std::ctype

Defined in header <locale>	?	?
template< class CharT > class ctype;	?	?

类Ctype封装字符分类功能。执行的所有流输入操作std::basic_istream<charT>使用std::ctype<charT>在流中插入区域设置，以标识用于输入标记化的空白字符。流输出操作应用std::ctype<charT>::widen()在输出之前缩小字符参数。

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继承图

标准库提供了两个独立的%28区域设置无关%29的专门化：

在标头中定义<locale>

*。

STD：：Ctype<char>提供最小“C”区域设置分类的窄字符等效项。此专门化使用表查找进行字符分类。

STD：：Ctype<wchar[医]T>提供适用于本机字符集的宽字符分类。

此外，在C++程序中构造的每个locale对象都实现了自己的%28 locale特定于这些专门化的%29版本。

成员类型

Member type	Definition
char_type	CharT

成员函数

(constructor)	constructs a new ctype facet (public member function)
(destructor)	destructs a ctype facet (protected member function)
is	invokes do_is (public member function)
scan_is	invokes do_scan_is (public member function)
scan_not	invokes do_scan_not (public member function)
toupper	invokes do_toupper (public member function)
tolower	invokes do_tolower (public member function)
widen	invokes do_widen (public member function)
narrow	invokes do_narrow (public member function)

成员对象

static std::locale::id id	id of the locale (public member object)

受保护成员函数

do_is virtual	classifies a character or a character sequence (virtual protected member function)
do_scan_is virtual	locates the first character in a sequence that conforms to given classification (virtual protected member function)
do_scan_not virtual	locates the first character in a sequence that fails given classification (virtual protected member function)
do_toupper virtual	converts a character or characters to uppercase (virtual protected member function)
do_tolower virtual	converts a character or characters to lowercase (virtual protected member function)
do_widen virtual	converts a character or characters from char to charT (virtual protected member function)
do_narrow virtual	converts a character or characters from charT to char (virtual protected member function)

从STD：：Ctype继承而来[医]底座

成员类型

Type	Definition
mask	unspecified bitmask type (enumeration, integer type, or bitset)

成员常数

space static	the value of mask identifying whitespace character classification (public static member constant)
print static	the value of mask identifying printable character classification (public static member constant)
cntrl static	the value of mask identifying control character classification (public static member constant)
upper static	the value of mask identifying uppercase character classification (public static member constant)
lower static	the value of mask identifying lowercase character classification (public static member constant)
alpha static	the value of mask identifying alphabetic character classification (public static member constant)
digit static	the value of mask identifying digit character classification (public static member constant)
punct static	the value of mask identifying punctuation character classification (public static member constant)
xdigit static	the value of mask identifying hexadecimal digit character classification (public static member constant)
blank static	the value of mask identifying blank character classification (public static member constant)
alnum static	alpha \| digit (public static member constant)
graph static	alnum \| punct (public static member constant)

例

下面的示例演示对C类型以外的其他类型的修改<char>来标记CSV文件。

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#include <iostream>
#include <locale>
#include <sstream>
 
struct csv_whitespace : std::ctype<wchar_t>
{
    bool do_is(mask m, char_type c) const
    {   
        if ((m & space) && c == L' ') {
            return false; // space will NOT be classified as whitespace
        }
        if ((m & space) && c == L',') {
            return true; // comma will be classified as whitespace
        }
        return ctype::do_is(m, c); // leave the rest to the parent class
    } 
};
 
int main()
{
    std::wstring in = L"Column 1,Column 2,Column 3\n123,456,789";
    std::wstring token;
 
    std::wcout << "default locale:\n";
    std::wistringstream s1(in);
    while (s1 >> token) {
        std::wcout << "  " << token << '\n';
    }
 
    std::wcout << "locale with modified ctype:\n";
    std::wistringstream s2(in);
    csv_whitespace* my_ws = new csv_whitespace; // note: this allocation is not leaked
    s2.imbue(std::locale(s2.getloc(), my_ws));
    while (s2 >> token) {
        std::wcout << "  " << token<< '\n';
    }
}

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产出：

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default locale:
  Column
  1,Column
  2,Column
  3
  123,456,789
locale with modified ctype:
  Column 1
  Column 2
  Column 3
  123
  456
  789

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另见

ctype<char>	specialization of std::ctype for type char (class template specialization)
ctype_base	defines character classification categories (class template)
ctype_byname	creates a ctype facet for the named locale (class template)

 ? cppreference.com

在CreativeCommonsAttribution下授权-ShareAlike未移植许可v3.0。

http：//en.cppreference.com/w/cpp/locale/ctype

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最后更新于：2017-12-18