25 Localization library [localization]

25.4 Standard locale categories [locale.categories]

25.4.6 The monetary category [category.monetary]

These templates handle monetary formats. A template parameter indicates whether local or international monetary formats are to be used.

All specifications of member functions for money_­put and money_­get in the subclauses of [category.monetary] only apply to the specializations required in Tables 69 and 70 ([locale.category]). Their members use their ios_­base&, ios_­base​::​iostate&, and fill arguments as described in [locale.categories], and the moneypunct<> and ctype<> facets, to determine formatting details.

25.4.6.1 Class template money_­get [locale.money.get]

namespace std {
  template <class charT, class InputIterator = istreambuf_iterator<charT>>
    class money_get : public locale::facet {
    public:
      using char_type   = charT;
      using iter_type   = InputIterator;
      using string_type = basic_string<charT>;

      explicit money_get(size_t refs = 0);

      iter_type get(iter_type s, iter_type end, bool intl,
                    ios_base& f, ios_base::iostate& err,
                    long double& units) const;
      iter_type get(iter_type s, iter_type end, bool intl,
                    ios_base& f, ios_base::iostate& err,
                    string_type& digits) const;

      static locale::id id;

    protected:
      ~money_get();
      virtual iter_type do_get(iter_type, iter_type, bool, ios_base&,
                               ios_base::iostate& err, long double& units) const;
      virtual iter_type do_get(iter_type, iter_type, bool, ios_base&,
                               ios_base::iostate& err, string_type& digits) const;
    };
}

25.4.6.1.1 money_­get members [locale.money.get.members]

iter_type get(iter_type s, iter_type end, bool intl, ios_base& f, ios_base::iostate& err, long double& quant) const; iter_type get(iter_type s, iter_type end, bool intl, ios_base& f, ios_base::iostate& err, string_type& quant) const;

Returns: do_­get(s, end, intl, f, err, quant).

25.4.6.1.2 money_­get virtual functions [locale.money.get.virtuals]

iter_type do_get(iter_type s, iter_type end, bool intl, ios_base& str, ios_base::iostate& err, long double& units) const; iter_type do_get(iter_type s, iter_type end, bool intl, ios_base& str, ios_base::iostate& err, string_type& digits) const;

Effects: Reads characters from s to parse and construct a monetary value according to the format specified by a moneypunct<charT, Intl> facet reference mp and the character mapping specified by a ctype<charT> facet reference ct obtained from the locale returned by str.getloc(), and str.flags(). If a valid sequence is recognized, does not change err; otherwise, sets err to (err|str.failbit), or (err|str.failbit|str.eofbit) if no more characters are available, and does not change units or digits. Uses the pattern returned by mp.neg_­format() to parse all values. The result is returned as an integral value stored in units or as a sequence of digits possibly preceded by a minus sign (as produced by ct.widen(c) where c is '-' or in the range from '0' through '9', inclusive) stored in digits. [Example: The sequence $1,056.23 in a common United States locale would yield, for units, 105623, or, for digits, "105623". end example] If mp.grouping() indicates that no thousands separators are permitted, any such characters are not read, and parsing is terminated at the point where they first appear. Otherwise, thousands separators are optional; if present, they are checked for correct placement only after all format components have been read.

Where money_­base​::​space or money_­base​::​none appears as the last element in the format pattern, no white space is consumed. Otherwise, where money_­base​::​space appears in any of the initial elements of the format pattern, at least one white space character is required. Where money_­base​::​none appears in any of the initial elements of the format pattern, white space is allowed but not required. If (str.flags() & str.showbase) is false, the currency symbol is optional and is consumed only if other characters are needed to complete the format; otherwise, the currency symbol is required.

If the first character (if any) in the string pos returned by mp.positive_­sign() or the string neg returned by mp.negative_­sign() is recognized in the position indicated by sign in the format pattern, it is consumed and any remaining characters in the string are required after all the other format components. [Example: If showbase is off, then for a neg value of "()" and a currency symbol of "L", in "(100 L)" the "L" is consumed; but if neg is "-", the "L" in "-100 L" is not consumed. end example] If pos or neg is empty, the sign component is optional, and if no sign is detected, the result is given the sign that corresponds to the source of the empty string. Otherwise, the character in the indicated position must match the first character of pos or neg, and the result is given the corresponding sign. If the first character of pos is equal to the first character of neg, or if both strings are empty, the result is given a positive sign.

