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std::numpunct

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Defined in header <locale>
template< class CharT >
class numpunct;

The facet std::numpunct encapsulates numeric punctuation preferences. Stream I/O operations use std::numpunct through std::num_get and std::num_put for parsing numeric input and formatting numeric output.

The numbers that are supported by std::numpunct have the format described below. Here digit represents the radix set specified by the fmtflags argument value, thousands-sep and decimal-point are the results of thousands_sep() and decimal_point() functions respectively. The format of integer values is as follows:

integer     ::= [sign] units
sign        ::= plusminus
plusminus   ::= '+' | '-'
units       ::= digits [thousands-sep units]
digits      ::= digit [digits]

The number of digits between the thousand-seps (maximum size of digits) is specified by the result of grouping().

The format of floating-point values is as follows:

floatval    ::= [sign] units [decimal-point [digits]] [e [sign] digits] |
                [sign]        decimal-point  digits   [e [sign] digits]
e           ::= ’e’ | ’E’
cpp/locale/locale/facetstd-numpunct-inheritance.svg
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Inheritance diagram

Two specializations are provided by the standard library

Defined in header <locale>
std::numpunct<char> provides equivalents of the "C" locale preferences
std::numpunct<wchar_t> provides wide character equivalents of the "C" locale preferences

Contents

Member types

Member type Definition
char_type charT
string_type std::basic_string<charT>

Member functions

constructs a new numpunct facet
(public member function) [edit]
destructs a numpunct facet
(protected member function) [edit]
invokes do_decimal_point
(public member function) [edit]
invokes do_thousands_sep
(public member function) [edit]
invokes do_grouping
(public member function) [edit]
invokes do_truename or do_falsename
(public member function) [edit]

Protected member functions

provides the character to use as decimal point
(virtual protected member function) [edit]
provides the character to use as thousands separator
(virtual protected member function) [edit]
[virtual]
provides the numbers of digits between each pair of thousands

separators
(virtual protected member function) [edit]

provides the string to use as the name of the boolean true and false
(virtual protected member function) [edit]

Member objects

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

Example

The following example changes the string representations of true and false

#include <iostream>
#include <locale>
 
struct french_bool : std::numpunct<char> {
    string_type do_truename() const { return "oui"; }
    string_type do_falsename() const { return "non"; }
};
 
int main()
{
    std::cout << "default locale: "
              << std::boolalpha << true << ", " << false << '\n';
    std::cout.imbue(std::locale(std::cout.getloc(), new french_bool));
    std::cout << "locale with modified numpunct: "
              << std::boolalpha << true << ", " << false << '\n';
}

Output:

default locale: true, false
locale with modified numpunct: oui, non

See also

creates a numpunct facet for the named locale
(class template)