std::ctype<CharT>:: is, std::ctype<CharT>:: do_is
From cppreference.com
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Defined in header
<locale>
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public
:
bool is ( mask m, CharT c ) const ; |
(1) | |
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public
:
const CharT * is ( const CharT * low, const CharT * high, mask * vec ) const ; |
(2) | |
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protected
:
virtual bool do_is ( mask m, CharT c ) const ; |
(3) | |
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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
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classifies a character or a character sequence, using the classification table
(public member function of
std::ctype
<char>
)
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classifies a wide character according to the specified
LC_CTYPE
category
(function) |