Re: Questions concerning /o regex modifier

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Re^2: Questions concerning /o regex modifier by Limbic~Region (Chancellor) on Nov 29, 2006 at 18:29 UTC
diotalevi, Ok, but I am still don't understand when and why /o is useful. Would you be kind enough to fill in the blanks? Use /o when _____ Use qr// when _____ Rely on /$regex/ implementation details when _____ Do not use /o when _____ Do not use qr// when _____ Do not rely on /$regex/ implementation details when _____ Cheers - L~R	[reply]
Re^3: Questions concerning /o regex modifier by diotalevi (Canon) on Nov 29, 2006 at 21:30 UTC
Use /o when writing for a perl 5.005 and less. You are nano-optimizing to avoid the null operation of a pp_regcomp given a qr// object Use qr// when writing for a perl 5.6 and greater. You want the syntax affordance of being able to say `qr/\s/` rather than `"\\s"` (assuming your interpolating into some larger expression) Rely on /$regex/ implementation details when you've bothered to read the source and know exactly what it's doing Do not use /o when writing for humans to read (because almost no one understands what /o does) on perls 5.6 and greater ever. It's just bad style now. Do not use qr// when on perl 5.005 and lower you're writing a sub expression that's going to be interpolated elsewhere and you care that the regexp compiler takes longer to compile strings like '(?-xism:...)' slower than '...'. Do not rely on /$regex/ implementation details when you haven't read the source to pp_regcomp. ⠤⠤ ⠙⠊⠕⠞⠁⠇⠑⠧⠊	[reply] [d/l] [select]
Re^4: Questions concerning /o regex modifier by Limbic~Region (Chancellor) on Nov 29, 2006 at 21:49 UTC
diotalevi, Thank you! I will point people to this anytime the discussion comes up. Cheers - L~R	[reply]
Re^2: Questions concerning /o regex modifier by tye (Sage) on Nov 29, 2006 at 18:36 UTC
/o is motivated by performance concerns. Significantly reducing the whole motivation for the existence of /o in the first place warrants documenting such a change. - tye	[reply]
Re^3: Questions concerning /o regex modifier by diotalevi (Canon) on Nov 29, 2006 at 21:19 UTC
That's qr// and it's documented. ⠤⠤ ⠙⠊⠕⠞⠁⠇⠑⠧⠊	[reply]
Re^2: Questions concerning /o regex modifier by bunnyman (Hermit) on Nov 29, 2006 at 18:36 UTC
In other words, /o is still more efficient than leaving it out? Also, it is a sign (a flag, if you will) to humans that the variables in this expression will not (and should not) change.	[reply]
Re^3: Questions concerning /o regex modifier by diotalevi (Canon) on Nov 29, 2006 at 21:17 UTC
It's not a signal to 99% of the humans that will read it because almost no one gets what /o does. There's just the "Oh! Optimized! Ok, it's more better n' good!" It is faster to avoid doing the concatenation and string comparison work than not but those are cheap operations. If you were optimizing for that then you could just as well pass in a qr// object. ⠤⠤ ⠙⠊⠕⠞⠁⠇⠑⠧⠊	[reply]
Re^4: Questions concerning /o regex modifier by sgt (Deacon) on Dec 01, 2006 at 22:48 UTC
really? I always thought /o had a good mnemonic from the start "compile once" ... and not many ... so you think once? why... the bad ones are /s and /m, I taught myself to read them as: /s superdot /m multi-anchor a rather long process actually if I remember correctly ... --steph	[reply]