std::numpunct
<locale>
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'
Inheritance diagram
Contents
[edit] Specializations
The standard library is guaranteed to provide the following specializations (they are required to be implemented by any locale object):
<locale> [edit] Nested types
char_type
CharT
string_type
std::basic_string <CharT>
[edit] Data members
[edit] Member functions
[edit] Protected member functions
(virtual protected member function) [edit]
(virtual protected member function) [edit]
(virtual protected member function) [edit]
[edit] 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 override { return "vrai"; } string_type do_falsename() const override { return "faux"; } }; 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: vrai, faux
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 338 | C++98 | the sign token allowed an optional whitespace following + or -
|
removed the whitespace |