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

Asmus Freytag asmusf at ix.netcom.com
Mon Apr 21 01:03:20 CDT 2014

On 4/20/2014 6:54 PM, James Clark wrote:
> On Mon, Apr 21, 2014 at 2:58 AM, Asmus Freytag <asmusf at ix.netcom.com 
> <mailto: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 at
>>     http://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.)
> James
In general, I heartily dislike "specifications" that just narrate a 
particular implementation...

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