[英]C++ regex string capture
Tring to get C++ regex string capture to work. Tring让C ++正则表达式字符串捕获工作。 I have tried all four combinations of Windows vs. Linux, Boost vs. native C++ 0x11.
我已经尝试了Windows与Linux的所有四种组合,Boost与本机C ++ 0x11。 The sample code is:
示例代码是:
#include <string>
#include <iostream>
#include <boost/regex.hpp>
//#include <regex>
using namespace std;
using namespace boost;
int main(int argc, char** argv)
{
smatch sm1;
regex_search(string("abhelloworld.jpg"), sm1, regex("(.*)jpg"));
cout << sm1[1] << endl;
smatch sm2;
regex_search(string("hell.g"), sm2, regex("(.*)g"));
cout << sm2[1] << endl;
}
The closest that works is g++ (4.7) with Boost (1.51.0). 最接近的是带有Boost(1.51.0)的g ++(4.7)。 There, the first cout outputs the expected
abhelloworld.
在那里,第一个cout输出预期的
abhelloworld.
but nothing from the second cout. 但第二个cout没什么。
g++ 4.7 with -std=gnu++11 and <regex>
instead of <boost/regex.hpp>
produces no output. g ++ 4.7 with -std = gnu ++ 11 and
<regex>
而不是<boost/regex.hpp>
产生输出。
Visual Studio 2012 using native <regex>
yields an exception regarding incompatible string iterators. 使用本机
<regex>
Visual Studio 2012会产生关于不兼容的字符串迭代器的异常。
Visual Studio 2008 with Boost 1.51.0 and <boost/regex.hpp>
yields an exception regarding "Standard C++ Libraries Invalid argument". 带有Boost 1.51.0和
<boost/regex.hpp>
Visual Studio 2008会产生关于“标准C ++库无效参数”的异常。
Are these bugs in C++ regex, or am I doing something wrong? 这些错误是在C ++正则表达式中,还是我做错了什么?
Are these bugs in C++ regex, or am I doing something wrong?
这些错误是在C ++正则表达式中,还是我做错了什么?
gcc doesn't support <regex>
as noted in the other answer. 如其他答案所述,gcc不支持
<regex>
。 As for the other problems, your problem is you are passing temporary string objects . 至于其他问题,你的问题是你传递的是临时字符串对象 。 Change your code to the following:
将您的代码更改为以下内容:
smatch sm1;
string s1("abhelloworld.jpg");
regex_search(s1, sm1, regex("(.*)jpg"));
cout << sm1[1] << endl;
smatch sm2;
string s2("hell.g");
regex_search(s2, sm2, regex("(.*)g"));
cout << sm2[1] << endl;
Your original example compiles because regex_search
takes a const reference which temporary objects can bind to, however, smatch
only stores iterators into your temporary object which no longer exists. 您的原始示例进行编译,因为
regex_search
采用临时对象可以绑定的const引用,但是, smatch
仅将迭代器存储到不再存在的临时对象中。 The solution is to not pass temporaries. 解决方案是不通过临时工。
If you look in the C++ standard at [§ 28.11.3/5], you will find the following: 如果你在[§28.11.3/ 5]中查看C ++标准,你会发现以下内容:
Returns: The result of regex_search(s.begin(), s.end(), m, e, flags).
返回:regex_search的结果(s.begin(),s.end(),m,e,flags)。
What this means is that internally, only iterators to your passed in string are used, so if you pass in a temporary, iterators to that temporary object will be used which are invalid and the actual temporary itself is not stored . 这意味着在内部,只使用传入的字符串的迭代器 ,因此如果传入临时对象,将使用无效的迭代器,并且不存储实际的临时对象。
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