Word by Word string partition in Lua, Lua

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-- This program demonstrates the use of loops, if statements, 
-- how to traverse through a loop using
-- the 'for' loop, declaring a function and using it as well.

local find_index = function(str, character) -- Custom function to find the index of a character
    for i = 1, #str do -- Going through the string using loop ('i' denotes the index.)
        
        if string.char(str:byte(i)) == character then -- Checking if we found the first occurance of the required character.
            return i -- Stopping the loop and returning the index.
        end
        -- Ending the 'if' statement.
    end
    -- Ending the 'for' loop.
    
    return nil 
    -- If the required character wasn't found then the 
    -- function won't stop running and will return 'nil'.
end

local str = io.read("*l") .. " " -- Taking the input.
local space_counter = 0 -- Number of spaces.

for i = 0, #str do -- Looping through the string.
   local space_index = find_index(str, " ") -- Index of the space character.
   
   if space_index == nil then -- If the string has come to an end then stop the loop.
       break
   else
       local substring = string.sub(str, 0, space_index) -- Slicing out the first word
       print(substring) -- Printing the word.
       str = string.sub(str, space_index + 1, #str) -- Removing the first word of the string and reassigning it.
       space_counter = space_counter + 1 -- Incrementing the number of space
   end
end

print("Number of space_indexes in String: " .. space_counter - 1) -- Printing (space - 1) as we increased the number of spaces at the beginning.

-- PROGRAM BY 'JAMES COLLINS'

[ - ] Show input
Absolute running time: 0.17 sec, cpu time: 0.01 sec, memory peak: 5 Mb, absolute service time: 0,37 sec