\rSec0[localization]{Localization library}

\rSec1[localization.general]{General}

This Clause describes components that \Cpp programs may use to

encapsulate (and therefore be more portable when confronting)

cultural differences.

The locale facility includes internationalization

support for character classification and string collation, numeric,

monetary, and date/time formatting and parsing, and message retrieval.

The following subclauses describe components for

locales themselves, the standard facets, and facilities

from the ISO C library, as summarized in Table~\ref{tab:localization.lib.summary}.

\begin{libsumtab}{Localization library summary}{tab:localization.lib.summary}

\ref{locales} & Locales & \tcode{<locale>} \\

\ref{locale.categories} & Standard \tcode{locale} Categories & \\ \rowsep

\ref{c.locales} & C library locales & \tcode{<clocale>} \\

\end{libsumtab}

\rSec1[locale.syn]{Header \tcode{<locale>} synopsis}

\indextext{\idxhdr{locale}}%

\indexlibrary{\idxhdr{locale}}%

\begin{codeblock}

namespace std {

// \ref{locale}, locale

class locale;

template <class Facet> const Facet& use_facet(const locale&);

template <class Facet> bool has_facet(const locale&) noexcept;

// \ref{locale.convenience}, convenience interfaces

template <class charT> bool isspace (charT c, const locale& loc);

template <class charT> bool isprint (charT c, const locale& loc);

template <class charT> bool iscntrl (charT c, const locale& loc);

template <class charT> bool isupper (charT c, const locale& loc);

template <class charT> bool islower (charT c, const locale& loc);

template <class charT> bool isalpha (charT c, const locale& loc);

template <class charT> bool isdigit (charT c, const locale& loc);

template <class charT> bool ispunct (charT c, const locale& loc);

template <class charT> bool isxdigit(charT c, const locale& loc);

template <class charT> bool isalnum (charT c, const locale& loc);

template <class charT> bool isgraph (charT c, const locale& loc);

template <class charT> bool isblank (charT c, const locale& loc);

template <class charT> charT toupper(charT c, const locale& loc);

template <class charT> charT tolower(charT c, const locale& loc);

// \ref{category.ctype}, ctype

class ctype_base;

template <class charT> class ctype;

template <> class ctype<char>; // specialization

template <class charT> class ctype_byname;

class codecvt_base;

template <class internT, class externT, class stateT> class codecvt;

template <class internT, class externT, class stateT> class codecvt_byname;

// \ref{category.numeric}, numeric

template <class charT, class InputIterator = istreambuf_iterator<charT>>

class num_get;

template <class charT, class OutputIterator = ostreambuf_iterator<charT>>

class num_put;

template <class charT>

class numpunct;

template <class charT>

class numpunct_byname;

// \ref{category.collate}, collation

template <class charT> class collate;

template <class charT> class collate_byname;

// \ref{category.time}, date and time

class time_base;

template <class charT, class InputIterator = istreambuf_iterator<charT>>

class time_get;

template <class charT, class InputIterator = istreambuf_iterator<charT>>

class time_get_byname;

template <class charT, class OutputIterator = ostreambuf_iterator<charT>>

class time_put;

template <class charT, class OutputIterator = ostreambuf_iterator<charT>>

class time_put_byname;

// \ref{category.monetary}, money

class money_base;

template <class charT, class InputIterator = istreambuf_iterator<charT>>

class money_get;

template <class charT, class OutputIterator = ostreambuf_iterator<charT>>

class money_put;

template <class charT, bool Intl = false>

class moneypunct;

template <class charT, bool Intl = false>

class moneypunct_byname;

// \ref{category.messages}, message retrieval

class messages_base;

template <class charT> class messages;

template <class charT> class messages_byname;

