Classstd::num_get encapsulates the rules for parsing string representations of numeric values. Specifically, typesbool,unsignedshort,unsignedint,long,unsignedlong,longlong,unsignedlonglong(since C++11),float,double,longdouble, andvoid* are supported. The standard formatting input operators (such ascin>> n;) use thestd::num_get facet of the I/O stream's locale to parse the text representations of the numbers.

Inheritance diagram

If astd::num_get specialization is not guaranteed to be provided by the standard library (see below), the behaviors of itsget() anddo_get() are not guaranteed as specified.

[edit]Specializations

The standard library is guaranteed to provide the following specializations (they arerequired to be implemented by any locale object):

In addition, the standard library is also guaranteed to provide every specialization that satisfies the following type requirements:

• CharT is one of
  • char,
  • wchar_t, and
  • any other implementation-definedcharacter container type that meets the requirements for a character on which any of theiostream components can be instantiated; and
• InputIt must meet the requirements ofLegacyInputIterator.

[edit]Nested types

[edit]Data members

[edit]Member functions

[edit]Protected member functions

[edit]Example

#include <iostream>#include <iterator>#include <locale>#include <sstream>#include <string> int main(){std::string de_double="1.234.567,89";std::string us_double="1,234,567.89"; // parse using streamsstd::istringstream de_in(de_double);    de_in.imbue(std::locale("de_DE.UTF-8"));double f1;    de_in>> f1; std::istringstream us_in(de_double);    us_in.imbue(std::locale("en_US.UTF-8"));double f2;    us_in>> f2; std::cout<<"Parsing "<< de_double<<" as double gives "<<std::fixed<< f1<<" in de_DE locale and "<< f2<<" in en_US\n"; // use the facet directlystd::istringstream s3(us_double);    s3.imbue(std::locale("en_US.UTF-8")); auto& f=std::use_facet<std::num_get<char>>(s3.getloc());std::istreambuf_iterator<char> beg(s3), end;double f3;    std::ios::iostate err;    f.get(beg, end, s3, err, f3); std::cout<<"parsing "<< us_double<<" as double using raw en_US facet gives "<< f3<<'\n';}

Parsing 1.234.567,89 as double gives 1234567.890000 in de_DE locale and 1.234000 in en_USparsing 1,234,567.89 as double using raw en_US facet gives 1234567.890000

[edit]Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit]See also

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