在boost匹配结果中查找不匹配

Question

我正在使用boost::regex_match，并试图找到一个函数来获取正则表达式停止匹配的位置。我在boost::match_results对象中找不到任何属性，但有几个使用boost::regex_search显示子匹配的代码片段。我的实现是在正确的道路上，还是我必须做一些不同的事情来实现它？我的代码如下所示：

int main(int args, char** argv)
{
    boost::match_results<std::string::const_iterator> what;

    if(args == 3) 
    {
        std::string text(argv[1]);
        boost::regex expression(argv[2]);

        std::cout << "Text : " << text << std::endl;
        std::cout << "Regex: " << expression << std::endl;

        if(boost::regex_match(text, what, expression, boost::match_default) != 0) 
        {
            int i = 0;

            for(boost::match_results<std::string::const_iterator>::const_iterator it=what.begin(); it!=what.end(); ++it) 
            {
                std::cout << "[" << (i++) << "] " << it->str() << std::endl;
            }
            std::cout << "Matched!" << std::endl;
        } 
        else 
        {
            std::string::const_iterator start = text.begin();
            std::string::const_iterator end   = text.end();

            while(boost::regex_search(start, end, what, expression)) 
            {
                std::string submatch(what[1].first, what[1].second);
                std::cout << submatch << std::endl;
                start = what[0].second;
            }
            std::cout << "Didn't match!" << std::endl;
        }
    } //if(args == 3)
    else 
    {
        std::cout << "Invalid usage! $> ./boost-regex <text> <regex>" << std::endl;
    }
    return 0;
}

输出：

$> ./boost_regex "We're building it up to burn it down" ".*(build.*)(to.*)(burn.*)"
Text : We're building it up to burn it down
Regex: .*(build.*)(to.*)(burn.*)
[0] We're building it up to burn it down
[1] building it up
[2] to
[3] burn it down
Matched!

$> ./boost_regex "We're building it up to burm it down" ".*(build.*)(to.*)(burn.*)"
Text : We're building it up to burm it down
Regex: .*(build.*)(to.*)(burn.*)
Didn't match!

对于最后一个输入，我希望得到类似如下的内容：

Text : We're building it up to burm it down
Regex: .*(build.*)(to.*)(burn.*)
[0] We're building it up to
[1] building it up
[2] to
Didn't match!

先谢谢你...

Answer 1

首先，您在示例中遇到了正则表达式问题。因为它不能匹配(burn.*)子组，所以整个正则表达式无法匹配任何内容，并且不返回任何结果。添加一个"?“在(burn.*)成功之后，前两个子组将匹配，而第三个子组不匹配。

我想看看rubular.com，它是一个调整正则表达式并实时观察它们工作的很好的工具。

要测试子组是否参与了匹配，需要检查for循环中的sub_match::matched布尔变量，如果子组匹配，则为true。查看boost::submatch here的文档

希望这对我有所帮助，这实际上是我的第一篇Stackoverflow帖子、答案或评论。:)