num_put Class

Artikel
08/03/2021

A class template that describes an object that can serve as a locale facet to control conversions of numeric values to sequences of type CharType.

Syntax

template <class CharType,
    class OutputIterator = ostreambuf_iterator<CharType>>
class num_put : public locale::facet;

Parameters

CharType
The type used within a program to encode characters in a locale.

OutputIterator
The type of iterator to which the numeric put functions write their output.

Remarks

As with any locale facet, the static object ID has an initial stored value of zero. The first attempt to access its stored value stores a unique positive value in id.

Constructors

Constructor	Description
num_put	The constructor for objects of type `num_put`.

Typedefs

Type name	Description
char_type	A type that is used to describe a character used by a locale.
iter_type	A type that describes an output iterator.

Member functions

Member function	Description
do_put	A virtual function that is called to convert a number into a sequence of `CharType`s that represents the number formatted for a given locale.
put	Converts a number into a sequence of `CharType`s which represents the number formatted for a given locale.

Requirements

Header: <locale>

Namespace: std

num_put::char_type

A type that is used to describe a character used by a locale.

typedef CharType char_type;

Remarks

The type is a synonym for the template parameter CharType.

num_put::do_put

A virtual function that is called to convert a number into a sequence of CharTypes that represents the number formatted for a given locale.

virtual iter_type do_put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    bool val) const;

virtual iter_type do_put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    long val) const;

virtual iter_type do_put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    unsigned long val) const;

virtual iter_type do_put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    double val) const;

virtual iter_type do_put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    long double val) const;

virtual iter_type do_put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    const void* val) const;

virtual iter_type do_put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    const long long val) const;

virtual iter_type do_put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    const unsigned long long val) const;

Parameters

next
An iterator addressing the first element of the inserted string.

_Iosbase
Specified the stream which contains locale with the numpunct facet used to punctuate the output and flags for formatting the output.

_Fill
A character that is used for spacing.

val
The number or Boolean type that is to be output.

Return Value

An output iterator the addresses the position one beyond the last element produced.

Remarks

The first virtual protected member function generates sequential elements beginning at next to produce an integer output field from the value of val. The function returns an iterator designating the next place to insert an element beyond the generated integer output field.

The integer output field is generated by the same rules used by the print functions for generating a series of char elements to a file. Each such char element is assumed to map to an equivalent element of type CharType by a simple, one-to-one mapping. Where a print function pads a field with either spaces or the digit 0, however, do_put instead uses fill. The equivalent print conversion specification is determined as follows:

If iosbase. flags & ios_base::basefield == ios_base::oct, the conversion specification is lo.
If iosbase.flags & ios_base::basefield == ios_base::hex, the conversion specification is lx.
Otherwise, the conversion specification is ld.

If iosbase. width is nonzero, a field width of this value is prepended. The function then calls iosbase. width(0) to reset the field width to zero.

Padding occurs only if the minimum number of elements N required to specify the output field is less than iosbase. width. Such padding consists of a sequence of N - width copies of fill. Padding then occurs as follows:

If iosbase. flags & ios_base::adjustfield == ios_base::left, the flag - is prepended. (Padding occurs after the generated text.)
If iosbase.flags & ios_base::adjustfield == ios_base::internal, the flag 0 is prepended. (For a numeric output field, padding occurs where the print functions pad with 0.)
Otherwise, no additional flag is prepended. (Padding occurs before the generated sequence.)

Finally:

If iosbase. flags & ios_base::showpos is nonzero, the flag + is prepended to the conversion specification.
If iosbase. flags & ios_base::showbase is nonzero, the flag # is prepended to the conversion specification.

The format of an integer output field is further determined by the locale facetfac returned by the call use_facet < numpunct< Elem>( iosbase. getloc). Specifically:

fac. grouping determines how digits are grouped to the left of any decimal point
fac. thousands_sep determines the sequence that separates groups of digits to the left of any decimal point

If no grouping constraints are imposed by fac. grouping (its first element has the value CHAR_MAX), then no instances of fac. thousands_sep are generated in the output field. Otherwise, separators are inserted after the print conversion occurs.

The second virtual protected member function:

virtual iter_type do_put(iter_type next,
    ios_base& _Iosbase,
    CharType _Fill,
    unsigned long val) const;

behaves the same as the first, except that it replaces a conversion specification of ld with lu.

The third virtual protected member function:

virtual iter_type do_put(iter_type next,
    ios_base& _Iosbase,
    CharType _Fill,
    double val) const;

behaves the same as the first, except that it produces a floating-point output field from the value of val. fac. decimal_point determines the sequence that separates the integer digits from the fraction digits. The equivalent print conversion specification is determined as follows:

If iosbase. flags & ios_base::floatfield == ios_base::fixed, the conversion specification is lf.
If iosbase. flags & ios_base::floatfield == ios_base::scientific, the conversion specification is le. If iosbase. flags & ios_base::uppercase is nonzero, e is replaced with E.
Otherwise, the conversion specification is lg. If iosbase. flags & ios_base::uppercase is nonzero, g is replaced with G.

