[locale.numpunct.general]

# 28 Text processing library [[text]](./#text)

## 28.3 Localization library [[localization]](localization#locale.numpunct.general)

### 28.3.4 Standard locale categories [[locale.categories]](locale.categories#locale.numpunct.general)

#### 28.3.4.4 The numeric punctuation facet [[facet.numpunct]](facet.numpunct#locale.numpunct.general)

#### 28.3.4.4.1 Class template numpunct [[locale.numpunct]](locale.numpunct#general)

#### 28.3.4.4.1.1 General [locale.numpunct.general]

[🔗](#lib:numpunct)

namespace std {template<class charT>class numpunct : public locale::facet {public:using char_type = charT; using string_type = basic_string<charT>; explicit numpunct(size_t refs = 0);

 char_type decimal_point() const;
 char_type thousands_sep() const;
 string grouping() const;
 string_type truename() const;
 string_type falsename() const; static locale::id id; protected:~numpunct(); // virtualvirtual char_type do_decimal_point() const; virtual char_type do_thousands_sep() const; virtual string do_grouping() const; virtual string_type do_truename() const; // for boolvirtual string_type do_falsename() const; // for bool};}

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/text.tex#L3137)

numpunct<> specifies numeric punctuation[.](#1.sentence-1)

The specializations
required in Table [91](locale.category#tab:locale.category.facets "Table 91: Locale category facets") ([[locale.category]](locale.category "28.3.3.1.2.1 Type locale​::​category")),
namely numpunct<​wchar_t> and numpunct<char>,
provide classic "C" numeric formats,
i.e., they contain information
equivalent to that contained in the "C" locale or
their wide character counterparts as if obtained by a call to widen[.](#1.sentence-2)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/text.tex#L3153)

The syntax for number formats is as follows,
where *digit* represents the radix set
specified by the fmtflags argument value, and*thousands-sep* and *decimal-point* are the results of corresponding numpunct<charT> members[.](#2.sentence-1)

Integer values have the format:

intval :  
[*sign*](lex.fcon#nt:sign "5.13.4 Floating-point literals [lex.fcon]")opt units

[*sign*](lex.fcon#nt:sign "5.13.4 Floating-point literals [lex.fcon]") :  
+  
-

units :  
digits  
digits thousands-sep units

digits :  
[*digit*](lex.name#nt:digit "5.11 Identifiers [lex.name]") digitsopt

and floating-point values have:

floatval :  
[*sign*](lex.fcon#nt:sign "5.13.4 Floating-point literals [lex.fcon]")opt units fractionalopt exponentopt  
[*sign*](lex.fcon#nt:sign "5.13.4 Floating-point literals [lex.fcon]")opt decimal-point digits exponentopt

fractional :  
decimal-point digitsopt

exponent :  
e [*sign*](lex.fcon#nt:sign "5.13.4 Floating-point literals [lex.fcon]")opt digits

e :  
e  
E

where the number of digits between *thousands-sep**s* is as specified by do_grouping()[.](#2.sentence-2)

For parsing,
if the *digits* portion contains no thousands-separators,
no grouping constraint is applied[.](#2.sentence-3)