问题
How would I do something like this in Treetop?
/.+?;/
It seems like the only way is to do:
[^;]+ ';'
Which is kind of ugly.. any other way? .+? doesn't seem to work..
回答1:
PEGs are greedy and blind by default, that means they eat as much input as they can and they do not consider what comes afterwards:
S <- P1* P2 (greedy, blind)
That can be considerably easy fixed though by making use of the ordered choice (and without using lookaheads):
S <- P1 S / P2 (greedy, non-blind)
S <- P2 / P1 S (lazy, non-blind)
回答2:
Well, I learnt PEGs are greedy, and there's no way around it. Lookaheads can be used to mimic this behavior though, like !(';' .)
回答3:
I don't know Treetop, but would /[^;]+;/ work?
From a quick search, I saw suggestion that Treetop doesn't do greedy nor lazy (non-greedy) quantifiers, and that the + is actually a possessive quantifier (represented by ++ in other regex flavours).
If this is the case, I'm not sure you've got any other regex-based options than the negated class.
来源：https://stackoverflow.com/questions/1045932/non-greedy-matching-in-treetop-peg