Niu Danny wrote, on 07 Mar 2025: > > > 2025年3月6日 23:06，Geoff Clare via austin-group-l at The Open Group > > <[email protected]> 写道： > >> > >> > >> > >> e.g. `([0-9]+)+?` > > > > This is a pathological case because you are simultaneously asking for > > both the longest and shortest match for the SAME part of the string. > > Such cases ought not to occur in real-world use. > > > > What I meant, when I said it is not recursive, is something like: > > > > ([0-9]+[a-z]*)+? > > > > where the inner + and * are individually greedy; they don't inherit > > the outer repetition's non-greediness. > > But greedy quantifiers are still nested in a non-greedy one. > Would you say that this is also pathological, or do you > have something else on your mind?
Here's a better example. This uses the code from bug note 7094 modified to take the ERE and string as arguments: $ ./a.out 'X(([0-9a-zA-Z]+)([a-zA-Z]*))+?Y' 'X000aaaYbbbY' regcomp returned: 0 regexec returned: 0 0 8 1 7 1 7 7 7 -1 -1 Because [0-9a-zA-Z]+ is greedy it matched 000aaa and [a-zA-Z]* was left matching the empty string. If the ? modifier was recursive then [0-9a-zA-Z]+ would have matched just the first 0 and [a-zA-Z]* would have matched 00aaa. -- Geoff Clare <[email protected]> The Open Group, Apex Plaza, Forbury Road, Reading, RG1 1AX, England
