Int length([Int] xs) {
	if (xs.nil) {
		return 0;
	} else {
		return 1 + length(xs.tl);
	}
}

Int get([Int] xs, Int i) {
	if (i == 0) {
		return xs.hd;
	} else {
		return get(xs.tl, i-1);
	}
}

// This is not really memoized, as this could be emulated by keeping the last
// two entries in memory. However, real memoization would only make sense with
// an array and sil does not have arrays (yet).
Int fib(Int n) {
	[Int] fibs;
	fibs := [1,1];
	n := n - 2;

	while (!(n == 0)) {
		fibs := get(fibs,0) + get(fibs,1) : fibs;
		n := n - 1;
	}

	return fibs.hd;
}

Int main() {
	return fib(92); // Largest to fit in a 64-bit integer
}