Issue returning desired data with Lua - lua

Question

Wondering if I could get some help with this:
function setupRound()
local gameModes = {'mode 1','mode 2','mode 3'} -- Game modes
local maps = {'map1','map2','map3'}
--local newMap = maps[math.random(1,#maps)]
local mapData = {maps[math.random(#maps)],gameModes[math.random(#gameModes)]}
local mapData = mapData
return mapData
end
a = setupRound()
print(a[1],a[2]) --Fix from Egor
What the problem is:
`
When trying to get the info from setupRound() I get table: 0x18b7b20
How I am trying to get mapData:
a = setupRound()
print(a)
Edit:
Output Issues
With the current script I will always the the following output: map3 mode 2.
What is the cause of this?
Efficiency; is this the best way to do it?
While this really isn't a question, I just wanted to know if this method that I am using is truly the most efficient way of doing this.

Answer 1

First of all
this line does nothing useful and can be removed (it does something, just not something you'd want)
local mapData = mapData
Output Issues
The problem is math.random. Write a script that's just print(math.random(1,100)) and run it 100 times. It will print the same number each time. This is because Lua, by default, does not set its random seed on startup. The easiest way is to call math.randomseed(os.time()) at the beginning of your program.
Efficiency; is this the best way to do it?
Depends. For what you seem to want, yes, it's definitely efficient enough. If anything, I'd change it to the following to avoid magic numbers which will make it harder to understand the code in the future.
--- etc.
local mapData = {
map = maps[math.random(#maps)],
mode = gameModes[math.random(#gameModes)]
}
-- etc.
print(a.map, a.mode)
And remember:
Premature optimization is the root of all evil.
— Donald Knuth

Answer 2

You did very good by creating a separate function for generating your modes and maps. This separates code and is modular and neat.
Now, you have your game modes in a table modes = {} (=which is basically a list of strings).
And you have your maps in another table maps = {}.
Each of the table items has a key, that, when omitted, becomes a number counted upwards. In your case, there are 3 items in modes and 3 items in maps, so keys would be 1, 2, 3. The key is used to grab a certain item in that table (=list). E.g. maps[2] would grab the second item in the maps table, whose value is map 2. Same applies to the modes table. Hence your output you asked about.
To get a random game mode, you just call math.random(#mode). math.random can accept up to two parameters. With these you define your range, to pick the random number from. You can also pass a single parameter, then Lua assumes to you want to start at 1. So math.random(3) becomes actually math.random(1, 3). #mode in this case stand for "count all game modes in that table and give me that count" which is 3.
To return your chosen map and game mode from that function we could use another table, just to hold both values. This time however the table would have different keys to access the values inside it; namely "map" and "mode".
Complete example would be:
local function setupRound()
local modes = {"mode 1", "mode 2", "mode 3"} -- different game modes
local maps = {"map 1", "map 2", "map 3"} -- different maps
return {map = maps[math.random(#maps)], mode = modes[math.random(#modes)]}
end
for i = 1, 10 do
local freshRound = setupRound()
print(freshRound.map, freshRound.mode)
end