}

\end{codeblock}

The header

\tcode{<locale>}

defines classes and declares functions that encapsulate and manipulate

the information peculiar to a locale.\footnote{In this subclause, the type name

\tcode{struct tm}

is an incomplete type that is defined in

\indextext{\idxhdr{ctime}}%

\indexlibrary{\idxhdr{ctime}}%

\tcode{<ctime>}.}

\rSec1[locales]{Locales}

\rSec2[locale]{Class \tcode{locale}}

\indextext{\idxhdr{locale}}%

\indexlibrary{\idxhdr{locale}}%

\begin{codeblock}

namespace std {

class locale {

public:

// types:

class facet;

class id;

using category = int;

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() noexcept;

locale(const locale& other) noexcept;

explicit locale(const char* std_name);

explicit locale(const string& std_name);

locale(const locale& other, const char* std_name, category);

locale(const locale& other, const string& std_name, category);

template <class Facet> locale(const locale& other, Facet* f);

locale(const locale& other, const locale& one, category);

~locale(); // not virtual

const locale& operator=(const locale& other) noexcept;

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

// locale operations:

basic_string<char> name() const;

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

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

template <class charT, class traits, class Allocator>

bool operator()(const basic_string<charT, traits, Allocator>& s1,

const basic_string<charT, traits, Allocator>& s2) const;

// global locale objects:

static locale global(const locale&);

static const locale& classic();

};

}

\end{codeblock}

Class

\tcode{locale}

implements a type-safe polymorphic set of facets, indexed by facet

\textit{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.

Access to the facets of a

\tcode{locale}

is via two function templates,

\tcode{use_facet<>}

and

\tcode{has_facet<>}.

\begin{example}

An iostream

\tcode{operator<<}

might be implemented as:\footnote{Note that in the call to

\tcode{put}

the stream is implicitly converted to an

\tcode{ostreambuf_iterator<charT, traits>}.}

\begin{codeblock}

template <class charT, class traits>

basic_ostream<charT, traits>&

operator<< (basic_ostream<charT, traits>& s, Date d) {

typename basic_ostream<charT, traits>::sentry cerberos(s);

if (cerberos) {

ios_base::iostate err = ios_base::iostate::goodbit;

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{codeblock}

\end{example}

In the call to

\tcode{use_facet<Facet>(loc)},

the type argument chooses a facet, making available all members

of the named type.

If

\tcode{Facet}

is not present in a

locale,

it throws the standard exception

\tcode{bad_cast}.

A \Cpp program can check if a locale implements a particular

facet with the

function template

\tcode{has_facet<Facet>()}.

User-defined facets may be installed in a locale, and used identically as

may standard facets~(\ref{facets.examples}).

\begin{note}

All locale semantics are accessed via

\tcode{use_facet<>}

and

\tcode{has_facet<>},

except that:

\begin{itemize}

A member operator template

\tcode{operator()(const basic_string<C, T, A>\&, const basic_string<\brk{}C, T, A>\&)}

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

\tcode{ctype}

functions such as

\tcode{isdigit()}

and

\tcode{isspace()},

so that given a locale

object \tcode{loc} a \Cpp program can call

\tcode{isspace(c, loc)}.

(This eases upgrading existing extractors~(\ref{istream.formatted}).)

\end{itemize}

\end{note}

Once a facet reference is obtained from a locale object by calling

\tcode{use_facet<>},

that reference remains usable, and the results from member functions

of it may be cached and re-used, as long as some locale object refers

to that facet.

In successive calls to a locale facet member function on a facet object

installed in the same locale, the returned result shall be identical.

A

\tcode{locale}

constructed from a name string (such as \tcode{"POSIX"}), or from parts of

two named locales, 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,

\tcode{locale::name()}

returns the string

\tcode{"*"}.

Whether there is one global locale object for the entire program or one global locale

object per thread is \impldef{whether locale object is global or per-thread}.

Implementations should provide one global locale object per

thread. If there is a single global locale object for the entire program,

implementations are not required to avoid data races on it~(\ref{res.on.data.races}).

