On Sat, 3 Aug 2019, ND via Pcre-dev wrote: > May be it can be useful to have ability to set a limits of lookbehind search > for performance reasons. > I can imagine a rule: If nonfixedlength lookbehind immediately preceded by > capture group, then it is restricted to start position of this group.
Non-fixed-length lookbehinds are almost certainly never going to be implemented with the current PCRE2 design. It was originally invented for Perl-4 patterns and is very much left-to-right oriented. Note that when Perl-5 invented lookarounds, they also restricted lookbehinds to fixed length, and I presume Perl implements them in the same way: move back a fixed number of characters, then run the lookbehind forwards. Philip -- Philip Hazel -- ## List details at https://lists.exim.org/mailman/listinfo/pcre-dev
