Re: Regexp Confuzzelemt

Regular expressions are greedy by default. That means (.*[^\?]) first matches the whole input for .*, backtracks one character and matches "c" for [^\?].

You want #(.*?)\? (the '?' makes the .* non-greedy).

#([^?]*) also works, of course. But it also matches "TTT" in "aaaaaaaa#TTT" (note that there is no question mark).

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Re^2: Regexp Confuzzelemt by ikegami (Patriarch) on Apr 28, 2007 at 02:37 UTC
But it also matches "TTT" in "aaaaaaaa#TTT" That's a difference you introduced. If you put the `\?` back in, it won't. `/#(.?)\?/` is equivalent to `/#([^?])\?/` The latter is safer. It's easy to introduced problems when using non-greedy quantifiers. They're not as resilient. For example, you can safely embed the greedy regexp in a larger regexp, but you can't safely embed the non-greedy regexp in a larger regexp.	[reply] [d/l] [select]

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Re^2: Regexp Confuzzelemt
by ikegami (Patriarch) on Apr 28, 2007 at 02:37 UTC

But it also matches "TTT" in "aaaaaaaa#TTT"

That's a difference you introduced. If you put the \? back in, it won't.
/#(.*?)\?/
is equivalent to
/#([^?]*)\?/

The latter is safer. It's easy to introduced problems when using non-greedy quantifiers. They're not as resilient. For example, you can safely embed the greedy regexp in a larger regexp, but you can't safely embed the non-greedy regexp in a larger regexp.

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