On Tue, 2 Jul 2019, Zoltán Herczeg wrote: > Perhaps the misunderstanding comes from the fact that we are talking > about the pattern and they talk about the matching process. So (*THEN) > simply starts a backtrack, and when an alternation is encountered, it > switches to the next alternative.
That is indeed what happens in the pcre2_match() interpreter. > But this happens normally as well, so what is the exact purpose of > this verb then? Not quite. (*THEN) suppresses going back to a previous backtrack inside the branch. In the Perl example ( COND (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) if COND matches, but FOO fails to match, it does not go back to backtrack points inside COND (which it would do without (*THEN)), but instead abandons the entire branch and jumps to try to match COND2. It's a sort of branch-level (*COMMIT). At a simple level I suppose it's also equivalent to ((?>COND) FOO | ... but perhaps there are more complicated examples that can't be written that way. Philip -- Philip Hazel -- ## List details at https://lists.exim.org/mailman/listinfo/pcre-dev
