std::ctype::is
STD：：Ctype：：is，std：：Ctype：：do[医]是
| Defined in header | | |
|---|---|---|
| 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%29的公共成员函数，调用受保护的虚拟成员函数。do_is最派生的类。
3%29检查字符是否c按面具分类m
4%29对字符数组中的每个字符[low, high)，标识完整的分类掩码%28例如。digit|xdigit|alnum|print|graph数字'0'在默认的locale%29中，并将掩码存储在指向vec
参数
| 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 |
返回值
1，3%29true如果c按m
2，4%29high
例
二次
#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';
}
}
二次
产出：
二次
'0' is a digit
U+7a is: alnum
U+df is: alnum
U+6c34 is: alnum
U+1d10b is: punct
二次
另见
| iswctype | classifies a wide character according to the specified LC_CTYPE category (function) |
|---|
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