#[derive(Debug)]
enum Shape { Circle { r: f64 }, Rect { w: f64, h: f64 }, Dot }

fn main() {
let shapes=[Shape::Circle {r:1.0},Shape::Rect {w:2.0,h:3.0},Shape::Dot];
fn area(s: &Shape) -> f64 {
    match s {
        Shape::Circle { r } => 3.14159 * r * r,
        Shape::Rect { w, h } => w * h,
        Shape::Dot => 0.0,
    }
}
for s in &shapes {
    let description = match s {
        Shape::Circle { r } => format!("Shape.Circle {{ {r} }}"),
        Shape::Rect { w, h } => format!("Shape.Rect {{ {w}, {h} }}"),
        Shape::Dot => "Shape.Dot".to_owned(),
    };
    println!("{description} area {}", area(s));
}

assert_eq!(area(&Shape::Rect {w:2.0,h:3.0}),6.0);
}