Unclear text in the UBA (UAX#9) of Unicode 6.3

Eli Zaretskii eliz at gnu.org
Tue Apr 22 12:02:18 CDT 2014

> Date: Tue, 22 Apr 2014 09:06:27 -0700
> From: Asmus Freytag <asmusf at ix.netcom.com>
> CC: Eli Zaretskii <eliz at gnu.org>, ken at unicode.org, 
>  unicode Unicode Discussion <unicode at unicode.org>,
>  James Clark <jjc at jclark.com>
> I believe that your scheme does not match the PBA in that it assumes 
> that brackets are hierarchical and attempts to preserve the best 
> hierarchy, whereas PBA assumes that pairs that are closer together are 
> more likely to be correct matches (for non-mathematical texts 
> hierarchies are not the norm (and they are shallow at best)).

Indeed, that's the somewhat counter-intuitive part of the PBA, one
that IMO should be explicitly pointed out in the text (as a note),
because many readers will not expect that.

> D  A bracket pair is a pair of an opening paired bracket and a closing
>    paired bracket characters within the same isolating run sequence,
>    such that the Bidi_Paired_Bracket property value of the former
>    character or its canonical equivalent equals the latter character or
>    its canonical equivalent.
> R  Characters are resolved into resolved bracket pairs as follows:
>    Starting at the beginning of the text, when the a closing bracket 
> character
>    is encountered, find the nearest preceding opening character that is 
> not part
>    of  a resolved pair, and not ignored for pair resolution and that can 
> form a
>    bracket pair. If one exists, resolve the pair, and mark any enclosed 
> opening
>    brackets of any kind as ignored. Otherwise, if no pair can be 
> resolved, mark
>    the closing bracket as ignored.

Please compare this with my latest suggestion.  I think I say the same

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