use fmt;
use math;

type interval = struct {a: f64, b: f64};

export fn main() void = {
	const a: [_](f64, f64) = [
		(1.0f64, 2.0f64),
		(0.1f64, 0.2f64),
		(1e100f64, 1e-100f64),
		(1e308f64, 1e308f64)];

	for (let i = 0z; i < len(a); i += 1) {
		let res = safe_add(a[i].0, a[i].1);
		fmt::printfln("{} + {} is within ({}, {})", a[i].0, a[i].1, res.a, res.b)!;
	};
};

fn safe_add(a: f64, b: f64) interval = {
	let orig = math::getround();
	math::setround(math::fround::DOWNWARD);
	let r0 = a + b;
	math::setround(math::fround::UPWARD);
	let r1 = a + b;
	math::setround(orig);
	return interval{a = r0, b = r1};
};