Getting answers back — return

Functions that only print are fine, but the real power is when a function computes something and hands it back. That hand-back is return.

#How return works

function double(value)
    return value * 2
end

local doubledScore = double(10)
print(doubledScore) --> 20

return sends the result out of the function, and the call site becomes that result. So double(10) becomes 20, and that's what lands in doubledScore.

Read it out loud: "the function takes 10, doubles it, and the place where I called it turns into 20."

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

print(add(4, 5))

#Calls become values

Because a call becomes its result, you can use it anywhere a value fits:

function triple(n)
    return n * 3
end

local total = triple(5) + triple(2)   --> 15 + 6
print(total)                          --> 21

The two calls are just numbers by the time + runs. That's the whole trick: return turns function call into value.

#Return stops the function

The moment a function hits return, it stops — nothing after it on that call runs:

function go()
    return "first"
    print("never printed")
end

That print is dead code. It's how you build early exits: check a condition, and return early if something's wrong.

function buyIfEnough(coins, price)
    if coins < price then
        return "not enough"
    end
    return "bought"
end

#Common mistakes

• Returning but never using the result. double(10) by itself does the math and throws it away. Catch it: local x = double(10).
• Expecting print and return to be the same. print shows you something. return hands a value back to the caller. A function can do one, the other, both, or neither.
• Putting work after return. It never runs.

Next: making decisions with if.