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