Looks good to me. I hope we can add this to Bug 1857's accepted texts' informative part.
Thank you very much, Geoff and everyone! > 2025年3月13日 20:39，Geoff Clare via austin-group-l at The Open Group > <austin-group-l@opengroup.org> 写道： > > Niu Danny wrote, on 12 Mar 2025: >> >>> I was thinking about something like this: >>> >>> The precedence of quantifiers are as follow (from highest to lowest): >>> >>> 1. The length of any minimal quantifier -modified subexpression >>> shall be such that they match the shortest substring of the >>> subject string, in descending priority from left to right. >>> >>> 2. Consistent with rule 1, the length of the overall match shall >>> be the longest possible. >>> >>> 3. The length of any greedy quantifier -modified subexpression >>> shall be such that they match the longest substring of the >>> subject string, in descending priority from left to right. > > That seems like a sound idea for some clarifying text, but it does not > use the right terminology, it needs to apply to all repetitions not > just those for subexpressions, and it needs an addition to make the > pathological cases unspecified. > > Here's my attempt: > > If an ERE contains repetitions with and without the repetition > modifier '?', the precedence between the repetitions shall be: > > 1. Each leftmost shortest match shall match the leftmost shortest > sequence in the string, in descending priority from left to right. > > 2. Consistent with rule 1, the length matched by the entire regular > expression shall be the leftmost longest. > > 3. Consistent with rules 1 and 2, each leftmost longest match shall > match the leftmost longest sequence in the string, in descending > priority from left to right. > > 4. If an attempt is made to match the same sequence of the string > using repetitions both with and without the repetition modifier '?', > the behavior is unspecified. For example, the ERE ([0-9]+)+? has > unspecified behavior. > > -- > Geoff Clare <g.cl...@opengroup.org> > The Open Group, Apex Plaza, Forbury Road, Reading, RG1 1AX, England >
