正则表达式与嵌套的Parens匹配

Question

OK,

I don't know if it is possible to write this regex, so I am going to start by askign for help - so far I have had no success.

source string:

,convert(varchar(8000), lt.text) as reason

desired match:

convert(varchar(8000), lt.text)

assumptions

• statement starts with a comma (outside of the parens)
• state will end with "as "

this is the regex i am starting with:

\(.+\)

Thank you

Answer 1

Bar Kiers - is correct, the inability to cope "with an arbitrary amount of nesting", is the root cause of both my memory as to why and the reason as to why I couldn't accomplish what I wanted.

HACK ALERT: I solved by grabbing the inner most instance and replacing it out with a placeholder, and then processing recursively until there were no more matches...

Answer 2

Use following regex :

^\\,(?<imp>[\\s\\S]*?)as

Answer 3

^,(.+\)) as [a-z]+$

I'm including the "reason" with [az]+.

I suggest you use the RightToLeft option, if you have it. It'll speed up the regex. And remember to escape the \\ , if your language require it.

Answer 4

I'm assuming PCRE syntax here. If you can guarantee that the characters " as " don't show up within the parens, something like this should work:

{,(.*) as }

If you can't guarantee that " as " won't show up in the parens, you need to define some other conditions that will be met. For example, if the line always ends after the " as ", something like this would work:

{,(.*) as \S+$}

Or you could use a real parser, which can keep context (the number of parens).