\rSec3[locale.types]{\tcode{locale} types}

\rSec4[locale.category]{Type \tcode{locale::category}}

\indexlibrarymember{locale}{category}%

\begin{itemdecl}

using category = int;

\end{itemdecl}

\textit{Valid}

\tcode{category}

values include the

\tcode{locale}

member bitmask elements

\tcode{collate},

\tcode{ctype},

\tcode{monetary},

\tcode{numeric},

\tcode{time},

and

\tcode{messages},

each of which represents a single locale category.

In addition,

\tcode{locale}

member bitmask constant

\tcode{none}

is defined as zero and represents no category. And

\tcode{locale}

member bitmask constant

\tcode{all}

is defined such that the expression

\begin{codeblock}

(collate | ctype | monetary | numeric | time | messages | all) == all

\end{codeblock}

is

\tcode{true},

and represents the union of all categories.

Further, the expression

\tcode{(X | Y)},

where

\tcode{X}

and

\tcode{Y}

each represent a single category, represents the union of the two categories.

\tcode{locale}

member functions expecting a

\tcode{category}

argument require one of the

\tcode{category}

values defined above, or the union of two or more such values.

Such a

\tcode{category}

value identifies a set of locale categories.

Each locale category,

in turn, identifies a set of locale facets, including at least those

shown in Table~\ref{tab:localization.category.facets}.

\begin{floattable}{Locale category facets}{tab:localization.category.facets}

{ml}

\lhdr{Category} & \rhdr{Includes facets} \\ \capsep

collate & \tcode{collate<char>}, \tcode{collate<wchar_t>} \\ \rowsep

ctype & \tcode{ctype<char>}, \tcode{ctype<wchar_t>} \\

& \tcode{codecvt<char, char, mbstate_t>} \\

& \tcode{codecvt<char16_t, char, mbstate_t>} \\

& \tcode{codecvt<char32_t, char, mbstate_t>} \\

& \tcode{codecvt<wchar_t, char, mbstate_t>} \\ \rowsep

monetary & \tcode{moneypunct<char>}, \tcode{moneypunct<wchar_t>} \\

& \tcode{moneypunct<char, true>}, \tcode{moneypunct<wchar_t, true>} \\

& \tcode{money_get<char>}, \tcode{money_get<wchar_t>} \\

& \tcode{money_put<char>}, \tcode{money_put<wchar_t>} \\ \rowsep

numeric & \tcode{numpunct<char>}, \tcode{numpunct<wchar_t>} \\

& \tcode{num_get<char>}, \tcode{num_get<wchar_t>} \\

& \tcode{num_put<char>}, \tcode{num_put<wchar_t>} \\ \rowsep

time & \tcode{time_get<char>}, \tcode{time_get<wchar_t>} \\

& \tcode{time_put<char>}, \tcode{time_put<wchar_t>} \\ \rowsep

messages & \tcode{messages<char>}, \tcode{messages<wchar_t>} \\

\end{floattable}

For any locale \tcode{loc}

either constructed, or returned by

\tcode{locale::classic()},

and any facet \tcode{Facet}

shown in Table~\ref{tab:localization.category.facets},

\tcode{has_facet<Facet>(loc)}

is \tcode{true}.

Each

\tcode{locale}

member function which takes a

\tcode{locale::category}

argument operates on the corresponding set of facets.

An implementation is required to provide those specializations for

facet templates identified as members of a category, and for those

shown in Table~\ref{tab:localization.required.specializations}.

\begin{floattable}{Required specializations}{tab:localization.required.specializations}

