouping is
checked after all syntactic elements have been read. If no grouping
is specified, any thousands separator characters encountered in the
input sequence are not considered part of the numeric format.
Where space or none appear in the format pattern, except at the end,
optional whitespace is consumed. If (str.flags() &
ios_base::showbase) is false, the currency symbol is optional, and
if it appears after all other required syntactic elements it is not
consumed. If the expression above is true, the currency symbol is
required, and is always consumed. If the first character of the a
sign appears in its correct position, any remaining sign characters
are required, and consumed. [Example: If showbase is off, then when
the sign is "()" and the currency symbol is "L", in "(100 L)" the
"L" is consumed; but in "-100 L" it is not. --end example] Sets
the argument units or digits from the sequence of digits found.
units is negated, or digits is preceded by '-', for a negative
value. On error, the units or digits argument is unchanged.
Returns:
An iterator pointing immediately beyond the last character recog
nized as part of a valid monetary quantity.
+------- BEGIN BOX 11 -------+
The description above needs further review.
+------- END BOX 11 -------+
22.2.6.2 Template class money_put [lib.locale.money.put]
namespace std {
template <class charT, bool Intl = false,
class OutputIterator = ostreambuf_iterator<charT> >
class money_put : public locale::facet {
public:
typedef charT char_type;
typedef OutputIterator iter_type;
typedef basic_string<charT> string_type;
explicit money_put(size_t refs = 0);
iter_type put(iter_type s, ios_base& f, char_type fill,
long double units) const;
iter_type put(iter_type s, ios_base& f, char_type fill,
const string_type& digits) const;
static const bool intl = Intl;
static locale::id id;
_________________________
yield, for units, 105623, or for digits, 105623".
protected:
~money_put(); // virtual
virtual iter_type
do_put(iter_type, ios_base&, char_type fill, long double units) const;
virtual iter_type
do_put(iter_type, ios_base&, char_type fill,
const string_type& digits) const;
};
}
22.2.6.2.1 money_put members [lib.locale.money.put.members]
iter_type put(iter_type s, ios_base& f, char_type fill,
long double quant) const;
iter_type put(iter_type s, ios_base& f, char_type fill,
const string_type& quant) const;
Returns:
do_put(s, f, loc, quant)
22.2.6.2.2 money_put virtual [lib.locale.money.put.virtuals]
functions
iter_type do_put(iter_type s, ios_base& str, char_type fill,
long double units) const;
iter_type do_put(iter_type s, ios_base& str, char_type fill,
const string_type& digits) const;
Effects:
Writes characters to s, according to the format specified by the
moneypunct<charT> facet of loc, and str.flags(). Ignores any frac
tional part of units, or any characters in digits beyond the
(optional) leading '-' and immediately subsequent digits.
Notes:
The currency symbol is generated only if (str.flags() &
ios_type::showbase) is true. If ((str.flags() &
ios_type::adjustfield) == ios_type::internal) the fill characters
are placed where none or space appears in the formatting pattern
(_lib.money.get.virtuals_).
Returns:
An iterator pointing immediately after the last character produced.
22.2.6.3 Template class moneypunct [lib.locale.moneypunct]
namespace std {
class money_base {
public:
enum part { none, space, symbol, sign, value };
struct pattern { char field[4]; };
};
template <class charT, bool International = false>
class moneypunct : public locale::facet, public money_base {
public:
typedef charT char_type;
typedef basic_string<charT> string_type;
explicit moneypunct(size_t refs = 0);
charT decimal_point() const;
charT thousands_sep() const;
string grouping() const;
string_type curr_symbol() const;
string_type positive_sign() const;
string_type negative_sign() const;
int frac_digits() const;
pattern pos_format() const;
pattern neg_format() const;
static locale::id id;
static const bool intl = International;
protected:
~moneypunct(); // virtual
virtual charT do_decimal_point() const;
virtual charT do_thousands_sep() const;
virtual string do_grouping() const;
virtual string_type do_curr_symbol() const;
virtual string_type do_positive_sign() const;
virtual string_type do_negative_sign() const;
virtual int do_frac_digits() const;
virtual pattern do_pos_format() const;
virtual pattern do_neg_format() const;
};
}
1 This provides money punctuation, similar to numpunct<> above
(_lib.locale.numpunct_). In particular, the value portion of the for
mat is:
value ::= units [decimal-point [digits]] |
decimal-point digits
if frac_digits returns a positive value, or just
value ::= units
otherwise. In these forms, the decimal-point and thousands-separator
are as determined below and the number of digits after the decimal
point is exactly the value returned by frac_digits.
