trait Shape {
    fn perimeter(&self) -> f32;
    fn area(&self) -> f32;
}

struct Rectangle { pub width: f32, pub height: f32 }
struct Triangle { pub side: f32 }
struct Circle { pub radius: f32 }

impl Shape for Rectangle {
    fn perimeter(&self) -> f32 {
        self.width * 2.0 + self.height * 2.0
    }
    fn area(&self) -> f32 {
        self.width * self.height
    }
}

impl Shape for Triangle {
    fn perimeter(&self) -> f32 {
        self.side * 3.0
    }
    fn area(&self) -> f32 {
        self.side * 0.5 * 3.0_f32.sqrt() / 2.0 * self.side
    }
}

impl Shape for Circle {
    fn perimeter(&self) -> f32 {
        self.radius * 2.0 * std::f32::consts::PI
    }
    fn area(&self) -> f32 {
        self.radius * self.radius * std::f32::consts::PI
    }
}


fn print_area(shape: &dyn Shape) {
    println!("{}", shape.area());
}

fn print_perimeters(shapes: Vec<&dyn Shape>) {
    for shape in shapes.iter() {
        println!("{}", shape.perimeter());
    }
}

#[test]
pub fn test_dynamic_dispatch() {
    let rectangle = Rectangle { width: 1.0, height: 2.0 };
    let circle = Circle { radius: 1.0 };

    let shapes: Vec<&dyn Shape> = vec![&rectangle, &circle];

    for shape in &shapes {
        print_area(*shape);
    }

    print_perimeters(shapes);

    print_area(&rectangle); 
    print_area(&circle); 

    print_perimeters(vec![ &rectangle, &circle ]);
}