Re: Boolean operators in PERL regexp?

I recommend against using these (a parser would work better), but here's a snippet from my scratchpad:

/^(?:(?!$re).)*$/          # NOT re
/$re1|$re2/                # re1 OR re2
/^(?=.*$re1)(?=.*$re2)/    # re1 AND re2
[download]

NOT must be anchored on both ends, but it doesn't have to be with ^ and $.

AND doesn't have to be anchored, but if the start is anchored (with ^ or by some other means), it should speed up the case where there is no match.

The .* in AND may need to be replaced so it doesn't look too far ahead.

Comment on Re: Boolean operators in PERL regexp? Select or Download Code

Replies are listed 'Best First'.
Re^2: Boolean operators in PERL regexp? by lenrobert (Initiate) on Feb 25, 2005 at 16:25 UTC
Friedo, Enlinl, Ikegami, thank you for your responses. Yes, my problem might be easily solved with an HTML parser, but beyond my question in my opinion a logical NOT would be essential for regexps. Lookahead and lookbehind assertions are very good, the only fatal problem with them, that they are non-capturing, i.e. I cannot extract non-matching. Maybe there is a reason for this, I don't know. Robert	[reply]
Re^3: Boolean operators in PERL regexp? by ikegami (Patriarch) on Feb 25, 2005 at 16:30 UTC
Whatcha talking about? `NOT /XYZ/ vvvvvvvvvvvvv >perl -e "$_ = 'ABCDEFGHIJKL'; print(/ABC((?:(?!XYZ).)*)JKL/);" DEFGHI` [download]	[reply] [d/l]
Re^4: Boolean operators in PERL regexp? by lenrobert (Initiate) on Feb 25, 2005 at 17:41 UTC
Ikegami, you're right. As it seems I needed some more help to use your code. Now it works, the final version is: `/(<a href=("\|))((?:(?!("\|\/\|#\|javascript)).)*)(\s\|"\|>)/gi` And $3 is the value of the href property. Thank you.	[reply] [d/l]


Do you know where your variables are?
	PerlMonks