______________________________________________________________________

  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();
    };
  }

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.

8 In successive calls to a locale facet member function during a call to
  an iostream inserter or extractor or a streambuf member function,  the
  returned  result  shall  be  identical.  [Note: This implies that such
  results may safely be reused without calling the locale  facet  member
  function  again,  and that member functions of iostream classes cannot
  safely call imbue() themselves, except as specified elsewhere.   --end
  note]

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:

                     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, or is null.
  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).
  Throws:
    runtime_error if the argument is not valid, or is null.
  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.  If f is null, the resulting object is  a  copy  of
    other.
  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.
  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.

  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.
  Returns:
    a reference to the corresponding facet of loc, if present.
  Throws:
    bad_cast if has_facet<Facet>(*this) is false.
  Notes:
    The reference returned remains valid at least as long as any copy of
    loc exists.

  +-------                 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:
    true if the facet requested is present in loc; otherwise 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_).3)
  _________________________
  3) When used in a loop, it is faster to cache the  ctype<>  facet  and

  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.

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]

  _________________________
  use it directly, or use the vector form of ctype<>::is.

  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 lower 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.4)
    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]

  _________________________
  4) 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;
      static const size_t table_size = IMPLEMENTATION_DEFINED;
    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.5)  The  implementation-defined
  value of member table_size is at least 256.

  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]
  In the following member descriptions, for unsigned char values v where
  (v  >=  table_size),  table()[v] is assumed to have an implementation-
  defined value (possibly different for each such value v) without  per­
  forming the array lookup.

  explicit ctype(const mask* tbl = 0, bool del = false,
                 size_t refs = 0);

  Precondition:
    tbl either 0 or an array of at least table_size elements.
  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.
  _________________________
  5) 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>.

  const char* scan_is(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 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 table_size which
    represents the classifications 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.6)

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
  _________________________
  6)  Parsing "-1" correctly into (e.g.) an unsigned short requires that
  the corresponding member get() at least extract the sign before  dele­
  gating.

  values                                (_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);
      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, 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, 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;

  +-------                 BEGIN BOX 8                -------+
  Change: This section reflects "aggressive editorial action" authorized
  by the iostream WG and motion ... in Monterey.
  +-------                  END BOX 8                 -------+

  +-------                 BEGIN BOX 9                -------+
  The  section  needs a locale, refered to a loc in what follows, but it
  is not clear where that locale is coming from.
  +-------                  END BOX 9                 -------+

  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.

1 The details of this operation occur in two stages

  --Stage 1: Determine a conversion specifier

  --Stage  2: Extract characters from in and transform them into char's,
    converting the value transformed characters according to the conver­
    sion specification determined in stage 1.

  --Stage 3: Store results
    The details of the stages are presented below
  Returns
  Stage 1:
    The function initializes local variables via
          fmtflags flags = str.flags();
          fmtflags basefield = (flags & ios_base::basefield)
          fmtflags uppercase = (flags & ios_base::uppercase);
          fmtflags basefield = (flags & ios_base::basefield);
          fmtflags boolalpha = (flags & ios_base::boolalpha);
     For  conversion  to  an  integral type, the function determines the
    integral conversion specifier as indicated in Table 5:

                        Table 5--Integer conversions

            +--------------------------------------------------+
            |            State                stdio equivalent |
            +--------------------------------------------------+
            |basefield == oct                        %o        |
            +--------------------------------------------------+
            |basefield == hex && !uppercase          %x        |
            +--------------------------------------------------+
            |basefield == hex                        %X        |
            +--------------------------------------------------+
            |basefield == 0                          %i        |
            +--------------------------------------------------+
            |signed integral type                    %d        |
            |__                                                |
            |unsigned integral type                  %u        |
            +--------------------------------------------------+
    For conversions to a  floating type the specifier is %g.
    A length specifier is added to the conversion specification as indi­
    cated in Table  6.

