CODEWITHSUNDEEP
regex
wkf
wkf

Reputation: 842

Is the lazy version of the 'optional' quantifier ('??') ever useful in a regular expression?

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

Upvotes: 8

Views: 691

Answers (2)

Markus Jarderot
Markus Jarderot

Reputation: 89181

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

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

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

Upvotes: 10

Daniel Brückner
Daniel Brückner

Reputation: 59655

I would use it as an optimization if the optional part is usually absent.

Foo(PartUsuallyPresent)?Bar

Foo(PartUsuallyAbsent)??Bar

But I definitly lack a real-world example, too.

Upvotes: 2

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