Positive look-ahead assertion (?=...)
Q
What is a positive look-ahead assertion? How to use it?
How to write a regular expression to find words with 'oo' in text like: how, to, look, google, school?
✍: FYIcenter.com
A
A positive look-ahead assertion is a zero-width assertion that allows you to match a subpattern beyond the current position (look-ahead) without moving the matching position. Positive look-ahead assertion is expressed as (?=pattern). For example:
\w+(?=\t) - matches a word followed by a tab without tab in the match
The regular expression to match find words with 'oo' is:
*(?=\w*oo)(\w+)
* - skip space characters
(?=\w*oo) - any word with '00' ahead?
(\w+) - capture the word
2013-01-26, 2508👍, 0💬