是否有支持内联代码的regex_replace的变体？ [英] Is There a Variant of regex_replace that Supports Inline Code?

问题描述

Perl有 e regex修饰符，允许Perl代码，而不只是一个字符串来形成替换： http://perldoc.perl.org/perlretut.html#Search-and-replace 虽然该示例并不是最大的，开关来实现这一点。对于那些理解Perl的人来说，这里的例子更有意义：

Perl has the e regex modifier which allows Perl code rather than just a string to formulate the replacement: http://perldoc.perl.org/perlretut.html#Search-and-replace Though that example is not the greatest as there are switches to accomplish this. For those of you who understand Perl here's an example that makes more sense:

$string = "StackOverflow user: Jonathan Mee";

$string =~ s/:\s*(.*)$/$1 == "Jonathan Mee" ? ": ".$1." is AWESOME!" : ": ".$1." is ???"/e;

print $string; #Will print "StackOverflow user: Jonathan Mee is AWESOME!"

在C ++中有一个 regex_replace 会让我做类似的事情吗？

Is there a regex_replace variant in C++ that will allow me to do something similar? As in code inline for the replacement.

推荐答案

regex_replace 有6种不同的重载。 fmt 参数对于每个参数使用相同的方式：

regex_replace has 6 different overloads. The fmt argument is used the same way for each of them:

与每个匹配的替换。
这可能包括由它们代表的字符替换的格式说明符和转义序列。

A string with the replacement for each match. This may include format specifiers and escape sequences that are replaced by the characters they represent.

sport a flags 参数，用于控制，如何格式化 fmt 。 fmt 相关选项包括：

Each of the 6 overloads also sport a flags argument which is used to control, "how fmt is formatted." The fmt related options are:

• format_default ：默认格式

使用标准格式化规则替换匹配（由ECMAScript的替换方法使用的匹配）。


• format_sed sed格式化
  
  使用与POSIX中的sed实用程序相同的规则替换匹配项。


• format_no_copy 无副本

替换匹配时，不会复制目标序列中与正则表达式不匹配的部分。


• format_first_only 首先只有
  
  只替换第一次出现的正则表达式。

• format_default: Default formatting
  Uses the standard formatting rules to replace matches (those used by ECMAScript's replace method).
• format_sed sed formatting
  Uses the same rules as the sed utility in POSIX to replace matches.
• format_no_copy No copy
  The sections in the target sequence that do not match the regular expression are not copied when replacing matches.
• format_first_only First only
  Only the first occurrence of a regular expression is replaced.

请注意， fmt 重载和标志都不支持内嵌代码。因此，答案是：不，没有支持在线代码的 regex_replace 变体。

Note that none of the fmt overloads, nor the flags support in-line code. So the answer is: No, there is no variant of regex_replace that supports in-line code.

但是，如果您愿意使用STD算法与 regex_iterator ，您可以使用lambda来完成在线代码。

However if you were willing to use a STD algorithm in conjunction with regex_iterator, you could use a lambda to accomplish in-line code.

const string foo("StackOverflow user: Jonathan Mee");
vector<string> bar;

transform(regex_iterator<string::const_iterator>(foo.cbegin(), foo.cend(), regex(".*:\\s*(.*)")),
          regex_iterator<string::const_iterator>(),
          back_inserter(bar),
          [](const smatch& i){auto result = i.str();

                              if (!result.empty()){
                                  result += (i.str(1) == "Jonathan Mee" ? " is AWESOME!" : " is ???");
                              }
                              return result;});

正如你可以看到一个lambda可以在 transform 接受当前 regex_iterator 的 smatch 。这对于多行字符串非常可扩展，在 string foo（StackOverflow user：Jonathan Mee \\\
StackOverflow user：user0）; 的输出将是：

As you can see a lambda is usable in the transform taking in the current regex_iterator's smatch. This is very extensible to multi-line strings, in the example of string foo("StackOverflow user: Jonathan Mee\nStackOverflow user: user0"); the output would be:

StackOverflow用户：Jonathan Mee很棒！

StackOverflow用户：user0是

StackOverflow user: Jonathan Mee is AWESOME!
StackOverflow user: user0 is ???

很明显，只有一个 smatch 和 regex_replace 。其中 str（1）属于中未指定str（）。在这里我利用了事实，它是正确的在 foo 的结尾，而不是某处必须在 foo 。但是应该提到的是，同样的困难降低了Perl的 e -modifier，所以我认为这是非常相似的。

Clearly there are some trade-offs working with just an smatch versus regex_replace. Where str(1) falls within str() is not specified. Here I take advantage of the fact that it is right at the end of foo rather than somewhere that has to be found in the middle of foo. But it should be mentioned that the same difficulty befalls Perl's e-modifier, so I think this is pretty much on par.

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