Standard C++ LibraryCopyright 1996, Rogue Wave Software, Inc.

NAME

  num_get - Numeric formatting facet for input.

SYNOPSIS

  #include <locale>
  template <class charT, class InputIterator > class num_get;

DESCRIPTION

  The num_get provides facilities for formatted input of numbers.
  basic_istream and all other input-oriented streams use this facet to
  implement formatted numeric input.

INTERFACE

  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, iter_type, ios_base&,
                 ios_base::iostate&, bool&)          const;
   iter_type get(iter_type, iter_type, ios_base& ,
                 ios_base::iostate&, long&)          const;
   iter_type get(iter_type, iter_type, ios_base&,
                 ios_base::iostate&, unsigned short&) const;
   iter_type get(iter_type, iter_type, ios_base&,
                 ios_base::iostate&, unsigned int&)  const;
   iter_type get(iter_type, iter_type, ios_base&,
                 ios_base::iostate&, unsigned long&) const;
   iter_type get(iter_type, iter_type, ios_base&,
                 ios_base::iostate&, float&)         const;
   iter_type get(iter_type, iter_type, ios_base&,
                 ios_base::iostate&, double&)        const;
   iter_type get(iter_type, iter_type, ios_base&,
                 ios_base::iostate&, long double&)   const;
   static locale::id id;

  protected:
    ~num_get();  // virtual
   virtual iter_type do_get(iter_type, iter_type, ios_base&,
                            ios_base::iostate&, bool&) const;
   virtual iter_type do_get(iter_type, iter_type, ios_base&,
                            ios_base::iostate&, long&) const;
   virtual iter_type do_get(iter_type, iter_type, ios_base&,
                            ios_base::iostate&,
                            unsigned short&) const;
   virtual iter_type do_get(iter_type, iter_type, ios_base&,
                            ios_base::iostate&,
                            unsigned int&) const;
   virtual iter_type do_get(iter_type, iter_type, ios_base&,
                            ios_base::iostate&,
                            unsigned long&) const;
   virtual iter_type do_get(iter_type, iter_type, ios_base&,
                            ios_base::iostate&, float&) const;
   virtual iter_type do_get(iter_type, iter_type, ios_base&,
                            ios_base::iostate&, double&) const;
   virtual iter_type do_get(iter_type, iter_type, ios_base&,
                            ios_base::iostate&,
                            long double&) const;
  };

TYPES

  char_type
     Type of character the facet is instantiated on.

  iter_type
     Type of iterator used to scan the character buffer.

CONSTRUCTOR AND DESTRUCTOR

  explicit num_get(size_t refs = 0)
     Construct a num_get facet.  If the refs argument is 0 then destruction
     of the object is delegated to the locale, or locales, containing it.
     This allows the user to ignore lifetime management issues.  On the other
     had, if refs  is 1 then the object must be explicitly deleted; the
     locale will not do so.  In this case, the object can be maintained
     across the lifetime of multiple locales.

  ~num_get();  // virtual and protected
     Destroy the facet

FACET ID

  static locale::id id;
     Unique identifier for this type of facet.

PUBLIC MEMBER FUNCTIONS

  The public members of the num_get facet provide an interface to protected
  members.  Each public member xxx has a corresponding virtual protected
  member do_xxx.  All work is delagated to these protected members.  For
  instance, the long version of the public get function simply calls its
  protected cousin do_get.

  iter_type
  get(iter_type in, iter_type end, ios_base& io,
     ios_base::iostate& err, bool& v)          const;
  iter_type
  get(iter_type in, iter_type end, ios_base& io,
     ios_base::iostate& err, long& v)          const;
  iter_type
  get(iter_type in, iter_type end, ios_base& io,
     ios_base::iostate& err, unsigned short& v) const;
  iter_type
  get(iter_type in, iter_type end, ios_base& io,
     ios_base::iostate& err, unsigned int& v)  const;
  iter_type
  get(iter_type in, iter_type end, ios_base& io,
     ios_base::iostate& err, unsigned long& v) const;
  iter_type
  get(iter_type in, iter_type end, ios_base& io,
     ios_base::iostate& err, float& v)         const;
  iter_type
  get(iter_type in, iter_type end, ios_base& io,
     ios_base::iostate& err, double& v)        const;
  iter_type
  get(iter_type in, iter_type end, ios_base& io,
     ios_base::iostate& err, long double& v)   const;
     Each of the eight overloads of the get function simply call the
     corresponding do_get function.

PROTECTED MEMBER FUNCTIONS

  virtual iter_type
  do_get(iter_type in, iter_type end, ios_base& io,
        ios_base::iostate& err, bool& v) const;
  virtual iter_type
  do_get(iter_type in, iter_type end, ios_base& io,
        ios_base::iostate& err, long& v) const;
  virtual iter_type
  do_get(iter_type in, iter_type end, ios_base& io,
        ios_base::iostate& err,
        unsigned short& v) const;
  virtual iter_type
  do_get(iter_type in, iter_type end, ios_base& io,
        ios_base::iostate& err,
        unsigned int& v) const;
  virtual iter_type
  do_get(iter_type in, iter_type end, ios_base& io,
        ios_base::iostate& err,
        unsigned long& v) const;
  virtual iter_type
  do_get(iter_type in, iter_type end, ios_base& io,
        ios_base::iostate& err, float& v) const;
  virtual iter_type
  do_get(iter_type in, iter_type end, ios_base& io,
        ios_base::iostate& err, double& v) const;
  virtual iter_type
  do_get(iter_type in, iter_type end, ios_base& io,
        ios_base::iostate& long double& v) const;

     The eight overloads of the do_get member function all take a sequence of
     characters [int,end), and extract a numeric value.  The numeric value is
     returned in v.   The io argument is used to obtain formatting
     information and the err argument is used to set error conditions in a
     calling stream.

EXAMPLE

  //
  // numget.cpp
  //

  #include <sstream>

  int main ()
  {
   using namespace std;

  typedef istreambuf_iterator<char,char_traits<char> > iter_type;

   locale loc;
   ios_base::iostate state;
   bool bval = false;
   long lval = 0L;
   long double ldval = 0.0;
   iter_type end;

    // Get a num_get facet
   const num_get<char,iter_type>& tg =
  #ifndef _RWSTD_NO_TEMPLATE_ON_RETURN_TYPE
   use_facet<num_get<char,iter_type> >(loc);
  #else
   use_facet(loc,(num_get<char,iter_type>*)0);
  #endif

    {
      // Build an istringstream from the buffer and construct
      // beginning and ending iterators on it.
     istringstream ins("true");
     iter_type begin(ins);

      // Get a bool value
     tg.get(begin,end,ins,state,bval);
    }
   cout << bval << endl;
    {
      // Get a long value
     istringstream ins("2422235");
     iter_type begin(ins);
     tg.get(begin,end,ins,state,lval);
    }
   cout << lval << endl;
    {
      // Get a long double value
     istringstream ins("32324342.98908");
     iter_type begin(ins);
     tg.get(begin,end,ins,state,ldval);
    }
   cout << ldval << endl;
   return 0;
  }

SEE ALSO

  locale, facets, num_put, numpunct, ctype

STANDARDS CONFORMANCE

  ANSI X3J16/ISO WG21 Joint C++ Committee



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