std::ctype::is,std::ctype::do_is (3) Linux Manual Page
std::ctype<CharT>::is,std::ctype<CharT>::do_is – std::ctype<CharT>::is,std::ctype<CharT>::do_is
Synopsis
Defined in header<locale>
public : (1)
bool is(mask m, CharT c) const;
public:
(2)
const CharT *is(const CharT *low, const CharT *high, mask *vec) const;
protected:
(3)
virtual bool do_is(mask m, CharT c) const;
protected:
(4)
virtual const CharT *do_is(const CharT *low, const CharT *high, mask *vec) const;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 <locale>
#include <utility>
#include <vector>
#include <iostream>
// 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+" << 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:
See also
is (public member function of std::ctype<char>)
iswctype (function)