I look here ANSI C grammar .
我在这里看ANSI C语法。
This page includes a lot of regular expressions in Lex/Flex for ANSI C.
此页面包含许多用于ANSI C的Lex / Flex中的正则表达式。
Having a problem in understanding regular expression for string literals.
在理解字符串文字的正则表达式时遇到问题。
They have mentioned regular expression as \"(\\.|[^\\"])*\"
他们将正则表达式称为\“（\\。| [^ \\”]）* \“
As I can understand \" this is used for double quotes, \\ is for escape character, . is for any character except escape character and * is for zero or more times.
我可以理解“这用于双引号，\\是转义字符，。是除了转义字符之外的任何字符，*是零次或多次。
[^\\"] implies characters except \ , " .
[^ \\“]表示除\，”之外的字符。
So, in my opinion, regular expression should be \"(\\.)*\".
所以，在我看来，正则表达式应该是\“（\\。）* \”。
Can you give some strings where above regular expression will fail?
你能给出一些正则表达式失败的字符串吗？
or
要么
Why they have used [^\\"]?
他们为什么用[^ \\“]？
1 个解决方案
#1
4
The regex \"(\\.)*\" that you proposed matches strings that consist of \ symbols alternating with any characters like:
你提出的正则表达式\“（\\。）* \”匹配包含\符号的字符串与任何字符交替，如：
"\z\x\p\r"
This regular expression would therefore fail to match a string like:
因此，这个正则表达式将无法匹配如下字符串：
"hello"
The string "hello" would be matched by the regex \".*\" but that would also match the string """" or "\" both of which are invalid.
字符串“hello”将匹配正则表达式\“。* \”，但也匹配字符串“”“”或“\”两者都无效。
To get rid of these invalid matches we can use \"[^\\"]*\", but this will now fail to match a string like "\a\a\a" which is a valid string.
为了摆脱这些无效的匹配，我们可以使用\“[^ \\”] * \“，但现在这将无法匹配像”\ a \ a \ a“这样的字符串，这是一个有效的字符串。
As we saw \"(\\.)*\" does match this string, so all we need to do is combine these two to get \"(\\.|[^\\"])*\".
当我们看到\“（\\。）* \”匹配这个字符串时，我们需要做的就是将这两个结合起来得到\“（\\。| [^ \\”]）* \“。
#1
4
The regex \"(\\.)*\" that you proposed matches strings that consist of \ symbols alternating with any characters like:
你提出的正则表达式\“（\\。）* \”匹配包含\符号的字符串与任何字符交替，如：
"\z\x\p\r"
This regular expression would therefore fail to match a string like:
因此，这个正则表达式将无法匹配如下字符串：
"hello"
The string "hello" would be matched by the regex \".*\" but that would also match the string """" or "\" both of which are invalid.
字符串“hello”将匹配正则表达式\“。* \”，但也匹配字符串“”“”或“\”两者都无效。
To get rid of these invalid matches we can use \"[^\\"]*\", but this will now fail to match a string like "\a\a\a" which is a valid string.
为了摆脱这些无效的匹配，我们可以使用\“[^ \\”] * \“，但现在这将无法匹配像”\ a \ a \ a“这样的字符串，这是一个有效的字符串。
As we saw \"(\\.)*\" does match this string, so all we need to do is combine these two to get \"(\\.|[^\\"])*\".
当我们看到\“（\\。）* \”匹配这个字符串时，我们需要做的就是将这两个结合起来得到\“（\\。| [^ \\”]）* \“。