Questions on the Unicode BiDirectional (BIDI) Algorithm

Doug Ewell doug at
Sun Jul 6 18:26:49 CDT 2014

Richard Wordingham <richard dot wordingham at ntlworld dot com> wrote:

>> Specifically, I am looking for realized/resolving examples of an
>> Arabic number (AN) and character-containing domain name, (such as
>> مصر.com), but that which employs the BIDI algorithm to change an
>> Arabic 1, to a European number (EN) 1?
> The only interchange of these types in the BiDi algorithm is from
> European number to Arabic number, and this chiefly affects the tags on
> the characters for controlling reversals of the forwards direction and
> whether European separators and terminators are treated as part of the
> run of digits.

To clarify, I would not expect the Unicode Bidirectional Algorithm to 
change an Arabic digit into a European digit, or vice versa. I would not 
ever expect it to change the identity of any character.

The UBA can change the bidirectional TYPE of a particular instance of a 
character, so that it can be rendered properly, which I think is what 
Richard meant. But it will never replace a "١" with a "1", nor will it 
ever replace a "1" with a "١", which I think is what William Blackwood 

Doug Ewell | Thornton, CO, USA | @DougEwell ­ 

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