有条件地替换字符串中的regex匹配项

I am trying to replace certain patterns in a string with different replacement patters.

我正在尝试用不同的替换模式来替换字符串中的某些模式。

Example:

例子:

string test = "test replacing \"these characters\"";

What I want to do is replace all ' ' with '_' and all other non letter or number characters with an empty string. I have the following regex created and it seems to tokenize correctly, but I am not sure how to (if possible) perform a conditional replace using regex_replace.

我要做的是用一个空字符串替换所有' ' ' '和所有其他非字母或数字字符。我创建了以下regex，它似乎正确地进行了标记，但是我不确定如何(如果可能的话)使用regex_replace执行条件替换。

string test = "test replacing \"these characters\"";
regex reg("(\\s+)|(\\W+)");

expected result after replace would be:

更换后的预期结果是:

string result = "test_replacing_these_characters";

EDIT: I cannot use boost, which is why I left it out of the tags. So please no answer that includes boost. I have to do this with the standard library. It may be that a different regex would accomplish the goal or that I am just stuck doing two passes.

编辑:我不能使用boost，这就是为什么我把它放在标签之外的原因。所以请不要回答包括boost的问题。我必须用标准库做这个。可能是一个不同的regex将完成目标，或者是我只做了两次传球。

EDIT2: I did not remember what characters were included in \w at the time of my original regex, after looking it up I have further simplified the expression. Again the goal is anything matching \s+ should be replaced with '_' and anything matching \W+ should be replaced with empty string.

在我最初的regex时，我不记得什么字符包含在\w中，在查找之后，我进一步简化了表达式。同样，目标是任何匹配的\s+应该被替换为“_”，任何匹配的\W+都应该被替换为空字符串。

1 个解决方案

#1

The c++ (0x, 11, tr1) regular expressions do not really work (*) in every case (look up the phrase regex on this page for gcc), so it is better to use boost for a while.

c++ (0x, 11, tr1)正则表达式并不能在所有情况下(*)都起作用(在这个页面上为gcc查找正则表达式短语regex)，所以最好暂时使用boost。

You may try if your compiler supports the regular expressions needed:

如果您的编译器支持所需的正则表达式，您可以尝试:

#include <string>
#include <iostream>
#include <regex>

using namespace std;

int main(int argc, char * argv[]) {
    string test = "test replacing \"these characters\"";
    regex reg("[^\\w]+");
    test = regex_replace(test, reg, "_");
    cout << test << endl;
}

The above works in Visual Studio 2012Rc.

以上作品在Visual Studio 2012Rc中。

Edit 1: To replace by two different strings in one pass (depending on the match), I'd think this won't work here. In Perl, this could easily be done within evaluated replacement expressions (/e switch).

编辑1:要在一次传递中替换两个不同的字符串(取决于匹配)，我认为这在这里行不通。在Perl中，这很容易在评估的替换表达式(/e开关)中完成。

Therefore, you'll need two passes, as you already suspected:

因此，您将需要两个通行证，正如您已经怀疑的:

 ...
 string test = "test replacing \"these characters\"";
 test = regex_replace(test, regex("\\s+"), "_");
 test = regex_replace(test, regex("\\W+"), "");
 ...

Edit 2:

编辑2:

If it would be possible to use a callback function tr() in regex_replace, then you could modify the substitution there, like:

如果可以在regex_replace中使用回调函数tr()，则可以在那里修改替换，如:

 string output = regex_replace(test, regex("\\s+|\\W+"), tr);

with tr() doing the replacement work:

使用tr()进行替换工作:

 string tr(const smatch &m) { return m[0].str()[0] == ' ' ? "_" : ""; }

the problem would have been solved. Unfortunately, there's no such overload in some C++11 regex implementations, but Boost has one. The following would work with boost and use one pass:

这个问题本来是可以解决的。不幸的是，在某些c++ 11 regex实现中没有这样的重载，但是Boost有一个。下面将使用boost和one pass:

...
#include <boost/regex.hpp>
using namespace boost;
...
string tr(const smatch &m) { return m[0].str()[0] == ' ' ? "_" : ""; }
...

string test = "test replacing \"these characters\"";
test = regex_replace(test, regex("\\s+|\\W+"), tr);   // <= works in Boost
...

Maybe some day this will work with C++11 or whatever number comes next.

也许有一天它会和c++ 11或者其他数字一起工作。

Regards

问候

rbo

投

#1