Regex++

Hi John "(?!foo)bar" matches "bar" in the last three lines of the following: foobar ??bar barfoo bar?? bar Why doesn't it match "bar" in all the lines? Yutaka Emura ---------------

I am using RegEx in Boost v1.29.0. (?= ) and (?! ) expressions do not seem to work at a certain condition.

In the following example, "(?=a)b" should match "b" in "xyzabcdefg", but does not.

Which is correct: (?=a) is a forward lookahead *possitive* assertion, so (?=a)b can never match anything since the next character can't be both an 'a' and a 'b' at the same time!

Similarly, "(?!a)b" should not match "b" in "xyzabcdefg" but it does.

It should match: (?!a) will match anything except 'a' so (?!a)b will match the next 'b' that it finds.