std::num_put (3) - Linux Manuals

std::num_put: std::num_put

NAME

std::num_put - std::num_put

Synopsis

Defined in header <locale>
template<
class CharT,
class OutputIt = std::ostreambuf_iterator<CharT>
> class num_put;

Class std::num_put encapsulates the rules for formatting numeric values as strings. Specifically, the types bool, long, unsigned long, long long, unsigned long long, double, long double, void*, and of all types implicitly convertible to these (such as int or float) are supported. The standard formatting output operators (such as cout << n;) use the std::num_put facet of the I/O stream's locale to generate text representation of numbers.
 std-num put-inheritance.svg
Inheritance diagram

Type requirements

-
OutputIt must meet the requirements of LegacyOutputIterator.

Specializations

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

Defined in header <locale>
std::num_put<char> creates narrow string representations of numbers
std::num_put<wchar_t> creates wide string representations of numbers
std::num_put<char, OutputIt> creates narrow string representations of numbers using custom output iterator
std::num_put<wchar_t, OutputIt> creates wide string representations of numbers using custom output iterator

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

Member types

Member type Definition
char_type CharT
iter_type OutputIt

Member functions

              constructs a new num_put facet
constructor (public member function)
              destructs a num_put facet
destructor (protected member function)
              invokes do_put
put (public member function)

Protected member functions

do_put formats a number and writes to output stream
          (virtual protected member function)
[virtual]

Member objects

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

Example

// Run this code

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

  int main()
  {
      double n = 1234567.89;
      std::cout.imbue(std::locale("de_DE"));
      std::cout << "Direct conversion to string:\n"
                << std::to_string(n) << '\n'
                << "Output using a german locale:\n"
                << std::fixed << n << '\n'
                << "Output using an american locale:\n";
      // use the facet directly
      std::cout.imbue(std::locale("en_US.UTF-8"));
      auto& f = std::use_facet<std::num_put<char>>(std::cout.getloc());
      f.put(std::ostreambuf_iterator<char>(std::cout), std::cout, ' ', n);
      std::cout << '\n';
  }

Output:

  Direct conversion to string:
  1234567.890000
  Output using a german locale:
  1.234.567,890000
  Output using an american locale:
  1,234,567.890000