[liblouis-liblouisxml] UK maths braille fraction weirdness
- From: James Teh <jamie@xxxxxxxxxxxx>
- To: liblouis/liblouisxml mailing list <liblouis-liblouisxml@xxxxxxxxxxxxx>
- Date: Mon, 13 Oct 2014 16:54:07 +1000
Hi all,
I am extremely confused by the way some of UK Maths has been implemented
in liblouis*. I'd greatly appreciate it if someone could help clarify.
Ultimately, I want Unicode braille output. This seems to be extremely
difficult for UK Maths because of the way it's implemented.
Let's take a simple fraction which I'll present in LaTeX for brevity:
\frac{a+b}{c}
As I understand it, in UK Maths, the braille should be (using US
computer braille encoding):
<a ;6b>_/c
In ukmaths_edit.ctb, \x0003 (which is defined as the start indicator for
a fraction in ukmaths.sem) is defined as dots 5 6. Similarly, \x0004
(the end indicator for a fraction) is defined as dots 4 5. As I
understand it, they should be dots 1 2 6 and 3 4 5, respectively.
From what I can see, this has been done because
ukmaths_single_cell_defs.cti defines "<" as dots 5 6 and ">" as dots 4
5. The practical upshot is that if you use us-table.dis as the first
table in mathExprTable for ukmaths.cfg, this does give you valid US
computer braille output. However, as far as I can see, it's impossible
to get valid Unicode braille output.
To make things more confusing, ukmaths_single_cell_defs.cti defines
digits as upper digits with dot 6, so dots 1 2 6 is actually the digit
"2" unless defined earlier (e.g. by us-table.dis).
Why is it implemented this way? Shouldn't how the output is encoded be
determined last, rather than the tables hacking around to get a specific
output encoding? That is, the dots in the tables should all be correct
so that any output encoding can be used, whether it be US computer
braille, Unicode braille or something else. So, \x0003 should be dots 1
2 6 and \x0004 should be dots 3 4 5.
Does anyone actually use these tables currently? Would such a change
break things and why?
Thanks,
Jamie
--
James Teh
Executive Director, NV Access Limited
Ph +61 7 3149 3306
www.nvaccess.org
Facebook: http://www.facebook.com/NVAccess
Twitter: @NVAccess
SIP: jamie@xxxxxxxxxxxx
For a description of the software, to download it and links to
project pages go to http://www.abilitiessoft.com
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