std::num_put(3)

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

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

Member objects
   static std::locale::id id id of the locale
                        (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

See also
   numpunct defines numeric punctuation rules
              (class template)
   num_get parses numeric values from an input character sequence
              (class template)
   to_string converts an integral or floating point value to string
   (C++11) (function)
   to_wstring converts an integral or floating point value to wstring
   (C++11) (function)