Digits in the numeric monetary component are extracted and placed in digits, or into a character buffer buf1 for conversion to produce a value for units, in the order in which they appear, preceded by a minus sign if and only if the result is negative. The value units is produced as if by248

for (int i = 0; i < n; ++i)
  buf2[i] = src[find(atoms, atoms+sizeof(src), buf1[i]) - atoms];
buf2[n] = 0;
sscanf(buf2, "%Lf", &units);

where n is the number of characters placed in buf1, buf2 is a character buffer, and the values src and atoms are defined as if by

static const char src[] = "0123456789-";
charT atoms[sizeof(src)];
ct.widen(src, src + sizeof(src) - 1, atoms);

Returns: An iterator pointing immediately beyond the last character recognized as part of a valid monetary quantity.

The semantics here are different from ct.narrow.

25.4.6.2 Class template money_­put [locale.money.put]

namespace std {
  template <class charT, class OutputIterator = ostreambuf_iterator<charT>>
    class money_put : public locale::facet {
    public:
      using char_type   = charT;
      using iter_type   = OutputIterator;
      using string_type = basic_string<charT>;

      explicit money_put(size_t refs = 0);

      iter_type put(iter_type s, bool intl, ios_base& f,
                    char_type fill, long double units) const;
      iter_type put(iter_type s, bool intl, ios_base& f,
                    char_type fill, const string_type& digits) const;

      static locale::id id;

    protected:
      ~money_put();
      virtual iter_type do_put(iter_type, bool, ios_base&, char_type fill,
                               long double units) const;
      virtual iter_type do_put(iter_type, bool, ios_base&, char_type fill,
                               const string_type& digits) const;
    };
}

25.4.6.2.1 money_­put members [locale.money.put.members]

iter_type put(iter_type s, bool intl, ios_base& f, char_type fill, long double quant) const; iter_type put(iter_type s, bool intl, ios_base& f, char_type fill, const string_type& quant) const;

Returns: do_­put(s, intl, f, loc, quant).

25.4.6.2.2 money_­put virtual functions [locale.money.put.virtuals]

iter_type do_put(iter_type s, bool intl, ios_base& str, char_type fill, long double units) const; iter_type do_put(iter_type s, bool intl, ios_base& str, char_type fill, const string_type& digits) const;

Effects: Writes characters to s according to the format specified by a moneypunct<charT, Intl> facet reference mp and the character mapping specified by a ctype<charT> facet reference ct obtained from the locale returned by str.getloc(), and str.flags(). The argument units is transformed into a sequence of wide characters as if by

ct.widen(buf1, buf1 + sprintf(buf1, "%.0Lf", units), buf2)

for character buffers buf1 and buf2. If the first character in digits or buf2 is equal to ct.widen('-'), then the pattern used for formatting is the result of mp.neg_­format(); otherwise the pattern is the result of mp.pos_­format(). Digit characters are written, interspersed with any thousands separators and decimal point specified by the format, in the order they appear (after the optional leading minus sign) in digits or buf2. In digits, only the optional leading minus sign and the immediately subsequent digit characters (as classified according to ct) are used; any trailing characters (including digits appearing after a non-digit character) are ignored. Calls str.width(0).

Remarks: The currency symbol is generated if and only if (str.flags() & str.showbase) is nonzero. If the number of characters generated for the specified format is less than the value returned by str.width() on entry to the function, then copies of fill are inserted as necessary to pad to the specified width. For the value af equal to (str.flags() & str.adjustfield), if (af == str.internal) is true, the fill characters are placed where none or space appears in the formatting pattern; otherwise if (af == str.left) is true, they are placed after the other characters; otherwise, they are placed before the other characters. [Note: It is possible, with some combinations of format patterns and flag values, to produce output that cannot be parsed using num_­get<>​::​get. end note]

Returns: An iterator pointing immediately after the last character produced.

25.4.6.3 Class template moneypunct [locale.moneypunct]

namespace std {
  class money_base {
  public:
    enum part { none, space, symbol, sign, value };
    struct pattern { char field[4]; };
  };

  template <class charT, bool International = false>
    class moneypunct : public locale::facet, public money_base {
    public:
      using char_type   = charT;
      using string_type = basic_string<charT>;

      explicit moneypunct(size_t refs = 0);

      charT        decimal_point() const;
      charT        thousands_sep() const;
      string       grouping()      const;
      string_type  curr_symbol()   const;
      string_type  positive_sign() const;
      string_type  negative_sign() const;
      int          frac_digits()   const;
      pattern      pos_format()    const;
      pattern      neg_format()    const;

      static locale::id id;
      static const bool intl = International;

    protected:
      ~moneypunct();
      virtual charT        do_decimal_point() const;
      virtual charT        do_thousands_sep() const;
      virtual string       do_grouping()      const;
      virtual string_type  do_curr_symbol()   const;
      virtual string_type  do_positive_sign() const;
      virtual string_type  do_negative_sign() const;
      virtual int          do_frac_digits()   const;
      virtual pattern      do_pos_format()    const;
      virtual pattern      do_neg_format()    const;
    };
}

The moneypunct<> facet defines monetary formatting parameters used by money_­get<> and money_­put<>. A monetary format is a sequence of four components, specified by a pattern value p, such that the part value static_­cast<part>(p.field[i]) determines the ith component of the format249 In the field member of a pattern object, each value symbol, sign, value, and either space or none appears exactly once. The value none, if present, is not first; the value space, if present, is neither first nor last.

