为什么必须在C ++中转义字符串文字中的反斜杠？ [英] Why must backslashes in string literals be escaped in C++?

问题描述

我想为两种语言声明相同的正则表达式模式。对于TCL我这样做

 设置模式\d\s\S
  

但对于C ++，我必须为同一模式执行此操作。

  boost :: regex pattern（\\d\\\\\\ s）; 
  

否则C ++编译器会告诉我们：

 警告C4129：'d'：无法识别的字符转义序列
  

所以为什么TCL不试图找到\d \s \S转义符号，只是忽略 \ -s但是C ++尝试和吸引？ p>

PS

解决方案

这就是C ++和PHP的区别;在PHP中，反斜杠后面的字符与一小组特殊字符（我相信rnvtx）匹配。如果匹配失败，它只是继续，而不改变意思。

但是，C ++期望字符在这个小集合（我认为集合是更大的btw），但如果匹配失败，您将看到错误。

I want to declare the same regex pattern for both languages. For TCL I do this

set pattern "\d\s\S" 

but for C++ I have to do this for the same pattern

boost::regex pattern("\\d\\s\\S");

otherwise C++ compiler will tell us the following:

warning C4129: 'd' : unrecognized character escape sequence

so why TCL don't try to find \d \s \S escape symbols and just ignores \-s but C++ tries and sucks?

P.S. PHP works as TCL as I remeber.

解决方案

This is just how C++ and PHP differ; in PHP, the character following a backslash is matched against a small set of special characters (I believe "rnvtx"). If the match fails it will just continue without altering the meaning.

However, C++ expects the character to be in that small set (I think the set is bigger btw) but if the match fails you will see an error instead.

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