String Manipulation in Lua: Make the odd char uppercase

Question

I'm trying to do a library in Lua with some function that manipulate strings. I want to do a function that changes the letter case to upper only on odd characters of the word.

This is an example:

Input: This LIBRARY should work with any string!
Result: ThIs LiBrArY ShOuLd WoRk WiTh AnY StRiNg!

I tried with the "gsub" function but i found it really difficult to use.

Answer 1

First, split the string into an array of words:

local original = "This LIBRARY should work with any string!"

local words = {}
for v in original:gmatch("%w+") do 
    words[#words + 1] = v
end

Then, make a function to turn words like expected, odd characters to upper, even characters to lower:

function changeCase(str)
    local u = ""
    for i = 1, #str do
        if i % 2 == 1 then
            u = u .. string.upper(str:sub(i, i))
        else
            u = u .. string.lower(str:sub(i, i))
        end
    end
    return u
end

Using the function to modify every words:

for i,v in ipairs(words) do
    words[i] = changeCase(v)
end

Finally, using table.concat to concatenate to one string:

local result = table.concat(words, " ")
print(result)
-- Output: ThIs LiBrArY ShOuLd WoRk WiTh AnY StRiNg