w3c
Numerical Fractions
A discussion happened on Unicode mailing list regarding properties of presenting numerical fraction in Arabic script. Although the W3C TR on math has some text on this topic, but it would be useful to cover it somewhere in ALReq.
The oblique bar / is used in many context, e.g. fraction or report symbol etc., to have the same meaning as in Latin script. Mirroring it to \ does not seem evident.
One can find the oblique sign in :
- Notation such as speed "50 km / h" كم / س 50
- Notation such as "Page / Volume", for example a reference to a page in a volume : ١٢٣/١ for volume ١, page ١٢٣
- or reference to Quran "Verse/Surah", ١٣/٩٠ for Surah 90, Verse 13
- etc.
However, writing order may vary with Arabic digits : 90/13 instead of the above (13/90).
A wiki page is being drafted on this topic. https://github.com/w3c/alreq/wiki/Arabic-numerals-(Draft)
I used to think that not mirroring the fraction slash was a limitation of computer typesetting, but then I found example of old school math books (circa 1930) and it was using un-mirrored fraction slash, so it seems to me not mirroring it is probably as old as modern Arabic math typesetting.
Discussion is related to Section on Numbers #101
Here are some pictures on Arabic fractions (excerpt from a recent book about an ancient work on Arabic mathematics).
1525 and 1/2 (a half)
the result of the operation 28022/7 = 4003.14
4003 and 1/7 (one seventh)
on top : 3 and 4/5 (three and four fifth, 3 + 4/5)
bellow : 4/5 3 (four fifth of three, 3*4/5 )
3/4 5 and 1/3 (three fouth of five and one third, 3/4*5 + 1/3)
