std::num_get::get

Parameters

in, end

Iterators pointing to the beginning and end characters of the sequence. The range used is [in,end), which contains all the characters between in and end, including the character pointed by in but not the character pointed by end.
Member type iter_type is the facet's iterator type (defined as an alias of num_get's second template parameter, InputIterator). By default, this is an istreambuf_iterator, allowing implicit conversions from basic_istream objects.

str

Object of a class derived from ios_base (generally an input stream object). It is only used to obtain formatting information.

err

Stream error state object, of type ios_base::iostate where the resulting state is stored.

val

Element of a numerical type.
The function stores the value in it if it successfully extracts a number (i.e. if err's failbit flag is not set).

Return value

Example

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// num_get example
#include <iostream>       // std::cin, std::cout, std::ios
#include <locale>         // std::locale, std::num_get, std::use_facet
#include <iterator>       // std::istreambuf_iterator
#include <string>         // std::string

int main ()
{
  std::locale loc;
  std::ios::iostate state;
  float mypi,yourpi;

  std::string number ("3.14159");
  // get from string:
  std::use_facet<std::num_get<char,std::string::iterator> > (loc).get
    (number.begin(), number.end(), std::cin, state, mypi);

  std::cout << "Please, enter PI: ";
  // get from istream:
  std::use_facet<std::num_get<char> >(loc).get
    (std::cin, std::istreambuf_iterator<char>(), std::cin, state, yourpi);

  if ( (mypi-yourpi>0.01) || (mypi-yourpi<-0.01) )
    std::cout << "Wrong!\n";
  else
    std::cout << "Right!\n";

  return 0;
}

Please, enter PI: 3.14
Right!

Data races

Exception safety

See also

num_put::put

Put numerical value (public member function)

istream::operator>>

Extract formatted input (public member function)