pub struct Duration;

pub struct Duration {
	seconds: f64,
}

    fn from(s: u64) -> Self {
        unimplemented!("s, measured in seconds: {}", s)
    }

	fn from(s: u64) -> Self {
		Duration { seconds: s as f64 }
	}

    fn years_during(d: &Duration) -> f64 {
        unimplemented!(
            "convert a duration ({:?}) to the number of years on this planet for that duration",
            d,
        );
    }

	fn years_during(d: &Duration) -> f64;

pub struct Mercury;
pub struct Venus;
pub struct Earth;
pub struct Mars;
pub struct Jupiter;
pub struct Saturn;
pub struct Uranus;
pub struct Neptune;

macro_rules! impl_planets {
	($($planet:ident : $period:literal),*) => {$(
		pub struct $planet;
		impl Planet for $planet {
			fn years_during(d: &Duration) -> f64 {
				d.seconds / 31557600.0 / $period
			}
		}
	)*};
}

impl Planet for Mercury {}
impl Planet for Venus {}
impl Planet for Earth {}
impl Planet for Mars {}
impl Planet for Jupiter {}
impl Planet for Saturn {}
impl Planet for Uranus {}
impl Planet for Neptune {}

impl_planets! {
	Mercury: 0.2408467,
	Venus: 0.61519726,
	Earth: 1.0,
	Mars: 1.8808158,
	Jupiter: 11.862615,
	Saturn: 29.447498,
	Uranus: 84.016846,
	Neptune: 164.79132
}