\iffalse
# The `Lua-UCA` package
\fi
This package adds support for the [Unicode collation algorithm](https://unicode.org/reports/tr10/) for Lua 5.3.
## Usage
To sort a table using Czech collation rules:
kpse.set_program_name "luatex"
local ducet = require "lua-uca.lua-uca-ducet"
local collator = require "lua-uca.lua-uca-collator"
local languages = require "lua-uca.lua-uca-languages"
local collator_obj = collator.new(ducet)
-- load Czech rules
collator_obj = languages.cs(collator_obj)
local t = {"cihla", "chochol", "hudba", "jasan", "čáp"}
table.sort(t, function(a,b)
return collator_obj:compare_strings(a,b)
end)
for _, v in ipairs(t) do
print(v)
end
The output:
> cihla
> čáp
> hudba
> chochol
> jasan
More samples of the library usage can be found in the source repository of this package on [Github](https://github.com/michal-h21/lua-uca).
% See `HACKING.md` file in the repo for more information.
## Use with Xindex processor
[Xindex](https://www.ctan.org/pkg/xindex) is flexible index processor written
in Lua by Herbert Voß. It has built-in `Lua-UCA` support starting with version
`0.23`. The support can be requested using the `-u` option:
xindex -u -l no -c norsk filename.idx
## Change sorting rules
The simplest way to change the default sorting order is to use the
`tailor_string` method of the `collator_obj` object. It updates the collator object using
special syntax which is subset of the format used by the [Unicode locale data
markup
language](https://www.unicode.org/reports/tr35/tr35-collation.html#Orderings).
collator_obj:tailor_string "&a<b"
Full example with Czech rules:
kpse.set_program_name "luatex"
local ducet = require "lua-uca.lua-uca-ducet"
local collator = require "lua-uca.lua-uca-collator"
local languages = require "lua-uca.lua-uca-languages"
local collator_obj = collator.new(ducet)
local tailoring = function(s) collator_obj:tailor_string(s) end
tailoring "&c<č<<<Č"
tailoring "&h<ch<<<cH<<<Ch<<<CH"
tailoring "&R<ř<<<Ř"
tailoring "&s<š<<<Š"
tailoring "&z<ž<<<Ž"
Note that the sequence of letters `ch`, `Ch`, `cH` and `CH` will be sorted after `h`
It is also possible to expand a letter to multiple letters, like this example for DIN 2:
tailoring "&Ö=Oe"
tailoring "&ö=oe"
Some languages, like Norwegian, sort uppercase letters before lowercase. This
can be enabled using `collator_obj:uppercase_first()` function:
local tailoring = function(s) collator_obj:tailor_string(s) end
collator_obj:uppercase_first()
tailoring("&D<<đ<<<Đ<<ð<<<Ð")
tailoring("&th<<<þ")
tailoring("&TH<<<Þ")
tailoring("&Y<<ü<<<Ü<<ű<<<Ű")
tailoring("&ǀ<æ<<<Æ<<ä<<<Ä<ø<<<Ø<<ö<<<Ö<<ő<<<Ő<å<<<Å<<<aa<<<Aa<<<AA")
tailoring("&oe<<œ<<<Œ")
% More information on a new language support is in the `HACKING.md`
% document in the [`Lua-UCA` Github repo](https://github.com/michal-h21/lua-uca/blob/master/HACKING.md).
### Script reordering
Many languages sort different scripts after the script this language uses. As
Latin based scripts are sorted first, it is necessary to reorder scripts in
such cases.
The `collator_obj:reorder` function takes table with scripts that need to be reordered.
For example Cyrillic can be sorted before Latin using:
collator_obj:reorder {"cyrillic"}
In German or Czech, numbers should be sorted after all other characters. This can be done using:
collator_obj:reorder {"others", "digits"}
The special keyword "others" means that the scripts that follows in the table
will be sorted at the very end.
# What is missing
- Algorithm for setting implicit sort weights of characters that are not explicitly listed in DUCET.
- Special handling of CJK scripts.
\iffalse
# Copyright
Michal Hoftich, 2021. See LICENSE file for more details.
\fi
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