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num_get



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num_get 

num_getlocale::facet

Summary

Numeric formatting facet for input.

Data Type and Member Function Indexes
(exclusive of constructors and destructors)

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 delegated 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






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