{ml}

\lhdr{Category} & \rhdr{Includes facets} \\ \capsep

collate & \tcode{collate_byname<char>}, \tcode{collate_byname<wchar_t>} \\ \rowsep

ctype & \tcode{ctype_byname<char>}, \tcode{ctype_byname<wchar_t>} \\

& \tcode{codecvt_byname<char, char, mbstate_t>} \\

& \tcode{codecvt_byname<char16_t, char, mbstate_t>} \\

& \tcode{codecvt_byname<char32_t, char, mbstate_t>} \\

& \tcode{codecvt_byname<wchar_t, char, mbstate_t>} \\ \rowsep

monetary & \tcode{moneypunct_byname<char, International>} \\

& \tcode{moneypunct_byname<wchar_t, International>} \\

& \tcode{money_get<C, InputIterator>} \\

& \tcode{money_put<C, OutputIterator>} \\ \rowsep

numeric & \tcode{numpunct_byname<char>}, \tcode{numpunct_byname<wchar_t>} \\

& \tcode{num_get<C, InputIterator>}, \tcode{num_put<C, OutputIterator>} \\ \rowsep

time & \tcode{time_get<char, InputIterator>} \\

& \tcode{time_get_byname<char, InputIterator>} \\

& \tcode{time_get<wchar_t, InputIterator>} \\

& \tcode{time_get_byname<wchar_t, InputIterator>} \\

& \tcode{time_put<char, OutputIterator>} \\

& \tcode{time_put_byname<char, OutputIterator>} \\

& \tcode{time_put<wchar_t, OutputIterator>} \\

& \tcode{time_put_byname<wchar_t, OutputIterator>} \\ \rowsep

messages & \tcode{messages_byname<char>}, \tcode{messages_byname<wchar_t>} \\

\end{floattable}

The provided implementation of members of facets

\tcode{num_get<charT>}

and

\tcode{num_put<charT>}

calls

\tcode{use_fac\-et<F>(l)}

only for facet

\tcode{F}

of types

\tcode{numpunct<charT>}

and

\tcode{ctype<charT>},

and for locale

\tcode{l}

the value obtained

by calling member

\tcode{getloc()}

on the

\tcode{ios_base\&}

argument to these functions.

In declarations of facets, a template parameter with name

\tcode{InputIterator}

or

\tcode{OutputIterator}

indicates the set of

all possible specializations on parameters that satisfy the

requirements of an Input Iterator or an Output Iterator, respectively~(\ref{iterator.requirements}).

A template parameter with name

\tcode{C}

represents the set

of types containing \tcode{char}, \tcode{wchar_t}, and any other

\impldef{set of character types that iostreams templates can be instantiated for}

character types that satisfy

the requirements for a character on which any of the iostream

components can be instantiated.

A template parameter with name

\tcode{International}

represents the set of all possible specializations on a bool parameter.

\rSec4[locale.facet]{Class \tcode{locale::facet}}

\indexlibrarymember{locale}{facet}%

\begin{codeblock}

namespace std {

class locale::facet {

protected:

explicit facet(size_t refs = 0);

virtual ~facet();

facet(const facet&) = delete;

void operator=(const facet&) = delete;

};

}

\end{codeblock}

Class \tcode{facet} is the base class for locale feature sets.

A class is a \defn{facet}

if it is publicly derived from another facet, or

if it is a class derived from \tcode{locale::facet} and

contains a publicly accessible declaration as follows:%

\footnote{This is a complete list of requirements; there are no other requirements.

Thus, a facet class need not have a public

copy constructor, assignment, default constructor, destructor, etc.}

\begin{codeblock}

static ::std::locale::id id;

\end{codeblock}

Template parameters in this Clause which are required to be facets are those named

\tcode{Facet}

in declarations.

A program that passes a type that is

\textit{not}

a facet, or a type that refers to a volatile-qualified facet, as an

(explicit or deduced) template parameter to a locale

function expecting a facet, is ill-formed. A const-qualified facet is a

valid template argument to any locale function that expects a Facet template

parameter.

The \tcode{refs}

argument to the constructor is used for lifetime management.

For

\tcode{refs == 0},

the implementation performs

\tcode{delete static_cast<locale::facet*>(f)}

(where

\tcode{f}

is a point\-er to the facet) when the last

\tcode{locale}

object containing the facet is destroyed;

for

\tcode{refs == 1},

the implementation never destroys the facet.