If iosbase. flags & ios_base::fixed is nonzero or if iosbase. precision is greater than zero, a precision with the value iosbase. precision is prepended to the conversion specification. Any padding behaves the same as for an integer output field. The padding character is fill. Finally:

If iosbase. flags & ios_base::showpos is nonzero, the flag + is prepended to the conversion specification.
If iosbase. flags & ios_base::showpoint is nonzero, the flag # is prepended to the conversion specification.

The fourth virtual protected member function:

virtual iter_type do_put(iter_type next,
    ios_base& _Iosbase,
    CharType _Fill,
    long double val) const;

behaves the same the third, except that the qualifier l in the conversion specification is replaced with L.

The fifth virtual protected member function:

virtual iter_type do_put(iter_type next,
    ios_base& _Iosbase,
    CharType _Fill,
    const void* val) const;

behaves the same the first, except that the conversion specification is p, plus any qualifier needed to specify padding.

The sixth virtual protected member function:

virtual iter_type do_put(iter_type next,
    ios_base& _Iosbase,
    CharType _Fill,
    bool val) const;

behaves the same as the first, except that it generates a Boolean output field from val.

A Boolean output field takes one of two forms. If iosbase.flags & ios_base::boolalpha is false, the member function returns do_put(_Next, _Iosbase, _Fill, (long)val), which typically produces a generated sequence of either 0 (for false) or 1 (for true). Otherwise, the generated sequence is either fac.falsename (for false), or fac.truename (for true).

The seventh virtual protected member function:

virtual iter_type do_put(iter_type next,
    ios_base& iosbase,
    Elem fill,
    long long val) const;

behaves the same as the first, except that it replaces a conversion specification of ld with lld.

The eighth virtual protected member function:

virtual iter_type do_put(iter_type next,
    ios_base& iosbase,
    Elem fill,
    unsigned long long val) const;

behaves the same as the first, except that it replaces a conversion specification of ld with llu.

Example

See the example for put, which calls do_put.

num_put::iter_type

A type that describes an output iterator.

typedef OutputIterator iter_type;

Remarks

The type is a synonym for the template parameter OutputIterator.

num_put::num_put

The constructor for objects of type num_put.

explicit num_put(size_t _Refs = 0);

Parameters

_Refs
Integer value used to specify the type of memory management for the object.

Remarks

The possible values for the _Refs parameter and their significance are:

0: The lifetime of the object is managed by the locales that contain it.
1: The lifetime of the object must be manually managed.
> 1: These values are not defined.

No direct examples are possible, because the destructor is protected.

The constructor initializes its base object with locale::facet(_ Refs).

num_put::put

Converts a number into a sequence of CharTypes that represents the number formatted for a given locale.

iter_type put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    bool val) const;

iter_type put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    long val) const;

iter_type put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    unsigned long val) const;

iter_type put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    Long long val) const;

iter_type put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    Unsigned long long val) const;

iter_type put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    double val) const;

iter_type put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    long double val) const;

iter_type put(
    iter_type dest,
    ios_base& _Iosbase,
    _Elem _Fill,
    const void* val) const;

Parameters

dest
An iterator addressing the first element of the inserted string.

_Iosbase
Specified the stream that contains locale with the numpunct facet used to punctuate the output and flags for formatting the output.

_Fill
A character that is used for spacing.

val
The number or Boolean type that is to be output.

Return Value

An output iterator the addresses the position one beyond the last element produced.

Remarks

All member functions return do_put( next, _Iosbase, _Fill, val).

Example

// num_put_put.cpp
// compile with: /EHsc
#include <locale>
#include <iostream>
#include <sstream>
using namespace std;
int main( )
{
   locale loc( "german_germany" );
   basic_stringstream<char> psz2;
   ios_base::iostate st = 0;
   long double fVal;
   cout << "The thousands separator is: "
        << use_facet < numpunct <char> >(loc).thousands_sep( )
        << endl;

   psz2.imbue( loc );
   use_facet < num_put < char > >
      ( loc ).put(basic_ostream<char>::_Iter(psz2.rdbuf( ) ),
                    psz2, ' ', fVal=1000.67);

   if ( st & ios_base::failbit )
      cout << "num_put( ) FAILED" << endl;
   else
      cout << "num_put( ) = " << psz2.rdbuf( )->str( ) << endl;
}

The thousands separator is: .
num_put( ) = 1.000,67

Dela via

num_put Class

Syntax

Parameters

Remarks

Constructors

Typedefs

Member functions

Requirements

num_put::char_type

Remarks

num_put::do_put

Parameters

Return Value

Remarks

Example

num_put::iter_type

Remarks

num_put::num_put

Parameters

Remarks

num_put::put

Parameters

Return Value

Remarks

Example

See also

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