Defined in header <locale> | ||
---|---|---|
template< class CharT, class InputIt = std::istreambuf_iterator<CharT> > class num_get; |
Class std::num_get
encapsulates the rules for parsing string representations of numeric values. Specifically, types bool
, unsigned short
, unsigned int
, long
, unsigned long
, long long
, unsigned long long
, float
, double
, long double
, and void*
are supported. The standard formatting input operators (such as cin >> n;
) use the std::num_get
facet of the I/O stream's locale to parse the text representations of the numbers.
Inheritance diagram.
Type requirements
- InputIt must meet the requirements of InputIterator . |
Specializations
Two standalone (locale-independent) full specializations and two partial specializations are provided by the standard library:
Defined in header <locale> | |
---|---|
std::num_get<char> | creates narrow string parsing of numbers |
std::num_get<wchar_t> | creates wide string parsing of numbers |
std::num_get<char, InputIt> | creates narrow string parsing of numbers using custom input iterator |
std::num_get<wchar_t, InputIt> | creates wide string parsing of numbers using custom input iterator |
In addition, every locale object constructed in a C++ program implements its own (locale-specific) versions of these specializations.
Member types
Member type | Definition |
---|---|
char_type | CharT |
iter_type | InputIt |
Member functions
constructs a new num_get facet (public member function) | |
(destructor)
| destructs a num_get facet (protected member function) |
invokes do_get (public member function) |
Member objects
static std::locale::id id | id of the locale (public member object) |
Protected member functions
[virtual] | parses a number from an input stream (virtual protected member function) |
Example
#include <iostream> #include <locale> #include <string> #include <sstream> #include <iterator> int main() { std::string de_double = "1.234.567,89"; std::string us_double = "1,234,567.89"; // parse using streams std::istringstream de_in(de_double); de_in.imbue(std::locale("de_DE")); 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 directly std::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'; }
Output:
Parsing 1.234.567,89 as double gives 1234567.890000 in de_DE locale and 1.234000 in en_US parsing 1,234,567.89 as double using raw en_US facet gives 1234567.890000
See also
defines numeric punctuation rules (class template) | |
formats numeric values for output as character sequence (class template) | |
extracts formatted data (public member function of std::basic_istream ) |
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