                          Table 6--Length Modifier

                     +---------------------------------+
                     |     type        length modifier |
                     +---------------------------------+
                     |short                   h        |
                     |-                                |
                     |unsigned short          h        |
                     |-                                |
                     |long                    l        |
                     |-                                |
                     |unsigned long           l        |
                     |-                                |
                     |long double             L        |
                     |-                                |
                     |                      none       |
                     +---------------------------------+
  Stage 2:
    If in==end then stage 2 terminates.  Otherwise a charT is taken from
    in and local variables are initialized as if by
          char_type ct = *in ;
          char c = use_facet<ctype<charT> >(loc).do_narrow(ct,' ');
          if ( ct ==  use_facet<numpunct<charT> >(loc).do_decimal_point() )
              c = '.';
          bool discard =
              ( ct == use_facet<numpunct<charT> >(loc).do_thousands_sep()
                  &&
               use_facet<numpunct<charT> >(loc).do_grouping().length != 0 );

  +-------                BEGIN BOX 10                -------+
  Change: The earlier text referred to "if no  grouping  is  specified".
  Is that the same as the test for length being 0?
  +-------                 END BOX 10                 -------+

    If discard is true then the position of the character is remembered,
    but the character is otherwise ignored.  If  it  is  not  discarded,
    then  a check is made to determine if c is allowed as the next char­
    acter of an input field of  the  conversion  specifier  returned  by
    stage 1. If so is accumulated.
     If  the  character  is neither discarded nor accumulated then in is
    advanced by ++in and processing returns to the beginning of stage 2.
  Stage 3:
    The result of stage 2 processing can be one of

  --A  sequence  of  chars  has been accumulated in stage 2 that is con­
    verted (according to the rules of std::scanf) to a value of the type
    of val.  This value is stored in val and ios_base::goodbit is stored
    in

  --The sequence of chars accumulated in stage 2 would have caused scanf

    to report an input failure.  ios_base::failbit is assigned to
    Digit grouping is checked.  That is, the positions of discarded sep­
    arators      is      examined       for       consistency       with
    use_facet<numpunct<charT>>(loc).do_grouping()

  +-------                BEGIN BOX 11                -------+
  Is the treatment of separators here clear?
  +-------                 END BOX 11                 -------+

  If they are not consistent then ios_base::failbit is assigned to

2 In  any  case,  if  stage  2 processing was terminated by the test for
  in==end then err|=ios_base::eofbit is performed.

  iter_type do_get(iter_type in, iter_type end, ios_base& str,
                   ios_base::iostate& err, bool& val) const;

  Effects:
    If (str.flags()&&ios_base::boolalpha)==0 then input proceeds  as  it
    would  for an int except that if a value is stored being stored into
    val.  If the value to be store is 0 then false is  stored.   If  the
    value is 1 then true is stored.  Otherwise err|=ios_base::failbit is
    performed and no value is stored.

3 Otherwise a target string to  be  matched  is  determined  by  calling
  either       use_facet<ctype<charT>       >(f6loc).truename()       or
  use_facet<ctype<charT> >(f6loc).falsename() depending on  whether  val
  is true or false (respectively).

4 As  long as in!=end and characters continue to match the target string
  charT's are obtained by doing *in++.  A value is assigned  to  err  as
  follows

  --If the target string was matched completely, then goodbit.

  --If input was terminated because in!=end, then eofbit

  --Otherwise, failbit.
  Returns:

  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,
                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;

  +-------                BEGIN BOX 12                -------+
  Change: This section reflects "aggressive editorial action" authorized
  by the iostream WG and motion ... in Monterey.  Most of this  material
  was moved from the description of insertors in the iostream chapter.
  +-------                 END BOX 12                 -------+

  Effects:
    Writes characters to the sequence out, formatting val as desired. In
    the following description, a local variable initialized with
          locale loc = str.getloc();

  +-------                BEGIN BOX 13                -------+
  The original text mentioned loc without saying  where  it  came  from.
  This seems the only place.
  +-------                 END BOX 13                 -------+

  The base class implementation is described in several stages

  --Stage  1: Determine a printf conversion specifier spec and determin­
    ing the characters that would be  printed  by  printf(_lib.c.files_)
    given this conversion specifier for
          std::printf(spec, val)
    assuming that the current locale is the "C" locale.

