Re: Using Look-ahead and Look-behind

[joewong]

Referring to the paragraph "Matching a pattern that doesn't include another pattern", I wonder why ?: is necessary. It seems to be working for me even without ?:. Please explain. thanks.

[Roy Johnson]

Generally, the decision about using ?: is not about whether it's necessary, but that capturing whatever you're grouping isn't necessary. The ?: modifier makes parentheses not capture, which is somewhat more efficient and might make the task of counting left parentheses less onerous.

By the way, it's not a lookaround feature.