“可选"量词 ('??') 的惰性版本在正则表达式中有用吗? [英] Is the lazy version of the 'optional' quantifier ('??') ever useful in a regular expression?

问题描述

我想不出我想在正则表达式中使用 ?? 的情况，但也许我想得不够仔细.

I cannot think of a situation where I'd want to use ?? in a regular expression, but maybe I'm not thinking hard enough.

推荐答案

可能是一个分隔符分隔的列表，而您不想匹配任何终止分隔符.

Maybe a delimiter-separated list, and you don't want to match any terminating delimiter.

^((?:[^,]+,??)+),?$

这将从 "a,b,c," 中捕获 "a,b,c"，其中非惰性变体将在捕获组.

That would capture "a,b,c" from "a,b,c,", where as the non-lazy variant would include the comma in the capture-group.

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