1 Jan
2003
1 Jan
'03
11:47 a.m.
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. John Maddock http://ourworld.compuserve.com/homepages/john_maddock/index.htm