The length of Arabic letters in Lua
arabic, lua, string, unicode
Solution
Lua is 8-bit clean.
In other words, a Lua string is a sequence of bytes, it doesn't support Unicode internally. The Arabic letter `"ف"` has 2 bytes, so Lua treats it as a string of length 2.
You need to use a special trick to manipulate Unicode, e.g, assuming UTF-8 is used, you can use this snippet to count the length of a string (Referece: Lua Unicode):
local _, count = string.gsub(unicode_string, "[^\128-\193]", "")
Problem
In Lua language when I want to get the length of a single Arabic letter (such as `"ف"`), the answer will be `2`! Ex. ``` local letter = "ف" print( letter:len() ) ``` Output: `2` The same problem occur when I use `(string.sub(a,b))`. If I want to print the first letter of an Arabic word, I can't say `(string.sub(1,1)`. Ex. ``` local word_1 = "فولت" print( word_1:sub(1,2) ) ``` Output: `ف` as you saw I put the second argument (2) not (1) to get the correct answer. if I put the first argument 1 the answer will be: ``` print( word_1:sub(1,1) ) ``` Output: `Ù` Why does Lua count the length of a single Arabic letter as a two? And is there a way to get the right length which is 1?