So far we have only worked with a single file, main.lua. We can use more files by using require.

-- main.lua
require("arithmetics")

print(add(7, 5)) -- Output: 12
print(subtract(7, 5)) -- Output: 2

-- arithmetics.lua
function add(a, b)
    return a + b
end

function subtract(a, b)
    return a - b
end

We call require("arithmetics"), which executes the file arithmetics.lua. Note that we don't need to add .lua in our require call.

Because the file has been executed, the global functions add and abstract have been created, which we can then use in our main.lua.

require "arithmetics"

We can put our Lua files in folders. File paths commonly use a slash (/), but when requiring a file, we use a dot.

-- main.lua
require "helpers.arithmetics"

If we want the functions to be local, we can assign the functions to a local object, and then return that object for the require.

-- main.lua
local arithmetics = require "arithmetics"

print(arithmetics.add(7, 5)) -- Output: 12
print(arithmetics.subtract(7, 5)) -- Output: 2

-- arithmetics.lua
local arithmetics = {}

function arithmetics.add(a, b)
    return a + b
end

function arithmetics.subtract(a, b)
    return a - b
end

return arithmetics

In arithmetics.lua we create a local table. At the end of the file, we return that table. So far we have only seen return in functions. By using it outside of a function, we can use it to decide what value we return upon the file being required.

In main.lua we catch that return value, the table, in a variable also named arithmetics. As always, the variable name is not important, but it's nice to be consistent. Having assigned the return value to a variable, we can use its functions.