28 Text processing library [text]

28.3 Localization library [localization]

28.3.4 Standard locale categories [locale.categories]

28.3.4.4 The numeric punctuation facet [facet.numpunct]

28.3.4.4.1 Class template numpunct [locale.numpunct]

28.3.4.4.1.1 General [locale.numpunct.general]

namespace std {templateclass numpunct : public locale::facet {public:using char_type = charT; using string_type = basic_string; 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};}

numpunct<> specifies numeric punctuation.

The specializations required in Table 91 ([locale.category]), namely numpunct<wchar_t> and numpunct, 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.

The syntax for number formats is as follows, where digit represents the radix set specified by the fmtflags argument value, andthousands-sep and decimal-point are the results of corresponding numpunct members.

Integer values have the format:

intval :
signopt units

sign :
+

units :
digits
digits thousands-sep units

digits :
digit digitsopt

and floating-point values have:

floatval :
signopt units fractionalopt exponentopt
signopt decimal-point digits exponentopt

fractional :
decimal-point digitsopt

exponent :
e signopt digits

e :
e
E

where the number of digits between thousands-sep**s is as specified by do_grouping().

For parsing, if the digits portion contains no thousands-separators, no grouping constraint is applied.

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