Please remove PCRE-compatible from features

Shean Gibber

Hello there, don’t know where the development issues are hosted, but please pass this along to them:

Please remove PCRE compatible tag from features, that’s not true, it does not handle lookbehinds. Either remove the tag, or specify that it does not handle lookbehinds, specifically. That’s misleading.

Thanks!

Claudia Frank

@Shean-Gibber

I don’t really understand what you mean but I assume it should be reported here anyway.

Cheers
Claudia

Scott Sumner

http://docs.notepad-plus-plus.org/index.php/Regular_Expressions mentions “PCRE” (Perl Compatible Regular Expressions) six times, the first of which is: “Notepad++ regular expressions use the standard PCRE (Perl) syntax…”

This may originate from the release notes of version 6 of Notepad++ (https://notepad-plus-plus.org/download/v6.0.html) which state: “PCRE (Perl Compatible Regular Expressions) is supported.”

Recent Notepad++ versions support Boost-compatible regular expressions, not PCRE. I don’t know the complete history–maybe in the beginning (6.0) the PCRE flavor of regex was supported? Or maybe it was always Boost’s engine and it was just referred to incorrectly in the beginning, and that has been allowed to persist?

Regardless, the OP is correct – “PCRE” has no business being in the documentation.

That being said, I’m not sure what the OP @Shean-Gibber is meaning with “does not handle lookbehinds”. Notepad++'s Boost regex engine DOES handle lookbehinds; both positive lookbehinds and negative lookbehinds. Examples:

Positive lookbehind: (?<=a)b matches a “b” only when preceded by an “a”
Negative lookbehind: (?<!a)b matches a “b” that is NOT preceded by an “a”

Lookbehinds must be of fixed length; it is hard for a regex engine to go backwards in a variable-length way.

MAPJe71

Notepad++ uses the Boost Regex library which is a PCRE (Perl Compatible Regular Expression) library. The confusion is the result of a different regular expression library named “PCRE”.

Scott Sumner

And we propagate the confusion… :-D