Where none or space appears, white space is permitted in the format, except where none appears at the end, in which case no white space is permitted. The value space indicates that at least one space is required at that position. Where symbol appears, the sequence of characters returned by curr_­symbol() is permitted, and can be required. Where sign appears, the first (if any) of the sequence of characters returned by positive_­sign() or negative_­sign() (respectively as the monetary value is non-negative or negative) is required. Any remaining characters of the sign sequence are required after all other format components. Where value appears, the absolute numeric monetary value is required.

The format of the numeric monetary value is a decimal number:

value ::= units [ decimal-point [ digits ]] |
  decimal-point digits

if frac_­digits() returns a positive value, or

value ::= units

otherwise. The symbol decimal-point indicates the character returned by decimal_­point(). The other symbols are defined as follows:

units ::= digits [ thousands-sep units ]
digits ::= adigit [ digits ]

In the syntax specification, the symbol adigit is any of the values ct.widen(c) for c in the range '0' through '9', inclusive, and ct is a reference of type const ctype<charT>& obtained as described in the definitions of money_­get<> and money_­put<>. The symbol thousands-sep is the character returned by thousands_­sep(). The space character used is the value ct.widen(' '). White space characters are those characters c for which ci.is(space, c) returns true. The number of digits required after the decimal point (if any) is exactly the value returned by frac_­digits().

The placement of thousands-separator characters (if any) is determined by the value returned by grouping(), defined identically as the member numpunct<>​::​do_­grouping().

An array of char, rather than an array of part, is specified for pattern​::​field purely for efficiency.

25.4.6.3.1 moneypunct members [locale.moneypunct.members]

charT        decimal_point() const;
charT        thousands_sep() const;
string       grouping()      const;
string_type  curr_symbol()   const;
string_type  positive_sign() const;
string_type  negative_sign() const;
int          frac_digits()   const;
pattern      pos_format()    const;
pattern      neg_format()    const;

Each of these functions F returns the result of calling the corresponding virtual member function do_­F().

25.4.6.3.2 moneypunct virtual functions [locale.moneypunct.virtuals]

charT do_decimal_point() const;

Returns: The radix separator to use in case do_­frac_­digits() is greater than zero.250

charT do_thousands_sep() const;

Returns: The digit group separator to use in case do_­grouping() specifies a digit grouping pattern.251

string do_grouping() const;

Returns: A pattern defined identically as, but not necessarily equal to, the result of numpunct<charT>​::​​do_­grouping().252

string_type do_curr_symbol() const;

Returns: A string to use as the currency identifier symbol.253

string_type do_positive_sign() const; string_type do_negative_sign() const;

Returns: do_­positive_­sign() returns the string to use to indicate a positive monetary value;254 do_­negative_­sign() returns the string to use to indicate a negative value.

int do_frac_digits() const;

Returns: The number of digits after the decimal radix separator, if any.255

pattern do_pos_format() const; pattern do_neg_format() const;

Returns: The specializations required in Table 70 ([locale.category]), namely moneypunct<char>, moneypunct<​wchar_­t>, moneypunct<char, true>, and moneypunct<wchar_­t, true>, return an object of type pattern initialized to { symbol, sign, none, value }.256

In common U.S. locales this is '.'.

In common U.S. locales this is ','.

To specify grouping by 3s, the value is "\003" not "3".

For international specializations (second template parameter true) this is typically four characters long, usually three letters and a space.

This is usually the empty string.

In common U.S. locales, this is 2.

Note that the international symbol returned by do_­curr_­sym() usually contains a space, itself; for example, "USD ".

25.4.6.4 Class template moneypunct_­byname [locale.moneypunct.byname]

namespace std {
  template <class charT, bool Intl = false>
  class moneypunct_byname : public moneypunct<charT, Intl> {
    public:
      using pattern     = money_base::pattern;
      using string_type = basic_string<charT>;

      explicit moneypunct_byname(const char*, size_t refs = 0);
      explicit moneypunct_byname(const string&, size_t refs = 0);

    protected:
      ~moneypunct_byname();
    };
}