Constructors of all

facets defined in this Clause take such an argument and pass it

along to their

\tcode{facet}

base class constructor.

All one-argument constructors defined

in this Clause are

\term{explicit},

preventing their participation in automatic conversions.

For some standard facets a standard

class, derived from it, implements the virtual function semantics

equivalent to that facet of the locale constructed by

\tcode{locale(const char*)}

with the same name.

Each such facet provides a constructor that takes a

\tcode{const char*}

argument, which names the locale, and a \tcode{refs}

argument, which is passed to the base class constructor.

Each such facet also provides a constructor that takes a

\tcode{string} argument \tcode{str} and a \tcode{refs}

argument, which has the same effect as calling the first constructor with the

two arguments \tcode{str.c_str()} and \tcode{refs}.

If there is no

version of a facet, the base class implements named locale

semantics itself by reference to other facets.

\rSec4[locale.id]{Class \tcode{locale::id}}

\indexlibrarymember{locale}{id}%

\begin{codeblock}

namespace std {

class locale::id {

public:

id();

void operator=(const id&) = delete;

id(const id&) = delete;

};

}

\end{codeblock}

The class \tcode{locale::id} provides identification of a locale facet

interface, used as an index for lookup

and to encapsulate initialization.

\begin{note}

Because facets are used by iostreams, potentially while static constructors are

running, their initialization cannot depend on programmed static

initialization.

One initialization strategy is for

\tcode{locale}

to initialize each facet's

\tcode{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~(\ref{basic.start.static}).

\end{note}

\rSec3[locale.cons]{\tcode{locale} constructors and destructor}

\indexlibrary{\idxcode{locale}!constructor}%

\begin{itemdecl}

locale() noexcept;

\end{itemdecl}

\begin{itemdescr}

Default constructor: a snapshot of the current global locale.

Constructs a copy of the argument last passed to

\tcode{locale::global(locale\&)},

if it has been called; else, the resulting facets have virtual

function semantics identical to those of

\tcode{locale::classic()}.

\begin{note}

This constructor is commonly used as the default value for arguments

of functions that take a

\tcode{const locale\&}

argument.

\end{note}

\end{itemdescr}

\indexlibrary{\idxcode{locale}!constructor}%

\begin{itemdecl}

locale(const locale& other) noexcept;

\end{itemdecl}

\begin{itemdescr}

Constructs a locale which is a copy of \tcode{other}.

\end{itemdescr}

\indexlibrary{\idxcode{locale}!constructor}%

\begin{itemdecl}

explicit locale(const char* std_name);

\end{itemdecl}

\begin{itemdescr}

Constructs a locale using standard C locale names, e.g., \tcode{"POSIX"}.

The resulting locale implements semantics defined to be associated

with that name.

\tcode{runtime_error}

if the argument is not valid, or is null.

The set of valid string argument values is \tcode{"C"}, \tcode{""},

and any \impldef{locale names} values.

\end{itemdescr}

\indexlibrary{\idxcode{locale}!constructor}%

\begin{itemdecl}

explicit locale(const string& std_name);

\end{itemdecl}

\begin{itemdescr}

\effects The same as \tcode{locale(std_name.c_str())}.

\end{itemdescr}

\indexlibrary{\idxcode{locale}!constructor}%

\begin{itemdecl}

locale(const locale& other, const char* std_name, category);

\end{itemdecl}

\begin{itemdescr}

Constructs a locale as a copy of

\tcode{other}

except for the facets identified by the

\tcode{category}

argument, which instead implement the same semantics as

\tcode{locale(std_name)}.

\tcode{runtime_error}

if the argument is not valid, or is null.

The locale has a name if and only if

\tcode{other}

has a name.

