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std::num_get(3)		      C++ Standard Libary	       std::num_get(3)

NAME
       std::num_get - std::num_get

Synopsis
	  Defined in header <locale>
	  template<

	  class	CharT,
	  class	InputIt	= std::istreambuf_iterator<CharT>

	  > class num_get;

	  Class	 std::num_get encapsulates the rules for parsing string	repre-
       sentations of
	  numeric values. Specifically,	types bool, unsigned  short,  unsigned
       int, long,
	  unsigned  long,  long	 long, unsigned	long long, float, double, long
       double, and void*
	  are supported. The standard formatting input operators (such as  cin
       >> n;) use the
	  std::num_get facet of	the I/O	stream's locale	to parse the text rep-
       resentations of
	  the numbers.

	  std-num get-inheritance.svg

					  Inheritance diagram

Type requirements
	  -
	  InputIt must meet the	requirements of	LegacyInputIterator.

Specializations
	  Two  standalone  (locale-independent)	 full  specializations and two
       partial
	  specializations are provided by the standard library:

	  Defined in header <locale>
	  std::num_get<char>		 creates narrow	string parsing of num-
       bers
	  std::num_get<wchar_t>		 creates wide string parsing  of  num-
       bers
	  std::num_get<char, InputIt>	 creates narrow	string parsing of num-
       bers using custom
					 input iterator
	  std::num_get<wchar_t,	 InputIt>  creates wide	string parsing of num-
       bers using custom
					 input iterator

	  In addition, every locale object constructed in a C++	program	imple-
       ments its own
	  (locale-specific) versions of	these specializations.

Member types
	  Member type Definition
	  char_type   CharT
	  iter_type   InputIt

Member functions
	  constructor	constructs a new num_get facet
			(public	member function)
	  destructor	destructs a num_get facet
			(protected member function)
	  get		invokes	do_get
			(public	member function)

Member objects
	  static std::locale::id id id of the locale
				    (public member object)

Protected member functions
	  do_get    parses a number from an input stream
	  [virtual] (virtual protected member function)

Example
       // Run this code

	#include <iostream>
	#include <locale>
	#include <string>
	#include <sstream>
	#include <iterator>

	int main()
	{
	    std::string	de_double = "1.234.567,89";
	    std::string	us_double = "1,234,567.89";

	    // parse using streams
	    std::istringstream de_in(de_double);
	    de_in.imbue(std::locale("de_DE"));
	    double f1;
	    de_in >> f1;

	    std::istringstream us_in(de_double);
	    us_in.imbue(std::locale("en_US.UTF-8"));
	    double f2;
	    us_in >> f2;

	    std::cout << "Parsing " << de_double << " as  double  gives	 "  <<
       std::fixed
		      << f1 << " in de_DE locale and " << f2 <<	" in en_US\n";

	    // use the facet directly
	    std::istringstream s3(us_double);
	    s3.imbue(std::locale("en_US.UTF-8"));
	    auto& f = std::use_facet<std::num_get<char>>(s3.getloc());
	    std::istreambuf_iterator<char> beg(s3), end;
	    double f3;
	    std::ios::iostate err;
	    f.get(beg, end, s3,	err, f3);
	    std::cout << "parsing " << us_double
		      <<  "  as	 double	using raw en_US	facet gives " << f3 <<
       '\n';
	}

Output:
	Parsing	1.234.567,89 as	double gives 1234567.890000  in	 de_DE	locale
       and 1.234000 in en_US
	parsing	  1,234,567.89	 as   double   using  raw  en_US  facet	 gives
       1234567.890000

See also
	  numpunct   defines numeric punctuation rules
		     (class template)
	  num_put    formats numeric values for	output as character sequence
		     (class template)
	  operator>> extracts formatted	data
		     (public	  member      function	     of	      std::ba-
       sic_istream<CharT,Traits>)

http://cppreference.com		  2022.07.31		       std::num_get(3)

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