std::basic_regex<CharT,Traits>::mark_count

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< cpp‎ | regex‎ | basic regex
 
C++
 
正则表达式库
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正则表达式文法
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std::basic_regex
 
unsigned mark_count() const;
 (C++11 起)

返回正则表达式内有标记的子表达式（又称捕获组）数。

参数

（无）

返回值

正则表达式内有标记的子表达式数。

异常

可能抛出实现定义的异常。

示例

运行此代码
#include <iostream>
#include <regex>
 
int main()
{    
    std::regex r1{"abcde"};
    std::cout << "r1 has " << r1.mark_count() << " subexpressions" <<  '\n';
    //  期待： 0
 
    std::regex r2{"ab(c)de"};
    std::cout << "r2 has " << r2.mark_count() << " subexpressions" << '\n';
    //  期待： 1
 
    std::regex r3{"a(bc)d(e)"}; 
    std::cout << "r3 has " << r3.mark_count() << " subexpressions" << '\n';
    //  期待： 2
 
    //  嵌套的子表达式
    std::regex r4{"abc(de(fg))"};
    std::cout << "r4 has " << r4.mark_count() << " subexpressions" << '\n';
    //  期待： 2
 
    //  转义的括号
    std::regex r5{"a(bc\\(\\)de)"};
    std::cout << "r5 has " << r5.mark_count() << " subexpressions" << '\n';
    //  期待： 1
 
    //  使用 nosubs 标志
    std::regex r6 {"ab(c)de", std::regex_constants::nosubs};
    std::cout << "r6 has " << r6.mark_count() << " subexpressions" << '\n';
    //  Expected: 0
}

输出： 

r1 has 0 subexpressions
r2 has 1 subexpressions
r3 has 2 subexpressions
r4 has 2 subexpressions
r5 has 1 subexpressions
r6 has 0 subexpressions
来自“https://zh.cppreference.com/mwiki/index.php?title=cpp/regex/basic_regex/mark_count&oldid=69293”