  +-------                BEGIN BOX 14                -------+
  Change: The original description (in clause 27) of this process speci­
  fied use of the global locale here, but I think that becomes  circular
  and I replaced the global locale reference by the fixed "C" locale.
  +-------                 END BOX 14                 -------+

  --Stage  2:  Adjust  the representation by converting each char deter­
    mined by stage 1 to a charT using a conversion and  values  returned
    by members of use_facet< numpunct<charT> >(str.getloc())

  --Stage 3: Determine where padding is required.

  +-------                BEGIN BOX 15                -------+
  This used to be done by the print formatting, but because fill isn't a
  char and because the transformation of Stage 2 needs to be done before
  padding, I have made this a separate stage.

  +-------                 END BOX 15                 -------+

  --Stage 4: Insert the sequence into the out.
    Detailed descriptions of each stage follow
  Returns:
    out.

  Stage 1:
    The  first action of stage 1 is to determine a conversion specifier.
    The tables that describe this determination use the following  local
    variables
          fmtflags flags = this->flags() ;
          fmtflags basefield =  (flags & (ios_base::basefield));
          fmtflags uppercase =  (flags & (ios_base::uppercase));
          fmtflags floatfield = (flags & (ios_base::floatfield));
          fmtflags showpos =    (flags & (ios_base::showpos));
          fmtflags showbase =   (flags & (ios_base::showbase));
     All  tables  used  in describing stage 1 are ordered.  That is. the
    first line whose condition is true applies.  A line without a condi­
    tion is the default behavior when none of the earlier lines apply.
     For  conversion  from an integral type other than a character type,
    the function determines the integral conversion specifier  as  indi­
    cated in Table 7.

                        Table 7--Integer conversions

      +---------------------------------------------------------------+
      |                   State                      stdio equivalent |
      +---------------------------------------------------------------+
      |basefield == ios_base::oct                           %o        |
      +---------------------------------------------------------------+
      |(basefield == ios_base::hex) && !uppercase           %x        |
      +---------------------------------------------------------------+
      |(basefield == ios_base::hex)                         %X        |
      +---------------------------------------------------------------+
      |for a signed integral type                           %d        |
      +---------------------------------------------------------------+
      |for an unsigned integral type                        %u        |
      +---------------------------------------------------------------+
     For  conversion from a floating-point type, the function determines
    the floating-point conversion specifier as indicated in Table 8:

                    Table 8--Floating-point conversions

    +--------------------------------------------------------------------+
    |                     State                         stdio equivalent |
    +--------------------------------------------------------------------+
    |floatfield == ios_base::fixed                             %f        |
    +--------------------------------------------------------------------+
    |floatfield == ios_base::scientific && !uppercase          %e        |
    +--------------------------------------------------------------------+
    |floatfield == ios_base::scientific                        %E        |
    +--------------------------------------------------------------------+
    |!uppercase                                                %g        |
    +--------------------------------------------------------------------+
    |                                                          %G        |
    +--------------------------------------------------------------------+
    For conversions from an integral or floating type a length  modifier
    is added to the conversion specifier as indicated in  Table 9.

                          Table 9--Length modifier

                     +---------------------------------+
                     |     type        length modifier |
                     +---------------------------------+
                     |short                   h        |
                     +---------------------------------+
                     |unsigned short          h        |
                     +---------------------------------+
                     |long                    l        |
                     +---------------------------------+
                     |unsigned long           l        |
                     +---------------------------------+
                     |long double             L        |
                     +---------------------------------+
                     |                      none       |
                     +---------------------------------+
    The conversion specifier has the following optional additional qual­
    ifiers prepended as indicated in Table 10:

                       Table 10--Numeric conversions

      +--------------------------------------------------------------+
      |       Type(s)                State          stdio equivalent |
      +--------------------------------------------------------------+
      |an integral type oth­   flags & showpos             +         |
      |er than a character     flags & showbase            #         |
      |type                                                          |
      +--------------------------------------------------------------+
      |a floating-point type   flags & showpos             +         |
      |                        flags & showpoint           #         |
      +--------------------------------------------------------------+
    For conversion from a floating-point type, if (flags() & fixed) != 0
    or  if precision() > 0, then precision() is specified in the conver­
    sion specification.
    The representations at the end of stage 1  consists  of  the  char's
    that  would  be  printed  by a call of printf(s, val) where s is the
    conversion specifier determined above.