22.2.6.3.1 moneypunct members [lib.locale.moneypunct.members]
charT decimal_point() const;
charT thousands_sep() const;
string grouping() const;
string_type curr_symbol() const;
string_type positive_sign() const;
string_type negative_sign() const;
int frac_digits() const;
pattern pos_format() const;
pattern neg_format() const;
1 Each of these functions F returns the result of calling the corre
sponding virtual member function do_F().
22.2.6.3.2 moneypunct virtual [lib.locale.moneypunct.virtuals]
functions
charT do_decimal_point() const;
Returns:
The radix separator to use in case do_frac_digits() is greater than
zero.14)
charT do_thousands_sep() const;
Returns:
The digit group separator to use in case do_grouping() specifies a
digit grouping pattern.15)
string do_grouping() const;
Returns:
A pattern defined identically as the result of
numpunct<charT>::do_grouping().16)
string_type do_curr_symbol() const;
Returns:
A string to use as the currency identifier symbol.17)
_________________________
14) In common U.S. locales this is '.'.
15) In common U.S. locales this is ','.
16) This is most commonly the value " 03" not "3").
17) For international instantiations (second template parameter true)
this is always four characters long, usually three letters and a
space.
string_type do_positive_sign() const;
string_type do_negative_sign() const;
Returns:
do_positive_sign() returns the string to use to indicate a positive
monetary value;18) do_negative_sign() returns the string to use to
indicate a negative value. The first character of the string (if
any) is placed in the position indicated for the sign in the format
pattern, and any remaining characters are placed after all other
format elements.
int do_frac_digits() const;
Returns:
The number of digits after the decimal radix separator, if any.19)
pattern do_pos_format() const;
pattern do_neg_format() const;
Returns:
A pattern, a four-element array specifying the order in which syn
tactic elements appear in the monetary format. In this array each
enumeration value symbol, sign, value, and either space or none
appears exactly once. none, if present, is not first; space, if
present, is neither first nor last. Otherwise, the elements may
appear in any order. The base class implementation returns an
object of type pattern initialized to { symbol, sign, none, value };
this value is also returned for all international instantiations.20)
22.2.6.4 Template class [lib.locale.moneypunct.byname]
moneypunct_byname
_________________________
18) This is usually the empty string.
19) In common U.S. locales, this is 2.
20) Note that the international symbol returned by do_curr_sym() usu
ally contains a space, itself; for example, "USD ".
namespace std {
template <class charT, bool Intl = false>
class moneypunct_byname : public moneypunct<charT, Intl> {
public:
explicit moneypunct_byname(const char*, size_t refs = 0);
protected:
~moneypunct_byname(); // virtual
virtual charT do_decimal_point() const;
virtual charT do_thousands_sep() const;
virtual string do_grouping() const;
virtual string_type do_curr_symbol() const;
virtual string_type do_positive_sign() const;
virtual string_type do_negative_sign() const;
virtual int do_frac_digits() const;
virtual pattern do_pos_format() const;
virtual pattern do_neg_format() const;
};
}
22.2.7 The message retrieval category [lib.category.messages]
1 Class messages<charT> implements retrieval of strings from message
catalogs.
