Re: Regular expression question

Rob Ellis wrote:

On Thu, May 27, 2004 at 09:59:05AM -0700, Dan Phiffer wrote:

So I'm trying to implement a simple wiki-like syntax for hyperlinking. Basically I want to match stuff like [this], where the word 'this' gets turned into a hyperlink. I have that working, but I want to be able to escape the opening bracket, so that it's possible to do \[that] without having it match as a link. Here's what I've got: // Matches fine, but without escaping $pattern = " /

       \[          # Open bracket
       ([^\]]+?)   # Text, including whitespace
       \]          # Close bracket

/x "; // Throws an unmatched bracket warning $pattern = " /

       [^\\]       # Don't match if a backslash precedes
       \[          # Open bracket
       ([^\]]+?)   # Text, including whitespace
       \]          # Close bracket

/x "; // Ignores escaping: \[example] still matches $pattern = " /

       [^\\\]      # Don't match if a backslash precedes
       \[          # Open bracket
       ([^\]]+?)   # Text, including whitespace
       \]          # Close bracket

/x "; Nothing seems to change if I keep adding backslashes to that first matching thingy (i.e. the escaping still doesn't work). Any ideas?

Try negative lookbehinds... $pattern = '

     /
        (?<!\\\\) \[    # open [ not preceded by a backslash
        (.*?)           # ungreedy match anything
        (?<!\\\\) \]    # close ] not preceded by a backslash
     /x

'; - Rob

BTW, instead of un-greedy maych anything (.*?) You could use a negative group....of course to deal with \] as well you have to do alittle more: ([^\]]|[\\\\\]])* -- paperCrane <Justin Patrin>