30 Localization library [localization]

30.4 Standard locale categories [locale.categories]

30.4.3 The numeric category [category.numeric]

30.4.3.3 Class template num_put [locale.nm.put]

30.4.3.3.1 General [locale.nm.put.general]

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namespace std { template<class charT, class OutputIterator = ostreambuf_iterator<charT>> class num_put : public locale::facet { public: using char_type = charT; using iter_type = OutputIterator; explicit num_put(size_t refs = 0); iter_type put(iter_type s, ios_base& f, char_type fill, bool v) const; iter_type put(iter_type s, ios_base& f, char_type fill, long v) const; iter_type put(iter_type s, ios_base& f, char_type fill, long long v) const; iter_type put(iter_type s, ios_base& f, char_type fill, unsigned long v) const; iter_type put(iter_type s, ios_base& f, char_type fill, unsigned long long v) const; iter_type put(iter_type s, ios_base& f, char_type fill, double v) const; iter_type put(iter_type s, ios_base& f, char_type fill, long double v) const; iter_type put(iter_type s, ios_base& f, char_type fill, const void* v) const; static locale::id id; protected: ~num_put(); virtual iter_type do_put(iter_type, ios_base&, char_type fill, bool v) const; virtual iter_type do_put(iter_type, ios_base&, char_type fill, long v) const; virtual iter_type do_put(iter_type, ios_base&, char_type fill, long long v) const; virtual iter_type do_put(iter_type, ios_base&, char_type fill, unsigned long) const; virtual iter_type do_put(iter_type, ios_base&, char_type fill, unsigned long long) const; virtual iter_type do_put(iter_type, ios_base&, char_type fill, double v) const; virtual iter_type do_put(iter_type, ios_base&, char_type fill, long double v) const; virtual iter_type do_put(iter_type, ios_base&, char_type fill, const void* v) const; }; }
1
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The facet num_put is used to format numeric values to a character sequence such as an ostream.

30.4.3.3.2 Members [facet.num.put.members]

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iter_type put(iter_type out, ios_base& str, char_type fill, bool val) const; iter_type put(iter_type out, ios_base& str, char_type fill, long val) const; iter_type put(iter_type out, ios_base& str, char_type fill, long long val) const; iter_type put(iter_type out, ios_base& str, char_type fill, unsigned long val) const; iter_type put(iter_type out, ios_base& str, char_type fill, unsigned long long val) const; iter_type put(iter_type out, ios_base& str, char_type fill, double val) const; iter_type put(iter_type out, ios_base& str, char_type fill, long double val) const; iter_type put(iter_type out, ios_base& str, char_type fill, const void* val) const;
1
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Returns: do_put(out, str, fill, val).