22.2.7.1 Template class messages [lib.locale.messages]
namespace std {
class messages_base {
public:
typedef int catalog;
};
template <class charT>
class messages : public locale::facet, public messages_base {
public:
typedef charT char_type;
typedef basic_string<charT> string_type;
explicit messages(size_t refs = 0);
catalog open(const basic_string<char>& fn, const locale&) const;
string_type get(catalog c, int set, int msgid,
const string_type& dfault) const;
void close(catalog c) const;
static locale::id id;
protected:
~messages(); // virtual
virtual catalog do_open(const basic_string<char>&, const locale&) const;
virtual string_type do_get(catalog, int set, int msgid,
const string_type& dfault) const;
virtual void do_close(catalog) const;
};
}
1 Values of type messages_base::catalog usable as arguments to members
get and close can be obtained only by calling member open.
22.2.7.1.1 messages members [lib.locale.messages.members]
catalog open(const basic_string<char>& name, const locale& loc) const;
Returns:
do_open(name, loc).
string_type get(catalog cat, int set, int msgid,
const string_type& dfault) const;
Returns:
do_get(cat, set, msgid, dfault).
void close(catalog cat) const;
Effects:
Calls do_close(cat).
22.2.7.1.2 messages virtual [lib.locale.messages.virtuals]
functions
catalog do_open(const basic_string<char>& name,
const locale& loc) const;
Returns:
A value that may be passed to get() to retrieve a message, from the
message catalog identified by the string name according to an imple
mentation-defined mapping. The result can be used until it is
passed to close().
Returns a value less than 0 if no such catalog can be opened.
Notes:
The locale argument loc is used for character set code conversion
when retrieving messages, if needed.
string_type do_get(catalog cat, int set, int msgid,
const string_type& dfault) const;
Requires:
A catalog cat obtained from open() and not yet closed.
Returns:
A message identified by arguments set, msgid, and dfault, according
to an implementation-defined mapping. If no such message can be
found, returns dfault.
void do_close(catalog cat) const;
Requires:
A catalog cat obtained from open() and not yet closed.
Effects:
Releases unspecified resources associated with cat.
Notes:
The limit on such resources, if any, is implementation-defined.
22.2.7.2 Template class [lib.locale.messages.byname]
messages_byname
namespace std {
template <class charT>
class messages_byname : public messages<charT> {
public:
explicit messages_byname(const char*, size_t refs = 0);
protected:
~messages_byname(); // virtual
virtual catalog do_open(const basic_string<char>&, const locale&) const;
virtual string_type do_get(catalog, int set, int msgid,
const string_type& dfault) const;
virtual void do_close(catalog) const;
};
}
22.2.8 Program-defined facets [lib.facets.examples]
1 A C++ program may define facets to be added to a locale and used iden
tically as the built-in facets. To create a new facet interface, C++
programs simply derive from locale::facet a class containing a static
member: static locale::id id.
2 [Note: The locale member function templates verify its type and stor
age class. --end note]
3 This initialization/identification system depends only on the initial
ization to 0 of static objects, before static constructors are called.
When an instance of a facet is installed in a locale, the locale
checks whether an id has been assigned, and if not, assigns one.
Before this occurs, any attempted use of its interface causes the
bad_cast exception to be thrown.
4 [Example: Here is a program that just calls C functions:
#include <locale>
extern "C" void c_function();
int main()
{
using namespace std;
locale::global(locale("")); // same as setlocale(LC_ALL, "");
c_function();
return 0;
}
In other words, C library localization is unaffected. --end example]
5 [Example: Traditional global localization is still easy:
#include <iostream>
#include <locale>
int main(int argc, char** argv)
{
using namespace std;
locale::global(locale("")); // set the global locale
cin.imbue(locale()); // imbue it on the std streams
cout.imbue(locale());
cerr.imbue(locale());
return MyObject(argc, argv).doit();
}
--end example]
6 [Example: Greater flexibility is possible:
#include <iostream>
#include <locale>
int main()
{
using namespace std;
cin.imbue(locale("")); // the user's preferred locale
cout.imbue(locale::classic());
double f;
while (cin >> f) cout << f << endl;
return (cin.fail() != 0);
}
In a European locale, with input 3.456,78, output is 3456.78. --end
example]
7 This can be important even for simple programs, which may need to
write a data file in a fixed format, regardless of a user's prefer
ence.
