// Rust generics map to Nim's, which are instantiated structurally at the call
// site much as Rust's are. Trait bounds and `where` clauses are dropped: an
// operation the bound permitted either exists for the instantiated type or is
// a compile error at that instantiation, so dropping it cannot change what an
// accepted program means.
#[derive(Copy, Clone)]
struct Pair<T> {
    a: T,
    b: T,
}

enum Holder<T> {
    Empty,
    One(T),
}

impl<T: Copy> Pair<T> {
    fn first(&self) -> T {
        self.a
    }
    fn swapped(&self) -> Pair<T> {
        Pair { a: self.b, b: self.a }
    }
}

fn largest<T: PartialOrd + Copy>(xs: &[T]) -> T {
    let mut m: T = xs[0];
    for x in xs.iter() {
        if *x > m {
            m = *x;
        }
    }
    m
}

fn count<T>(h: &Holder<T>) -> i32 {
    match h {
        Holder::Empty => 0,
        Holder::One(_) => 1,
    }
}

fn main() {
    let p: Pair<i32> = Pair { a: 1, b: 2 };
    let q: Pair<i32> = p.swapped();
    println!("{} {} {}", q.a, q.b, p.first());

    let f: Pair<f64> = Pair { a: 1.5, b: -0.5 };
    println!("{} {}", f.swapped().a, f.first());

    let v: Vec<i32> = vec![3, 9, 4];
    println!("{}", largest(&v));
    let w: Vec<f64> = vec![1.5, 0.25, 9.75];
    println!("{}", largest(&w));
    let b: Vec<u8> = vec![7, 200, 3];
    println!("{}", largest(&b));

    let h: Holder<i32> = Holder::One(7);
    let e: Holder<i32> = Holder::Empty;
    println!("{} {}", count(&h), count(&e));
    match h {
        Holder::Empty => println!("empty"),
        Holder::One(v) => println!("one {}", v),
    }
}