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# std::num_put

From cppreference.com
< cpp‎ | locale

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.

Inheritance diagram

### [edit] Type requirements

- `OutputIt` must meet the requirements of `OutputIterator`.

### [edit] 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.

### [edit] Member types

Member type | Definition
`char_type` | `CharT`
`iter_type` | `OutputIt`

### [edit] 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)

### [edit] Protected member functions

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

### [edit] Member objects

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

### [edit] 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

### [edit] See also

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

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