From: Richard Wordingham <>
Date: Mon, 22 Aug 2011 03:19:39 +0100

On Sun, 21 Aug 2011 23:55:46 +0000
"Doug Ewell" <> wrote:


There are *three* strong directionalities - 'L' left-to-right, 'AL'
right-to-left as in Arabic, 'R' right-to-left (as in Hebrew, I
suspect). 'AL' and 'R' have different effects on certain characters
next to digits - it's the mind-numbing part of the BiDi algorithm.
With one a $ sign after a string of European (or is it Arabic?) digits
appears on the left and in the other it appears on the right. I
can't remember whether 'higher-level protocols' have an effect on this
logic. LRM has a BC of L, RLM has a BC of R, but no invisible character
has a BC of AL. That's why I tentatively raised the notion of ARABIC
LANGUAGE MARK. Incidentally, an RLO gives characters with a
temporary BC of R, not AL.

Received on Sun Aug 21 2011 - 21:23:15 CDT

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