Backward running version look-behinds (Re: Look-behind proposal in trouble)

Yang Guo yangguo at
Thu Nov 19 20:42:52 UTC 2015

FWIW this is precisely how it works in .NET as well (reverse order of
capture and back reference). While it might be surprising, it makes sense
with the backward read direction in mind.

I'm not fond of the idea of throwing syntax error if the back reference is
to the right of the capture inside a lookbehind. /\1(.)/ and /(.\1)/ are
both perfectly valid regexps as well, with the semantic that these back
references always match, as their corresponding captures are empty at that

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