30.4.3.3.3 Virtual functions [facet.num.put.virtuals]

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iter_type do_put(iter_type out, ios_base& str, char_type fill, long val) const; iter_type do_put(iter_type out, ios_base& str, char_type fill, long long val) const; iter_type do_put(iter_type out, ios_base& str, char_type fill, unsigned long val) const; iter_type do_put(iter_type out, ios_base& str, char_type fill, unsigned long long val) const; iter_type do_put(iter_type out, ios_base& str, char_type fill, double val) const; iter_type do_put(iter_type out, ios_base& str, char_type fill, long double val) const; iter_type do_put(iter_type out, ios_base& str, char_type fill, const void* val) const;
1
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Effects: Writes characters to the sequence out, formatting val as desired.
In the following description, loc names a local variable initialized as locale loc = str.getloc();
2
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The details of this operation occur in several stages:
  • (2.1)
    Stage 1: Determine a printf conversion specifier spec and determine the characters that would be printed by printf ([c.files]) given this conversion specifier for printf(spec, val) assuming that the current locale is the "C" locale.
  • (2.2)
    Stage 2: Adjust the representation by converting each char determined by stage 1 to a charT using a conversion and values returned by members of use_facet<numpunct<charT>>(loc).
  • (2.3)
    Stage 3: Determine where padding is required.
  • (2.4)
    Stage 4: Insert the sequence into the out.
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Detailed descriptions of each stage follow.
4
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Returns: out.
5
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  • Stage 1:
    The first action of stage 1 is to determine a conversion specifier.
    The tables that describe this determination use the following local variables
    fmtflags flags = str.flags(); fmtflags basefield = (flags & (ios_base::basefield)); fmtflags uppercase = (flags & (ios_base::uppercase)); fmtflags floatfield = (flags & (ios_base::floatfield)); fmtflags showpos = (flags & (ios_base::showpos)); fmtflags showbase = (flags & (ios_base::showbase)); fmtflags showpoint = (flags & (ios_base::showpoint));
    All tables used in describing stage 1 are ordered.
    That is, the first line whose condition is true applies.
    A line without a condition is the default behavior when none of the earlier lines apply.
    For conversion from an integral type other than a character type, the function determines the integral conversion specifier as indicated in Table 110.
    Table 110: Integer conversions [tab:facet.num.put.int]
    State
    stdio equivalent
    basefield == ios_base​::​oct
    %o
    (basefield == ios_base​::​hex) && !uppercase
    %x
    (basefield == ios_base​::​hex)
    %X
    for a signed integral type
    %d
    for an unsigned integral type
    %u
    For conversion from a floating-point type, the function determines the floating-point conversion specifier as indicated in Table 111.
    Table 111: Floating-point conversions [tab:facet.num.put.fp]
    State
    stdio equivalent
    floatfield == ios_base​::​fixed
    %f
    floatfield == ios_base​::​scientific && !uppercase
    %e
    floatfield == ios_base​::​scientific
    %E
    floatfield == (ios_base​::​fixed | ios_base​::​scientific) && !uppercase
    %a
    floatfield == (ios_base​::​fixed | ios_base​::​scientific)
    %A
    !uppercase
    %g
    otherwise
    %G
    For conversions from an integral or floating-point type a length modifier is added to the conversion specifier as indicated in Table 112.
    Table 112: Length modifier [tab:facet.num.put.length]
    Type
    Length modifier
    long
    l
    long long
    ll
    unsigned long
    l
    unsigned long long
    ll
    long double
    L
    otherwise
    none
    The conversion specifier has the following optional additional qualifiers prepended as indicated in Table 113.
    Table 113: Numeric conversions [tab:facet.num.put.conv]
    Type(s)
    State
    stdio equivalent
    an integral type
    showpos
    +
    showbase
    #
    a floating-point type
    showpos
    +
    showpoint
    #
    For conversion from a floating-point type, if floatfield != (ios_base​::​fixed | ios_base​::​​scientific), str.precision() is specified as precision in the conversion specification.
    Otherwise, no precision is specified.
    For conversion from void* the specifier is %p.
    The representations at the end of stage 1 consists of the char's that would be printed by a call of printf(s, val) where s is the conversion specifier determined above.
  • Stage 2:
    Any character c other than a decimal point(.) is converted to a charT via use_facet<ctype<charT>>(loc).widen(c)
    A local variable punct is initialized via const numpunct<charT>& punct = use_facet<numpunct<charT>>(loc);
    For arithmetic types, punct.thousands_sep() characters are inserted into the sequence as determined by the value returned by punct.do_grouping() using the method described in [facet.numpunct.virtuals].
    Decimal point characters(.) are replaced by punct.decimal_point().
  • Stage 3:
    A local variable is initialized as fmtflags adjustfield = (flags & (ios_base::adjustfield));
    The location of any padding250 is determined according to Table 114.
    Table 114: Fill padding [tab:facet.num.put.fill]
    State
    Location
    adjustfield == ios_base​::​left
    pad after
    adjustfield == ios_base​::​right
    pad before
    adjustfield == internal and a sign occurs in the representation
    pad after the sign
    adjustfield == internal and representation after stage 1 began with 0x or 0X
    pad after x or X
    otherwise
    pad before
    If str.width() is nonzero and the number of charT's in the sequence after stage 2 is less than str.​width(), then enough fill characters are added to the sequence at the position indicated for padding to bring the length of the sequence to str.width().
    str.width(0) is called.
  • Stage 4:
    The sequence of charT's at the end of stage 3 are output via *out++ = c
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iter_type do_put(iter_type out, ios_base& str, char_type fill, bool val) const;
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Returns: If (str.flags() & ios_base​::​boolalpha) == 0 returns do_put(out, str, fill,
(int)val), otherwise obtains a string s as if by string_type s = val ? use_facet<numpunct<charT>>(loc).truename() : use_facet<numpunct<charT>>(loc).falsename(); and then inserts each character c of s into out via *out++ = c and returns out.
250)250)
The conversion specification #o generates a leading 0 which is not a padding character.