nth Fibbonacci number in lua

nth fib.lua

function floor(n)
    return math.floor(n)
end
 
function sqrt(n)
    return math.sqrt(n)
end

Phi = (1+sqrt(5))/2
phi = (1-sqrt(5))/2
 
--^ because I'm lazy and i like clean code^

function fib(n)
    n = floor(n+0.5) --rounds the input
    return floor(((Phi^n)-(-phi^n))/sqrt(5))
end

--[[
Usage: fib(int)

> Fib(10):
55
>
--]]