Hacker News Reader

Comment by melling | Hacker News Reader

Perl is famous for it regex performance. For many years people have compared Python, Ruby, and Perl performance and it has usually been Perl as the fastest followed by Python then Ruby. I've seen many posts like this:

http://stackoverflow.com/questions/12793562/text-processing-...

These days, however, it appears that Python has really come into its own. I started using Sublime Text so that got me into trying out Python.

View on HN

I think regex performance of Perl is nothing extraordinary. What it is famous for is pushing the scope of matching beyond regular languages.

Of all the common scripting languages I think TCL uses a different algorithm for regex matching and is considerably faster than Perl, especially on longer strings. Let me find some corroborating docs.

Ok this has some info http://swtch.com/~rsc/regexp/regexp1.html

Exactly. Perl regexes have _poor_ performance in terms of running time, but good usability, including by squeezing non-regular features into their allegedly-regular expressions, and also things like numerous and flexible character classes, consistent behaviour for escapes, etc.

I love vim, but jesus I can never remember which vim regex metacharacters need escaping to get their meta-meaning, and which need escaping to get their non-meta meaning.

\v is your friend.

http://vimdoc.sourceforge.net/htmldoc/pattern.html#/magic

I sort of prefer \V, but same difference

I dunno, I haven't used it in the past, because...

1) "It is recommended to always keep the 'magic' option at the default setting, which is 'magic'. This avoids portability problems."

2) Nor do I want to type two extra characters in every damn regex!

So, it only occurs to me right now, the right thing to do for me is this: the first instant I'm confused about whether \( means grouping or literal paren, I should immediately start my pattern with \v or \V. No unportability of plugins, no marginal cost on regexes that don't care, marginal benefit when it does matter.

Yeah, that's basically what I do too. No \v on trivial regexes, \v on ones where there's more than one or two groups.

Reply on news.ycombinator.com