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Re: Crafting a regex

by ahunter (Monk)
on Oct 11, 2000 at 21:29 UTC ( #36262=note: print w/replies, xml ) Need Help??


in reply to Crafting a regex

Perl is fairly good at compiling regexps, and provided you only use the constructs that can be simulated with a 'standard' regexp (which is to say, provided you can construct a deterministic finite automata from the expression), the running time should be O(n), where n is the length of the string being matched against.

This means you should avoid using anything that might cause perl to backtrack or lookahead - mostly that means the (?...) operators.

Anyhow, from your example, it looks like the closing quote is always the last one, so you could just take advantage of perl's greediness and use the following regexp, which should run at exactly the same speed as your original:

/^(\S+).*?\[(\S+).*?] (\S+) "(.+)" (\d+)/
Andrew.

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[stevieb]: I don't know what you mean. I write the code in C/C++ that accesses the ICs per the datasheet, wrap it for Perl, then use them. My code ensures that the functions/methods from Perl do the right thing for the chips/sensors etc

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