Class std::num_put
encapsulates the rules for formatting numeric values as strings. Specifically, the types bool, long, unsigned long, long long, unsigned long long(since C++11), double, long double, void*, and of all types implicitly convertible to these (such as int or float) are supported. The standard formatting output operators (such as cout << n;) use the std::num_put
facet of the I/O stream's locale to generate text representation of numbers.
Inheritance diagram
If a std::num_put
specialization is not guaranteed to be provided by the standard library (see below), the behaviors of its put() and do_put() are not guaranteed as specified.
The standard library is guaranteed to provide the following specializations (they are required to be implemented by any locale object):
std::num_put<char> creates narrow string representations of numbers std::num_put<wchar_t> creates wide string representations of numbersIn addition, the standard library is also guaranteed to provide every specialization that satisfies the following type requirements:
CharT
is one of
OutputIt
must meet the requirements of LegacyOutputIterator.char_type
CharT
iter_type
OutputIt
[edit] Data members [edit] Member functions constructs a new num_put
facet
do_put
num_put
facet
Possible output:
Direct conversion to string: 1234567.890000 Output using a german locale: 1.234.567,890000 Output using an american locale: 1,234,567.890000[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior LWG 427 C++98num_put
was guaranteed to accept any CharT
that
CharT
could be
num_put
can guarantee to accept implementation-
string
wstring
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