std::num_put

 

C++

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Localizations library

Locales and facets
locale
use_facet	has_facet
Character classification
isspace isblank (C++11) iscntrl isupper islower isalpha	isdigit ispunct isxdigit isalnum isprint isgraph
Conversions
toupper tolower	wstring_convert (C++11) wbuffer_convert (C++11)
Facet category base classes
ctype_base codecvt_base messages_base	time_base money_base
Facet categories
ctype ctype<char> codecvt collate messages time_get time_put	num_get num_put numpunct money_get money_put moneypunct
Locale-specific facets
ctype_byname ctype_byname<char> codecvt_byname messages_byname collate_byname	time_get_byname time_put_byname numpunct_byname moneypunct_byname
Code conversion facets
codecvt_utf8 (C++11) codecvt_utf16 (C++11)	codecvt_utf8_utf16 (C++11) codecvt_mode (C++11)
C locale
setlocale localeconv lconv	LC_ALL LC_COLLATE LC_CTYPE LC_MONETARY LC_NUMERIC LC_TIME

 

std::num_put

Member functions

num_put::num_put

num_put::~num_put

num_put::put num_put::do_put

 

Defined in header <locale>
template< class charT,           class OutputIterator = std::ostreambuf_iterator<charT> > class num_put : public std::locale::facet;

Class std::num_put encapsulates the rules for formatting values of type 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), as strings. 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.

Two specializations and two partial specializations are provided by the standard library and are implemented by all locale objects created in a C++ program:

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, OutputIterator>	creates narrow string representations of numbers using custom output iterator
std::num_put<wchar_t, OutputIterator>	creates wide string representations of numbers using custom output iterator

Member types

Member type	Definition
char_type	charT
iter_type	OutputIterator

Member objects

Member name	Type
id (static)	std::locale::id

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

Example

#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 (C++11)	converts an integral or floating point value to string (function)
to_wstring (C++11)	converts an integral or floating point value to wstring (function)