std::numpunct
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Defined in header <locale> | ||
template<class CharT> class numpunct; | ||
The facetstd::numpunct encapsulates numeric punctuation preferences. Stream I/O operations usestd::numpunct throughstd::num_get andstd::num_put for parsing numeric input and formatting numeric output.
The numbers that are supported bystd::numpunct have the format described below. Heredigit represents the radix set specified by thefmtflags argument value,thousands-sep anddecimal-point are the results ofthousands_sep() anddecimal_point() functions respectively.
The format of integer values is as follows:
integer ::= [sign] unitssign ::= plusminusplusminus ::= '+' | '-'units ::= digits [thousands-sep units]digits ::= digit [digits]
The number of digits between thethousand-seps (maximum size ofdigits) is specified by the result ofgrouping().
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 arerequired to be implemented by any locale object):
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 |
[edit]Nested types
| Type | Definition |
char_type | CharT |
string_type | std::basic_string<CharT> |
[edit]Data members
| Member | Description |
std::locale::idid[static] | the identifier of thefacet |
[edit]Member functions
constructs a newnumpunct facet(public member function)[edit] | |
destructs anumpunct facet(protected member function)[edit] | |
invokesdo_decimal_point(public member function)[edit] | |
invokesdo_thousands_sep(public member function)[edit] | |
invokesdo_grouping(public member function)[edit] | |
invokesdo_truename ordo_falsename(public member function)[edit] |
[edit]Protected member functions
[virtual] | provides the character to use as decimal point (virtual protected member function)[edit] |
[virtual] | 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] |
[virtual] | provides the string to use as the name of the booleantrue andfalse (virtual protected member function)[edit] |
[edit]Example
The following example changes the string representations oftrue andfalse:
#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, falselocale 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 | thesign token allowed an optional whitespace following+ or- | removed the whitespace |
[edit]See also
| creates a numpunct facet for the named locale (class template) |
