Why are bugs from September still untouched?

[Dar Scott]

On Wednesday, January 14, 2004, at 10:39 AM, Dave Cragg wrote:

>
> Just out of interest, is "(?>x)*" a valid regular expression? If so, 
> what does it do?

Yes.  It is a non-backtracking, non-capturing group.  Non-backtracking 
has many uses, but I use it especially to keep match failures from 
taking a very long time.

This particular trivial example can be done other ways, of course.  In 
trying to narrow down the bug I reduced the problem to the trivial.

Other non-capturing groups have the same or similar problem.  The most 
common is simple clustering:  "(?:x)"  Assertions also do not capture.

I discovered this when trying to make a regex to test whether text is 
field safe, that is, whether it has certain control characters or long 
lines.  (That was before I realized that there is also a formatedWidth 
limit on lines, too.)

Dar Scott