My take on regexp greediness, is that this affects the order in which matches are tried.

The greedy form of * and + try the longest match first, and successively decreasing the candidate match. Non-greedy forms *? and +? start with the shortest match and gradually increase the length.

The ? operator matches 0 or 1 occurrence. 1 occurrence is tried first. The ?? operator tries 0 occurrences first.

In the example you have given, it does not matter which is tried first, as you will get the same result. If there were another quantifier downstream of the ??, this could make a difference, as it would see the string to the left of the clause matching the ?? first, wherease a greedy ? would present the remainder of the string to the right of the match, first.

--

Oh Lord, won’t you burn me a Knoppix CD ?
My friends all rate Windows, I must disagree.
Your powers of persuasion will set them all free,
So oh Lord, won’t you burn me a Knoppix CD ?
(Missquoting Janis Joplin)

In reply to Re: Dominus on the non-greedy version of the ? quantifier by rinceWind
in thread Dominus on the non-greedy version of the ? quantifier by Aristotle

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