Ruby正则表达式：否定匹配

Question

I was wondering if it was possible to use negative matching on whole words, so that something like [^(<em>.*?<\\/em>)] would match everything but text between (and including) <em>...</em> .

I was thinking about using negative lookahead, but I don't think this will work, as I need to check for the opening <em> as well.

Of course, I could just use the positive regex and then subtract the matches from the original text, but I'm looking for a more 'elegant' solution.

thx for any help

Answer 1

String#split works as negative match. It returns you an array of whatever part that does not match the regex.

'XXXXXXXX<em>YYYYYYY</em>ZZZZZZZZ'.split(%r|<em>.*?</em>|)
# => ['XXXXXXX', 'ZZZZZZZZ']

And if want it back into a string, just do join .

'XXXXXXXX<em>YYYYYYY</em>ZZZZZZZZ'.split(%r|<em>.*?</em>|).join
 # => 'XXXXXXXZZZZZZZZ'

Answer 2

The whole thing with lookaround is that it doesn't consume any of the input. If you want to match everything but a pattern, it means that you want to match the prefix and the suffix of that pattern. To match the suffix, you probably want to consume --- and throw away -- the pattern that you don't want. But negative lookahead doesn't consume.