Your description of \b is flawed.

\b matches only if each side is different from the other (or the trivial case where there is only one side -- but note that it won't match the empty string). It's already looking on both sides!

On the other hand, if you only want \W\b\w, but not \w\b\W, you'll have to do that yourself. [I suppose someone could come up with the backslash equivalents for these.]

In a complementary vein, if you want (?=...) to look both ways, how do you ask for only lookahead, or only lookbehind?

-QM

In reply to Re: Why do zero width assertions care about lookahead/behind? by QM
in thread Why do zero width assertions care about lookahead/behind? by davido

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