Each language port of Diff Match Patch uses the same API. These are the language-specific notes regarding Lua.

A critical note with Lua is that (unlike most other languages) it does not have any awareness of Unicode. Thus:

string.len("中国") → 6

Strings in Lua are treated as a series of bytes, not a series of characters. This means that the functions in Diff Match Patch may return unexpected and non-printable results as it splits characters at the byte level.

A side effect of the lack of Unicode support is that the line-mode speedup in diff is not available.

Here's a minimal example of a diff in Lua:

local dmp = require 'diff_match_patch'
diff = dmp.diff_main('Hello World.', 'Goodbye World.')
-- Result: [(-1, "Hell"), (1, "G"), (0, "o"), (1, "odbye"), (0, " World.")]
dmp.diff_cleanupSemantic(diff)
-- Result: [(-1, "Hello"), (1, "Goodbye"), (0, " World.")]
for i,tuple in ipairs(diff) do
  print('(' .. tuple[1] .. ', ' .. tuple[2] .. ')')
end

Go to the lua directory and save the above program as hello.lua. Then execute lua hello.lua.

Unit tests can be performed from the lua/tests directory by executing lua diff_match_patch_test.lua. Over twenty test groups should run, with zero failures.

Speed test for diff can be performed from the lua/tests directory by executing lua speedtest.lua. It takes about 15 seconds.