25 Localization library [localization]

25.4 Standard locale categories [locale.categories]

25.4.2 The numeric category [category.numeric]

25.4.2.2 Class template num_­put [locale.nm.put]

25.4.2.2.2 num_­put virtual functions [facet.num.put.virtuals]

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;

Effects: Writes characters to the sequence out, formatting val as desired. In the following description, a local variable initialized with:

locale loc = str.getloc();

The details of this operation occur in several stages:

  • 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.

  • 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>>(str.getloc())

  • Stage 3: Determine where padding is required.

  • Stage 4: Insert the sequence into the out.

Detailed descriptions of each stage follow.

Returns: out.

  • 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 75.

    Table 75 — Integer conversions
    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 76.

    Table 76 — Floating-point conversions
    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 77.

    Table 77 — Length modifier
    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 78.

    Table 78 — Numeric conversions
    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>>(str.getloc());

    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 padding240 is determined according to Table 79.

    Table 79 — Fill padding
    StateLocation
    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

iter_type do_put(iter_type out, ios_base& str, char_type fill, bool val) const;

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.

The conversion specification #o generates a leading 0 which is not a padding character.