8 [Example: Here is an example of the use of locales in a library inter
face.
// file: Date.h
#include <iosfwd>
#include <string>
#include <locale>
...
class Date {
...
public:
Date(unsigned day, unsigned month, unsigned year);
std::string asString(const std::locale& = std::locale());
};
istream& operator>>(istream& s, Date& d);
ostream& operator<<(ostream& s, Date d);
...
This example illustrates two architectural uses of class locale.
9 The first is as a default argument in Date::asString(), where the
default is the global (presumably user-preferred) locale.
10The second is in the operators << and >>, where a locale "hitchhikes"
on another object, in this case a stream, to the point where it is
needed.
// file: Date.C
#include "Date" // includes <ctime>
#include <sstream>
std::string Date::asString(const std::locale& l)
{
using namespace std;
ostringstream s; s.imbue(l);
s << *this; return s.str();
}
std::istream& operator>>(std::istream& s, Date& d)
{
using namespace std;
istream::sentry cerberos;
if (cerberos) {
ios_base::iostate err = goodbit;
struct tm t;
use_facet< time_get<char> >(s.getloc()).get_date(s, 0, s, err, &t);
if (!err) d = Date(t.tm_day, t.tm_mon + 1, t.tm_year + 1900);
s.setstate(err);
}
return s;
}
--end example]
11A locale object may be extended with a new facet simply by construct
ing it with an instance of a class derived from locale::facet. The
only member a C++ program must define is the static member id, which
identifies your class interface as a new facet.
12[Example: Classifying Japanese characters:
// file: <jctype>
#include <locale>
namespace My {
using namespace std;
class JCtype : public locale::facet {
public:
static locale::id id; // required for use as a new locale facet
bool is_kanji(wchar_t c);
JCtype() {}
protected:
~JCtype() {}
};
}
// file: filt.C
#include <iostream>
#include <locale>
#include "jctype" // above
std::locale::id JCtype::id; // the static JCtype member declared above.
int main()
{
using namespace std;
typedef ctype<wchar_t> wctype;
locale loc(locale(""), // the user's preferred locale ...
new My::JCType); // and a new feature ...
wchar_t c = use_facet<wctype>(loc).widen('!');
if (use_facet<My::JCType>(loc).is_kanji(c))
cout << "no it isn't!" << endl;
return 0;
}
13The new facet is used exactly like the built-in facets. --end exam
ple]
14[Example: Replacing an existing facet is even easier. Here we do not
define a member id because we are reusing the numpunct<charT> facet
interface:
// my_bool.C
#include <iostream>
#include <locale>
#include <string>
namespace My {
using namespace std;
typedef numpunct_byname<char> cnumpunct;
class BoolNames : public cnumpunct {
protected:
string do_truename() { return "Oui Oui!"; }
string do_falsename() { return "Mais Non!"; }
~BoolNames() {}
public:
BoolNames(const char* name) : cnumpunct(name) {}
};
}
int main(int argc, char** argv)
{
using namespace std;
// make the user's preferred locale, except for...
locale loc(locale(""), new My::BoolNames(""));
cout.imbue(loc);
cout << boolalpha << "Any arguments today? " << (argc > 1) << endl;
return 0;
}
--end example]
22.3 C Library Locales [lib.c.locales]
1 Header <clocale> (Table 5):
Table 5--Header <clocale> synopsis
+-------------------------------------------------+
| Type Name(s) |
+-------------------------------------------------+
|Macros: |
| LC_ALL LC_COLLATE LC_CTYPE |
| LC_MONETARY LC_NUMERIC LC_TIME |
| NULL |
+-------------------------------------------------+
|Struct: lconv |
+-------------------------------------------------+
|Functions: localeconv setlocale |
+-------------------------------------------------+
2 The contents are the same as the Standard C library.
SEE ALSO: ISO C clause 7.4.