  Stage 2:
    Any character c other than a decimal  point(.)  is  converted  to  a
    charT via charT(c)

1 A local variable punct is initialized via
      numpunct<charT> punct = use_facet< numpunct<charT> >(str.getloc())
     For  integral  types, punct.thousands_sep() characters are inserted
    into  the  sequence  as  determined  by  the   value   returned   by
    punct.do_grouping()     using     the     method     described    in
    _lib.facet.numpunct.virtuals_
    Decimal point characters(.) are replaced by punct.decimal_point()

  Stage 3:
    A local variable is initialized as
          fmtflags adjustfield=   (flags & (ios_base::adjustfield));
    The location of any padding is determined according to Table 11:

                           Table 11--Fill padding

     +-----------------------------------------------------------------+
     |              State                           Location           |
     +-----------------------------------------------------------------+
     |adjustfield == ios_base::left        pad after                   |
     +-----------------------------------------------------------------+
     |adjustfield == ios_base::right       pad before                  |
     +-----------------------------------------------------------------+
     |adjustfield==internal and a sign                                 |
     |occurs in the representation                                     |
     |pad after the sign                                               |
     +-----------------------------------------------------------------+
     |adjustfield==internal and                                        |
     |representation after stage 1 began                               |
     |with 0x or 0X                                                    |
     +-----------------------------------------------------------------+
     |                                     pad before stage 2 sequence |
     +-----------------------------------------------------------------+

  +-------                BEGIN BOX 16                -------+
  The  above  table has been rewritten to make internal padding explicit
  rather than depend on the conversion specifier. Since the  C  standard
  had
  +-------                 END BOX 16                 -------+

     width()  is nonzero and the number of charT's in the sequence after
    stage 3 is less than width(), then enough fill characters are  added
    to  the  sequence at the position indicated for padding to bring the
    length of the sequence to width().
    width(0) is called.

  Stage 4:
    The sequence of charT's at the end of stage 3 are output via
          *out++ = c
    If at any point out.failed() becomes true,  then  output  is  termi­
    nated.

  iter_type put(iter_type out, ios_base& str, char_type fill,
                bool val) const;

  Effects:
    If (str.flags()&ios_base::boolalpha)==0 then do
          outP = put(out, str, fill, (int)val)
    Otherwise do
  _________________________
  7) The conversion specification #o generates a leading 0 which is  not
  a padding character.

          string_type s =
              val ? use_facet<ctype<charT> >(f6loc).truename()
                        : use_facet<ctype<charT> >(f6loc).falsename() ;
    and then insert the characters of s into out.

  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 17                -------+
  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 17                 -------+

  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 18                -------+
  Change: The  previous  version  said  thousands_sep()  returned  thou­
  sands_sep() (itself).  Changed to do_thousands_sep().
  +-------                 END BOX 18                 -------+

  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".

  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]

  _________________________
  8)  Thus,  the string " 03" specifies groups of 3 digits each, and "3"
  probably indicates groups of 51 (!) digits each.

  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,
    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;
    };

  _________________________
  9) This function is useful when one string is being compared  to  many
  other strings.

  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)

  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)

  _________________________
  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.

  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 19                -------+
  Change: Changed X to x above; the C strftime format %X does not  spec­
  ify any date components.
  +-------                 END BOX 19                 -------+

  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.

  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;
  _________________________
  11) This function is intended as a convenience only, for  common  for­
  mats, and may return no_order in valid locales.

  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.

  _________________________
  12) Interpretation of the modifier argument is implementation-defined,
  but should follow POSIX conventions.

  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.

  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)
    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.

  _________________________
  13) For  example, the sequence $1,056.23 in a common U.S. locale would
  yield, for units, 105623, or for digits, 105623".

  +-------                BEGIN BOX 20                -------+
  The description above needs further review.
  +-------                 END BOX 20                 -------+

  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;
    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

  format 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)
  _________________________
  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").

  string_type do_curr_symbol() const;

  Returns:
    A string to use as the currency identifier symbol.17)

  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

  _________________________
  17)  For international instantiations (second template parameter true)
  this is always four characters  long,  usually  three  letters  and  a
  space.
  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 12):

                   Table 12--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.