\end{itemdescr}

\indexlibrary{\idxcode{locale}!constructor}%

\begin{itemdecl}

locale(const locale& other, const string& std_name, category cat);

\end{itemdecl}

\begin{itemdescr}

\effects The same as \tcode{locale(other, std_name.c_str(), cat)}.

\end{itemdescr}

\indexlibrary{\idxcode{locale}!constructor}%

\begin{itemdecl}

template <class Facet> locale(const locale& other, Facet* f);

\end{itemdecl}

\begin{itemdescr}

Constructs a locale incorporating all facets from the first

argument except that of type

\tcode{Facet},

and installs the second argument as the remaining facet.

If \tcode{f}

is null, the resulting object is a copy of \tcode{other}.

The resulting locale has no name.

\end{itemdescr}

\indexlibrary{\idxcode{locale}!constructor}%

\begin{itemdecl}

locale(const locale& other, const locale& one, category cats);

\end{itemdecl}

\begin{itemdescr}

Constructs a locale incorporating all facets from the first argument

except those that implement

\tcode{cats},

which are instead incorporated from the second argument.

The resulting locale has a name if and only if the first two arguments

have names.

\end{itemdescr}

\indexlibrarymember{operator=}{locale}%

\begin{itemdecl}

const locale& operator=(const locale& other) noexcept;

\end{itemdecl}

\begin{itemdescr}

Creates a copy of \tcode{other}, replacing the current value.

\tcode{*this}.

\end{itemdescr}

\indexlibrary{\idxcode{locale}!destructor}%

\begin{itemdecl}

~locale();

\end{itemdecl}

\begin{itemdescr}

A non-virtual destructor that throws no exceptions.

\end{itemdescr}

\rSec3[locale.members]{\tcode{locale} members}

\indexlibrarymember{locale}{combine}%

\begin{itemdecl}

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

\end{itemdecl}

\begin{itemdescr}

Constructs a locale incorporating

all facets from

\tcode{*this}

except for that one facet of

\tcode{other}

that is identified by

\tcode{Facet}.

The newly created locale.

\tcode{runtime_error}

if

\tcode{has_facet<Facet>(other)}

is \tcode{false}.

The resulting locale has no name.

\end{itemdescr}

\indexlibrarymember{locale}{name}%

\begin{itemdecl}

basic_string<char> name() const;

\end{itemdecl}

\begin{itemdescr}

The name of

\tcode{*this},

if it has one; otherwise, the string \tcode{"*"}.

\end{itemdescr}

\rSec3[locale.operators]{\tcode{locale} operators}

\indexlibrarymember{locale}{operator==}%

\begin{itemdecl}

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

\end{itemdecl}

\begin{itemdescr}

\tcode{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;

\tcode{false}

otherwise.

\end{itemdescr}

\indexlibrarymember{locale}{operator"!=}%

\begin{itemdecl}

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

\end{itemdecl}

\begin{itemdescr}

\returns \tcode{!(*this == other)}.

\end{itemdescr}

\indexlibrarymember{locale}{operator()}%

\begin{itemdecl}

template <class charT, class traits, class Allocator>

bool operator()(const basic_string<charT, traits, Allocator>& s1,

const basic_string<charT, traits, Allocator>& s2) const;

\end{itemdecl}

\begin{itemdescr}

Compares two strings according to the

\tcode{collate<charT>}

facet.

This member operator template (and therefore

\tcode{locale}

itself) satisfies requirements for a comparator predicate template argument

(Clause~\ref{algorithms}) applied to strings.

\begin{codeblock}

use_facet<collate<charT>>(*this).compare(s1.data(), s1.data() + s1.size(),

s2.data(), s2.data() + s2.size()) < 0

\end{codeblock}

\begin{example}

A vector of strings

\tcode{v}

can be collated according to collation rules in locale

\tcode{loc}

simply by~(\ref{alg.sort}, \ref{vector}):

\begin{codeblock}

std::sort(v.begin(), v.end(), loc);

\end{codeblock}

\end{example}

\end{itemdescr}

\rSec3[locale.statics]{\tcode{locale} static members}

\indexlibrarymember{locale}{global}%

\begin{itemdecl}

static locale global(const locale& loc);

\end{itemdecl}

\begin{itemdescr}

Sets the global locale to its argument.

