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Re: Using Look-ahead and Look-behind

by joewong (Initiate)
on Nov 12, 2007 at 03:34 UTC ( #650210=note: print w/replies, xml ) Need Help??


in reply to Using Look-ahead and Look-behind

Referring to the paragraph "Matching a pattern that doesn't include another pattern", I wonder why ?: is necessary. It seems to be working for me even without ?:. Please explain. thanks.

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Re^2: Using Look-ahead and Look-behind
by Roy Johnson (Monsignor) on Nov 12, 2007 at 17:54 UTC
    Generally, the decision about using ?: is not about whether it's necessary, but that capturing whatever you're grouping isn't necessary. The ?: modifier makes parentheses not capture, which is somewhat more efficient and might make the task of counting left parentheses less onerous.

    By the way, it's not a lookaround feature.


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[marto]: not if you keep telling people :P
[zentara]: I had to disable hyperthreading on my machine because of that.
[Discipulus]: thanks marto but... at the moment this seems a bit beyond my faculties.. ;=)
[zentara]: a thread goes into a wait state after emitting a wait to all other threads. It locks up a machine completely.
[marto]: if you mean the recent hyperthreading bug, I don't think that's NSA related?
[zentara]: s/thread/cpu/
[marto]: xkcd://538
[Discipulus]: these opcodes mentioned in the wiki pages are the same opcode perl is translated into? or is just the same term but in different fields?
[zentara]: it's useful if you want to lockup a multicore machine :-)

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