Re: Xcode Editor's Regex now uses PCRE instead of ICU?
Re: Xcode Editor's Regex now uses PCRE instead of ICU?
- Subject: Re: Xcode Editor's Regex now uses PCRE instead of ICU?
- From: Alastair Houghton <email@hidden>
- Date: Tue, 11 Mar 2008 13:25:50 +0000
On 11 Mar 2008, at 04:19, Stuart Malin wrote:
This question of what Xcode uses aside, I am curious though: I seem
to be sensing the reason for the use of ICU is its support of
Unicode. But doesn't PCRE support Unicode?
Not to the same extent that ICU does. ICU is the canonical
implementation of the Unicode spec.
Also, ICU's regex engine is implemented natively for UTF-16. PCRE's
interface is UTF-8. If, as is commonly the case for Cocoa apps,
strings are stored internally in UTF-16, you would have to convert to
use PCRE whereas ICU's engine can handle the native representation.
Another difference IIRC is that the set support is very much more
sophisticated in ICU. In Perl and PCRE, there is basic support for
character sets (the square-bracket syntax), but AFAIK there are no set
operations (besides inversion), and I think the set of Unicode
properties you can query is somewhat smaller than for ICU. ICU also
supports string values as members of character sets, presumably so
that you can use combining marks and the like in a set.
Kind regards,
Alastair.
--
http://alastairs-place.net
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