Causes future calls to the constructor

\tcode{locale()}

to return a copy of the argument.

If the argument has a name, does

\begin{codeblock}

setlocale(LC_ALL, loc.name().c_str());

\end{codeblock}

otherwise, the effect on the C locale, if any, is \impldef{effect on C locale of calling

\tcode{locale::global}}.

No library function other than

\tcode{locale::global()}

shall affect the value returned by

\tcode{locale()}.

\begin{note} See~\ref{c.locales} for data race considerations when

\tcode{setlocale} is invoked. \end{note}

The previous value of

\tcode{locale()}.

\end{itemdescr}

\indexlibrarymember{locale}{classic}%

\begin{itemdecl}

static const locale& classic();

\end{itemdecl}

\begin{itemdescr}

The \tcode{"C"} locale.

A locale that implements the classic \tcode{"C"} locale semantics, equivalent

to the value \tcode{locale("C")}.

This locale, its facets, and their member functions, do not change

with time.

\end{itemdescr}

\rSec2[locale.global.templates]{\tcode{locale} globals}

\indexlibrarymember{locale}{use_facet}%

\begin{itemdecl}

template <class Facet> const Facet& use_facet(const locale& loc);

\end{itemdecl}

\begin{itemdescr}

\tcode{Facet}

is a facet class whose definition contains the public static member

\tcode{id}

as defined in~\ref{locale.facet}.

A reference to the corresponding facet of \tcode{loc}, if present.

\tcode{bad_cast}

if

\tcode{has_facet<Facet>(loc)}

is

\tcode{false}.

The reference returned remains valid at least as long as any copy of

\tcode{loc} exists.

\end{itemdescr}

\indexlibrarymember{locale}{has_facet}%

\begin{itemdecl}

template <class Facet> bool has_facet(const locale& loc) noexcept;

\end{itemdecl}

\begin{itemdescr}

\tcode{true} if the facet requested is present in \tcode{loc}; otherwise \tcode{false}.

\end{itemdescr}

\rSec2[locale.convenience]{Convenience interfaces}

\rSec3[classification]{Character classification}

\indexlibrary{\idxcode{isspace}}%

\indexlibrary{\idxcode{isprint}}%

\indexlibrary{\idxcode{iscntrl}}%

\indexlibrary{\idxcode{isupper}}%

\indexlibrary{\idxcode{islower}}%

\indexlibrary{\idxcode{isalpha}}%

\indexlibrary{\idxcode{isdigit}}%

\indexlibrary{\idxcode{ispunct}}%

\indexlibrary{\idxcode{isxdigit}}%

\indexlibrary{\idxcode{isalnum}}%

\indexlibrary{\idxcode{isgraph}}%

\indexlibrary{\idxcode{isblank}}%

\begin{itemdecl}

template <class charT> bool isspace (charT c, const locale& loc);

template <class charT> bool isprint (charT c, const locale& loc);

template <class charT> bool iscntrl (charT c, const locale& loc);

template <class charT> bool isupper (charT c, const locale& loc);

template <class charT> bool islower (charT c, const locale& loc);

template <class charT> bool isalpha (charT c, const locale& loc);

template <class charT> bool isdigit (charT c, const locale& loc);

template <class charT> bool ispunct (charT c, const locale& loc);

template <class charT> bool isxdigit(charT c, const locale& loc);

template <class charT> bool isalnum (charT c, const locale& loc);

template <class charT> bool isgraph (charT c, const locale& loc);

template <class charT> bool isblank (charT c, const locale& loc);

\end{itemdecl}

Each of these functions