substrate homework4

enum TrafficTight {
    Red,
    Green,
    Yellow,
}


impl TrafficTight {
    
    fn time(&self) -> u8 {
        match &self {
            TrafficTight::Red => 60,
            TrafficTight::Green => 30,
            TrafficTight::Yellow => 10,
        }
    }
}


fn sum(input: &[u32]) -> Option<u32> {
    let mut result:u32 = 0;
    for i in input {
        match result.checked_add(*i) {
            None => {return None},
            Some(r) => result = r,
        }
    }
    return Some(result);
}

trait Area {
    type Output;
    fn area(&self) -> Self::Output;
}

struct Circle {
    radius: f64,
}

struct Rectangle {
    width: f64,
    height: f64,
}

use  std::f64::consts::PI;

impl Area for Circle {
    type Output = f64;
    fn area(&self) -> Self::Output {
        self.radius * self.radius * PI
    }
}

impl Area for Rectangle {
    type Output = f64;
    fn area(&self) -> Self::Output {
        self.width * self.height
    }
}


fn get_area<T: Area>(graph: T)-> <T as Area>::Output {
    return graph.area();
}

fn main() {
    println!("Hello, world!");
    let light = TrafficTight::Red;
    println!("red is {}", light.time());

    let s = sum(&[1, 2, 56, 232, 45]);
    println!("{:?}", s);

    let circle = Circle {radius: 0.123};
    println!("circle area is {}", get_area(circle));

    let rect = Rectangle {width: 1.12, height: 2.23};

    println!("rect area is {}", get_area(rect));


}