lily/programs/fib.lily

defn if c t e = {
    case c of {
        True -> { t }
        False -> { e }
    }
}

defn fibtr a b n = {
    if (eq n 0) a (fibtr b (a+b) (n-1))
}

defn fib n = { fibtr 1 1 n }

defn main = { fib 40 }