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

James Clark jjc at jclark.com
Sun Apr 20 20:54:34 CDT 2014

On Mon, Apr 21, 2014 at 2:58 AM, Asmus Freytag <asmusf at ix.netcom.com> wrote:

>  On 4/20/2014 3:24 AM, Eli Zaretskii wrote:
> Would someone please help understand the following subtleties and
> obscure language in the UBA document found athttp://www.unicode.org/reports/tr9/?  Thanks in advance.
>   3. Paragraph 3.3.2 says, under "Non-formatting characters":
>    X6. For all types besides B, BN, RLE, LRE, RLO, LRO, PDF, RLI, LRI,
>        FSI, and PDI:
>        . Set the current character’s embedding level to the embedding
>          level of the last entry on the directional status stack.
>     [...]
>    Note that the current embedding level is not changed by this rule.
> What does this last sentence mean by "the current embedding level"?
> The first bullet of X6 mandates that "the current character’s
> embedding level" _is_ changed by this rule, so what other "current
> embedding level" is alluded to here?
>  I'm punting on that one - can someone else answer this?

I assume "current embedding level" here meant "the embedding level of the
last entry on the directional status stack". (This is a natural slip to
make if you think in terms of an optimized implementation that stores each
component of the top of the directional status stack in a variable, as
suggested in 3.3.2.)

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