The difference between them is subtle (and I've long been convinced that having the distinction was a mistake, but that's water under the bridge).
It is in their effect on European numbers that occur after them, in http://www.unicode.org/reports/tr9/#W2 (and following). Mark *— Il meglio è l’inimico del bene —* On Wed, Aug 24, 2011 at 08:35, Doug Ewell <[email protected]> wrote: > UAX #44, Table 13 ("Bidi_Class Values") includes the following > descriptions: > > R - Right_To_Left - any strong right-to-left (non-Arabic-type) character > AL - Arabic_Letter - any strong right-to-left (Arabic-type) character > > But I can't find any definition, here or elsewhere, of what constitutes > an "Arabic-type" or a "non-Arabic-type" letter. > > Looking in UnicodeData.txt, I see that Arabic, Syriac, and Thaana > letters are assigned a value of 'AL', while other RTL letters, including > Hebrew, N'Ko, Samaritan, Mandaic, and some archaic scripts in plane 1 > are 'R'. Clearly, shaping behavior and ligation isn't what makes a > letter or script "Arabic-type" or "non-Arabic-type." > > How would I make this distinction for an arbitrary letter or script, > other than by association with an existing letter or script already > designated as one or the other? (Yes, I admit, I am thinking about RTL > scripts in CSUR.) > > -- > Doug Ewell | Thornton, Colorado, USA | RFC 5645, 4645, UTN #14 > www.ewellic.org | www.facebook.com/doug.ewell | @DougEwell > > > > >
