programming-lua/exercises/ch04/ex4_6.lua

local function remove(str, start, length)
    local slice_start = utf8.offset(str, start - 1)
    local slice_end = utf8.offset(str, start + length)
    local start_part = str:sub(1, slice_start)
    local end_part = str:sub(slice_end)
    return start_part .. end_part
end

print(remove("ação", 2, 2))