std::ctype<CharT>::is, std::ctype<CharT>::do_is
From cppreference.com
| Defined in header <locale>
|
||
| public: bool is( mask m, CharT c ) const; |
(1) | |
| public: const CharT* is( const CharT* low, const CharT* high, mask* vec ) const; |
(2) | |
| protected: virtual bool do_is( mask m, CharT c ) const; |
(3) | |
| protected: virtual const CharT* do_is( const CharT* low, const CharT* high, mask* vec ) const; |
(4) | |
1,2) Public member function, calls the protected virtual member function
do_is of the most derived class.3) Checks if the character c is classified by the mask m.
4) For every character in the character array
[low, high), identifies the complete classification mask (e.g. digit|xdigit|alnum|print|graph for the digit '0' in the default locale), and stores the masks in the corresponding elements of the array pointed to by vec.Parameters
| c | - | character to classify |
| m | - | mask to use for classifying a single character |
| low | - | pointer to the first character in an array of characters to classify |
| high | - | one past the end pointer for the array of characters to classify |
| vec | - | pointer to the first element of the array of masks to fill |
Return value
1,3) true if c is classified by m.
2,4) high
Example
Run this code
#include <cstddef> #include <iostream> #include <locale> #include <utility> #include <vector> // utility wrapper to make locale-bound facets destructible template<class Facet> struct deletable_facet : Facet { template<class ...Args> deletable_facet(Args&& ...args) : Facet(std::forward<Args>(args)...) {} ~deletable_facet() {} }; int main() { // classify a single character using the default locale auto& f = std::use_facet<std::ctype<char>>(std::locale()); char c = '0'; if (f.is(std::ctype_base::digit, c)) // or isdigit(c, locale()); std::cout << '\'' << c << "' is a digit\n"; // classify every character in a string using a named locale deletable_facet<std::ctype_byname<wchar_t>> f2("en_US.utf8"); std::wstring str = L"z\u00df\u6c34\U0001d10b"; std::vector<std::ctype_base::mask> vec(str.size()); f2.is(&str[0], &str[0] + str.size(), &vec[0]); for (std::size_t n = 0; n < str.size(); ++n) { std::cout << std::hex << "U+" << static_cast<wint_t>(str[n]) << " is: "; if (vec[n] & std::ctype_base::alnum) std::cout << "alnum"; if (vec[n] & std::ctype_base::punct) std::cout << "punct"; std::cout << '\n'; } }
Output:
'0' is a digit U+7a is: alnum U+df is: alnum U+6c34 is: alnum U+1d10b is: punct
See also
| classifies a character or a character sequence, using the classification table (public member function of std::ctype<char>) | |
classifies a wide character according to the specified LC_CTYPE category (function) |